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

sediment transport over an accretional intertidal flat with influences of reclamation jiangsu coast china this paper focuses on the hydrodynamic and suspended sediment transport processes in response to sequential reclamations over the intertidal flat jiangsu coast which used to be one of the widest intertidal flats in china investigations into the sediment transport patterns reveal that net suspended sediment fluxes increased from 102 kg m 1 on the upper intertidal flat to 103 4 kg m 1 on the lower intertidal flat per tidal cycle this variation was caused mainly by the phases of the current velocity suspended sediment concentration ssc local bed geomorphology inundation patterns and extreme weather conditions the longshore component of tidal currents intensifies seaward over the intertidal flat extreme weather conditions e g storms and strong winds were important factors affecting the current velocity structures the intensity of residual currents and the sscs the sscs were characterized by several peaks throughout the tidal cycle these peaks were associated with strong currents combined wave current interactions and intense turbulences due to the initial flood surge furthermore the suspended sediment was finer and contained more clay materials during the flood phase of the tidal cycle than during the ebb fine particles were transported within the upper water column by landward residual currents but coarse particles were transported within the lower water column by seaward residual currents overall residual currents were apt to transport fine grained sediment landward and coarse grained sediment seaward this pattern indicates that the suspended sediment fluxes are highly variable in the water column even for very shallow tidal environments the cross shore component accounted only for a small percentage of the total sediment flux however this part of sediment supply dominated accretion over the intertidal flat the intertidal flat has become narrower and steeper following sequential reclamations a negative feedback process existed to maintain the convex profile shape although the human activities i e reclamation could have modified the natural process the surficial sediment tended to become finer on the mid upper intertidal flat but coarser on the lower intertidal flat following reclamations in response to a reduction in the tidal currents over the intertidal zone and enhancement of wave action over the lower intertidal flat accretion with high rates was maintained by landward transport of sediment in such an accretional system with influences of reclamation the width or slope of the intertidal flat is adjusted continuously before the cease of reclamation the intertidal flat is unable to achieve an equilibrium shape

sedimentary facies of the tide dominated paleo changjiang yangtze estuary during the last transgression abstract a large estuary was formed by marine inundation of the paleo changjiang yangtze incised valley during the transgression after the last glacial maximum this paper presents the sedimentary facies and architecture of the estuary fill based on the analysis of three sediment cores cm97 js98 and hq98 obtained from the present changjiang delta plain estuary fill deposits showing an upward fining succession were grouped into five depositional facies tidal river distributary channel muddy intertidal to subtidal flats transgressive lag and estuary front based on sedimentary textures lithology and physical sedimentary structures sand mud couplets are common in these deposits indicating that tides played a significant role in producing these sedimentary structures and that the estuary type was tide dominated some of the successive sand mud couplets probably recorded neap spring cycles as well as semidiurnal tidal cycles the nature of the estuary was very different from other representative tide dominated estuaries in sediment facies its distribution and sediment source for estuarine fill unlike the other estuaries that receive sediments mainly from the sea the paleo changjiang estuarine fill deposits were supplied largely from the river this difference would also have a great influence on the sedimentological and morphological component in the estuary the sediment distribution of the estuary showed fining seaward and estuary mouth sand bodies fed by marine source sand were absent the architecture model of tide dominated estuaries should be divided into two types by the degree of fluvial sediment supply the paleo changjiang estuary shows a good example for an estuary of large rivers

evolution of the coastal depositional systems of the changjiang yangtze river in response to late pleistocene holocene sea level changes abstract the paleo changjiang yangtze incised valley fills approximately 80 90 m thick provide an opportunity to document the evolution of coastal depositional systems with large sediment supply in response to late pleistocene holocene sea level fluctuations on time scales of 103 to 104 years the sedimentary facies of the incised valley fills record three main depositional systems fluvial tide dominated estuary and tide dominated delta radiocarbon ages for the incised valley fills suggest that these depositional systems developed before about 11 ka between 11 and 8 ka and after approximately 8 ka respectively by applying sequence stratigraphic concepts the evolution of the depositional systems can be divided into three systems tracts a lowstand systems tract lst a transgressive systems tract tst and a highstand systems tract hst sea level changes on a 104 year time scale controlled the basic architecture of the sequence of the incised valley fill on the other hand sea level changes on a millennial time scale affected the stacking pattern of the systems tracts in particular the continuous sea level rise with episodic rapid rises during the last deglaciation affected the stacking pattern of the tst which is characterized by a combination of aggradation and backstepping the aggradation of fluvial and estuarine systems was dominant and the shoreline migrated only gradually landward under the relatively slow rise in sea level and a very rapid sea level rise around 12 and 10 ka caused the system to migrate abruptly landward unlike the transgressive estuarine phase the stacking pattern of the regressive tide dominated delta hst which developed within the almost filled incised valley and on the surrounding interfluve zones was characterized by seaward progradation with clinoform architecture it was initiated with aggradational and progradational stacking about 8 ka during the last phase of decelerated sea level rise and was followed by a progradational phase after the highest sea level about 6 ka

