plate kinematics in the western pacific derived from geodetic observations 1 plate kinematics have been derived from gps site velocities spanning australasia and the western pacific and define a framework in which deformation fields at plate boundaries can be investigated the australian plate appears to be rigid from cocos island in the west to noumea in the east and incorporating all of the australian continent a revision of the angular velocity vector of the pacific plate using six site velocities has led to the detection of significant relative motion between the pacific plate and sites in northern papua new guinea this provides strong evidence in support of a north bismarck plate between the south bismarck and pacific plates and we model the motion of the north bismarck plate with the angular velocity vector 45 0 s 126 4 e 0 85 myr these new angular velocity vectors model the rigid plate motions of a substantial part of the australasian and western pacific regions with an accuracy better than 3 mm yr

new insights on the tectonics along the new hebrides subduction zone based on gps results 1 at the new hebrides nh subduction zone ridges born by the subducting australia plate enter the trench and collide with the overriding margin results from gps surveys conducted on both sides of the trench and new bathymetry maps of the nh archipelago bring new light on the complex tectonics of this area convergence vectors present large variations that are not explained by australia pacific a p poles and that define four segments vectors remain mostly perpendicular to the trench and parallel to the earthquake slip vectors slow convergence i e 30 40 mm yr is found at the central segment facing the d entrecasteaux ridge the southern segment moves faster than a p motion predicts 89 to 124 mm yr relatively to a western north fiji basin wnfb reference the northern and southern segments rotate in opposite directions consistently with the extension observed in the troughs east of both segments both rotations combine in central vanuatu into an eastward translation that bulldozes the central segment into the wnfb at 55 mm yr that model suggests that the motion of the central segment forced by the subduction collision of the d entrecasteaux ridge influences the motion of the adjoining segments the new caledonia archipelago is motionless with respect to the rest of the australia plate despite the incipient interaction between the loyalty ridge and the nh margin southeast of the interaction area convergence is partitioned into a 50 mm yr trench normal component accommodated at the trench and a 90 mm yr trench parallel component close to the a p convergence and presumably accommodated by a transform boundary at the rear of the nh arc

a study of the hydrogeological environment of the lishan landslide area using resistivity image profiling and borehole data abstract resistivity image profiling rip surveys was used to develop a lithological and hydrogeological model of the subsurface in the southeastern part of lishan landslide area of central taiwan the bedrock consists of slate in the study area based on rip and rock samples collected from boreholes results three electrical strata are recognized colluvium the shear zone composed of shear gouges and shattered slate and the undisturbed slate formation the steep shear zone with resistivity ranging between 100 260 m plays a crucial role in the local hydrogeological environment because it forms a natural barrier which blocks and retains groundwater flowing down the slope groundwater will brim over the barrier when the water level is high thus the inclined groundwater table remains stable from long term monitoring it strongly indicates that the groundwater recharge is greater than that of discharge therefore the shear zone can provide information about the optimum locations for draining the excess groundwater in situ for slope stability consideration the curved basal surface of the colluvium and the weathered slate can also be discerned from the resistivity variations and boreholes data a series of circular patterns may associate with the main slope failure which migrated upwards from the lower slope

groundwater recharge connectivity between a hills and plains area of western taiwan using water isotopes and electrical conductivity water isotopes d 18o as well as electrical conductivity were employed to clarify hydrological relationships among precipitation stream water and groundwater in the douliou hills dlh of taiwan they are also used to evaluate the importance of groundwater recharge sources in the proximal fan of choshuichi alluvial plain csap which is connected to the eastern extreme of the dlh results indicate that the most important source of groundwater in the dlh comes from summer precipitation in most cases the summer precipitation recharges stream water via base flow based on 18o and ec values groundwater in the proximal fan of the csap can be divided into groundwater from 5 wells nearby the dlh near dhl group and groundwater from 6 wells nearby the choshui stream near cs group semi quantitative results calculated by ternary end member mixing analysis emma for 18o and electrical conductivity values indicate that for the near dlh group precipitation in the csap contributes 40 50 of water to the proximal fan groundwater while dlh groundwater donates 20 55 and choshui stream water 0 29 precipitation in the csap is the most important recharge source dlh groundwater s contribution is more notable in deep groundwater and choshui stream water s contribution decreases with distance from the choshui stream for the near cs group anthropogenic pollution adds ions to the groundwater restricting the effectiveness of the ternary emma approach this study provides new insights into groundwater recharge in the csap it should be applicable to future studies of hill and plains water connectivity in other regions

