back arc opening in the western end of the okinawa trough revealed from gnss acoustic measurements we measured seafloor movement using a global navigation satellite systems gnss acoustic technique at the south of the rifting valley in the western end of the okinawa trough back arc basin 60 km east of northeastern corner of taiwan the horizontal position of the seafloor benchmark measured eight times between july 2012 and may 2016 showed a southeastward movement suggesting a back arc opening of the okinawa trough the average velocity of the seafloor benchmark shows a block motion together with yonaguni island the westernmost part of the ryukyu arc rotates clockwise and is pulled apart from the taiwan island which should cause the expansion of the yilan plain taiwan comparing the motion of the seafloor benchmark with adjacent seismicity we suggest a gentle episodic opening of the rifting valley accompanying a moderate seismic activation which differs from the case in the segment north off yonaguni island where a rapid dyke intrusion occurs with a significant seismic activity

a model study of the buoyancy driven circulation in the gulf of maine abstract a quasi linear prognostic numerical model has been used to study the three dimensional baroclinic circulation in the gulf of maine region with a focus on the buoyancy driven circulation in the inner basins and near the coast where the influence of relatively fresh water from rivers and the scotian shelf is important the model uses a horizontal grid with 6 km resolution and a terrain following vertical coordinate with ten levels to represent the bathymetry and stratification several model experiments explore the influences of fluxes from the principal rivers tidal mixing and shelf water inflow beginning with a case with no initial horizontal density gradients and ending with cases initialized by temperature and salinity data from cruises in june of 1982 and 1983 augmented by climatological data with composite initialization the model develops a circulation containing realistic elements including an anticlockwise gyre in the interior of the gulf and a prominent southwestward coastal curre

a new gps acoustic method for measuring ocean floor crustal deformation application to the nankai trough 1 we developed a new geodetic method of monitoring crustal deformation on the ocean floor the measurements were conducted at two sites beneath the pacific ocean near the nankai trough where the philippine sea plate subducts into the pacific plate the first site was at a depth of 700 m in suruga bay and the second one was at a depth of 2000 m in the kumano basin at each survey site three seafloor transponders whose positions were repetitively measured were deployed to define a benchmark unit an ultrasonic signal was generated from a surface vessel drifting over the benchmark unit that was transmitting and receiving the signal and the replies from the transponders both sound speed structure and the benchmark unit positions were determined simultaneously using a tomographic technique we repeatedly carried out measurements over the two sites for the kumano basin we made six measurements from july 2004 to august 2005 the benchmark unit location s horizontal precision was 5 cm and its vertical precision was 10 cm for suruga bay we made five measurements and the positions were less accurate with horizontal variation of 7 cm and vertical variation of 16 cm we investigated the reason for the decreased precision in suruga bay with a numerical experiment and the results revealed that the geometry of the measurement that is the vessel s path is one of the most important variables in our method at the kumano basin a 21 5 cm southward displacement of the benchmark unit was detected just below the site before and after a large earthquake mw 7 5 our observation system therefore proved itself capable of detecting seafloor crustal deformation associated with crustal activities in offshore areas

a new method to assess long term sea bottom vertical displacement in shallow water using a bottom pressure sensor application to campi flegrei southern italy we present a new methodology using bottom pressure recorder bpr measurements in conjunction with sea level water column and barometric data to assess the long term vertical seafloor deformation to a few centimeters accuracy in shallow water environments the method helps to remove the apparent vertical displacement on the order of tens of centimeters caused by the bpr instrumental drift and by seawater density variations we have applied the method to the data acquired in 2011 by a bpr deployed at 96 m depth in the marine sector of the campi flegrei caldera during a seafloor uplift episode of a few centimeters amplitude lasted for several months the method detected a vertical uplift of the caldera of 2 5 1 3 cm achieving an unprecedented level of precision in the measurement of the submarine vertical deformation in shallow water the estimated vertical deformation at the bpr also compares favorably with data acquired by a land based gps station located at the same distance from the maximum of the modeled deformation field while bpr measurements are commonly performed in deep waters where the oceanic noise is relatively low and in areas with rapid large amplitude vertical ground displacement the proposed method extends the capability of estimating vertical uplifts from bpr time series to shallow waters and to slow deformation processes

reservoir monitoring and characterization using satellite geodetic data interferometric synthetic aperture radar observations from the krechba field algeria deformation in the material overlying an active reservoir is used to monitor pressure change at depth a sequence of 11 field estimates allows us to construct a measure of diffusive traveltime throughout a reservoir the dense distribution of traveltime values means that we can construct an exactly linear inverse problem for reservoir flow properties application to interferometric synthetic aperture radar insar data gathered over a carbon dioxide c o2 injection site in algeria reveals pressure propagation along two northwest trending corridors an inversion of the traveltimes indicates the existence of two northwest trending high permeability zones the high permeability features trend in the same direction as the regional fault and fracture zones model parameter resolution estimates indicate the features are well resolved

the kinematic and hydrographic structure of the gulf of maine coastal current the gulf of maine coastal current gmcc which extends from southern nova scotia to cape cod massachusetts was investigated from 1998 to 2001 by means of extensive hydrographic surveys current meter moorings tracked drifters and satellite derived thermal imagery the study focused on two principal branches of the gmcc the eastern maine coastal current emcc that extends along the eastern coast of maine to penobscot bay and the western maine coastal current wmcc that extends westward from penobscot bay to massachusetts bay results confirm that gmcc is primarily a pressure gradient driven system with both principal branches increasing their transport in the spring and summer due to fresh water inflows and flowing southwestward against the mean wind forcing during this period in the spring and summer the subtidal surface currents in the emcc range from 0 15 to 0 30 ms 1 while subtidal wmcc currents range from 0 05 to 0 15 ms 1 the reduction of southwestward transport near penobscot bay is accomplished via an offshore veering of a variable portion of the emcc some of which recirculates cyclonically within the eastern gulf of maine the degree of summer offshore veering versus leakage into the wmcc varied strongly over the three study years from nearly complete disruption in 1998 to nearly continuous through flow in 2000 observations show strong seasonal and interannual variability in both the strength of the gmcc and the degree of connectivity of its principal branches r 2005 elsevier ltd all rights reserved

precise gps acoustic positioning of seafloor reference points for tectonic studies abstract global networks for crustal strain measurement provide important constraints for studies of tectonic plate motion and deformation to date crustal strain measurements have been possible only in terrestrial settings on continental plates and island sites within oceanic plates we report the development of technology for horizontal crustal motion determination at seafloor sites allowing oceanic plates to be monitored where islands are not available seafloor crustal monitoring is an important component of global strain measurement because about 70 of the earth s surface is covered by water and this region contains most of the tectonic plate boundaries and zones of crustal deformation using the global positioning system gps satellites and underwater acoustics we have established a geodetic reference site on the juan de fuca plate at 2 6 km depth approximately 150 km off the northwest coast of north america we measure the baselines between this site and two terrestrial gps stations on vancouver island british columbia the juan de fuca plate site is an appropriate setting to develop seafloor observation methods since it is a well studied area easily accessible from west coast canadian and united states ports determination of seafloor motion at this site addresses questions related to convergence between the juan de fuca and north american plates across the cascadia subduction zone at the juan de fuca seafloor geodetic reference site we installed precision acoustic transponders on the seafloor and measured ranges to them from a sound source at a surface platform ship or buoy the platform is equipped with a set of three gps antennas allowing determination of the sound source position at times of signal transmission and reception merging the satellite and acoustic data allows determination of the transponder network location in global reference frame coordinates data processing to date suggests repeatabilities of 0 8 cm north and 3 9 cm east in the seafloor transponder network position relative to reference points on vancouver island