full interseismic locking of the nankai and japan west kurile subduction zones an analysis of uniform elastic strain accumulation in japan constrained by permanent gps we analyze permanent global positioning system gps data obtained over japan between 1995 and 1997 to estimate the instantaneous interseismic coupling ratio of the seismogenic zones due to the subduction of the pacific and philippine sea plates below the japanese islands we first derive the gps strain rate fields that characterize the crustal deformation of southern and northern japan and invert them to determine the effective subduction velocity along the central nankai trough on one side and the japan west kurile trench on the other these reference free velocities are close to those predicted by plate motion models with respect to eurasia we conclude that the eurasian reference frame gives a good approximation to the subduction motion and that to first order both subduction zones were fully locked during the period of measurements we then test whether the coupling ratio shows local variations within the seismogenic zones to do this we divide the subduction interface into 35 km 30 km elements that we model by point source groups and we invert the gps velocity field referenced to eurasia to derive the coupling ratio between 0 and 1 on each fault element the results are coherent over the 3 years and confirm that both the central nankai and the japan west kurile seismogenic zones are homogeneously fully locked most of the coupling ratios are close to 1 and a few are close to 0 intermediate values are rare the zones of decoupling correspond either to strong postseismic afterslip associated with the 1994 sanriku oki interplate earthquake japan trench or to a small overestimation of the actual lower limit of the locked zone we conclude that within the resolution of the gps data and the model 1 partial coupling did not exist during these 3 years along the nankai and japan west kurile trenches 2 the small seismic coupling ratio previously derived from earthquakes analysis for the japan and kurile trenches may indicate that a significant part of the elastic energy is dissipated silently through slow earthquakes and postseismic afterslip and 3 the heterogeneous coseismic slip pattern observed for the large and great earthquakes that rupture both subduction zones is in great contrast to the homogeneous loading finally we discuss the nonelastic residual deformation within the frame of the long term deformation of the japanese islands

a review on the provenance discrimination of sediments in the yellow sea the yellow sea has been extensively studied for the understanding of dispersal patterns and limits of sediments from neighboring countries including china and korea although sedimentological mineralogical and geochemical approaches have been tried to solve the problems especially including the identification of sediment sources in and around the yellow sea the published results are not enough for understanding them suggestions on sediment origins budgets sediment accumulation rates mineralogical and geochemical compositions are not coincident to each other and sometimes even controversial for example conflicts on the distribution patterns of smectite and calcium carbonate the provenance of the southeastern yellow sea mud and sedimentation rates in there the ratios of v al and mn al in korea and china river sediments the origin of ba and pb in sandy sediments of the northeastern yellow sea and so on various geochemical indicators from the literature for the provenance discrimination in the yellow sea are reviewed here in depth and corresponding discussions are described separately research topics for the future study also are suggested for the proper access to the understanding of the origin and dispersal patterns of the yellow sea sediments especially focusing on the geochemical approaches d 2003 elsevier science b v all rights reserved

the provenance of the southeastern yellow sea sediments constrained by detrital zircon u pb age abstract u pb ages of detrital zircon grains collected from sandy sediments in the southeastern yellow sea were analyzed to infer their provenance the zircon age spectra show e w direction differences with a wide age range from early cenozoic to late archean the western samples were dominated by paleozoic to neoproterozoic zircons whereas the eastern samples by paleoproterozoic zircons this age distribution suggests diversity of age populations in the source terranes and changes in sediment supply to the sample locations comparison of these results with the basement rock geology and detrital zircon ages of river sediments in the surrounding land areas indicates that the eastern and western parts of the southeastern yellow sea sandy sediments were mainly supplied from the korean peninsula and southern china along with now submerged shelf bedrocks respectively with a mixing zone in the middle differences in zircon age populations resulted from the change of proportions in sediment supply from two dominant provenances due to sea level rising and associated reworking during the holocene transgression

yangtze shoal a modern tidal sand sheet in the northwestern part of the east china sea abstract from an analysis of other s data on tidal currents bedforms and sediment grain sizes it is concluded that the yangtze shoal in the northwestern east china sea is a typical modern tidal sand sheet rather than a paleo changjiang submarine delta or a relict sedimentary accumulation on the continental shelf formed during a stillstand of the postglacial transgressive sea the yangtze shoal and the jiangsu offshore tidal ridges of the subei shoal to the northwest jointly comprise the active tidal geomorphic system off the changjiang estuary