rapid change in drift of the australian plate records collision with ontong java plateau earth s largest and thickest oceanic plateau the ontong java plateau is currently colliding with the australian plate but it has been difficult to date the start of this momentous event with much accuracy now a team from the university of queensland presents strong evidence for a collision starting about 26 million years ago the dating comes from geochronological data on hotspot volcanoes in the tasman sea east of australia which reveal a link between collision of the plateau with the melanesian arc and motion of the australian plate the timing and brevity of this collisional event correlate well with offsets in hotspot seamount tracks in the pacific including the archetypal hawaiian chain suggesting that immense oceanic plateaus like ontong java can contribute to initiating rapid change in plate boundaries and motions on a global scale geochronological data on hotspot volcanoes in eastern australia are presented which reveal a strong link between collision of the plateau with the melanesian arc and motion of the australian plate the timing and brevity of this collisional event correlate well with offsets in hotspot seamount tracks in the pacific including the archetypal hawaiian chain and thus provide strong evidence that immense oceanic plateaus can contribute to initiating rapid change in plate boundaries and motions on a global scale the subduction of oceanic plateaux which contain extraordinarily thick basaltic crust and are the marine counterparts of continental flood basalt provinces is an important factor in many current models of plate motion1 2 3 4 and provides a potential mechanism for triggering plate reorganization5 to evaluate such models it is essential to decipher the history of the collision between the largest and thickest of the world s oceanic plateaux the ontong java plateau and the australian plate but this has been hindered by poor constraints for the arrival of the plateau at the melanesian trench here we present 40ar 39ar geochronological data on hotspot volcanoes in eastern australian that reveal a strong link between collision of the greenland sized ontong java plateau with the melanesian arc and motion of the australian plate the new ages define a short lived period of reduced northward plate motion between 26 and 23 myr ago coincident with an eastward offset in the contemporaneous tracks of seamount chains in the tasman sea east of australia these features record a brief westward deflection of the australian plate as the plateau entered and choked the melanesian trench 26 myr ago from 23 myr ago australia returned to a rapid northerly trajectory at roughly the same time that southwest directed subduction began along the trobriand trough6 the timing and brevity of this collisional event correlate well with offsets in hotspot seamount tracks on the pacific plate including the archetypal hawaiian chain7 and thus provide strong evidence that immense oceanic plateaux like the ontong java can contribute to initiating rapid change in plate boundaries and motions on a global scale

submarine venting of magmatic volatiles in the eastern manus basin papua new guinea abstract the susu knolls and desmos hydrothermal fields are located in the back arc extensional transform zone of the eastern manus basin in 2006 highly acidic and so4 rich vent fluids were collected at both sites and analyzed for the chemical and isotopic composition of major and trace species fluids exiting the seafloor have measured temperatures from 48 to 215 c and are milky white in appearance due to precipitation of elemental s0 vent fluid concentrations of na k and mg are depleted by as much as 30 relative to seawater but have the same relative abundance in contrast the fluids are highly enriched in dissolved co2 cl sio2 aq fe and al relative to seawater measured ph 25 c ranged from 0 95 to 1 87 and aqueous so4 ranged from 35 to 135 mmol kg the chemical and isotopic composition points to formation via subsurface mixing of seawater with a na k mg and ca free volatile rich magmatic fluid exsolved from subsurface magma bodies during a process analogous to subaerial fumarole discharge estimates of the magmatic end member composition indicate a fluid phase where h2o so2 co2 cl f the hydrogen and oxygen isotopic composition of h2o and carbon isotopic composition of co2 in the vent fluids strongly suggest a contribution of slab derived h2o and co2 to melts generated in the mantle beneath the eastern manus volcanic zone abundant magmatically derived so2 undergoes disproportionation during cooling in upflow zones and contributes abundant acidity so42 and s0 to the venting fluids interaction of these highly acidic fluids with highly altered mineral assemblages in the upflow zone are responsible for extensive aqueous mobilization of sio2 aq fe and al temporal variability in the speciation and abundance of aqueous s species between 1995 and 2006 at the desmos vent field suggests an increase in the relative abundance of so2 in the magmatic end member that has mixed with seawater in the subsurface results of this study constrain processes responsible for the formation of hot spring fluids in magmatically active back arc environments and the resulting chemical exchange between the lithosphere and water column