evidence of viscoelastic deformation following the 2011 tohoku oki earthquake revealed from seafloor geodetic observation the gps acoustic seafloor positioning has detected significant postseismic movements after the 2011 tohoku oki earthquake m9 0 just above the source region off the pacific coast of eastern japan in contrast to the coastal global navigation satellite systems sites where trenchward upward movements were reported the offshore sites above the main rupture zone in the northern part of the source region exhibit landward displacements of tens of centimeters with significant subsidence from almost 3 years of repeated observations at the sites above around the edge of the main rupture zone smaller amount of trench normal movements was found although the terrestrial movements were reasonably interpreted by afterslip beneath the coastal area these offshore results are rather consistent with effects predicted from viscoelastic relaxation in the upper mantle providing definitive evidence of its occurrence on the other hand the results in the southern part of the source region imply superposition of effects from viscoelastic relaxation and afterslip

global positioning system gps and gps acoustic observations insight into slip along the subduction zones around japan the global positioning system gps is one of the most powerful tools available for observation of earth s surface deformation in particular coseismic postseismic slow transient and interseismic deformation have all been observed globally by gps over the past two decades especially in subduction zones moreover gps acoustic techniques have been developed for practical use in the past decade allowing observation of offshore deformation immediately above slip regions here we describe the application of gps and gps acoustic observations to the detection of deformation due to plate boundary slip for interplate earthquakes as well as afterslip and slow slip events in subduction zones around japan where geodetic data coverage is particularly dense the data demonstrate temporally variable strain accumulation in the source region of the 2011 mw 9 0 tohoku oki earthquake and observation of the huge slip of the tohoku oki earthquake near the trench using gps acoustic methods has considerably advanced o

interplate locking condition derived from seafloor geodetic data at the northernmost part of the suruga trough japan we observed seafloor crustal deformation at two observation sites on opposite sides of the suruga trough off japan from 2005 to 2011 to investigate the interplate locking condition at the source region of the anticipated great subduction earthquake named tokai earthquake we estimated the displacement velocity vectors relative to the amurian plate on the basis of repeated observations our results at the two points suruga northeast and suruga northwest snw were 42 8 mm yr toward n94 3 w and 39 11 mm yr toward n84 9 w respectively these directions are the same as those measured at on land gps stations the magnitudes of the velocity vectors indicate a significant shortening of approximately 4 mm yr between snw and on land gps stations located to the west of the suruga trough the results show that the plate interface is strongly locked no slip shallower than the source region of the anticipated tokai earthquake

forearc structures and tectonic regimes at the oblique subduction zone between the hikurangi plateau and the southern kermadec margin the convergent southern kermadec margin is examined to study the structural development and mechanical parameters of the inner trench slope in response to the oblique subduction of the oceanic hikurangi plateau swath bathymetric data have been combined with other geophysical data to reveal that the south kermadec inner trench wall is segmented into distinct upper middle and lower margins the lower margin is a nongrowing compressionally unstable accretionary wedge that is dissected by transcurrent faults the wedge has been thinned and narrowed as a result of tectonic erosion the middle margin is stable by comparison and separated from the lower margin by the 220 km long awanui fault this fault is a landward dipping strike slip reverse fault the middle upper margin including east cape ridge ecr forms a deforming backstop with a sharp along strike change in tectonic regime south of 36 40 s transpression characterizes the ecr shear zone north of 36 40 s the ecr is marked by uplift by extension and farther north by subsidence it is suggested that subsidence and subsequent tectonic erosion of the margin north of 35 50 s in the wake of hikurangi plateau subduction have broken the link between once continuous segments of the ecr tonga platform the unstable nature of the southern kermadec wedge under compression together with a comparison of its taper characteristics with those of modern convergent margins implies that the wedge deforms under a relatively high internal pore pressure but high effective basal friction regime strike slip deformation in the wedge is attributable to a relatively strong interplate coupling related to the buoyancy and ruggedness of the hikurangi plateau

interplate coupling beneath ne japan inferred from three dimensional displacement field 1 the northeastern japan arc is located in a typical subduction zone and is a seismically active region where large interplate earthquakes have occurred repeatedly the nationwide gps network has made it possible to investigate the crustal deformation in unprecedented detail however vertical displacements are less accurate than the horizontal ones and have not been used to constrain interplate coupling models in this study gps carrier phase data are analyzed in order to estimate three components of site displacements the result indicates uplift along the japan sea coast and subsidence along the pacific ocean coast using the vertical site velocities together with the horizontal ones as the data for a geodetic inversion method a new model of interplate coupling is constructed to explain both the horizontal and vertical velocities for the interseismic period from 1997 to 2001 the model demonstrates strong coupling in the area off miyagi and in the area off aomori through the area off tokachi including the areas of asperities the downdip limit of the locked fault zone on the plate boundary has been estimated seismologically to be at a depth of 50 60 km in northeastern japan and the distribution of slip deficits derived in this study indicates that the transition zone extends down to a depth of about 100 km

interplate coupling distribution along the nankai trough in southwest japan estimated from the block motion model based on onshore gnss and seafloor gnss a observations

first measurement of the displacement rate of the pacific plate near the japan trench after the 2011 tohoku oki earthquake using gps acoustic technique the subduction rate of an oceanic plate may accelerate after large earthquakes rupture the interplate coupling between the oceanic and overriding continental plates to better understand postseismic deformation processes in an incoming oceanic plate we directly measured the displacement rate of the pacific plate near the japan trench after the 2011 tohoku oki earthquake using a gps acoustic technique over a period of 2 years september 2012 to september 2014 the displacement rate was measured to be 18 0 4 5 cm yr 1 n302 0 e relative to the north american plate which is almost twice as fast as the predicted interseismic plate motion because the sum of steady plate motion and viscoelastic response to the tohoku oki earthquake roughly accounts for the observed displacement rate we conclude that viscoelastic relaxation is the primary mechanism responsible for postseismic deformation of the pacific plate and that significant subduction acceleration did not occur at least not during the observation period

suboceanic geodetic measurements this paper reviews the needs for geodetic ties among seafloor points and between such points and others on land as well as the environmental constraints on potential systems for making such measurements underwater acoustic techniques provide the best opportunities and an essential element on which to build acoustic systems a precision transponder system capable of making travel time measurements over ranges of several kilometers with an accuracy of a few microseconds is described finally three particular systems are discussed one uses direct transmission between transponders to achieve one part in 105 accuracy over ranges from a few meters to about a kilometer the second using a larger transponder network and an intermediate vehicle can achieve similar accuracy over ranges up to about 10 km the third is a composite acoustic global positioning system gps which should be able to achieve subdecimeter accuracy over ranges of a few hundred kilometers

joint inversion for transponder localization and sound speed profile temporal variation in high precision acoustic surveys this letter develops a bayesian inversion for localizing underwater acoustic transponders using a surface ship which compensates for sound speed profile ssp temporal variation during the survey the method is based on dividing observed acoustic travel time data into time segments and including depth independent ssp variations for each segment as additional unknown parameters to approximate the ssp temporal variation ssp variations are estimated jointly with transponder locations rather than calculated separately as in existing two step inversions simulation and sea trial results show this localization ssp joint inversion performs better than two step inversion in terms of localization accuracy agreement with measured ssp variations and computational efficiency