response of the san andreas fault to the 1983 coalinga nunez earthquakes an application of interaction based probabilities for parkfield 1 the parkfield cholame section of the san andreas fault site of an unfulfilled earthquake forecast in 1985 is the best monitored section of the world s most closely watched fault in 1983 the m 6 5 coalinga and m 6 0 nunez events struck 25 km northeast of parkfield seismicity rates climbed for 18 months along the creeping section of the san andreas north of parkfield and dropped for 6 years along the locked section to the south right lateral creep also slowed or reversed from parkfield south here we calculate that the coalinga sequence increased the shear and coulomb stress on the creeping section causing the rate of small shocks to rise until the added stress was shed by additional slip however the 1983 events decreased the shear and coulomb stress on the parkfield segment causing surface creep and seismicity rates to drop we use these observations to cast the likelihood of a parkfield earthquake into an interaction based probability which includes both the renewal of stress following the 1966 parkfield earthquake and the stress transfer from the 1983 coalinga events we calculate that the 1983 shocks dropped the 10 year probability of a m 6 parkfield earthquake by 22 from 54 22 to 42 23 and that the probability did not recover until about 1991 when seismicity and creep resumed our analysis may thus explain why the parkfield earthquake did not strike in the 1980s but not why it was absent in the 1990s we calculate a 58 17 probability of a m 6 parkfield earthquake during 2001 2011 index terms 7223 seismology seismic hazard assessment and prediction 7230 seismology seismicity and seismotectonics 7260 seismology theory and modeling keywords coalinga earthquake parkfield stress change earthquake probability seismicity rate

depositional development of an isolated mound and adjacent area in the southern yellow sea during the last postglacial sea level rise abstract a detailed analysis of the chirp 2 7 khz profiles core sediments and 14c ages from an isolated mound and adjacent area in the southern yellow sea off the jiangsu coastal area reveals a highly complex development of transgressive and highstand deposits during the last postglacial sea level rise in water depths of 50 60 m the terrace consists of thin transgressive sediments directly above transgressive surface the isolated mound 40 7 km long and 29 6 km wide occurs above 40 50 m in water depth and is detached from the jiangsu and east china sea tidal sand ridges it comprises the sse ward prograding sandy unit pu and the overlying muddy flank unit fu at the outer margin the terrace with thin transgressive sediments was most likely formed when sea level rose rapidly from 58 to 45 m around about 11 6 ka as rate of sea level rise was attenuated from 45 to 36 m between ca 11 6 and 9 6 ka the nearly flat lower boundary of the pu was produced at water depths of 37 42 m by a ravinement process subsequent rapid sea level rise from 36 to 16 m between ca 9 6 and 9 1 ka created accommodation for deposition of the pu sea level rise stagnated from 16 to 10 m between ca 9 1 and 7 5 ka during which the huanghe river apparently shifted south of the shandong peninsula and discharged directly into the western yellow sea the combination of slow sea level rise and sediment supply from the early holocene huanghe delta by the southward flowing coastal currents most likely favoured the formation of the sse ward prograding transgressive sandy pu the highstand muddy fu overlying the pu was accumulated after ca 7 5 when sea level approached its present position and the huanghe river shifted back to the north development of transgressive and highstand deposits in the study area during the last postglacial sea level rise was highly variable in time and space in response to changes in rate of sea level rise together with variations in sediment supply caused by the shifting of the huanghe river

the butterfly delta system of qiongzhou strait morphology seismic stratigraphy and sedimentation abstract analysis of high resolution sub bottom profiles topographical data and sediment samples reveals that the tidal delta system of qiongzhou strait is morphologically a butterfly delta system consisting of western mouth tidal delta wmtd and eastern mouth tidal delta emtd wmtd covers an area of about 11 000 km 2 and is more than two times larger than emtd 4000 km 2 wmtd is fan shaped with a tributary branch extending southwards along hainan island while emtd is typically fan shaped seismic architectures of wmtd and emtd are both characterized by a thick progradational unit overlying a thin transgression unit both wmtd and emtd start to develop at about 8 7 cal ka bp when qiongzhou strait completely opened and have the same three sedimentary facies tidal delta top tidal delta slope and tidal delta toe the formation of wmtd and emtd is attributed to qiongzhou strait s hydrodynamic regime which is dominated by the strong east west reciprocal tidal currents and influenced by the year round westward mean flow modified by the wind driven seasonal currents

holocene evolution of bottom sediment distribution on the continental shelves of the bohai sea yellow sea and east china sea abstract coastline shifts due to transgression and regression can remodel tidal fields of continental shelves and this can control transport of sediments and modulate sediment distribution accordingly tidal currents have become the dominant hydrodynamic processes on the continental shelves of the bohai sea yellow sea and east china sea byecs since the transgression after the last glacial maximum lgm to examine the evolution of the bottom sediment distributions on the continental shelves of the byecs we simulated patterns of tides and tidal currents sediment transport and bottom sediment types sand mud and mixed sediments for five periods corresponding to sea level lowstands of 80 m 52 m and 30 m below present the holocene transgression maximum htm and the present the simulation shows that both sediment transport and shelf sediment distribution patterns were controlled by the strength type and asymmetry of tidal currents in the byecs since the lgm evolution of shelf sediment distribution patterns occurred in two stages 1 sediment emplacement and formation stage before the htm and 2 local adjustment after the htm the marked changes in coastline configuration since the lgm are the dominant factor controlling tide and tidal current evolution distribution of shelf sediment types in the byecs is closely related to tidal current fields during transgression after the lgm