the itrf96 realization and its associated velocity field this text intends to present and to analyse the quality of the new 1996 edition of the international terrestrial reference system called the itrf96 the itrf96 represents a key step forward in the activity of the iers terrestrial system determinations a new physical combination model has been developed as well as a new stochastic model for the first time the level of accuracy has reached 1 cm or better in position for about 50 of itrf96 stations and 30 of the stations have their velocities determined free of any aditional tectonic plate model assumption with an uncertainty better than 3 mm yr the itrf96 also provides a more complete solution a new software has been developed which makes available the itrf96 full variance covariance matrix whereas this information was restricted to station positions in the previous itrf94 edition moreover the network coverage is clearly the largest set of globally distributed terrestrial space geodesy stations that have ever been computed 521 stations located among 290 sites in addition station velocities are also determined at a very accurate level allowing possible determination of kinematic plate motion models free of any geological assumption

geomorphological processes and their palaeoenvironmental significance at the shum laka cave bamenda western cameroon abstract the climatic environmental history of the shum laka cave western cameroon and its surroundings has been established by means of geomorphological sedimentological and botanical data tied in a well dated stratigraphical sequence since 30 000 yr bp this mountainous area 1 650 2 000 m asl has never been a desert nor a tropical forest temperatures seldom significantly dropped below freezing mountain forest with galleries along the water courses and grassland in between prevailed most of the time a certain evolution can be observed from 31 000 to 20 000 yr bp annual precipitation was initially higher than today and subsequently somewhat lower from 13 000 yr bp onwards humidity and temperatures increased again around 9 000 yr bp they probably reached higher values than today from 9 000 yr bp human activity became very apparent this may have influenced the evolution of the natural landscape and obliterated climatological effects this evolution has been interrupted three times by dryer climatic conditions which each time lasted for only 1 or 2 millennia respectively at 33 000 at 11 000 and at 3 000 yr bp another important less humid episode occurred between 6 070 and 3 180 yr bp finally there is some evidence for a drier period between 8 480 and 7 150 yr bp the climatic evolution established for the shum laka cave confirms and refines former data from the area and is in good agreement with data from barombi mbo and chad

evolution of pyrite trace element compositions from porphyry style and epithermal conditions at the lihir gold deposit implications for ore genesis and mineral processing the lihir also known as ladolam au deposit in papua new guinea is a telescoped ore deposit in which volcanic sector collapse s led to superimposition of shallow level au rich epithermal mineralization upon preexisting but genetically related porphyry style alteration this superimposition created a giant 56 moz au resource but also created complications for ore processing specifically with regard to the difficulties in processing the refractory au rich pyritic ore we have analyzed trace element zonation and composition of pyrite grains using laser ablation inductively coupled plasma mass spectrometry imaging coupled with naocl etching from a subset of spatially and paragenetically constrained pyrite bearing samples from the lienetz orebody pyrite grains belong to either porphyry or epithermal stages or are composite pyrite grains with a multistage history trace element zonation and metal contents of pyrite are unique for each paragenetic event providing insights into the nature of the mineralizing fluids early generations of coarse grained pyrites that formed under higher temperature porphyry style conditions have low trace element contents compared with epithermal stage pyrites except for co ni and se later generations of oscillatory zoned pyrites that formed under lower temperature epithermal conditions are enriched in trace elements such as as mo ag sb au and tl the composite pyrites are relatively coarse grained and display textural and geochemical evidence of modification i e dissolution and reprecipitation they are interpreted to be porphyry stage pyrite grains that have been overgrown by rims of delicate banded epithermal style pyrite enriched in au as and other trace elements the composite pyrite grains are volumetrically dominant in the deep seated anhydrite zone at lienetz because au is concentrated only along the rims of these pyrite grains the pyrite can be subjected to a shorter period of oxidation and leaching to liberate most of the au this is in contrast to areas dominated by high grade epithermal stage mineralization where pyrite grains are as and au rich throughout and thus require longer oxidation and processing time understanding au deportment in telescoped deposits is therefore essential for optimizing mineral processing and can significantly impact the economics of mining complex hybrid ore deposits

interactions between a transform fault and arc volcanism in the bismarck sea papua new guinea 1 we present a new interpretation of the geological evolution of the western branch of the bismarck sea seismic lineation bssl region offshore the northwestern coast of papua new guinea from mapping and interpretation of bathymetry and backscatter data acquired aboard r v kilo moana in 2004 at present the schouten islands parallel the papua new guinea coast but this distribution results from the left lateral displacement of some of these volcanic islands by the bismarck sea seismic lineation the trend of the islands and seamounts was initially aligned n s and then displaced by the bssl wei island lies on a large submarine edifice that may have formed as part of a leaky transform subsequent to forming wei island was bisected and its pieces were displaced 45 km using this distance together with the strike slip rate for the bismarck sea seismic lineation predicted from the north bismarck plate south bismarck plate pole the division occurred approximately 385 000 years ago

