global positioning system measurements of strain accumulation across the imperial valley california 1986 1989 global positioning system gps data collected in southern california from 1986 to 1989 indicate considerable strain accumulation across the imperial valley displacements are computed at 29 stations in and near the valley from 1986 to 1988 and at 11 sites from 1988 to 1989 the earlier measurements indicate 5 9 1 0 cm yr right lateral differential velocity across the valley although the data are heavily influenced by the 1987 superstition hills earthquake sequence the 1988 1989 gps displacements are best modeled by 5 0 0 9 cm yr of valley crossing deformation but rates calculated from 15 years of terrestrial geodetic measurements 3 7 0 1 cm yr fit the data nearly as weh1 the relatively high gps rates are suspect because some measurements especially the east trending displacements have large errors there is evidence from gps and very long baseline interferometry observations that the present strain rate along the southern san andreas fault is smaller than the long term geologic estimate suggesting a lower earthquake potential than is currently assumed correspondingly a higher earthquake potential is suggested for the san jacinto fault

tectonic motion in the western united states inferred from very long baseline interferometry measurements 1980 1986 we use over 6 years of mobile very long baseline interferometry vlbi baseline measurements between 12 sites in the western united states to infer their velocities relative to the north american plate we find these velocities to be generally consistent with those determined from geologic data and contemporaneous satellite laser ranging measurements in the same region the discrepancy between the largest velocities determined from the vlbi measurements of 40 48 mm yr 1 and the relative plate velocity of 50 56 mm yr 1 predicted from plate motion models is found to be consistent with a broadened distribution of interseismic strain from cyclic activity on the san andreas and subsidiary faults the vlbi data are best explained by a cumulative rate of strike slip motion near the plate boundary of approximately 48 mm yr 1 although exclusion of competing values of 56 and 41 mm yr 1 is based upon very few data the rates of offshore fault slip inferred from this study range from 15 mm yr 1 in central california to negligible amounts in the san francisco region finite element calculations of multiple fault strain distributions show good agreement with systematic variations in the distribution of shear strain along the san andreas system as revealed by previous geodetic measurements

north american pacific relative plate motion in southern california from interferometry very long baseline interferometry measurements of baselines crossing the san andreas fault zone in southern california have provided observational constraints on rates of elastic tectonic strain accumulation the single site located near this fault the jet propulsion laboratory site moves in a direction concordant with the pacific plate motion vector but at approximately half the net rate relative to north america this motion agrees approximately in amount with geologically determined displacement rates on the san andreas fault alone but not with the local strike of the fault when considered together with complementary geodetic data these results suggest a complex relation between the short term accumulation of elastic strain and its permanent accommodation on existing faults

strain accumulation in western united states this review is principally concerned with recent geodetic strain measure ments in western united states undertaken by the us geological survey as part of the earthquake studies program and as a consequence is heavily biased toward the author s own publications most of the publications reporting crustal strain measurements in western united states prior to about 1968 have been compiled in one volume national geodetic survey 1973 and more recent work with complete bibliographies is summarized in three successive quadrennial reports to the international union of geodesy and geophysics meade 1971 savage 1975 thatcher 1979b the following conventions are employed in this paper strain a dimensionless quantity is reported in units of 10 6 extension is taken as positive to distinguish between engineering and tensor shear strain we denote the former by y and quote the units as j lrad whereas the latter is denoted by e and given the units of j lstrain uncertainties in all cases are quoted as one standard deviation at the present time geodetic techniques furnish the only reliable measure of strain accumulation in the seismic regions of the world the superiority of geodetic techniques derives principally from the long baseline of the measurements difficulties in coupling fiducial marks to the earth have generally made short baseline measurements of strain accumulation questionable wyatt 1982 however long baselines introduce the dis advantage that the measured strain is not closely localized the current technique of measuring strain accumulation involves the

the gutenberg richter or characteristic earthquake distribution which is it abstract paleoearthquake and fault slip rate data are combined with the cit usgs catalog for the period 1944 to 1992 to examine the shape of the magnitude frequency distribution along the major strike slip faults of southern california the resulting distributions for the newport inglewood elsinore garlock and san andreas faults are in accord with the characteristic earthquake model of fault behavior the distribution observed along the san jacinto fault satisfies the gutenberg richter relationship if attention is limited to segments of the san jacinto that are marked by the rupture zones of large historical earthquakes or distinct steps in fault trace the observed distribution along each segment is consistent with the characteristic earthquake model the gutenberg richter distribution observed for the entirety of the san jacinto may reflect the sum of seismicity along a number of distinct fault segments each of which displays a characteristic earthquake distribution the limited period of instrumental recording is insufficient to disprove the hypothesis that all faults will display a gutenberg richter distribution when averaged over the course of a complete earthquake cycle but given that 1 the last 5 decades of seismicity are the best indicators of the expected level of small to moderate size earthquakes in the next 50 years and 2 it is generally about this period of time that is of interest in seismic hazard and engineering analysis the answer to the question posed in the title of the article at least when concerned with practical implementation of seismic hazard analysis at sites along these major faults appears to be the characteristic earthquake distribution

redistribution of energy available for ocean mixing by long range propagation of internal waves ocean mixing which affects pollutant dispersal marine productivity and global climate1 largely results from the breaking of internal gravity waves disturbances propagating along the ocean s internal stratification a global map of internal wave dissipation would be useful in improving climate models but would require knowledge of the sources of internal gravity waves and their propagation towards this goal i present here computations of horizontal internal wave propagation from 60 historical moorings and relate them to the source terms of internal waves as computed previously2 3 analysis of the two most energetic frequency ranges near inertial frequencies and semidiurnal tidal frequencies reveals that the fluxes in both frequency bands are of the order of 1 kw m 1 that is 15 50 of the energy input and are directed away from their respective source regions however the energy flux due to near inertial waves is stronger in winter whereas the tidal fluxes are uniform throughout the year both varieties of internal waves can thus significantly affect the space time distribution of energy available for global mixing

geomorphological response of fluvial and coastal terraces to quaternary tectonics and climate as revealed by geostatistical topographic analysis geostatistical topographic analysis is widely recognized as a useful tool for the statistical reconstruction of planar geomorphic markers from relict surfaces this work is aimed at improving the geostatistical approach used in previous works and developing a method for evaluating the incision rates of rivers in their lower catchments during the late quaternary we chose the major valleys of the adriatic foothills central italy affected since late miocene by a differential tectonic uplift which is still active in particular i we applied the geostatistical analysis to reconstruct the original top surfaces of fluvial to coastal terrace bodies at the metauro river and cesano river mouths ii we performed correlations between the height distribution of the alluvial terrace sequences and the quaternary climatic curve to estimate the average long term fluvial incision rates in the lowermost reaches of the metauro cesano misa and esino rivers the obtained averaged incision rates have been interpreted also in the light of the stream length gradient index sl index steepness index ks and concavity index as proxies of the stream power per unit length results confirm that geostatistical and terrain analysis of topographic and geometric arrangements of fluvial and coastal terraces is an effective tool in detecting geomorphic and tectonic factors inducing perturbations on planar geomorphic markers in particular we better delineated the surface geometry and boundaries of well developed coastal fans at the mouths of the metauro and cesano rivers already recognized in previous works through sedimentological morphostratigraphic and chronological data moreover we found evidence for cut and fill phases that took place during and immediately after the river aggradation of the late quaternary glacial periods despite the slope area analysis evidenced a widespread influence of the regional differential uplift on single river basin configuration we observed some space and time variability of averaged incision rates for adjacent valleys mainly explained by physiographic configuration and dynamics of drainage network copyright 2011 john wiley sons ltd

modeling surface deformations at complex strike slip plate boundaries two new versions of the physical base traction model of li and rice 1987 have been developed to study the loading processes and surface deformation near plate boundaries with geometric complexities including a shallow creeping fault segment and two subparallel faults predictions of surface velocity and surface slip rate for the region between the san andreas fault and the pacific coast at the latitude of the parkfield cholame segment using model parameters based on geologic geodetic and seismic considerations were found to be in good agreement with contemporary geodetic field data not used in constraining model parameters also predicted surface velocity for the salton sea coachella valley area were fit to recently derived contemporary geodetic data and very large baseline interferometry data although here the model parameters are not well constrained

what is the thermohaline circulation the term thermohaline circulation is widely used in the context of past and future climate change in his perspective wunsch argues that there are many different and inconsistent definitions for this term he defines ocean circulation in terms of mass fluxes which are largely driven by surface forces such as wind and tides and argues that thermohaline circulation should only refer to the separate transport of heat and salinity in the ocean

tectonic evolution of the japanese island arc system abstract growth of the japanese arc system which has mainly taken place along the continental margin of asia since the permian is the result of subduction of the ancient pacific ocean floor backarc basin formation in the tertiary shaped the present day arc configuration the neotectonic regime which is characterized by strong east west compression has been triggered by the eastward motion of the amur plate in the quaternary the tectonic evolution of the japanese arc system includes formation of rock assemblages common in most orogenic belts because the origin and present day tectonics of these assemblages are better defined in the case of the japanese arc system study of the system provides useful insight into orogenesis and continental crust evolution