tidal hydrodynamics and fine grained sediment transport on the radial sand ridge system in the southern yellow sea abstract the large radial sand ridge rsr system located in the southern yellow sea off the jiangsu coast is characterized by a radial current field and high suspended sediment concentrations sscs significant rectilinear currents are present over the northern sand ridge area whereas rotary currents prevail over the southern area the transition between the two being dominated by a locally generated trapped wave observations undertaken in 2006 and 2007 indicate a seasonal pattern in the ssc and associated dynamic characteristics the results of a calibrated hydrodynamic model show that the m2 tide dominates the rsr area the maximum tidal amplitude in the core region close to land being approximately 2 m an amphidromic point is located some distance north of the rsr off the abandoned yellow river mouth 121 686 e 34 6 n specifically the eulerian and lagrangian residual currents flow southward in both summer and winter whereas the stokes drift is directed southward in the north and northward in the south moreover in deep water the lagrangian residual current is mainly determined by the eulerian residual current whereas it is strongly influenced by the stokes drift in shallow water the seasonal variation in the residual current in the southern yellow sea is a good indicator for the location of the yellow sea warm current yswc in both summer and winter measurements show that a ssc peak appears off the abandoned yellow river delta in response to the strong currents and plentiful supply of fine grained sediment from coastal erosion another ssc peak lying close to the north branch of the changjiang river mouth is related to the abundant suspended sediment supplied by the river seasonal variations in ssc are observed in the study area maximum average values and widest diffusion from land occurring in winter this being contrasted by minimum mean values in summer sensitivity experiments demonstrate that the main factor influencing the distribution of ssc is the tide while river discharge wind and wave effects are small and very localized to explain the seasonal variation in ssc the role of hydrodynamics initial conditions and temperature are tested in the model the results show that the hydrodynamics play a significant role whereas the initial conditions only have a minor regional influence temperature on the other hand is also shown to greatly influence the seasonal variation in ssc because of substantial changes in the viscosity of the water and the erosion shear stress the modeled results are used to calculate sediment fluxes which are shown to be consistent with the lagrangian residual current pattern while wind waves can significantly change the fluxes in winter bed elevations change substantially on a monthly time scale in general the deep channels are undergoing erosion while the shallow ridges and coastal tidal flats are accreting the net sediment transport being directed towards the coastal tidal flat and the changjiang yangtze river subaqueous delta

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

an application of numerical simulation techniques to improve the resolution of offshore fault kinematics using seafloor geodetic methods abstract geodetic measurements reveal a number of tectonic phenomena such as coseismic and postseismic displacements of earthquakes and interplate coupling on plate interfaces however since geodetic measurements are limited to land slip distribution is poorly resolved offshore though well constrained in the landward areas due to the poverty of offshore data tectonic motion near trench axes has not been measured seafloor geodetic observations provide important information on offshore tectonics improved offshore resolution would allow determination of strain accumulation and release processes near trench axes in this study using numerical simulation we discuss the potential for improvement of slip resolution in an offshore area using seafloor geodetic measurements the plate interface along the nankai trough is modeled by 36 planar fault segments whose length and width respectively are set to 60 km and 50 km three hundred and seventy five gps observation sites on land and 10 seafloor sites aligned 60 km off the coast are used for the simulation we carry out a checkerboard test and compare the estimated slip pattern with the given checkerboard pattern models that do not include seafloor sites generate large discrepancies in offshore deformation between the initial and estimated slip patterns although there are similarities in coastal regions this indicates poor resolution in offshore areas when we apply our model to include seafloor sites the difference between the initial and estimated slip patterns decreases for most of the modeled fault segments comparison between these two cases suggests the potential for use of seafloor geodetic techniques to improve offshore resolution

sedimentary facies and holocene progradation rates of the changjiang yangtze delta china abstract the changjiang yangtze river one of the largest rivers in the world has formed a broad tide dominated delta at its mouth during the holocene sea level highstand three boreholes cm97 js98 and hq98 were obtained from the changjiang delta plain in 1997 1998 to clarify the characteristics of tide dominated delta sediments and architecture based on sediment composition and texture and faunal content core sediments were divided into six depositional units in ascending order they were interpreted as tidal sand ridge prodelta delta front subtidal to lower intertidal flat upper intertidal flat and surface soil deposits the deltaic sequence from the prodelta deposits to the delta front deposits showed an upward coarsening succession overlain by an upward fining succession from the uppermost part of the delta front deposits to the surface soil thinly interlaminated to thinly interbedded sand and mud sand mud couplets and bidirectional cross laminations in these deposits show that tide is the key factor affecting the formation of changjiang deltaic facies sediment facies and their succession combined with ams 14c dating revealed that isochron lines cross unit boundaries clearly and delta progradation has occurred since about 6000 to 7000 years bp when the rising sea level neared or reached its present position the average progradation rate of the delta front was approximately 50 km kyear over the last 5000 years the progradation rate however increased abruptly ca 2000 years bp going from 38 to 80 km kyear the possible causes for this active progradation could have been an increase in sediment production in the drainage basin due to widespread human interference and or decrease in deposition in the middle reaches related to the channel stability caused by human activity and climatic cooling after the mid holocene