a model study of the seasonal circulation in the gulf of maine the princeton ocean model is used to study the circulation in the gulf of maine and its seasonal transition in response to wind surface heat flux river discharge and the m2 tide the model has an orthogonal curvature linear grid in the horizontal with variable spacing from 3 km nearshore to 7 km offshore and 19 levels in the vertical it is initialized and forced at the open boundary with model results from the east coast forecast system the first experiment is forced by monthly climatological wind and heat flux from the comprehensive ocean atmosphere data set discharges from the saint john penobscot kennebec and merrimack rivers are added in the second experiment the semidiurnal lunar tide m2 is included as part of the open boundary forcing in the third experiment it is found that the surface heat flux plays an important role in regulating the annual cycle of the circulation in the gulf of maine the spinup of the cyclonic circulation between april and june is likely caused by the differential heating between the interior gulf and the exterior shelf slope region from june to december the cyclonic circulation continues to strengthen but gradually shrinks in size when winter cooling erodes the stratification the cyclonic circulation penetrates deeper into the water column the circulation quickly spins down from december to february as most of the energy is consumed by bottom friction while inclusion of river discharge changes details of the circulation pattern the annual evolution of the circulation is largely unaffected on the other hand inclusion of the tide results in not only the anticyclonic circulation on georges bank but also modifications to the seasonal circulation

structure and variability of the western maine coastal current abstract analyses of ctd and moored current meter data from 1998 and 2000 reveal a number of mechanisms influencing the flow along the western coast of maine on occasions the eastern maine coastal current extends into the western gulf of maine where it takes the form of a deep order 100 m deep and broad order 20 km wide southwestward flow with geostrophic velocities exceeding 20 cm s 1 this is not a coastally trapped flow however in fields of geostrophic velocity computed from shipboard ctd data the core of this current is roughly centered at the 100 m isobath and its onshore edge is no closer than 10 km from the coast geostrophic velocity fields also reveal a relatively shallow order 10 m deep baroclinic flow adjacent to the coast this flow is also directed to the southwest and appears to be principally comprised of local river discharge analyses of moored current meter data reveal wind driven modulations of the coastal flow that are consistent with expectations from simple theoretical models however a large fraction of the near shore current variance does not appear to be directly related to wind forcing sea surface temperature imagery combined with analysis of the moored current meter data suggests that eddies and meanders within the coastal flow may at times dominate the near shore current variance

on the use of quasi static deformation to understand reservoir fluid flow deformation above a producing reservoir provides a valuable source of information concerning fluid flow and flow properties quasi static deformation occurs when the displacements are so slow that we may neglect inertial terms in the equations of motion we present a method for inferring reservoir volume change and flow properties such as permeability from observations of quasi static deformation such displacements may represent surface deformation such as tilt leveling interferometric synthetic aperture radar insar or bathymetry observations or subsurface deformation as inferred from time lapse seismic surveys in our approach the equation for fluid flow in a deforming reservoir provides a mapping from estimated fractional volume changes to reservoir permeability variations if the reservoir behaves poroelastically over the interval of interest all the steps in this approach are linear thus the inference of reservoir permeability from deformation data becomes a linear inverse problem in an application to the wilmington oil field in california we find that observed surface displacements obtained by leveling and insar are indeed compatible with measured reservoir volume fluxes we find that the permeability variations in certain layers coincide with fault block boundaries suggesting that in some cases faults are controlling fluid flow at depth

no spreading across the southern juan de fuca ridge axial cleft during 1994 1996 direct path acoustic measurements between seafloor transponders observed no significant extension 10 14 mm yr from august 1994 to september 1996 at the southern juan de fuca ridge 44 40 n and 130 20 w the acoustic path for the measurement is a 691 m baseline straddling the axial cleft which bounds the pacific and juan de fuca plates given an expected full spreading rate of 56 mm yr these data suggest that extension across this plate boundary occurs episodically within the narrow 1 km region of the axial valley floor and that active deformation is occurring between the axial cleft and the plate interior a cleft parallel 714 m baseline located 300 m to the west of the cleft on the pacific plate monitored system performance and as expected observed no motion 5 7 mm yr between the 1994 and 1996 surveys

interseismic seafloor crustal deformation immediately above the source region of anticipated megathrust earthquake along the nankai trough japan 1 we monitored seafloor crustal deformation using the gps acoustic seafloor geodetic observation technique at three sites on the kumano basin off southwestern japan which is located immediately above the source region of the anticipated tonankai megathrust earthquake we directly measured landward crustal movements of 40 mm y in the n80 w direction with respect to the amurian plate on the seafloor the directions were found to be the same as those measured at the on land gps stations the magnitudes of the velocity vectors indicated significant crustal shortenings of approximately 10 20 mm y between the kumano basin and the southeastern coast of the kii peninsula of the japanese islands the present observational results show strong and direct evidence for interplate locking during the interseismic period coupling ratios were roughly estimated at 0 6 0 8 on the plate interface up to at least 10 km in depth

on equations for the speed of sound in seawater long range acoustic transmissions made in conjunction with extensive environmental measurements and accurate mooring position determinations have been used to test the accuracy of equations used to calculate sound speed from pressure temperature and salinity the sound speed field computed using the del grosso equation v a del grosso j acoust soc am 56 1084 1091 1974 give predictions of acoustic arrival patterns which agree significantly better with the long range measurements than those computed using the chen and millero equation c chen and f j millero j acoust soc am 62 1129 1135 1977 the predicted ray travel times and travel time error have been calculated using objectively mapped sound speed fields computed from ctd and xbt data using the measured and predicted ray travel times a negligible correction to del grosso s equation of 0 05 0 05 m s at 4000 m depth is calculated small errors of about 50 m in the gps determination of mooring positions lends a depth independent error of 0 1 m s to the sound speed equation correction work supported by nsf and onr

accretion and recent deformation of sediments along the northern cascadia subduction zone new multichannel seismic reflection profiles acoustic imagery and swath bathymetric data from the vancouver island continental margin reveal the surface morphology cross sectional geometry and deformation style of this part of the cascadia accretionary prism the incoming 3 to 5 km thick sediment section fails most commonly along landward dipping thrusts that penetrate to or very close to the top of the underlying oceanic crust the faults are listric with approximately circular cross sections and hanging wall sediments are back tilted in a planar manner high near lithostatic pore pressures in the deeper part of the section are inferred from the flattening of the faults near the decollement and from the long distances over which the decollement has propagated seaward the faults dip more steeply at 40 45 near the surface where pleistocene turbidites are displaced similar folds have developed where the turbidites are particularly thick 4 km and near hydrostatic pore pressures are inferred to occur in the turbidite part of the section an increase in pore pressure with depth is expected as a consequence of sedimentation and tectonic loading particularly because the deeper hemipelagic sediments are probably far less permeable than are the overlying turbidites the top of the downgoing juan de fuca plate which defines the base of the accreted sedimentary wedge beneath the margin is well imaged in the new seismic reflection profiles and is further defined by land reflection data seismic refraction and earthquake hypocenters the landward dipping continental backstop to the prism is also well located if these constraints are used for the geometry of the accretionary prism a general balance is found between the present prism volume and the estimated total sediment supply over the approximately 42 m y accretion history this result along with the observation that deformation front faults penetrate most or all of the sediment section suggests that little or no sediment has been subducted since initiation of the present phase of subduction in the eocene application of the critically tapered wedge model of davis and others to the observed prism geometry suggests that high average pore pressures occur in the prism particularly the seawardmost part beneath the lower slope beneath the continental shelf the dip of the subducting slab increases to greater than 11 a dip that according to the critically tapered wedge model is too steep to allow upward growth of an accretionary prism this provides a simple explanation for ongoing subsidence of the tofino sedimentary basin over the older part of the accretionary complex to the southeast the juan de fuca plate dips much more gently beneath the olympic peninsula of northern washington allowing the accretionary prism to grow upward well above sea level to form the olympic mountains