seismotectonics of the easternmost transverse ranges california relevance for seismic potential of the southern san andreas fault earthquake locations depths and focal mechanisms from the southern california regional network 1977 1985 are used to identify the orientation and sense of slip of active subsurface faults in the easternmost transverse ranges etr the etr are separated from the salton trough province by the southernmost strands of the san andreas fault saf much of the seismicity in the etr is concentrated well northeast of the saf at relatively shallow depths under the little san bernardino mountains many of these earthquakes reflect slip on steeply dipping left lateral faults striking northeast to east at relatively high angles to the adjacent saf focal mechanisms in the etr show predominantly strike slip normal or oblique normal faulting and share common near horizontal t axes striking wnw p axes range from near vertical to near horizontal and strike mostly nne in contrast reverse and strike slip focal mechanisms that exhibit persistent north trending near horizontal p axes characterize the san gorgonio pass area immediately to the west these different patterns of strain geometries are inferred to represent changes in local stress regime and clearly establish a boundary between contrasting tectonic styles of contemporary secondary deformation along the saf this boundary which in the coachella valley may be the mission creek fault is also distinguished by abrupt changes in 1 rate and depth of seismic activity 2 topography 3 quaternary vertical deformation 4 strikes and dips of major branches of the saf and 5 seismic velocities in the crust and upper mantle the preponderance of secondary normal faulting in the etr versus secondary reverse faulting in the san gorgonio pass region suggests that fault normal stress is much less across the saf adjacent to the etr if a friction law where strength is proportional to normal stress applies to the saf then a smaller tectonic shear stress would be required tor slip in large earthquakes along the salton trough segment in this case the southernmost saf may have shorter repeat times smaller average displacements and lower moment release rates than earthquakes that rupture through the major restraining bend in san gorgonio pass

advective spreading of storm induced inertial oscillations in a model of the northwest atlantic ocean the spreading of inertial oscillations induced by the passage of hurricane juan 2003 across the gulf stream and the scotian shelf is examined using a regional model of the northwest atlantic ocean it is found that surface intensified inertial oscillations develop at locations remote from the storm track after a period of 5 10 days a diagnostic technique reveals the importance of advection by the background geostrophic flow for explaining this effect the results suggest that advection by mean circulation can play a role in redistributing near inertial energy in the ocean we argue that advective redistribution could have important consequences for understanding diapycnal mixing in the ocean

work done by atmospheric winds on mesoscale ocean eddies mesoscale eddies are ubiquitous in the ocean and dominate the ocean s kinetic energy however physical processes influencing ocean eddy energy remains poorly understood mesoscale ocean eddy wind interaction potentially provides an energy flux into or out of the eddy field but its effect on ocean eddies has not yet been determined here we examine work done by atmospheric winds on more than 1 200 000 mesoscale eddies identified from satellite altimetry data and show that atmospheric winds significantly damp mesoscale ocean eddies particularly in the energetic western boundary current regions and the southern ocean furthermore the large scale wind stress curl is found to on average systematically inject kinetic energy into anticyclonic cyclonic eddies in the subtropical subpolar gyres while mechanically damps anticyclonic cyclonic eddies in the subpolar subtropical gyres

on the spatial and temporal distribution of near inertial energy in the southern ocean 1 we use an eddying realistic primitive equation model of the southern ocean to examine the spatial and temporal distribution of near inertial wind power input wpi and near inertial energy nie in the southern ocean we find that the modeled near inertial wpi is almost proportional to inertial wind stress variance iwsv while the modeled nie is modulated by the inverse of the mixed layer depth we go on to assess recent decadal trends of near inertial wpi from trends of iwsv based on reanalysis wind stress averaged over the southern ocean annual mean iwsv is found to have increased by 16 over the years 1979 2011 part of the increase of iwsv is found to be related to the positive trend of the southern annular mode over the same period finally we show that there are horizontal local maxima of nie at depth that are almost exclusively associated with anticyclonic eddies

using soils as indicators of past slope instability in forested terrain kamienne mts sw poland abstract the kamienne mts in sw poland abound in geomorphic evidence for past landslides developed at the rhyolite sedimentary rock contact but it remains unknown when the displacements occurred the slopes generally have been stable in the last 200 years or so covered by historical records in this paper we use the presence of periglacial solifluction layers cover beds and soil characteristics as indicators of the status of hillslopes and relative age of landslides we follow an assumption that if landslides predate the holocene then solifluction layers should be present and soils within and outside landslide affected slopes should have similar characteristics allowing for differences caused by local factors cover beds are not expected to be associated with holocene landslides differences in the degree of soil development may be used to argue for different ages of some landslides within the holocene the absence of solifluction layers cannot always be regarded as the evidence of post pleistocene landsliding since such a layer is unlikely to have ever formed on densely jointed but otherwise strong rhyolite soil morphological properties particularly horizonation helped to establish the relative chronology of mass movement and to recognize both early to mid holocene and late holocene landslides soils are good relative dating tools and their usage does not necessarily require adherence to any particular soil classification system this is because morphological features of entire profiles provide more information than diagnostic properties used in these systems

propagation of wind energy into the deep ocean through a fully turbulent mesoscale eddy field abstract the authors analyze the 3d propagation of wind forced near inertial motions in a fully turbulent mesoscale eddy field with a primitive equation numerical model although the wind stress is uniform the near inertial motion field quickly becomes spatially heterogeneous involving horizontal scales much smaller than the eddy scales analysis confirms that refraction by the eddy relative vorticity is the main mechanism responsible for the horizontal distortion of the near inertial motions which subsequently triggers their vertical propagation an important result is the appearance of two maxima of near inertial vertical velocity both with rms values reaching 40 m day 1 one at a depth of 100 m and another unexpected one much below the main thermocline around 1700 m the shallow maximum captured by the highest vertical normal modes involves near inertial motions with a spatial heterogeneity close to the eddy vorticity gradient field these characteristics match analytical results obtained with y

constraints on pacific plate kinematics and dynamics with global positioning system measurements global positioning system gps receivers are capable of generating precise geodetic data that can yield important constraints on both plate kinematics and dynamics geodetic measurements can determine plate motion rates over time scales for which little data are currently available high quality geodetic data may also allow the investigation of plate driving forces because changes in the intraplate stress field can potentially be inferred from measurement of the resulting crustal strain a measurement program designed to investigate kinematic and dynamic aspects of plate tectonics should be concentrated in the pacific region this area contains the largest and fastest moving plate up to 17 cm year furthermore subduction zones which play a quantitatively important role in plate driving forces are largely restricted to the pacific region we summarize accuracy studies showing that for short 100 km baselines centimeter level accuracy can be expected using only mobile stations for longer baselines uncertainty in the orbit ephemeris of the gps satellites is a major error source performing simultaneous observations at widely separated 3000 km fiducial stations near the region of interest however should allow centimeter level accuracy for baselines up to several thousand kilometers in length this performance level is predicated upon the assumption that fiducial baselines are known a priori to the centimeter level for example from very long baseline interferometry and that corrections for tropospheric path delay are accurate to the centimeter level the fiducial network location is flexible limited mainly by the requirement for mutual satellite visibility

observed near inertial kinetic energy in the northwestern south china sea based on more than 3 years of moored current meter records this study examined seasonal variability of near inertial kinetic energy nike as well as all large greater than one standard deviation from the mean nike events related to storms and eddies in the northwestern south china sea the nike in the subsurface layer 30 450 m exhibited obvious seasonal variability with larger values in autumn herein defined as august september and october all large nike events during the observation period were generated by passing storms most of the nike events had an e folding timescale longer than 7 d the phase velocity vertical wavelength and frequency shift of these events were examined the maximum nike induced by typhoon neoguri was observed in april 2008 normal mode analysis suggested that the combined effects of the first four modes determined the vertical distribution of nike with higher nike below 70 m but lower nike from 30 to 70 m another near inertial oscillation event observed in august 2007 had the longest e folding timescale of 13 5 d moreover the nike propagated both upward and downward during this event a ray tracing model indicated that the smaller brunt vaisala frequency and the stronger vertical shear of horizontal currents in an anticyclonic eddy and the near inertial wave with larger horizontal scale facilitated the unusual propagation of the nike and the long decay timescale although the nike originated from wind the water column structure affected by diverse oceanographic processes contributed substantially to its complex propagation and distribution