the shallow marine architecture knowledge store a database for the characterization of shallow marine and paralic depositional systems abstract the shallow marine architecture knowledge store smaks is a relational database devised for the storage of hard and soft data on the sedimentary architecture of ancient shallow marine and paralic siliciclastic successions and on the geomorphological organization of corresponding modern environments the database allows incorporation of data from the published literature which are uploaded to a common standard to ensure consistency in data definition the database incorporates data on geological entities of varied nature and scale i e surfaces depositional tracts architectural elements sequence stratigraphic units facies units geomorphic elements including attributes that characterize their type geometry spatial relations hierarchical relations and temporal significance furthermore geological entities are assigned to depositional systems or to parts thereof that can be classified on multiple parameters e g shelf width delta catchment area tied to metadata e g data types data sources the smaks permits the quantitative characterization of modern and ancient shallow marine and paralic clastic depositional systems it aims to serve as a repository of analogue information for hydrocarbon bearing successions and as a research tool that can be applied to aid the development of facies models or to assess the sensitivity of depositional systems to particular controlling factors for example to demonstrate the wide applicability of the database in fields of both fundamental and applied research example database output is presented that i includes data from wave tide and fluvial dominated shallow seas and sedimentary successions and ii covers a wide depositional spectrum from backshore to shelf edge settings the examples include information on the facies organization of different types of paralic sub environments on the hierarchical arrangement of architectural elements that form deltaic constructional units in quaternary deltas on the morphometry of modern and quaternary tidal sand ridges and on the geometry of parasequence scale nearshore sandstone belts from the upper cretaceous of the western interior seaway in utah usa

transgressive sand ridges on the mid shelf of the southern sea of korea korea strait formation and development in high energy environments abstract the mid shelf of the southern sea of korea korea strait is covered by a series of shore parallel sand ridges up to 63 km long 3 9 km wide and 22 m thick the ridges are a moribund type but show well organized dipping strata indicating appreciable progradation the submerged paleo channel system the paleo seomjin river associated with the sand ridge field suggests that the ridges primarily originated from river mouth sandy shoals which subsequently developed into shore parallel linear sand bodies in high energy environments the combined effect of coastal tidal and longshore and offshore ocean currents was possibly responsible for shore parallel sediment transport and growth of the ridges 14c dates core lithology and sea level data suggest that the sand ridges mainly formed and developed during the middle period of the postglacial transgression they are postulated to have developed sequentially from offshore to onshore in response to sea level rise during that time very slow sea level rise and high sediment supply through the paleo channel system probably provided favorable conditions for forming the sand ridges the ridges became inactive during the late transgression period as a result of a substantial reduction of wave and current strength and remained on the mid shelf

an overview of geodetic volcano research in the canary islands the canary islands are mostly characterized by diffuse and scattered volcanism affecting a large area with only one active stratovolcano the teide pico viejo complex tenerife more than 2 million people live and work in the 7 447 km2 of the archipelago resulting in an average population density three times greater than the rest of spain this fact together with the growth of exposure during the past 40 years increases volcanic risk with respect previous eruptions as witnessed during the recent 2011 2012 el hierro submarine eruption therefore in addition to purely scientific reasons there are economic and population security reasons for developing and maintaining an efficient volcano monitoring system in this scenario geodetic monitoring represents an important part of the monitoring system we describe volcano geodetic monitoring research carried out in the canary islands and the results obtained we consider for each epoch the two main existing constraints the level of volcanic activity in the archipelago and the limitations of the techniques available at the time theoretical and observational aspects are considered as well as the implications for operational volcano surveillance current challenges of and future perspectives in geodetic volcano monitoring in the canaries are also presented

tidal current ridges in the southwestern yellow sea abstract large tidal current ridges tidal sand banks in the southwestern yellow sea are located offshore of northern jiangsu province china these ridges radiate to a depth of 20 30 m the dimensions of the ridge system are about 200 km long and 90 km wide their morphology indicates the strong influence of tidal currents the ridges are composed of well sorted fine sands size range is 2 4 the grain size distributions of the sands show that the sands are transported and deposited by tidal currents the ridge system formed on the abandoned yellow river and ancient yangtze river deltas has an abundant sand supply from the former deltas of particular importance is the existence of two tidal wave systems in the yellow sea the rotary ti al wave system in the southern yellow sea and the pacific progressive tidal wave system propagated into the southern ridge area of the southwestern yellow sea under the interaction of the two tidal wave systems the huge tidal current system in the southwestern yellow sea has formed