continuous gps observations across the hayward fault california 1991 1994 in september 1991 the u s geological survey began continuous operation of two permanent global positioning system gps sites near the hayward fault we use two and one half years of data from an 8 km baseline to investigate gps processing strategies errors in the time and frequency domains and the uncertainties of rates of change calculated from such data experiments with session lengths show that at least 6 hours of data should be used to obtain a precision of 2 to 4 mm experiments with broadcast and improved orbits show that the broadcast orbit is sufficient for this short baseline single frequency solutions have larger rms scatter for scenarios made mostly in daylight ionospheric delay systematically shortens the baseline length by 2 4 parts per million for l1 and 4 0 parts per million for l2 for the dual frequency results the rms scatter about the best fitting straight line is 2 1 mm for baseline length 2 2 mm for north 2 9 mm for east and 11 2 mm for vertical for winton relative to chabot the rates of change are 0 6 0 1 mm yr in length 2 8 0 1 mm yr in north 8 1 0 2 mm yr in east and 8 1 0 6 mm yr in vertical the baseline rate of change is consistent with right lateral shear across the hayward fault but is not consistent with the 3 5 mm yr predicted by the model of lienkaemper et al 1991 the large westward and downward motion of winton relative to chabot may be due to monument instability power spectra appear white at high frequencies the estimated standard deviations for periods shorter than 5 days are 1 2 mm for length and north 1 9 mm for east and 5 5 mm for vertical power spectral density increases only slightly as frequency decreases from 0 2 to 0 03 cycle per day and there is no distinct corner in particular no characteristic 1 2 signature of random walk monument noise emerges from the white noise estimated autocorrelations for length north east and vertical fall to about 0 1 for lag times shorter than 10 days and fluctuate about zero for lag times longer than about 25 days because the time series is short it is possible that random walk monument noise exists but is undetectable in the estimated power spectral density and autocorrelation functions we use the estimated full covariance matrix to calculate the standard deviations of the baseline rate of change for various sampling schemes the theoretical standard deviation of dl dt determined from 1 year of daily observations is 0 28 times that determined from 1 year of annual observations we can obtain a similar uncertainty from 2 years of measurements made every 30 days and better results from 5 years of annual measurements however daily measurements allow the detection and correction of offsets that sometimes occur with equipment or firmware changes

circulation and dispersion in a cancellate coast the rivers bays and estuaries of central maine the glacially carved central coast of maine is incised by river systems with interconnecting channels offshore trending submarine ridges and narrow passages between nearshore islands and headlands the tidal range exceeds 3 m leading to complex and vigorous circulation patterns with strong flows in narrow channels near river mouths and between islands the spongiform coastal morphology allows enhanced exchange between offshore waters estuaries and internecine bays resulting in rapid dispersal of nutrients larvae and contaminants throughout the region a fine grid numerical circulation model has been used to examine the influences of the tides river flows and winds on the dispersion of lobster larvae and pollutants in the nearshore and riverine environment this paper describes the model application presents a few salient features of the circulation patterns and examines some implications for the coastal environment for example under realistic tides and variable southwest summer winds about 80 of neutral near surface particles introduced near the offshore islands a proxy for stage iv lobster larvae from offshore sources remain within a few km of the islands over a two week period on the other hand a persistent periodic sea breeze can remove more than two thirds of the particles from the domain over the same period tidal mixing disperses pollutants entering the upper kennebec river to the offshore and through internecine passages in about one week

space geodetic measurement of crustal deformation in central and southern california 1984 1992 we estimate the velocity field in central and southern california using global positioning system gps observations from 1986 to 1992 and very long baseline interferometry vlbi observations from 1984 to 1991 our core network includes 12 gps sites spaced approximately 50 km apart mostly in the western transverse ranges and the coastal borderlands the precision and accuracy of the relative horizontal velocities estimated for these core stations are adequately described by a 95 confidence ellipse with a semiminor axis of approximately 2 mm yr oriented roughly north south and a semimajor axis of approximately 3 mm yr oriented east west

assessment of global positioning system measurements for studies of crustal deformation the u s geological survey has been using the global positioning system gps to perform repeated surveys of networks of different sizes since january 1986 the intersite distances from these various networks are 223 km for a single line connecting the palos verdes and vandenberg sites in southern california 30 50 km for a network of three sites south of the san francisco bay near loma prieta 9 30 km for a network located near hebgen lake montana 7 12 km for a network of sites in the vicinity of parkfield california and 240 m for a line located at the goldstone antenna complex in the mojave desert the lengths quoted do not include the intersite distances for the fiducial sites included in the solutions for orbit determination which can be up to 8000 km we have attempted to assess the long term precision and accuracy of determinations of relative site position for a range of line lengths this assessment has consisted of several different studies in assessing precision we have generally investigated repeatability usually about a best fit linear temporal trend the smallest fractional repeatability was yielded by the measurements on the palos verdes to vandenberg line the root mean square rms residual about the best fit line for these determinations was 6 mm 0 03 parts per million or ppm for the north component 11 mm 0 05 ppm for the east component and 40 mm 0 18 ppm for the vertical component for these determinations gps data from 3 4 consecutive days were combined to produce a single estimate of the vector separation we also used the day to day scatter from these measurements to perform an analysis of variance and found that these multiday determinations can be significantly more precise than estimates determined from a single observing session the worst results were obtained for the loma prieta network where we obtained rms residuals of 11 12 mm 0 3 0 4 ppm for north 14 18 mm 0 3 0 6 ppm for east and 18 21 mm 0 4 0 7 ppm for vertical we cannot definitely explain these poor results but we have evidence to indicate that this poor scatter is due to the short observing session 4 5 hours compared to 6 5 hours for the palos verdes to vandenberg results in assessing accuracy we compared the gps results to those from independent techniques at parkfield we compared the gps estimates of fault parallel motion to those from creep meters and alignment arrays and found excellent agreement within 1 2 mm yr 1 not only for the slip but also for the variation of slip along the san andreas fault we compared the loma prieta and hebgen lake line length estimates to those obtained from a geodolite a high precision laser distance measurement device that the u s geological survey has used for 20 years for studies of crustal deformation if we model the geodolite minus gps line length differences l as l l where l is the line length then we find 0 6 0 5 mm and 0 1 0 1 mm km 1 the uncertainties quoted are one standard deviation from this comparison we conclude that at this level of significance there is no detectable difference between lengths determined from geodolite and gps data finally we compared the gps estimates of the palos verdes to vandenberg line length to those obtained from very long baseline interferometry vlbi the mean difference between the six gps estimates of line length and a best fit line through the vlbi estimates was 1 mm and the rms difference was 12 mm 0 05 ppm close to the standard deviation of the gps measurements for this predominantly east west line