tectonic motions in california inferred from very long baseline interferometry observations 1980 1984 very long baseline interferometry vlbi has been used to measure three baselines of 150 300 km length within california and three baselines of 1500 km length between california and texas these measurements which span nearly 4 years beginning in 1980 and have typical individual uncertainties of approximately 2 cm have been fitted to a steady plane strain rotation model after solving for internal network strains and velocities with respect to the north american plate interior the jet propulsion laboratory site 35 km sw of the san andreas fault trace is found to move toward the northwest with respect to points 100 km ne of the fault at an average rate of 25 4 mm yr 1 along an azimuth of n40 w 7 no reliably determined motion is registered between the other sites all of which are 100 km from the inferred pacific north american plate boundary the observed rate of displacement across the san andreas fault agrees with independent determinations of contemporary slip rates but appears to conflict with the rigid global plate tectonic rate differences between this rate determination and those from satellite laser ranging observations provide potentially important constraints on the distribution of tectonic strain in the region these results are taken as evidence for a regional distribution of elastic strain that is offset in approximately the same sense and amount as the big bend of the southern san andreas fault finite element simulations support the conjecture that tractions on the base of the crust that accompany mantle downwelling beneath the transverse ranges could contribute to these strain inhomogeneities

improved global maps and 54 year history of wind work on ocean inertial motions 1 the global distribution and 54 year time dependence of the energy flux from the wind to near inertial motions is computed by driving a slab mixed layer model with ncep ncar reanalysis winds improving upon previous estimates alford 2001 watanabe and hibiya 2002 the slab model is solved spectrally with frequency dependent damping the resulting solutions are more physically sensible than the previous and more skillful at high latitudes where the inertial frequency approaches the 4 daily sampling of the reanalysis winds this enables alford s calculation whose domain was limited to 50 to be extended to the poles the high latitude reliability is demonstrated by direct comparison with a high resolution regional model remo in the ne atlantic the total power input 0 47 tw has increased by 25 since 1948 paralleling observed increases in extratropical cyclone frequency and intensity if believable the trend may have important consequences for modulation of the meridional overturning circulation

spatially heterogeneous diapycnal mixing in the abyssal ocean a comparison of two parameterizations to observations 1 the spatial distributions of the diapycnal diffusivity predicted by two abyssal mixing schemes are compared to each other and to observational estimates based on microstructure surveys and large scale hydrographic inversions the parameterizations considered are the tidal mixing scheme by jayne st laurent and co authors jsl01 and the roughness diffusivity model rdm by decloedt and luther comparison to microstructure surveys shows that both parameterizations are conservative in estimating the vertical extent to which bottom intensified mixing penetrates into the stratified water column in particular the jsl01 exponential vertical structure function with fixed scale height decays to background values much nearer topography than observed jsl01 and rdm yield dramatically different horizontal spatial distributions of diapycnal diffusivity which would lead to quite different circulations in ogcms yet they produce similar basin averaged diffusivity profiles both parameterizations are shown to yield smaller basin mean diffusivity profiles than hydrographic inverse estimates for the major ocean basins by factors ranging from 3 up to over an order of magnitude the canonical 10 4 m2 s 1abyssal diffusivity is reached by the parameterizations only at depths below 3 km power consumption by diapycnal mixing below 1 km of depth between roughly 32 s and 48 n for the rdm and jsl01 parameterizations is 0 40 tw 0 28 tw respectively the results presented here suggest that present day mixing parameterizations significantly underestimate abyssal mixing in conjunction with other recently published studies a plausible interpretation is that parameterizing the dissipation of bottom generated internal waves is not sufficient to approximate the global spatial distribution of diapycnal mixing in the abyssal ocean

a tomographic image of mantle structure beneath southern california we determined the variations in seismic structure beneath southern california by using a tomographic method of inversion on teleseismic p delays recorded with the southern california array the algorithm employed was a modified form of an algebraic reconstruction technique art used in medical x ray imaging deconvolution with an empirically estimated point spread function was also used to help in focusing the image the inversion reveals two prominent features beneath the region the first is a thin vertical wedge directly beneath the transverse ranges that is 2 3 faster than the surrounding region this feature deepens to the east attaining a maximum depth of about 250 km beneath the san bernardino mountains the second feature is a major zone of low velocity material that is 2 4 slow under the salton trough rift valley extending to a depth of about 125 km two possible explanations for the spatial association of the transverse ranges with the velocity anomaly below are lithospheric subduction or small scale sublithospheric convection in the region of the big bend of the san andreas fault the low velocity anomaly beneath the salton trough is consistent with convective upwelling there

interactions between near inertial mixed layer currents and the mesoscale the importance of spatial variabilities in the vorticity field abstract satellite tracked mixed layer drifter data from the 1987 ocean storms experiment in the northeast pacific are used to study the temporal and spatial variability in the near inertial currents of the surface mixed layer the data suggest that the near inertial currents interact with the mesoscale vorticity to explore the exact nature of this relationship an asymptotic analysis is extended to include the mesoscale and it is shown that not only gradients in the planetary vorticity but also the gradients in the mesoscale vorticity affect the generation and evolution of near inertial mixed layer currents while the effect is relevant for the large scale evolution of the near inertial currents the vorticity gradients of the mesoscale field determine the local behavior of near inertial currents using a three dimensional model it is shown that areas of large gradients in the mesoscale vorticity coincide with areas of low near inertial energy the smaller spatial scales in the near inertial energ

reduced mixing from the breaking of internal waves in equatorial waters in the oceans heat salt and nutrients are redistributed much more easily within water masses of uniform density than across surfaces separating waters of different densities but the magnitude and distribution of mixing across density surfaces are also important for the earth s climate as well as the concentrations of organisms most of this mixing occurs where internal waves break overturning the density stratification of the ocean and creating patches of turbulence predictions of the rate at which internal waves dissipate were confirmed earlier at mid latitudes here we present observations of temperature and velocity fluctuations in the pacific and atlantic oceans between 42 degrees n and 2 degrees s to extend that result to equatorial regions we find a strong latitude dependence of dissipation in accordance with the predictions in our observations dissipation rates and accompanying mixing across density surfaces near the equator are less than 10 of those at mid latitudes for a similar background of internal waves reduced mixing close to the equator will have to be taken into account in numerical simulations of ocean dynamics for example in climate change experiments

geodetic measurement of deformation in the loma prieta california earthquake with very long baseline interferometry following the loma prieta earthquake two mobile very long baseline interferometry vlbi systems operated by the nasa crustal dynamics project and the noaa national geodetic survey were deployed at three previously established vlbi sites in the earthquake area fort ord near monterey the presidio in san francisco and point reyes from repeated vlbi occupations of these sites since 1983 the pre earthquake rates of deformation have been determined with respect to a north american reference frame with 1 formal standard errors of 1 mm yr the vlbi measurements immediately following the earthquake showed that the fort ord site was displaced 49 4 mm at an azimuth of 11 4 and that the presidio site was displaced 12 5 mm at an azimuth of 148 13 no anomalous change was detected at point reyes with 1 uncertainty of 4 mm the estimated displacements at ford ord and the presidio are consistent with the static displacements predicted on the basis of a coseismic slip model in which slip on the southern segment is shallower than slip on the more northern segment of the fault rupture we also give the cartesian positions at epoch 1990 0 of a set of vlbi fiducial stations and the three mobile sites in the vicinity of the earthquake

penetration of wind generated near inertial waves into a turbulent ocean abstractan idealized storm scenario is examined in which a wind generated inertial wave interacts with a turbulent baroclinic quasigeostrophic flow the flow is initialized by spinning up an eady m

influence of stratification and topography upon internal wave spectra in the region of sills 1 a non hydrostatic model in vertical cross section form is used to examine the role of sill width and buoyancy upon the energy cascade into the internal tidal band and higher frequencies in sill regions power spectra analysis of computed time series show that as sill width is reduced the energy transfer from the baroclinic tide to its higher harmonics is reduced however there is an increase in energy at higher frequencies corresponding to lee wave periods in addition internal mixing on the lee side of the sill increases the addition of small scale topography on the sill slope produces a similar spectral change in the internal wave distribution and mixing for a narrow sill the addition of a surface buoyant layer with a higher buoyancy frequency significantly reduces the energy cascade to higher frequencies with a corresponding reduction in mixing the associated spectra have characteristics resembling wide sill topography

role of near inertial internal waves in subthermocline diapycnal mixing in the northern gulf of mexico abstractmoored adcp data collected in the northern gulf of mexico are analyzed to examine near inertial internal waves and their contribution to subthermocline diapycnal mixing based on a finescale parameterization of deep ocean mixing the focus of the study is on the impact of near inertial internal waves generated by an extreme weather event that is hurricane katrina and by month to month variation in weather patterns on the diapycnal mixing the inferred subthermocline diapycnal mixing exhibits pronounced elevation in the wake of katrina both the increased near inertial 0 8 1 8f where f is the coriolis frequency and superinertial 1 8f shear variances contribute to the elevated diapycnal mixing but the former plays a more dominant role the intense wind work on near inertial motions by the hurricane is largely responsible for the energetic near inertial shear variance energy transfer from near inertial to superinertial internal waves however appears to play an important role in elevating th