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

exploratory morphodynamic modeling of the evolution of the jiangsu coast china since 1855 contributions of old yellow river derived sediment abstract in this study we aim to investigate the overall morphological evolution of the jiangsu coast after 1855 when the yellow river shifted northward we focus on fine sediment transport between two large scale geomorphological units i e the abandoned yellow river delta ayd and the radial sand ridges rsrs an existing morphodynamic model which was established for reproducing the development of the ayd before 1855 is modified and extended in addition to the tidal forcing waves and human interventions i e revetments are considered in the model the model results are compared with the existing data both the evolution trend of the jiangsu coast and the spatial distribution of the offshore shoals show good agreement the simulated fine sediment depositions in different periods are consistent with the geological measurements the results reveal that the old yellow river derived sediment not only contributes to the sedimentation in the rsrs but can also be transported to the adjacent zones especially farther south southeast moreover the spatial distribution of fine sediment deposits varies in the rsrs the different sedimentary environments in the dongsha and tiaozini ridges result in significant grain size differences in these two neighboring ridges a sensitivity analysis indicates that tides play a key role in dominating the long term morphological evolution of the jiangsu coast and the total erosion from the ayd on smaller scales the effect of revetments built since the 1930s on the evolution of the nearshore zone and the effect of wind waves on the erosion of offshore shoals are relatively important the effect of a gradual coarsening process of bottom sediment along the jiangsu coast which may be due to continuous fine sediment removal is identified fine sediment depositions in the tiaozini ridge and in the northern offshore zone of the rsrs are relatively more sensitive to the coarsening trend of bottom sediment than other areas

delta development and channel incision during marine isotope stages 3 and 2 in the western south yellow sea abstract approximately 4100 km of high resolution seismic profiles recently obtained from the western south yellow sea were subdivided into seven seismic units by six major seismic surfaces three sediment cores between 60 and 71 m in length obtained from localities on the seismic profile lines were analyzed for sedimentary characteristics clay mineral components and benthic foraminiferal and ostracod assemblages and were also dated by ams 14 c and optically stimulated luminescence to document the environmental history of the region stratigraphic units in the cores were confidently correlated with seismic units in the profiles stratigraphic correlation among these three cores and the previous well studied core qc 2 was facilitated by the cold water deposits in marine isotope stage mis 5 the three cores document the sedimentary sequence during the period from mis 6 up to mis 1 strata formation and sedimentary environment changes since mis 5 are strongly controlled by sea level fluctuations most of the successions were formed in mis 5 mis 3 and mis 1 with major erosions in mis 4 and mis 2 particularly our data revealed the presence of a large delta active during mis 3 likely from the early stage of mis 3 to about 40 cal kyr bp that was subsequently affected by channel incision the delta succession and incised channel fills have a high concentration of smectite in their clay mineral components suggesting that the paleo yellow river was the main contributor to the delta development and channel incision the delta sequence has a coarsening upward trend and consists of two seismic facies the upper facies shows lateral alternations of chaotic and oblique or very low angle reflectors which correspond to sandy proximal delta front and delta plain facies and the lower facies is characterized by seaward dipping clinoforms which correspond to muddy distal delta front and prodelta facies the top surface of the delta inclines very gently seaward consistent with a deltaic development associated with the sea level fall in mis 3 the incised channel system consists of two main channels with multiple tributaries in a dendritic pattern the incised channel fills begin with fluvial and then estuarine sediments which are truncated by a transgressive ravinement surface and capped by transgressive deposits the main incision channels have a terraced cross sectional morphology which is interpreted to reflect multiple episodes of sea level fall during incision presumably from the late mis 3 to the last glacial maximum

subaqueous deltaic formation of the old yellow river ad 1128 1855 on the western south yellow sea abstract the yellow river presently flows into the bohai sea but during the period ad 1128 1855 the river called the old yellow river oyr flowed into the western south yellow sea sys where the dispersal of its sediment load was controlled by the interactions among alongshore currents waves and tides and shelf morphology in this study high resolution shallow seismic profiles vibrocores boreholes and water depth data which were obtained during geological surveys in the western sys in recent years are used to examine the depositional pattern and stratigraphic record related to the oyr entering the sea our data reveal compound clinoform morphologies double clinoforms a subaerial subaqueous delta couplet sourced by the oyr in the western sys the subaerial delta comprises the currently onshore delta plain and deltafront extending to 17 m in water depth while the subaqueous delta is composed of a wide gently inclined topset and a relatively narrow steeply sloping foreset stretching seaward about 160 km away from the shoreline and showing a morphological asymmetry with a generally southward deflection relative to the oyr mouth the topset is 25 100 km wide in a shore normal direction at water depths of 10 25 m but is generally less than 4 m thick the foreset is much narrower and thicker than the topset is generally 5 30 km wide at 10 45 m water depth and is mostly 4 16 m thick with a maximum thickness of 20 m it shows seaward dipping internal reflectors generally 0 3 0 5 the rollover points topset foreset transition of the subaqueous clinoform range mostly between 10 and 25 m water depth results of 210pb and 137cs geochronology indicate that maximum sediment accumulation rates 1 06 to 2 16 cm yr correspond to the foreset region with much lower rates in the topset and surrounding shallow sea regions 97 in ad 1128 1855 has accumulated on the subaerial delta and that about 10 16 of the total load on the subaqueous delta our data also reveal that the subaqueous delta related to the oyr is underlain by a large scale clinoform broadly confined to 2 5 9 8 cal kyr bp in age as thick as 4 13 m with seaward dipping lower angled