post eruption inflation of the east pacific rise at 9 50 n in june 2008 we installed a geodetic network at 9 50 n on the east pacific rise to track the long term movement of magma following the 2005 6 eruption this network consists of 10 concrete benchmarks stretching from the ridge to 9 km off axis during three campaign style surveys measurements of vertical seafloor motions were made at each of these benchmarks by precisely recording ambient seawater pressure as a proxy for seafloor depth with a mobile pressure recorder mpr the mpr was deployed using the manned submersible alvin in 2008 and 2009 and the remotely operated vehicle jason in 2011 the mpr observations are supplemented with data from a multiyear deployment of continuously recording bottom pressure recorders bprs extending along this segment of the ridge that can record rapid changes in seafloor depth from seafloor eruptions and or dike intrusions these measurements show no diking events and up to 12 cm of volcanic inflation that occurred from december 2009 to october 2011 in the area of the 2005 6 eruption these observations are fit with an inflating point source at a depth of 2 7 km and volume change of 2 3 106 m3 yr located on the ridge axis at approximately 9 51 166 n 407 m from our northernmost benchmark suggesting that the magma chamber underlying this segment of the ridge is being recharged from a deeper source at a rate that is about half the long term inflation rate observed at axial seamount on the juan de fuca ridge these data represent the second location that active volcanic uplift has been measured on a mid ocean ridge segment and the first on a nonhotspot influenced segment

observation of coseismic seafloor crustal deformation due to m7 class offshore earthquakes 1 we have developed an observation system for seafloor crustal deformation measurement combining the two following techniques the precise acoustic ranging and kinematic gps global positioning system positioning on july 14 2003 we installed the units for this observation system at the seafloor of the kumano basin japan 33 58 n 136 60 e we performed repeated observation six times on 1 july 15 16 and 21 2004 2 november 9 10 2004 3 may 18 and 20 2005 4 july 19 20 2005 5 august 18 19 2005 and 6 august 29 30 2005 the present observation system can stably determine the seafloor position with an rms repeatability of 3 cm in both horizontal components two m7 class offshore intraplate earthquakes occurred only 60 km from the kumano basin site on september 5 2004 we observed the coseismic horizontal displacement of 18 cm at the kumano basin site using the presently developed seafloor observation system our observation system can provide seafloor crustal deformation associated with crustal activities in offshore areas

evidence for aseismic deformation rate changes prior to earthquakes abstractfor ten earthquakes in nonmagmatic settings there are credible published accounts of pre earthquake deformation rate changes lasting hundreds of seconds to more than a decade although most m 7 5 earthquakes have occurred without detectable pre earthquake deformation the detection threshold for aseismic deformation remains high in that aseismic slip with moment equivalent to an m5 earthquake would in most although not all cases have been missed interseismic deformation rates vary without being followed by earthquakes and a strain rate change prior to the 1989 mw6 9 loma prieta california earthquake is shown to be similar in size to many other rate changes that have occurred since that time most examples of pre earthquake aseismic deformation lasting hundreds of seconds or more probably originate adjacent to or downdip of the seismic rupture plane rather than within the zone that undergoes seismic failure

measuring the onset of locking in the peru chile trench with gps and acoustic measurements the subduction zone off the west coast of south america marks the convergence of the oceanic nazca plate and the continental south america plate nazca south america convergence over the past 23 million years has created the 6 km deep peru chile trench 150 km offshore high pressure between the plates creates a locked zone leading to deformation of the overriding plate the surface area of this locked zone is thought to control the magnitude of co seismic release and is limited by pressure temperature sediment type and fluid content1 here we present seafloor deformation data from the submerged south america plate obtained from a combination of global positioning system gps receivers and acoustic transponders we estimate that the measured horizontal surface motion perpendicular to the trench is consistent with a model having no slip along the thrust fault between 2 and 40 km depth a tsunami in 1996 200 km north of our site was interpreted as being the result of an anomalously shallow interplate earthquake2 seismic coupling at shallow depths such as we observe may explain why co seismic events in the peruvian subduction zone create large tsunamis

carrier phase ambiguity resolution for the global positioning system applied to geodetic baselines up to 2000 km the global positioning system gps carrier phase data are biased by an integer number of cycles a successful strategy has been developed and demonstrated for resolving these integer ambiguities for geodetic baselines of up to 2000 km in length resulting in a factor of 3 improvement in baseline accuracy and giving centimeter level agreement with coordinates inferred by very long baseline interferometry in the western united states for this experiment a method using pseudorange data is shown to be more reliable than one using ionospheric constraints for baselines longer than 200 km an automated algorithm exploits the correlations between the many phase biases of a gps receiver network to enable the resolution of ambiguities for very long baselines a method called bias optimizing has been developed which unlike traditional bias fixing does not require an arbitrary confidence test bias optimizing is expected to be preferable to bias fixing for poorly configured networks in order to enable ambiguity resolution for long baselines it is recommended that future gps networks have a wide spectrum of baseline lengths ranging from 1000 km and that gps receivers be used which can acquire dual frequency p code data

confidence intervals for motion and deformation of the juan de fuca plate finite rotation parameters for 17 isochrons from anomalies 1 4a for the juan de fuca pacific plate pair are reported comparison of confidence intervals for plate rotations derived by different techniques indicates that a single plate misfit criterion significantly underestimates the confidence region defining the confidence interval by a threshold level of misfit determined by an f statistic gives similar results to the technique of bootstrap resampling for internally consistent data bootstrap resampling offers far greater robustness in the case of inconsistent data precision of about 1 km in the direction normal to isochrons is available for the younger anomalies this precision allows confident recognition of 2 5 km of eastward deformation of the pacific plate 50 100 km south of the active sovanco transform slight deformation of the northern juan de fuca plate adjacent to the nootka fault zone is also apparent east of the northern gorda ridge younger 3 ma anomalies do not show measurable deformation near the blanco fracture zone but older anomalies are up to 30 km east of their position predicted by rigid behavior of the juan de fuca plate reconstruction of the overlap geometry of past propagators shows no evidence that the extent of overlap has ever exceeded 70 km even with offset of 75 km in one case and 140 km in another new techniques for testing for intervals of constant plate motion require at least two changes in instantaneous motion at 99 confidence a clockwise change in motion direction at about 5 ma and an increase in the gradient of spreading rate since 2 ma two other changes in gradient since 5 ma are required at 95 confidence

the northern cascadia subduction zone at vancouver island seismic structure and tectonic history the structure and tertiary tectonic history of the northern cascadia subduction zone have been delineated by a series of new multichannel seismic lines acquired across the continental shelf to the