fault slip in southern california measurements of slip on major faults in southern california have been performed over the past 18 yr using principally theodolite alignment arrays and tautwire extensometers they provide geodetic control within a few hundred meters of the fault traces which complements measurements made by other techniques at larger distances approximately constant slip rates of from 0 5 to 5 mm yr over periods of several years have been found for the southwestern portion of the garlock fault the banning and san andreas faults in the coachella valley the coyote creek fault the superstition hills fault and an unnamed fault 20 km west of el centro these slip rates are typically an order of magnitude below displacement rates that have been geodetically measured between points at greater distances from the fault traces exponentially decaying postseismic slip in the horizontal and vertical directions due to the 1979 imperial valley earthquake has been measured it is similar in magnitude to the coseismic displacements analysis of seismic activity adjacent to slipping faults has shown that accumulated seismic moment is insufficient to explain either the constant or the decaying postseismic slip thus the mechanism of motion may differ from that of slipping faults in central california which move at rates close to the plate motion and are accompanied by sufficient seismic moment seismic activity removed from the slipping faults in southern california may be driving their relatively aseismic motion

kinematics of present crust and mantle flow in southern california in the southern california region published geologic studies of prehistoric fault offsets yield at least 81 rates of slip covering various periods of time chiefly since the opening of the gulf of california these rates together with the known geometries of active faults are used to constrain a hand fit block model for present horizontal velocity of the crust the assumptions employed are that these rates apply to the present that the blocks are internally rigid down to the greatest depth of earthquakes and that the over all pacific north american plate motion is correctly given by global models the resulting model fits 67 data within their uncertainties 10 more with a small discrepancy 1 mm yr and fails to accommodate only 4 data 2 of which are inconsistent with other data nominal precision is good 3 mm yr but accuracy and uniqueness are both suspect because many block boundaries are questionable despite its many local defects this model suggests four reliable regional conclusions first the rate of shortening on the south side of the transverse ranges varies from 6 to 14 mm yr increasing eastward which implies an unrecognized seismic hazard unless the motion is taken up by folding or fault creep second the pattern of block rotation rates is quite different from the pattern of rotations shown by tertiary paleomagnetic declinations which implies some major pliocene reorganization of blocks third the great bend left step of the plate boundary fault system in the transverse ranges appears to be straightening gradually by a 3 m y clockwise rotation relative to both plates finally if it is assumed that plate shortening has been occurring at this bend since the early pliocene and that crust and upper mantle velocities are similar then this model predicts mantle lithosphere downwelling to at least 250 km depth beneath the transverse ranges this prediction is consistent with upper mantle seismic velocity structure

enhanced vertical propagation of storm induced near inertial energy in an eddying ocean channel model the interaction between inertial oscillations generated by a storm and a mesoscale eddy field is studied using a southern ocean channel model it is shown that the leakage of near inertial energy out of the surface layer is strongly enhanced by the presence of the eddies with the anticyclonic eddies acting as a conduit to the deep ocean given the ubiquity of the atmospheric storm tracks a source of near inertial energy for the ocean and regions of strong ocean mesoscale variability we argue that this effect could be important for understanding pathways by which near inertial energy enters the ocean and is ultimately available for mixing

modulation of near inertial oscillations by low frequency current variations on the inner scotian shelf abstractnear inertial oscillations nios on the inner scotian shelf are studied using observations a simple slab model and two operational shelf circulation models high frequency radar and adcp

utilization of mobile vlbi for geodetic measurements three mobile vlbi systems have been fabricated under the direction of the jet propulsion laboratory of the california institute of technology for the nasa crustal dynamics project these include the 9 m diameter mv 1 telescope the 3 6 m mv 2 telescope and the 5 m diameter mv 3 telescope since 1980 mobile systems have been operated in conjunction with several fixed base stations in the western united states as part of a geodetic survey program determining relative motions and regional strain fields near the tectonic plate boundaries in california and alaska in this paper we present a description of the three mobile systems and the environment in which they must function the inherent accuracy of moble vlbi measurements is assessed based on a considcration of major sources of error some recent results are presented which serve to illustrate various aspects of the error model and are of geodetic interest as they span the broad region surrounding the surface trace of the san andreas fault these results indicate that baseline measurements utilizing the current mobile vlbi systems have attained an accuracy of 2 cm or better in the horizontal plane since average geological rates of horizontal motion are of order 5 cm year across the plate boundary regions being studied it is likely that crustal motions will be detected within the next few years provided they are presently occurring at the geological rates

the use of the stream length gradient index in morphotectonic analysis of small catchments a case study from central italy abstract the aim of this work is to test an integrated quantitative geomorphic approach based on stream length gradient index sl index analysis within the small catchment of the tarugo river in the northern marchean apennines central italy the tarugo river basin 92 km 2 wide strikes sw ne across the marchean ridge and the western sector of marchean piedmont the area is characterized by a series of nw se trending ne verging thrust folds affecting the meso cenozoic bedrock that pass upward from dominantly carbonate to dominantly terrigenous rocks the area investigated has been affected since the pliocene by extensional tectonics accompanying a regional uplift decreasing in rate north eastwards in this work the sl index analysis has been integrated with the spatial analysis of the amplitude of relief a r and compared to geological and geomorphological field data results of this work indicate that the sl index is a valid tool to detect the long wavelength structural effect on topography as well as the incipient local response to regional processes i e regional uplift that is often undetectable by other morphotectonic parameters in contrast the sl index analysis seems not be a valid tool for discriminating the local lithological influence from the tectonic one

a unified analysis of crustal motion in southern california 1970 2004 the scec crustal motion map 1 to determine crustal motions in and around southern california we have processed and combined trilateration data collected from 1970 to 1992 vlbi data from 1979 to 1992 and gps data from 1986 to 2004 a long temporal coverage required in part by the occurrence of several large earthquakes in this region from a series of solutions for station positions we have estimated interseismic velocities coseismic displacements and postseismic motions within the region from 31 n to 38 n and east to 114 w the final product includes estimated horizontal velocities for 1009 gps 190 trilateration and 16 vlbi points with ties between some of these used to stabilize the solution all motions are relative to the stable north american reference frame snarf as realized through the velocities of 20 gps stations this provides a relatively dense set of horizontal velocity estimates with well tested errors for the past quarter century over the plate boundary from 31 n to 36 5 n these velocities agree well with those from the plate boundary observatory which apply to a later time period we also estimated vertical velocities 533 of which have errors below 2 mm yr most of these velocities are less than 1 mm yr but they show 2 4 mm yr subsidence in the ventura and los angeles basins and in the salton trough our analysis also included estimates of coseismic and postseismic motions related to the 1992 landers 1994 northridge 1999 hector mine and 2003 san simeon earthquakes postseismic motions increase logarithmically over time with a time constant of about 10 days and generally mimic the direction and relative amplitude of the coseismic offsets

spreading of near inertial energy in a 1 12 model of the north atlantic ocean near inertial energy in the ocean is thought to be redistributed by s dispersion whereby near inertial waves generated at the surface by wind forcing propagate downward and equatorward in this letter we examine the spreading of near inertial energy in a realistic 1 12 model of the north atlantic driven by synoptically varying wind forcing we find that 1 near inertial energy is strongly influenced by the mesoscale eddy field and appears to be locally drained to the deep ocean largely by the chimney effect associated with anticyclonic eddies and 2 the interior of the subtropical gyre shows very low levels of near inertial energy contrary to expectations based on the s dispersion effect

global positioning system network analysis with phase ambiguity resolution applied to crustal deformation studies in california a 5 year campaign is in progress in central and southern california to monitor tectonic motions using observations of the global positioning system gps satellites evidence from geological and space geodetic data indicates that significant horizontal deformations of order 10 mm yr are occurring west of the san andreas fault along the california margin we demonstrate using data from initial epoch measurements in january 1987 that the goal of measuring horizontal deformations with an accuracy of 5 mm yr over the duration of the campaign should be readily achievable the gps network was designed to span a wide range of baseline lengths within california and across north america to aid in phase ambiguity resolution an important factor in achieving highest accuracy baseline determinations we present an efficient algorithm for multisession network analysis of gps data with simultaneous orbit determination and ambiguity resolution using this algorithm with the california data we demonstrate the improvement obtained in station position and satellite orbit estimation when the phase ambiguities are resolved we demonstrate several millimeters 1 part in 108 short term repeatability over five single session daily analyses for horizontal baseline components and length and several tens of millimeters for the vertical comparison with the independently determined very long baseline interferometry baseline between mojave and owens valley suggests that the accuracy is at the same level as the repeatability we show that simultaneous multisession analyses with ambiguity resolution improve the baseline and satellite orbit estimates compared to the single session analyses with the single session analyses we were able to resolve all phase ambiguities on baselines within california with the multisession analyses we were able to resolve the phase ambiguities for most of the network over regional and continental scales