depositional patterns of sand ridges in tide dominated shallow water environments yellow sea coast and south sea of korea abstract the continental shelf of the yellow sea and the korean south sea is a tide dominated shelf a number of sand ridges occur in this area which form bathymetric highs surveyed were one large sand ridge jangan satoe along the western yellow sea coast and a group of mid shelf sand ridges in the south sea to delineate their depositional pattern and probable origin in tide dominated shallow water environments analyses of sediment samples side scan sonographs and seismic profiles reveal that these ridges show regionally different characteristics in morphology bedforms and sediment the sand ridge in the yellow sea shows a composite form of various bedforms including sand waves and megaripples this ridge is interpreted to be in an accretional active stage maintained by strong tidal currents in contrast the sand ridges on the mid shelf of the south sea show rounded single forms without bedforms on them they are interpreted to represent moribund type sand ridges in the shelf environment which were formed near the shoreline during the holocene sea level transgression these ridges developed off the paleo seomjin river during a period of a stillstand or slow sea level rise approximately between 10 000 and 7000 yrs b p

morphodynamics of a tidal ridge system in the southwestern yellow sea hf radar study abstract a radial tidal ridge system is present throughout the coastal waters of the southwestern yellow sea china with varied and complicated ridges and channels between them a newly designed ground wave high frequency hf radar with full coverage and high spatial temporal resolution was employed in this study to measure the surface currents and bathymetric features correlated wave celerity in the study area from july 17 to august 6 2011 we found that the spatial distribution pattern of the tidal channels is generally stable with periodic adjustments during a spring neap tidal cycle and with higher degree of spatial orderliness from neap to spring tides than from spring to neap tides the nearshore part of the channels is most stable in lateral the middle part is relatively lateral unstable and the offshore part changes complicatedly flood dominated channels and ebb dominated ridges are identified using hf radar signals the horizontal kelvin number k eh is workable in lateral stability evaluation this study reveals the potential of hf radar in morphodynamic studies on shallow coastal waters

tidal deposition systems of china s continental shelf with special reference to the eastern bohai sea abstract the continental shelf of china has undergone a large scale marine transgression tidal currents have become the main active agent and have had a profound influence on the deposition and geomorphology of the shelf the continental shelf of china has five modern tidal deposition systems 1 the eastern part of the yellow sea 2 the eastern part of the bohai sea 3 off the mouth of yangtze river 4 to the west of taiwan and 5 the strait of qiongzhou when the tidal current speed is above 150 cm s erosion dominates and reciprocating currents form deep scour furrows when the tidal current speed is 50 to 150 cm s deposition is dominant and tidal currents form tidal shoals i e tidal sand ridges and tidal sand sheets whose margins are near an absolute ellipticity value for the m2 tidal component of 0 4 when the absolute m2 value is less than 0 4 a reciprocating current is strong enough to form tidal sand ridges when the absolute value is above 0 4 a rotating current increases so as to form a tidal sand sheet tidal deposition material came mainly from tidal erosion and locally redeposition of late pleistocene sediments and from the neighbouring sea bottom the tidal deposition system in the eastern bohai sea is a typical example it consists of the laotieshan channel scour furrow the liaodong shoal sand ridges and the bozhong shoal sand sheet the maximum tidal current speed in the laotieshan channel where strong erosion occurs is up to 250 cm s in the liaodong shoal the maximum tidal current speed is 64 115 cm s and the absolute ellipticity value of the m2 tidal component is less than 0 4 in the bozhong shoal the maximum tidal speed is 58 79 cm s and the absolute ellipticity value of the m2 tidal component is above 0 4 the small scale bedforms surveyed in detail in the area show that the sand ridges and sand sheet are still under the action of tidal current processes at the present time based on the interpretation of tidal currents bedforms and sediment thickness it is inferred that the general direction of sediment transport within the study area is nnw from the laotieshan channel to the liaodong and bozhong shoals the small scale bedforms in the detailed survey area indicate a local net sediment transport from south to north

crustal velocity field of southwest japan subduction and arc arc collision we investigate crustal deformation in southwest japan over a 3 year period revealed by a permanent dense global positioning system gps array southwest japan is a part of the amurian plate a microplate moving about 10 mm yr toward the east with respect to the eurasian plate it overrides the philippine sea plate at the nankai trough and collides with the northeast japan arc in the central part of japan in this paper we first derive gps site velocities relative to the stable part of the amurian plate in order to isolate signals of crustal deformation caused by the subduction and or the collision the velocity field has a conspicuous feature indicating the interseismic elastic loading by the philippine sea plate slab at the nankai trough characterized by the northwestward movements of points throughout the studied area their amplitudes are the largest at the pacific coast and decay toward the japan sea coast with a subtle systematic shift of azimuths a model assuming an elastic half space the convergence rate at the nankai trough based on a refined euler vector and the strength of the coupling inferred from a thermal model could explain the velocity field in the western part of the studied area to a large extent those in the eastern part systematically deviate from them and the residual components there show east west shortening and north south extension this may represent crustal thickening and trenchward extrusion of crustal blocks caused by the collision between southwest and northeast japan this suggests that the collision between southwest and northeast japan gives rise to not only crustal thickening but also trenchward extrusion of crustal block a velocity contrast was found across the median tectonic line the largest inland active fault in japan but the current permanent gps network is not dense enough for us to discuss its coupling depth