plate motion at the ridge transform boundary of the south cleft segment of the juan de fuca ridge from gps acoustic data 1 we measure the present day plate velocity of the juan de fuca ridge 25 km off axis to be 63 6 3 6 mm a at s67 2 e 7 9 degrees 1 relative to the pacific plate pa this velocity was derived from gps acoustic gpsa measurements in 2000 2001 2002 and 2003 that observed the position of a seafloor array 44 43 n 130 03 w 2900 m depth with a repeatability of 4 6 mm three transient events at the juan de fuca ridge and blanco transform account for 10 of this motion in viscoelastic modeling suggesting that the observed gpsa pa velocity is due primarily to steady state plate dynamics subtracting the modeled transient motion gives a velocity of 57 3 3 9 mm a at s72 9 e 12 1 degrees 1 which is consistent at the 95 confidence level with the velocity calculated from the wilson 1993 0 0 78 ma euler pole therefore this site is interpreted to be in a region of continuous full rate plate motion a robust result of this study which holds with and without correcting for transient motions these results provide direct geodetic evidence that spreading occurs predominantly within 25 km of the axis at this intermediate spreading rate ridge previously reported geodetic monitoring across the 1 km wide axial valley from 1994 1999 and 2000 2003 shows no significant extension chadwell et al 1999 hildebrand et al 1999 chadwick and stapp 2002 w w chadwick personal communication 2006 and seismic monitoring shows no activity this suggests the crust between 0 5 and 25 km off axis accommodates 26 mm of aseismic deformation each year through some combination of near axis fault motion and elastic strain accumulation

offshore postseismic deformation of the 2011 tohoku earthquake revisited application of an improved gps acoustic positioning method considering horizontal gradient of sound speed structure

millimeter level precision in a seafloor geodesy experiment at the discovery transform fault east pacific rise 1 direct path acoustic ranging is a promising seafloor geodetic technique for continuous high resolution monitoring of geodynamical process such as fault slip and magma intrusion here we report on a yearlong acoustic ranging experiment conducted across the discovery transform fault at 4 s on the east pacific rise the ranging instruments utilized a novel acoustic signal designed to enhance precision we find that after correcting for variations in sound speed at the path end points the ranging measurements have a precision of 1 mm over baselines approaching 1 km in length the primary difficulty in this particular experiment was with the physical stability of the benchmarks which were deployed free fall from a ship despite the stability issues it appears that the portion of the transform fault that the array covered was locked during the year of our survey the primary obstacle to continuous high sample rate high precision geodetic monitoring of oceanic ridges and transform faults is now limited to the construction of geodetic monuments that are well anchored into bedrock

evidence for major input of riverine organic matter into the ocean abstract the changes in the structure of xad 8 isolated dissolved organic matter dom samples along a river penobscot river to estuary penobscot bay to ocean across the gulf of maine transect and from the pacific ocean were investigated using selective and two dimensional 2d nuclear magnetic resonance nmr spectroscopy coupled with elemental and carbon isotope analysis the results provide important insights into the nature of relatively stable structures in the river to ocean continuum and the enigma of the fate of terrestrial dom in the marine system first lignin and carboxyl rich alicyclic molecules crams which are indistinguishable from mass spectrometry were clearly differentiated with nmr spectroscopy nmr unambiguously showed that crams persisted along the river to ocean transect and in the pacific ocean while lignin residues dramatically decreased in abundance from the river to the coastal ocean and the pacific ocean the results challenge a previous conclusion that lignin derived compounds are refractory and can accumulate in the coastal ocean the loss of terrestrial plant derived aromatic compounds such as lignin and tannin residues throughout the sequence of riverine coastal and open ocean dom extracts could also partially explain the decreasing organic carbon recovery by xad 8 isolation and the change in carbon stable isotope composition from riverine dom 13 c 27 6 to ocean dom 13 c 23 0 extracts the observation from advanced nmr of similar cram molecules in xad 8 isolated dom samples from the penobscot river to the penobscot bay and from the ocean refutes a previous conclusion that xad isolated dom samples from seawater and river are distinctly different the alicyclic structural features of crams and their presence as the major structural units in dom extracts from the penobscot river to gulf of maine transect together with the deduced old 14 c age of crams in the ocean imply that terrestrial crams may persist on timescales long enough to be transported into the ocean

observations of the eastern maine coastal current and its offshore extensions in 1994 cold surface temperatures reflecting scotian shelf origins and local tidal mixing serve as a tracer of the eastern maine coastal current and its offshore extensions which appear episodically as cold plumes erupting from the eastern maine shelf a cold water plume emanating from the eastern maine coastal current in may 1994 was investigated using advanced very high resolution radiometer avhrr imagery shipboard surveys of physical and biochemical properties and satellite tracked drifters evidence is presented that suggests that some of the plume waters were entrained within the cyclonic circulation over jordan basin while the major portion participated in an anticyclonic eddy at the distal end of the plume calculations of the nitrate transported offshore by the plume show that this feature can episodically export significant quantities of nutrients from the eastern maine coastal current to offshore regions that are generally nutrient depleted during spring summer a series of avhrr images is used to document the seasonal along shelf progression of the coastal plume separation point we speculate on potential causes and consequences of plume separation from the coastal current and suggest that this feature may be an important factor influencing the patterns and overall biological productivity of the eastern gulf of maine

trench normal variation in observed seafloor displacements associated with the 2011 tohoku oki earthquake 1 seafloor geodetic measurements using the gps acoustic technique just above the rupture area of the 2011 tohoku oki earthquake revealed strong trench normal variation in the horizontal crustal displacement associated with the earthquake one set of observations at a site only 50 km away from the trench yielded the most trench ward data ever reported with an accuracy better than 1 m it showed a coseismic displacement of up to 31 m whereas another set of observations 100 km away from the trench showed a 15 m displacement these horizontal data as well as vertical data from pressure gauges and tsunami observations strongly indicate that the seismic slip reached the trench they are also likely to contribute quantitatively to further investigations that reveal the coseismic behavior of the frontal wedge of the overriding plate in the source region along the japan trench

vertical deformation monitoring at axial seamount since its 1998 eruption using deep sea pressure sensors pressure measurements made on the seafloor at depths between 1500 and 1700 m at axial seamount an active submarine volcano on the juan de fuca ridge in the northeast pacific ocean show evidence that it has been inflating since its 1998 eruption data from continuously recording bottom pressure sensors at the center of axial s caldera suggest that the rate of inflation was highest in the months right after the eruption 20 cm month and has since declined to a steady rate of 15 cm year independent campaign style pressure measurements made each year since 2000 at an array of seafloor benchmarks with a mobile pressure recorder mounted on a remotely operated vehicle also indicate uplift is occurring in the caldera at a rate up to 22f1 3 cm year relative to a point outside the caldera the repeatability of the campaign style pressure measurements progressively improved each year from f15 cm in 2000 to f0 9 cm in 2004 as errors were eliminated and the technique was refined assuming that the uplift has been continuous since the 1998 eruption these observations suggest that the center of the caldera has re inflated about 1 5f0 1 m thus recovering almost 50 of the 3 2 m of subsidence that was measured during the 1998 eruption this rate of inflation can be used to calculate a magma supply rate of 1410 6 m 3 year if this rate of inflation continues it also suggests a recurrence interval of 16 years between eruptions at axial assuming that it will be ready to erupt again when it has re inflated to 1998 levels d 2005 elsevier b v all rights reserved