vertical velocity and vertical heat flux observed within loop current eddies in the central gulf of mexico abstract sixteen months of observations from a surface to bottom mooring in the central gulf of mexico show that acoustic doppler current profilers adcps are useful for directly measuring the vertical velocity within mesoscale anticyclonic eddies such as those shed from the loop current and combining simultaneous temperature measurements vertical heat flux can also be estimated as a covariance of both variables there is evidence of significant and coherent signals of vertical velocity 2 3 mm s 1 and vertical heat temperature transport 10 3 c m s 1 during the presence of three anticyclones a simple analysis shows downward flow near the eddies centers above 350 m and essentially upward flow in the peripheries but below 700 m depth the pattern is indeed the opposite however further study is necessary to determine the eddies interior structures the observations also suggest the existence of a vertical convergence of heat somewhere around 600 m depth and estimations of adiabatic heat flux

seasonal and spatial variations of southern ocean diapycnal mixing from argo profiling floats in the large scale ocean circulation and climate 4 6 here we use high resolution hydrographic profiles from argo floats in combination with the iridium communications system to investigate diapycnal mixing in the southern ocean we find that the spatial distribution of turbulent diapycnal mixing in the southern ocean at depths between 300 and 1 800 m is controlled by the topography by means of its interaction with the antarctic circumpolar current the seasonal variation of this mixing can largely be attributed to the seasonal cycle of surface wind stress and is more pronounced in the upper ocean over flat topography we suggest that additional highresolution profiles from argo floats will serve to advance our understanding of mixing processes in the global ocean interior the southern ocean is an important source of bottom water in the world s oceans and is a key upwelling site of deep water pointing to diapycnal mixing that is mixing across surfaces of equal density in the region as an important controlling factor of the global meridional overturning circulation moc refs 7 8 modelling studies have demonstrated that the global strength of the moc depends critically on the details of the representation of mixing processes in the southern ocean interior 9 a few existing observations 1014 in this region have revealed dramatic spatial heterogeneity in diapycnal mixing with values of diffusivity over smooth topography comparable to those in the mid latitude ocean interior of the order of 10 5 m 2 s 1 and enhanced mixing of the order of 10 4 m 2 s 1 or larger extending far from rough topography however discerning the nature of diapycnal mixing over the entire southern ocean is still a formidable challenge because of the very limited sampling of the necessary parameters in the region furthermore in general the temporal variability of diapycnal mixing remains poorly assessed and understood throughout most of the world s oceans but in some cases the causes of such variability might be reasonably straightforward to document asanexample recentanalysisofhistoricalhydrographic data reveals that the subsurface turbulent diapycnal mixing in the northwestern pacific displays a pronounced seasonal variability stirred by surface wind stress 15 the international argo program has created the first global array for observing the subsurface ocean a subset of argo floats deployed are designed to use the iridium communications system henceforth referred to as argo iridium floats and are able to provide high resolution 2m profiles that are able to resolve fine scale tens to hundreds of meters strain these floats

on the behavior of internal waves in the wakes of storms abstract the rossby adjustment process in the wake of a storm is studied with a view to finding within the context of linear theory how wave dispersion in both the vertical and meridional directions spreads energy which is initially confined entirely to the mixed layer comparisons are made between three cases 1 a periodic storm on the f plane where dispersion is purely vertical 2 a bounded storm on the f plane and 3 a bounded storm centered 2700 km from the equator on an equatorial beta plane particular attention is paid to the initial rate of loss of energy from the mixed layer and some simple formulas which work very well in the cases studied are derived these show that the rate of loss goes up when the mixed layer depth is increased and also that the rate scales as the square of the wavenumber values of the rates are sufficient to provide a major source of energy for internal waves below the mixed layer the often observed tendency for phase lines to propagate upward is found in all case

adularia in epithermal veins queensland morphology structural state and origin four types of adularia i e sub rhombic rhombic tabular and pseudo acicular are recognised from examination of samples from ten epithermal vein deposits and prospects in queensland based on morphology of the individual crystals further investigation of the structural state of adularia reveals that each group has some specific features in terms of the degree of al si disordering which can be related to various crystallisation conditions and the thermal history sub rhombic adularia is commonly 2 4 mm in size and subhedral with more or less rhombic outlines and has a relatively ordered al si distribution 2t1 0 84 reflecting slow crystallisation conditions adularia of this type in association with coarse grained quartz is predominant at deep levels of epithermal systems where boiling is initiated in an environment of low permeability and the fluid is slightly supersaturated with respect to adularia and quartz tabular adularia characterised by its lath shape and disordered structure 2t1 values ranging from 0 64 to 0 74 is likely to have formed when the fluid moves up to a more permeable environment and starts boiling violently relatively high temperatures and rapidly changing conditions account for its special morphology and disordered structure rhombic adularia showing very small crystal size 0 2 mm with euhedral rhombic form has an intermediate degree of al si ordering pseudo acicular adularia is interpreted as pseudomorphs after carbonate and its high al si ordered structure is attributed to the presence of a carbonate precursor these two types of adularia commonly occur within crustiform and colloform bands in association with high grade ore and chalcedony or fine grained quartz which often displays various recrystallisation textures it is most likely that adularias of these two types are formed when extensive boiling is protracted microprobe analyses indicate the composition of all adularia types close to pure kalsi3o8 sericite and or carbonate altered adularias consistently display more ordered structures suggesting that the post crystallisation thermal regime affects the structural state of altered adularia even at temperatures as low as in epithermal environments

potential effects of ongoing postglacial adjustment on very long baseline interferometry measurements very long baseline interferometry vlbi has the potential to estimate the rates of postglacial adjustment across northern north america by employing glacial isostatic adjustment theory the radial rates of uplift or subsidence were computed at five vlbi sites the expected rates of baseline extension or reduction between these sites and seven static sites with respect to postglacial adjustment were estimated these first order estimates may act as a guide in organizing a vlbi network to measure ongoing postglacial adjustment and help determine how many years would be required to observe the deglaciation signal ideally using a network which includes sites in the region of maximum postglacial uplift and sites in the southern united states this signal should be observed in 10 years of annual measurements

spatial and temporal patterns of small scale mixing in drake passage temperature and salinity profiles obtained with expendable ctd probes throughout drake passage between february 2002 and july 2005 are analyzed to estimate turbulent diapycnal eddy diffusivities to a depth of 1000 m diffusivity values are inferred from density temperature inversions and internal wave vertical strain both methods reveal the same pattern of spatial variability across drake passage diffusivity estimates from inversions exceed those from vertical strain by a factor of 3 over most of drake passage the polar front pf separates two dynamically different regions strong thermohaline intrusions characterize profiles obtained north of the pf south of the pf stratification is determined largely by salinity and temperature is typically unstably stratified between 100 and 600 m depth in the upper 400 m turbulent diapycnal diffusivities are o 10 3 m2 s 1 north of the pf but decrease to o 10 4 m2 s 1 or smaller south of the pf below 400 m diffusivities typically exceed 10 4 m 2 s 1 diffusivities decay weakly with depth north of the pf whereas diffusivities increase with depth and peak near the local temperature maximum south of the pf the meridional pattern in near surface mixing corresponds to local maxima and minima of both wind stress and wind stress variance near surface diffusivities are also found to be larger during winter months north of the pf wind driven near inertial waves strong mesoscale eddy activity and double diffusive convection are suggested as possible factors contributing to observed mixing patterns

plates and their motions the last reviews which covered research in plate motions were those of herron and pitman 1975 on marine magnetic anomalies and dewey 1975 on plate tectonics both reporting on research for the period 1971 1974 in the last 12 years there has been considerable refinement of relative motion models as well as further development of global models also major effort has gone into defining reference frames for the study of plate motions and discriminating between them more recently the role of errors in individual plate rotations and the associated uncertainties in reconstructions have received attention in this report i concentrate on work published in the last 4 years 1983 1986 citing a minimum of publications from previous years however some papers in press for early 1987 have been included this report first reviews work on relative plate motions for the present and past and reconstructions and then models for these motions global ones for driving forces and local ones determining subduction history and back arc spreading the problem of reference frames both hotspot and paleomagnetic is discussed next i end with a review of work on the errors in plate motions

deformation kinematics in the western united states determined from quaternary fault slip rates and recent geodetic data we estimate the horizontal velocity gradient tensor field from quaternary fault slip rates and recent global positioning system gps and very long baseline interferometry vlbi velocity solutions in the western united states transform plate boundary zone the total velocity obtained from the quaternary fault slip rate data across the entire plate boundary is within 1 mm yr of the nuvel 1a predicted pacific pa north american na plate motion velocity but directions are 5 6 anticlockwise of directions given by nuvel 1a the total velocity obtained from inversion of recent geodetic data is 2 3 anticlockwise from the nuvel 1a na pa velocity but the difference between the two is not significant at the 95 confidence level the discrepancy between the total pa na motion obtained from the geological data and nuvel 1a indicates that a marginally significant amount of ne sw shortening possibly as much as 5 mm yr is missing overall in the geologic data shortening may occur in the long term in the offshore and coastal areas of california where such shortening is required in the shorter term geodetic solution the seismic moment released in the last 148 years is 59 of the total moment release rate expected from long term strain rate field including both seismic and aseismic deformation derived from the inversion of geological data with nuvel 1a far field pa na motion constraints the accumulated strain in the areas containing the southern san andreas fault san jacinto fault the san francisco bay area and the area containing the ventura basin in the western transverse ranges in the last 148 years is the equivalent to that which could be released by an mw 7 0 earthquake in each 50 100 15 km3 crustal volume if strain is to be released seismically in these areas