interplate coupling along the nankai trough off southwest japan derived from gps measurements we investigate interplate coupling between the philippine sea and the eurasian plates at the nankai trough off southwest japan during the interseismic period plate coupling is modeled by imaginary backward normal slip superposed on the steady state subduction we divide the plate interface into several segments and estimate coupling on each segment from gps horizontal velocity data estimated coupling is in general agreement with the rate of steady state subduction predicted from a plate motion model this implies that current coupling at the nankai trough is so strong that much of the relative plate motion is taken up by shortening of the leading edge of the overriding plate it seems that stronger interseismic coupling is realized on the segment where larger coseismic dislocation occurred and vice versa time fluctuation of plate coupling from 1995 to 1996 is found on a small segment

dynamic sedimentation and geomorphologic evolution of the laizhou shoal bohai sea northern china abstract as a headland associated sandbank off an unconsolidated coast cape in a progression process the laizhou shoal is just located at the coalescent position of the two tidal residual current circumferences its formation and maintenance dynamics sedimentation and geomorphology are different from the models proposed up till the present moment our findings indicate that 1 the tidal residual tidal current circumferences are located along the flanks of the shoal itself instead of the flanks of the headland cape and the sediments under the two circumferences are quite different from those at their coalescent position 2 the sediments made up of the shoal have an ultimate resource of river sediment instead of an erosion recession cape or seafloor nearby and are transported directly from the coastal zone through the wave resulted coastal current rather than through the tidal residual tidal eddies 3 the shoal continually migrates from southwest to northeast extending into the laizhou bay northwest the cape in the past 50 years 4 because more than 100 reservoirs have been built across the rivers in the northwestern shandong peninsula and have greatly reduced the sediments especially gravel and sand grains transported into the coastal zone some locations of the shoal have evolved from deposition to erosion and the shoal itself has become narrower but has not evolved from deposition to erosion as a whole

buried sandbodies within present day estuaries atlantic coast of france revealed by very high resolution seismic surveys abstract studies of sandbanks within estuaries and macrotidal bays are critical for management of those coastal environments where human activity concentrates they are also excellent analogues of reservoirs new very high resolution vhr seismic profilers are now available for studying at the outcrop resolution scale sandbodies in very shallow water we present here a vhr seismic study constrained by vibrocores repetitive bathymetric surveys and radiocarbon dating which provide evidence of buried sandbodies in mixed tide and wave influenced estuaries of the french atlantic coast the three selected buried sandbodies are chosen because they are located at various water depths and have different internal architecture and outer shape they include 1 a very shallow water around 2 m under low tide elongated nearshore sandbody emplaced during the last centuries 2 a 6 to 7 m deep elongated nearshore sandbody dated to 2965 30 bp and 3 sandwaves lying around 17 m of water depth over the top of a large rounded shape sandbody dated to 5260 30 bp deepest 6 and 17 m sandbodies are interpreted as remnants of lower sea levels and thus transgressive sandbodies all those sandbodies are buried under estuarine mud which have been mainly emplaced during the last millenium such major sedimentary transition from basal sand to upper mud is assumed to record a major environmental change in relation to both natural infilling of estuaries climate change and increasing human activities anthropogenic perturbations are however believed to be the most important factor they have mainly consisted of land reclamation and are responsible for 1 rapid infilling of tidal bays 2 tidal prism and tidal current energy decreases and 3 deposition of muddy sediments upon sandbodies

plate convergence and long term crustal deformation in central japan surveys by continuous global positioning system in and around japan revealed that the amurian plate collides with the north american plate in central japan by 2 cm yr long term crustal deformation seems to be influenced mainly by this collision although subduction of oceanic plates governs short term elastic deformation over the arc here we study the long term deformation field by carefully removing the short term signals inferred from a priori plate convergence vectors and coupling strengths predicted by a thermal model the obtained field shows that the change in velocities occurs along the longitude 135 137 and there exist a relatively rigid block and zones accommodating strains characteristic compressional deformation is found northwest of izu due possibly to the collision of the izu bonin arc with honshu plate convergence rate along the nankai suruga trough is considerably smaller in eastern parts due partly to the transition from the amurian to the north american plate of the landward side and partly to the motion of the izu microplate relative to the philippine sea plate this accounts for longer recurrence intervals of interplate earthquakes in the suruga trough where the tokai earthquake is anticipated to occur