seafloor geodetic constraints on interplate coupling of the nankai trough megathrust zone seafloor geodetic data from the nankai trough off southwestern japan show that most offshore sites in this earthquake prone region have high slip deficit rates revealing previously unknown locations that could be important for the mitigation of future earthquake and tsunami associated disasters yusuke yokota et al have used seafloor geodetic observations to visualize the seismogenic zone along the nankai trough off southwestern japan which is thought to be one of the most dangerous megathrust zones in the world they suggest that most offshore sites in this region have positive slip deficit rates revealing previously unknown locations that could be potential sources of future earthquakes and tsunamis low slip deficit rates are observed in other regions consistent with distributions of shallow slow earthquakes and subducting seamounts interplate megathrust earthquakes have inflicted catastrophic damage on human society such an earthquake is predicted to occur in the near future along the nankai trough off southwestern japan an economically active and densely populated area in which megathrust earthquakes have already occurred1 2 3 4 5 megathrust earthquakes are the result of a plate subduction mechanism and occur at slip deficit regions also known as coupling regions 6 7 where friction prevents plates from slipping against each other and the accumulated energy is eventually released forcefully many studies have attempted to capture distributions of slip deficit rates sdrs in order to predict earthquakes8 9 10 however these studies could not obtain a complete view of the earthquake source region because they had no seafloor geodetic data the hydrographic and oceanographic department of the japan coast guard jhod has been developing a precise and sustainable seafloor geodetic observation network11 in this subduction zone to obtain information related to offshore sdrs here we present seafloor geodetic observation data and an offshore interplate sdr distribution model our data suggest that most offshore regions in this subduction zone have positive sdrs specifically our observations indicate previously unknown regions of high sdr that will be important for tsunami disaster mitigation and regions of low sdr that are consistent with distributions of shallow slow earthquakes and subducting seamounts this is the first direct evidence that coupling conditions might be related to these seismological and geological phenomena our findings provide information for inferring megathrust earthquake scenarios and interpreting research on the nankai trough subduction zone

current deformation and the width of the seismogenic zone of the northern cascadia subduction thrust evidence has been obtained for the accumulation of elastic strain across the northern cascadia subduction zone that may be released in a future very large subduction thrust earthquake vertical and horizontal strain rates across the southern vancouver island region have been determined through 1 long term trends in tide gauge data 2 changes in repeated accurate leveling surveys 3 changes in repeated high accuracy gravity profiles and 4 horizontal shortening observed in repeated precise positioning surveys the outer coast is uplifting at a rate of a few millimeters per year decreasing landward and shortening is occurring across the 100 km wide coastal region at a rate of about 0 1 microstrain per year mm km 1yr 1 the results are compared with the distribution of strain accumulation predicted from elastic dislocation and viscoelastic models for a subduction thrust fault the location of the fault as used in the models is well defined by multichannel seismic reflection and other geophysical data most of the observed current deformation can be explained by interseismic strain accumulation associated with the subduction thrust of southern vancouver island and northern washington provided the locked portion is restricted to a 60 km wide band offshore beneath the continental shelf and slope this conclusion also results from modeling the coseismic subsidence on the outer coast of vancouver island about 300 years ago deduced from paleoseismicity data the unusually narrow downdip extent of the subduction thrust seismogenic zone that extends little if at all beneath the coast is a consequence of high temperatures associated with the young age of the subducted oceanic lithosphere and the thick blanket of insulating sediments the high temperatures limit brittle seismogenic behavior downdip to where the thrust fault is at a depth of less than 15 km the distance from the seismic portion of the megathrust limits the estimated ground motion at the major centers of vancouver and victoria from this source the narrow width may also limit the earthquake size however events of magnitude well over 8 are possible

seafloor geodesy from repeated sidescan sonar surveys accurate seafloor geodetic methods are critical to the study of marine natural hazards such as megathrust earthquakes landslides and volcanoes we propose digital image correlation of repeated shipboard sidescan sonar surveys as a measurement of seafloor deformation we test this method using multibeam surveys collected in two locales 2500 m deep lightly sedimented seafloor on the flank of a spreading ridge and 4300 m deep heavily sedimented seafloor far from any plate boundary correlation of these surveys are able to recover synthetic displacements in the across track range direction accurate to within 1 m and in the along track azimuth direction accurate to within 1 10 m we attribute these accuracies to the inherent resolution of sidescan data being better in the range dimension than the azimuth dimension these measurements are primarily limited by the accuracy of the ship navigation dual frequency gps units are accurate to 10 cm but single frequency gps units drift on the order of 1 m h and are insufficient for geodetic application

geodetic observations of an earthquake cycle at the sumatra subduction zone role of interseismic strain segmentation 1 we use survey mode and continuous gps data from 1991 to 2007 to examine fault segmentation in the earthquake cycle at the sumatra megathrust site of the 26 december 2004 mw 9 1 sumatra andaman the 28 march 2005 mw 8 7 nias simeulue and the 12 september 2007 mw 8 4 mentawai earthquakes these data including new observations from 2006 and 2007 allow us to observe the final few years of one earthquake cycle and the beginning of the next our analysis reveals that the megathrust is segmented a characteristic that may persist through multiple earthquake cycles the nias simeulue earthquake ruptured approximately the same region that broke in 1861 a 300 km long segment abutting the sumatra andaman rupture zone farther southeast the mentawai segment of the megathrust 0 5 s 5 s which produced m 8 earthquakes in 1797 and 1833 is fully locked in the interseismic period but is flanked by two freely slipping regions the batu islands in the nw and enggano in the se the 12 september 2007 mentawai earthquake sequence ruptured only the southern one third of the 1833 rupture zone we model postseismic deformation from the sumatra andaman and nias simeulue earthquakes and find that afterslip was concentrated updip and downdip respectively from the main shocks comparing the velocity fields before and after 2001 we find the subduction zone underneath the batu islands and enggano which prior to the earthquakes was partially to fully coupled appears now to be slipping freely thus while the segmentation of the subduction zone is preserved interseismic coupling on the subduction fault may vary with time

comprehensive analysis of traveltime data collected through gps acoustic observation of seafloor crustal movements we have developed a comprehensive inversion scheme to analyze traveltime data collected through gps acoustic observations on a campaign basis our method uses a quantity called the nadir total delay ntd which is analogous to the zenith total delay ztd in gnss analyses to represent the time variation of the sound speed the observation equation using the ntd is an approximated formulation we examine its applicable scope using numerical experiments and demonstrate that the approximation holds well enough in practice traveltime data from all our observation campaigns were utilized together for inversion calculation to determine 1 the positions of individual precision acoustic transponders pxps at the time of a particular reference campaign 2 the displacement from these positions of a rigid array at the time of each campaign and 3 the time variation of the ntd during each campaign we applied this method to actual data to fix the array geometry more precisely also we have made a first step in detecting vertical motions as well as horizontal motions though further enhancement of the accuracy will be required in performing linear regression of array displacements obtained from the inversion their error covariance has a significant effect on the resulting velocities when the covariance is taken into account nearly the same velocities are obtained no matter what campaign is taken as reference in the inversion

cranial morphology of sinornithosaurus millenii xu et al 1999 dinosauria theropoda dromaeosauridae from the yixian formation of liaoning china the recent discovery of the early dromaeosaurid sinornithosaurus millenii xu et al 1999 is especially important for our understanding of maniraptoran evolution particularly of avian origins this paper presents a thorough description of the skull of this species revises the diagnosis based on cranial features and discusses similarities to those of other dromaeosaurids and archaeopteryx distinctive cranial characteristics of s millenii include the presence of a deep excavation on the posteroventral margin of the premaxilla a diastema between the premaxillary and maxillary teeth a number of pits and ridges on the anterolateral surface of the antorbital fossa long posterolateral process of the parietal that are sharply posteriorly directed the column like margin of the pterygoid process of the quadrate the bifurcated posterior end of the dentary and a distinctive groove posterior to the anterior carina on the lingual surface of the premaxillary tooth crowns the present study on the skull of s millenii provides new information on the poorly known cranial anatomy of dromaeosaurid dinosaurs revealing that dromaeosaurids share more similarities with archaeopteryx than previously thought it also provides evidence suggesting that early dromaeosaurids are more bird like than the later more derived ones thus contradicting claims that more bird like dinosaurs appeared later in fossil record than the earliest birds