determination of relative site motions in the western united states using mark iii very long baseline interferometry four years of very long baseline interferometry vlbi measurements involving fixed and mobile stations in the western united states are analyzed using weighted least squares baseline solution time series are used to estimate rates of change of the vector baselines between pairs of vlbi stations horizontal vector motions are determined for 18 sites with respect to a site in the mojave desert six sites west of and two sites just to the east of the san andreas fault show northwestward motion closely parallel to the san andreas fault their motions range from 18 to 43 mm yr and are significant at confidence levels greater than 99 motions in california relative to interior north american plate sites are used to estimate an integrated contribution from basin and range spreading to the total relative pacific plate motion as 9 10 mm yr a maximum relative velocity of 50 51 mm yr is found between the interior north american sites and the western california sites in close agreement with the nuvel i plate motion model

surface wave effects on the wind power input to mixed layer near inertial motions abstractocean surface waves play an essential role in a number of processes that modulate the momentum fluxes through the air sea interface in this study the effects of evolving surface waves on the wind power input wpi to near inertial motions nims are examined by using momentum fluxes from a spectral wave model and a simple slab ocean mixed layer model single point numerical experiments show that without waves the wpi and the near inertial kinetic energy ni ke are overestimated by about 20 and 40 respectively globally the overestimate in wpi is about 10 during 2005 08 the largest surface wave effects occur in the winter storm track regions in the midlatitude northwestern atlantic pacific and in the southern ocean corresponding to large inverse wave age and rapidly varying strong winds a relatively low frequency of occurrence of wind sea is found in the midlatitudes which implies that the influence of evolving surface waves on wpi is intermittent occurring less than 10 of the tot

radio interferometric determination of intercontinental baselines and earth orientation utilizing deep space network antennas 1971 to 1980 a series of experiments has been conducted during the last decade to develop a radio interferometry system capable of measuring crustal and rotational motions of the earth as well as source positions for a reference frame based on compact extragalactic radio sources with the exception of one session between big pine california and westford massachusetts the observing stations have been those of nasa s deep space network in california spain and australia approximately 2400 observations of extragalactic radio sources were made between august 1971 and february 1980 during 48 separate sessions a single multiparameter fit was applied to the observed values of delay and delay rate to extract astrometric and geophysical parameters from this decade long sequence the fit produced estimates of 684 parameters including station locations radio source positions polar motion universal time the precession constant and solid earth tides the a priori model included gravitational bending the 1980 international astronomical union iau nutation series the 1976 iau expressions for greenwich mean sidereal time and precession bureau international de l heure estimates of universal time and polar motion and monthly mean values for zenith troposphere delay the rms residuals were 0 52 ns for delay and 0 30 ps s for delay rate intercontinental baseline lengths have been determined with formal uncertainties of 4 to 10 cm universal time and polar motion were measured at 49 epochs with formal uncertainties for the more recent data of 0 5 ms for ut1 and 6 and 2 milliseconds of arc mas respectively for the x and y components of polar motion our 1971 1980 data produced an estimate of the lunisolar precession constant that is smaller than the 1976 iau value by 3 8 mas yr with an approximate accuracy 1 of 2 mas yr the earth tide results agree with the commonly accepted values

measurement of horizontal motions in alaska using very long baseline interferometry we have analyzed 6 years of very long baseline interferometry vlbi data beginning in 1984 from a network of sites in alaska the yukon and the conterminous united states the analysis of these 53 data sets includes constrained continuous piecewise linear estimation of the site atmospheres and clocks application of values and correlations from a self consistent earth orientation series derived from other vlbi data and simultaneous estimation of site positions and velocities from a solution that includes 21 007 observations with a fit of 40 ps in delay and 64 fs s in delay rate we have determined the horizontal velocities of seven sites with precisions of 0 5 2 mm yr 1 standard deviation the three vlbi sites within the alaska aleutian subduction boundary zone yakataga kodiak and sand point have higher instantaneous velocities relative to eastern north america than the interior sites of alaska fairbanks and sourdough the estimated velocity of yakataga relative to fairbanks is 37 8 1 3 mm yr at n27 w 2 modeling of the yakataga data suggests that the observed motion is the result of elastic straining of the overriding plate due to a locked main thrust zone with a component of oblique slip the estimated velocity of kodiak relative to fairbanks is 13 6 0 8 mm yr at n41 w 3 this result is lower than the rate predicted on the basis of simple elastic dislocation models the estimated velocity of sand point relative to fairbanks is 6 4 0 9 mm yr at n65 w 8 the component of this velocity in the plate direction 3 5 1 1 mm yr is not consistent with either an aseismic slip model i e no strain accumulation in the overriding plate or a model in which the site is undergoing compressional strain 10 9 mm yr at n28 w due to simple subduction at the predicted orientation of pacific plate convergence in a north america fixed reference frame the estimated velocities of fairbanks 1 5 0 5 mm yr at s12 e 20 and sourdough 3 9 1 0 mm yr at s13 w 13 are both southward these results may imply motion of this region relative to stable north america but more observations are required to reduce the uncertainties in the azimuths the time evolution of the estimated site positions from vlbi in alaska are in general consistent with constant velocity however in 1988 the yakataga site showed a significant departure from the position predicted from a constant velocity model obtained from the previously estimated position this departure may be static displacement associated with two major strike slip earthquakes that occurred in the gulf of alaska between the 1987 and 1988 measurement sessions

on the loss of wind induced near inertial energy to turbulent mixing in the upper ocean wind induced near inertial energy has been believed to be an important source for generating the ocean mixing required to maintain the global meridional overturning circulation in the present study the near inertial energy budget in a realistic 1 12 degrees model of the north atlantic ocean driven by synoptically varying wind forcing is examined the authors find that nearly 70 of the wind induced near inertial energy at the sea surface is lost to turbulent mixing within the top 200 m and hence is not available to generate diapycnal mixing at greater depth assuming this result can be extended to the global ocean it is estimated that the wind induced near inertial energy available for ocean mixing at depth is at most 0 1 tw this confirms a recent suggestion that the role of wind induced near inertial energy in sustaining the global overturning circulation might have been overemphasized

space age geodesy the nasa crustal dynamics project the nasa crustal dynamics project has deployed satellite laser ranging slr systems and very long baseline interferometer vlbi systems for measurements of global and regional crustal motions and earth rotation parameters in 1984 the several year buildup of the network approached full capability during 1984 the slr systems measured 142 unique baselines between stations for the purpose of determining plate motion between the north american pacific south american nazca australian and eurasian plates 31 baselines for internal deformation of the same plates and 9 baselines for regional deformation in the area of the western north american plate boundary during 1984 the vlbi systems measured 24 baselines for plate motion between the north american pacific and eurasian plates 37 baselines for internal deformation of the same plates and 101 baselines for regional deformation in the area of the western north american plate boundary both the slr and vlbi stations operated throughout the september 1983 to october 1984 international merit campaign of measurements of the earth s polar motion and changes in rotation rate nasa s future plans are to continue these measurements through at least 1990 and to initiate a joint nasa european slr measurement campaign for determining regional crustal deformation in the mediterranean area

influence of multiple sills upon internal wave generation and the implications for mixing a cross sectional non hydrostatic model of a fjord is used to examine to what extent the internal tide is modified by two closely spaced sills the model is forced with an m2 barotropic tide and internal tides unsteady lee waves and a jet are generated at the sills in contrast to an isolated sill calculations with two closely spaced sills show that the presence of the second sill leads to standing internal wave generation with associated changes in wave spectrum and richardson number in the inter sill region associated with these there is a cascade of energy towards short waves leading to enhanced mixing between the sills this increase in mixing is consistent with enhanced mixing between closely spaced sills found in observations it is also relevant to enhanced oceanic and lake mixing and suggest that future mixing measurements in both oceans and lakes should focus on these regions

low frequency modulation of turbulent diapycnal mixing by anticyclonic eddies inferred from the hot time series profiles of potential density obtained from ctd measurements during the hawaii ocean time series hot programin thevicinityoftheislandofoahu hawaii areusedtoevaluatelow frequencyvariabilityof turbulent kinetic dissipation rates based on a finescale parameterization method a distinct seasonal cycle as well asan increasingtrendofdissipationrates is foundin the upper300 600 m thetrendis mainlydueto the much weaker diapycnal mixing in the first four years of the record that is 1988 92 in the upper 300 600 m enhanced diapycnal mixing is found under anticyclonic eddies with the mean dissipation rate about 53 larger than that under eddy free conditions the modulation of dissipation rates by anticyclonic eddies becomes more evident with increasing eddy strength the role of cyclonic eddies in modulating diapycnal mixing is almost negligible compared with that of anticyclonic eddies the mean dissipation rate under cyclonic eddies is comparable to that under eddy free conditions with a difference of less than 10 seasonality of the dissipation rates is partly modulated by the seasonal variation of anticyclonic eddies

oceanography mixing with latitude measurements over a range of latitudes support a theory relating ocean turbulence to internal waves the upshot should be easier mapping of ocean mixing and eventually better climate models

ultra high precision 40ar 39ar ages for fish canyon tuff and alder creek rhyolite sanidine new dating standards required abstract the 40 ar 39 ar dating technique is a high precision 40 ar 39 ar standards include sanidine from the ca 28 ma fish canyon tuff fct and the ca 1 2 ma alder creek rhyolite acr despite common usage the ages of fct and acr sanidine have proven contentious with reported values varying by 2 well outside the 0 1 aspiration of earthtime www earth time org the current study presents ultra high precision multi collector 40 ar 39 ar results for fct and acr sanidine using a new generation argusvi mass spectrometer these analyses demonstrate the significantly higher by a factor of 10 level of precision achievable using the argusvi system compared to most previous studies significantly 40 ar 39 ar step heating analyses resolve distinct age gradients for both fct and acr sanidine possible explanations for these gradients include combinations of recoil loss of 39 ar instrumental bias isotopic fractionation during step heating thermally induced argon loss and or extraneous argon contamination minor recoil loss of 39 ar and partial retention of inherited argon during extended magma residence are deemed the most plausible causes of the age discordance given this assumption we calculate revised maximum eruption ages of 28 01 0 04 ma 2 for fct and 1 178 0 002 ma 2 for acr relative to the astronomically calibrated age of a1 tephra sanidine crete rivera et al 2011 earth planet sci lett 311 420 426 nonetheless the argusvi data demonstrate that fct and acr sanidine are non ideal as high precision 40 ar 39 ar standards with different heating protocols likely to induce inter laboratory bias the current findings account for at least some of the scatter in inter calibration ages reported previously for various 40 ar 39 ar standards in broader terms the results mandate a re evaluation of the astronomically calibrated ages for these and other sanidine samples while the new generation of multi collector mass spectrometers provides the means to further evaluate 40 ar 39 ar ages used to define new decay constants and standard ages

latest pleistocene and holocene slip rate for the san bernardino strand of the san andreas fault plunge creek southern california implications for strain partitioning within the southern san andreas fault system for the last 35 k y an alluvial succession on the northeast side of the san bernardino strand of the san andreas fault includes distinctive aggradational and degradational features that can be matched with correlative features on the southwest side of the fault key among these are 1 a terrace riser on the northeast side of the fault that correlates with an offset channel wall on the southwest side of the fault and forms a basis for slip estimates for the period ca 35 ka to the present and 2 a small alluvial fan on the southwest side of the fault that has been matched with its most likely source gullies on the northeast side of the fault and forms a basis for slip estimates for the last 10 5 k y slip rate estimates for these two separate intervals are nearly identical the rate for the older feature is most likely between 8 3 and 14 5 mm yr with a 95 confidence interval of 7 0 15 7 mm yr the rate for the younger feature is most likely between 6 8 and 16 3 mm yr with a 95 confidence interval of 6 3 18 5 mm yr these rates are only half the previously published slip rate for the san andreas fault 35 km to the northwest in cajon pass a rate that traditionally is extrapolated southeastward along the san bernardino section of the fault results from plunge creek suggest that about half of the 25 mm yr rate at cajon pass transfers southeastward to the san jacinto fault as proposed by other workers on the basis of regional geologic relations these results indicate that the discrepancy between latest quaternary slip rates and present day rates of strain accumulation across the san bernardino section of the san andreas fault from geodesy can be largely explained by slip transfer between faults leading to spatial variation in rate along the san andreas fault nonetheless the latest pleistocene and holocene slip rate at plunge creek is still somewhat faster than rates inferred for the san bernardino section of the san andreas fault based on elastic block modeling of geodetic data and may be more appropriate than those rates for hazard estimation

offset along the san andreas fault of eocene strata from the san juan bautista area and western san emigdio mountains california analyses of eocene strata that rest on gabbroic basement rocks in the western san emigdio mountains and northernmost gabilan range indicate that the 2 sequences have been offset right laterally 305 320 km along the san andreas fault in both areas basal shallow marine conglomerate of penutian age grades upward into shale of ulatisian and narizian age that was deposited at bathyal water depths in a basin with access to open ocean additional similarities in the upper eocene and oligocene stratigraphic units suggest original contiguity of the depositional basins the inferred offset indicates that the salinian block was attached to western california by at least early eocene time the longer distances of northward transport of the salinian block that are suggested by preliminary paleomagnetic data from upper mesozoic granitic rocks and upper cretaceous and paleocene strata must have occurred during paleocene or earlier time

tectonic geomorphology of the san andreas fault zone in the southern indio hills coachella valley california geomorphic investigation of the san andreas fault zone in the indio hills indicates many tectonically produced landforms including beheaded streams right lateral deflected and offset streams sags shutter ridges pressure ridges and fault scarps near biskra palms an alluvial fan pediment complex has an apparent cumulative offset of about 0 7 km along the mission creek fault zone north branch san andreas fault many of the tectonic landforms as well as the fracture pattern that has developed during the pleistocene are explainable by simple shear or uplift associated with a small left bend in the main trace of the mission creek fault the ratio of vertical to horizontal displacement in the vicinity of the bend is about 0 04 exposed in pushawalla canyon 5 km northwest of the alluvial fan pediment complex are 1 a sequence of stream terraces 2 folded plio pleistocene fanglomerates and 3 an example of stream capture following a right lateral deflection or offset of several hundred metres a left step of the mission creek fault in pushawalla canyon is a probably cause of folds and sporadic uplift that produced the stream terraces possible cause of recent stream capture are 1 juxtaposition of pushawalla canyon with a relict canyon moving northwestward along the mission creek fault or 2 right lateral deflection or offset of pushawalla canyon along the fault with simultaneous headward erosion of a shorter steep stream flowing toward the coachella valley estimation of a slip rate and identification of paleoseismicity for the san andreas fault in the indio hills is difficult however degree of topographic dissection formation and preservation of desert pavement and relative soil profile development suggest that the age of the offset fan may be as old as 70 000 yr but that most likely it is on the order of 20 000 to 30 000 yr these age estimates for the offset fan indicate a minimum slip rate for the san andreas fault of 10 to 35 mm yr with about 23 to 35 mm yr the most likely the pattern of observed offset drainages is complex but suggests that during the past few thousand years creep events or moderately large earthquakes have periodically produced several metres of right lateral displacement

contemporary plate motion and crustal deformation the measurement of relative plate velocities during the past few years is a signal accomplishment in earth science leading to refinement of the precepts of steady motion of plate interiors and cyclic deformation along plate margins regrettably deformation premonitory to an earthquake has yet to be detected with confidence delineation of the spatial and temporal buildup of strain between earthquakes however has put limits on models of the earthquake cycle a diverse set of fault structures and crustal rheologic conditions can explain the pattern of surface strain accumulation and release along strike slip faults in contrast the geometry of thrusts and normal faults revealed by earthquake deformation has been found to differ markedly from expectations geodetic observations have proved vital to monitor the ascent of magma through the earth s crust and to predict volcanic eruptions at the earth s surface episodic vertical and horizontal deformation in southern california remains a subject of dispute if anything it is less certain than it once seemed