detection of crustal deformation from the landers earthquake sequence using continuous geodetic measurements the measurement of crustal motions in technically active regions is being performed increasingly by the satellite based global positioning system gps 1 2 which offers considerable advantages over conventional geodetic techniques3 4 continuously operating gps arrays with ground based receivers spaced tens of kilometres apart have been established in central japan5 6 and southern california to monitor the spatial and temporal details of crustal deformation here we report the first measurements for a major earthquake by a continuously operating gps network the permanent gps geodetic array pgga 7 9 in southern california the landers magnitude afw of 7 3 and big bear mw 6 2 earthquakes of 28 june 1992 were monitored by daily observations ten weeks of measurements centred on the earthquake events indicate significant coseismic motion at all pgga sites significant post seismic motion at one site for two weeks after the earthquakes and no significant preseismic motion these measurements demonstrate the potential of gps monitoring for precise detection of precursory and aftershock seismic deformation in the near and far field

the mean and seasonal circulation off southwest nova scotia abstract long term measurements off southwest nova scotia reveal the following features of the mean circulation a a westward longshore coastal current 4 10 cm s 1 b an anticyclonic gyre around brown bank 5 15 cm s 1 and c an upwelling circulation off cape sable 1 2 cm s 1 at bottom the gyre circulation appears permanent but the coastal current and upwelling exhibit annual variations of the same order as the means there is a distinct annual signal in the longshore transport at cape sable maximum westward in winter whereas the mean transport 0 14 106 m4 s 1 is consistent with both geostrophic estimates and budget requirements in the gulf of marine strong seasonal cycles are also found in the salinity and density fields at cape sable which appear to be controlled both by buoyancy input from the coastal current and local mixing effects a linear diagnostic model indicates that the primary dynamical balance for the circulation is between a longshore pressure gradient and longshore mean

interplate coupling model off the southwestern coast of java indonesia based on continuous gps data in 2008 2010 abstract we present an interplate coupling model of the australia java plate interface off the southwestern coast of java indonesia based on data from the indonesian permanent gps station network from 2008 to 2010 the majority of vertical data indicate uplift while the baseline change rate indicates coastal contraction in the middle of the network and coastal extension in the eastern part of the network using the rate of baseline length changes and the absolute rate of vertical displacements we apply a geodetic inversion method by yabuki and matsu ura 1992 from the inversion result we interpret the main source of the observed velocity in west java as resulting from contributions of 1 interplate coupling off ujung kulon pelabuhan ratu at 20 to 40 km depth with a slip rate range from 48 to 56 mm yr 2 interplate coupling off pangandaran at 37 to 45 km depth with a slip rate of 48 to 55 mm yr 3 afterslip off pangandaran within the rupture area of the 2006 m7 8 java earthquake in the depth range of 15 20 km with a slip excess rate of 57 61 mm yr the absence of a megathrust earthquake for at least 300 years in this region implies seismic moment accumulation during this time period of 1 6 10 21 nm mw 8 7 off ujung kulon pelabuhan ratu and 3 9 10 21 nm mw 8 3 off pangandaran unless episodic slow slips release tectonic stress

vernal circulation in the gulf of maine the circulation in the gulf of maine has an important baroclinic component it appears to be driven mostly by the density contrast between high salinity slope water which enters from the atlantic and fresher waters which are formed in the gulf or which enter from the scotian shelf hydrographie surveys in three successive spring seasons suggest that slope water accumulates in georges basin driving a counterclockwise surface circulation which brings scotian shelf water westward into the gulf and contributes to the eastward jet along the inner edge of georges bank the slope water also crosses a sill and enters jordan basin where it provides a potential energy source which may enhance a counterclockwise gyre partly driven by nearshore buoyancy sources and perhaps the wind the coastal limb of the gyre turns offshore east of penobscot bay part of the separated coastal current recirculates in jordan basin and part of it continues into wilkinson basin generating a clockwise eddy as it passes over jeffreys bank there is little evidence for recirculating surface flow in wilkinson basin instead the surface water appears to split into branches feeding the jordan basin gyre the georges bank jet and an export path to nantucket shoals the jordan and georges branches seem to be divided by the denser slope water in georges basin and this may be the central process controlling the vernal intensification of the circulation in the gulf a more complete dynamical understanding awaits models which include the baroclinic influence of boundary waters

suspended alexandrium spp hypnozygote cysts in the gulf of maine abstract the life cycle of dinoflagellates of the genus alexandrium includes sexual reproduction followed by the formation of a dormant hypnozygote cyst which serves as a resting stage negatively buoyant cysts purportedly fall to the benthos where they undergo a mandatory period of quiescence previous reports of cysts in the surficial sediments of the gulf of maine where alexandrium blooms are well documented show a broad distribution of cysts with highest concentrations generally in sediments below 100 m depth we report here an exploration of cysts suspended in the water column where they would be better positioned to inoculate springtime alexandrium populations during cruises in february april and june of 2000 water samples were collected at depths just off the bottom within 5 m at the top of the bottom nepheloid layer and near the surface 1 m and examined for cyst concentrations suspended cysts were found throughout the gulf of maine and westernmost bay of fundy planktonic cyst densities were generally greater in near bottom and top of the bottom nepheloid layer samples than in near surface water samples densities were of the order of 10 2 cysts m 3 in surface waters and 10 2 10 3 cysts m 3 at near bottom depths temporally they were most abundant in february and least abundant in april reports by earlier workers of cysts in the underlying sediments were on the order of 10 3 cysts cm 3 we present calculations that demonstrate the likelihood of cyst resuspension from bottom sediments forced by swell and tidal currents and propose that such resuspended cysts are important in inoculating the seasonal bloom we estimate that suspended cysts may contribute significantly to the annual vegetative cell population in the gulf of maine

gulf of maine shells reveal changes in seawater temperature seasonality during the medieval climate anomaly and the little ice age article i nfo in this study we use subannually resolved oxygen isotope values of fossil dead collected and modern live caught bivalve shells arctica islandica l from the northwestern atlantic gulf of maine usa to reconstruct past seasonal changes in seawater temperature our results indicate decreased seasonal temperature amplitude of about 1 6 c or 21 during medieval times ca ad 1033 1062 compared to shells from the early little ice age ca ad 1321 1391 and during the late 19th century ad 1864 1886 additionally seasonal oxygen isotope data suggest that summers were cooler and winters were warmer in the gulf of maine during the 11th century compared to summers and winters in the 14th century and the late 19th century the inferred decreased seasonality during medieval times likely resulted from increased stratification of the coastal waters due to warmer seawater temperatures as seawater cooled during the little ice age we suggest that increased vertical mixing of the coastal surface waters was a major driving factor for the observed increase in the amplitude of the seasonal seawater temperature cycle