pongkor west java indonesia a pliocene supergene enriched epithermal au ag mn deposit the pongkor gold silver epithermal deposit with reserves of at least 98 tonnes of gold and 1026 tonnes of silver average grades 16 4 g t au and 171 2 g t ag is one of the most recent and largest gold and silver discoveries in indonesia proven within a short period 1988 1991 40ar 39ar dating on adularia samples give an age of 2 05 0 05 ma the deposit is of the low sulfidation epithermal type and consists of four main mineralized quartz veins located close to the internal rim of a volcano tectonic depression caldera this resulted from an explosive ignimbritic eruption that produced pyroclastic flows and accretionary lapilli with rare intercalations of epiclastic rocks this volcanic unit unconformably overlies miocene subaqueous volcanic andesitic rocks with interbedded epiclastic rocks the mineralized bodies are thick average 4 2 m steeply dipping quartz carbonate adularia veins with a very low sulfide content 0 5 wt their genesis is related to an extensional episode within a tectonic corridor showing nw se and nne ssw conjugate strike slip faults the major vein being located on the inner rim of the caldera the vein fill reveals four successive stages of deposition marked by a specific facies 1 carbonate quartz breccia with dominant quartz and calcite and minor kutnahorite rhodochrosite and rhodonite cq facies 2 a network of banded quartz and former carbonate transformed into manganese oxides through supergene alteration moq facies 3 banded opaline milky quartz boq facies and 4 grey locally banded sulfide rich quartz breccia cutting all the other types gsq facies adularia was deposited at the same time as the quartz the mineralogy and internal structures of the veins crustiform banding vugs collapse breccia clearly indicate a dilational context which is common in low sulfidation epithermal systems gold and silver grades as well as sulfide mineral abundances increase steadily through stages 1 to 4 locally reaching 1 kg t in the gsq facies the sulfides are dominated by pyrite accompanied by common acanthite aguilarite polybasite pearceite and electrum in which the gold content ranges from 48 to 74 wt sphalerite galena chalcopyrite and hessite are fairly rare although present within the cq facies the fluid inclusions of the four facies show homogenization temperatures ranging from 150 to 382 c indicating boiling of a hydrothermal fluid with an initial temperature of around 205 c no marked difference is seen in the gsq facies which has the highest gold content salinities are low generally below 1 wt eq nacl lead isotope compositions of the associated volcanic rocks and the mineralization are very similar 206pb 204pb between 18 706 and 18 814 and between 18 744 and 18 801 respectively demonstrating a genetic link between the pliocene volcanism and the auriferous hydrothermal activity the isotopic signature suggests that the source of the mineralization and associated volcanic rocks is an underlying ancient continental crust that melted and remobilized during the pliocene volcanic and hydrothermal events these conclusions seem applicable to the entire bayah dome the existence of both a tectonic corridor and a caldera favoured channelling of the hydrothermal fluids and the deposition of primary ore in the veins late intense weathering of the ore deposit to depths of 250 m below the surface has given rise to manganese oxide layers limonite zones and silver micronuggets within the veins as well as to gold enrichment

fault slip rates effects of elastic heterogeneity on geodetic data and the strength of the lower crust in the salton trough region southern california 1 in southernmost california the salton trough sedimentary basin lies between the subparallel san jacinto and san andreas faults that together with the elsinore fault accommodate 80 of the 50 mm yr of pacific north american relative motion the slip rates on the san andreas and san jacinto faults have been a matter of recent debate and one source of uncertainty has been the influence of crustal strength heterogeneity due to elastically weak basin sediments on geodetic data to evaluate these effects we have modeled regional kinematics with elastic and viscoelastic finite element models that incorporate laterally and vertically varying crustal material properties we find that in general the effects of the sedimentary basin on surface deformation are relatively small and that to explain the geodetic velocity data the slip rate on the san andreas must be higher than that on the san jacinto fault consistent with traditional geologic estimates we also conclude that a relatively strong lower crust of viscosity 5 x 10 19 pa s exists in this region

40ar 39ar geochronology of the pongkor low sulfidation epithermal gold mineralisation west java indonesia abstract the pongkor gold deposit located approximately 90 km southwest of jakarta is well known as the typical low sulfidation ls epithermal gold deposit and the largest gold vein deposit in indonesia the pongkor gold mineralisation has been the subject of several geological studies determination of the duration of gold mineralisation events however is less well understood the mineralisation events are important for understanding the genesis of ore deposits this study presents 40ar 39ar age results for four adularia samples from ciguha gold bearing quartz vein yielding plateau ages of 1 80 0 03 ma 2 33 0 32 ma and 1 88 0 02 ma plus one weighted mean age of 1 95 0 04 ma adularia from the kubang cicau gold bearing quartz veins yielded a 40ar 39ar plateau age of 2 02 0 03 ma the period of adularia growth in the ciguha vein may have extended from ca 2 07 to 1 77 ma that includes the ages of 1 95 0 04 ma and 1 88 0 02 ma the time interval indicates multiple generations of the adularia the data suggest that mineralisation of ciguha may have continued episodically or continuously the age of adularia from the kubang cicau gold bearing quartz vein 2 02 0 03 ma is within the error of the ciguha vein age and the adularia growth of kubang cicau vein reveals at the beginning of ciguha s adularia growth the data suggest that gold mineralisation in the pongkor deposit for kubang cicau and ciguha veins was initiated at the relatively similar time the 40ar 39ar adularia ages of this study are within error of the previously reported 40ar 39ar results milesi et al 1999 but significantly younger than the previously reported k ar adularia dating result kageyama 1999 in rosana and matsueda 2002

the inertial chimney the near inertial energy drainage from the ocean surface to the deep layer a three dimensional primitive equation numerical model is used to study the behavior of near inertial waves generated by surface wind stress on an plane the model is fixed depth with a rigid lid on the surface and is horizontally periodic this study shows the behaviors of the wind generated near inertial waves for four different eddies 1 a subtropical cold core eddy 2 a subtropical warm core eddy 3 a california subsurface warm core eddy and 4 the gulf stream warm core ring the mean secondary circulation generated by the wind eddy interaction has magnitude to comparable to that of the ekman current and its characteristics are determined by the relative angle between wind and current the propagation characteristics of near inertial waves are quite different depending upon the sign of the relative vorticity in a cyclonic eddy near inertial wave propagation is outward from the core of the eddy the propagation direction in an anticyclonic eddy is downward and toward the core vertically propagating waves inside the eddy are trapped above a critical layer and slowly dissipated by parameterized viscous effects the model shows that anticyclones efficiently drain near inertial energy from the surface to the deep layer below the thermocline

response of the internal wave field to remote wind forcing by tropical cyclones abstractin the tropical north atlantic mean winds introduce relatively little energy into the internal wave field but hurricanes act as very energetic sources for near inertial waves in addition to the eventlike passage of such tropical cyclones changes in the wind speed north of the trade wind system induce a seasonal cycle in surface swell with potential implications for the high frequency part of the internal wave field using a 5 yr mooring time series in the interior of the tropical north atlantic at 16 n the temporal variability of internal wave energy south of the main hurricane track in different frequency bands is studied and the magnitude of its variability along with possible energy transfer mechanisms is analyzed the results show that changes in near inertial energy are dominated by the passage of internal waves generated by hurricanes centered several hundred kilometers north of the mooring the major role of hurricanes in the generation of near inertial waves is also seen in an ext

turbulent diapycnal mixing in the subtropical northwestern pacific spatial seasonal variations and role of eddies both spatial and seasonal variation of turbulent diapycnal mixing in the subtropical northwestern pacific are evaluated by employing a fine scale parameterization method based on profiles of potential density which are obtained from ctd measurements during our recent hydrographic surveys implemented by the china national key basic research project from 2008 to 2010 and the world ocean circulation experiment over smooth seafloor the value of diffusivity away from the boundary is comparable with the values observed in the stratified midlatitude ocean interior i e o 10 5 m 2 s 1 on the other hand enhanced diapycnal mixing i e o 10 4 m 2 s 1 or larger has been found over rough topography such as the central basin trough okidaito ridge the origin of the kuroshio current and especially luzon strait which might result from dissipation of baroclinic energy generated when barotropic tides rub over rough topography over flat bathymetry mixing is probably stirred by the wind work on near inertial motions in the upper 600 m and enhanced downward propagating energy has been found in the presence of anticyclonic eddies which points to the important role of anticyclonic eddies in enhancing the diapycnal mixing at greater depth the diffusivity also displays a distinct seasonal variation with strong weak mixing corresponding to strong weak wind input energy in winter summer which however is only confined to upper 600 m this is different from the midlatitude northwestern pacific where seasonality of diffusivity can be found at 1500 m depth

the history of vein formation determined by 40ar 39ar dating of adularia in the hosen 1 vein at the hishikari epithermal gold deposit japan the hosen 1 vein has a symmetrical banded structure within the hishikari epithermal gold deposit in japan the vein can be divided into four macroscopic bands we used 40ar 39ar dating of adularia by incremental step heating to determine the duration of mineralization in the individual bands of the vein and the history of vein formation plateau ages were obtained from all adularia samples and no significant excess 40ar is recognized from inverse isochrons the derived age spectra suggest that thermal overprinting of the epithermal system did not affect the plateau ages although early bands must have been reheated by the thermal pulses associated with later bands the 40ar 39ar ages of adularia indicate that vein formation occurred episodically in distinct periods separated by intervals of about 30 000 to 110 000 yr the hosen 1 vein grew in at least six increments at the 20 m level and at least four increments at the 62 5 m level the total duration of mineralization from the margin to the center of the hosen 1 vein was about 260 000 yr during which time the temperature of the hydrothermal fluid decreased from 190 to 210 c to less than 170 c

geodesy by radio interferometry intercontinental distance determinations with subdecimeter precision analysis of very long baseline interferometer vlbi observations yielded estimates of the distances between three radio telescopes in the united states and one in sweden with formal standard errors of a few centimeters westford massachusetts onsala sweden 5 599 714 66 or 0 03 m green bank west virginia onsala sweden 6 319 317 75 or 0 03 m and owens valley california onsala sweden 7 914 131 19 or 0 04 m where the earth fixed reference points are defined in each case with respect to the axes of the telescopes the actual standard errors are difficult to estimate reliably but are probably not greater than twice the formal errors