modelling the erosional susceptibility of landslide catchments in thick loess chinese variations on a theme by jan de ploey abstract in his 1990 paper catena 17 175 183 jan de ploey proposed a system whereby catchments are viewed as functional units in which geomorphic work results from the combined effects of water erosion and mass movements his measure of erosional susceptibility of catchments es introduced the gravitational potential in addition to the kinetic energy of the eroding agents this modelling of the erosional susceptibility of catchments in terms of energy was being used to explore time dependent variations of es when jan de ploey died also at this time he extended an invitation to the present authors to test and extend his model using our data base on the landslide dominated catchments in the thick loess country of north central china this paper presents a series of new equations expressing variations in es using a data base for over 200 landslides in the loess covered mountainous terrain relative relief up to 1500 m of the lanzhou region of eastern gansu province these equations express the loss of potential energy of the landslide mass in relation to the relative relief and the pressure energy input in the form of rainfall these indices of erosional susceptibility can be used to analyse the differences in response from one catchment to another and through time between the characteristics of vegetation cover including land use hydrology geomechanical behaviour and mechanisms of movement on slopes using certain assumptions on percentage area of catchments affected by mass movement and long term mean annual precipitation in the lanzhou region the es equation suggests an estimate for non clayey materials of about 10 4 m 2 s 2 which is a significantly higher susceptibility value than the mean worldwide value for non clayey materials obtained by de ploey

identification of sources and causes of leakage on a zoned earth dam in northern taiwan hydrological and isotopic evidence abstract seepage through an earth dam body must be regulated as a well planned process if it is not properly managed the abnormal seepage may cause dam failure this study employed stable isotopic and statistical methods to identify the source and cause of an abnormal leakage on the zoned earth dam of the xin shan reservoir located in northern taiwan water samples from the dam area over a 2 a period were collected and analyzed for their stable o and h isotope compositions in addition a 4 a period of hydrological data including rainfall reservoir level well level seepage of filter drainage and leakage were statistically analyzed with a stepwise multiple regression approach both the stable isotopic and hydrological results indicate that the abnormal leakage on the dam shell comes from the filter drainage in the dam the reason for abnormal leakage is due to unexpected and significant precipitation sourced water flowing into the dam s body the dam filter fails to drain out the incoming water sufficiently thus generating the abnormal seepage in addition the defect in the dam filter may also cause the drainage filter to drain off reservoir seepage inadequately therefore it is suggested that checking the filter function and preventing excessive precipitation sourced water from flowing into the dam are the two top priorities for the follow up remedial strategy of the dam

tidal fluctuations in a multi unit coastal aquifer abstract groundwater tidal fluctuations were studied in a multi layered sandy coastal aquifer at dor bay israel 35 m from shore the aquifer at the site is ca 50 m thick and it consists of a superficial phreatic unit underlain by two confined units separated by 1 3 m thick clay layers while the top of the deep unit is at 30 m below sea level the top of the intermediate unit is irregular and it is exposed in a nearby onshore ridge as well as in the bay the phreatic unit showed negligible tidal amplitudes while the two deeper units showed relatively strong amplitudes with those in the deeper unit exceeding those in the shallow unit 4 month average agw asw of 0 72 and 0 53 using li and jiao s 2001 solution we showed that the deeper unit is in hydraulic contact with the sea at 100 400 m from shore which should be due to the termination or breaching of the deeper clay this is probably the result of a buried ridge similar to the submerged calcareous sandstone ridge that exists today in the same location the weaker amplitudes in the intermediate unit are not in accordance with its closer to shore exposure we suggest that this is a consequence of the nearby onshore exposure of this unit which suppresses the tidal signal

environmental significance and hydrochemical processes at a cold alpine basin in the qilian mountains isotope geochemistry of precipitation river water well water and spring water in the babao river basin china during different seasons showed that regional runoff was dominated by precipitation in summer and autumn and by underground water in winter and spring the 18o and d values of precipitation and spring water displayed a clear altitude effect water from the main stream and tributaries displayed a converse altitude effect in the summer wet season the isotopic composition of the various water sources was not well correlated with elevation during the winter dry season the spatial distribution of the stable isotope signals of river water demonstrated the influence of rainfall inputs evaporation and variable flow an end member mixing model used for hydrograph separation indicated that in the summer wet season the babao river water was recharged by precipitation 71 9 spring water 11 7 and well water 16 4 whereas the winter dry season recharge was sourced from spring water 28 2 and well water 71 8

the influence of fish ponds and salinization on groundwater quality in the multi layer coastal aquifer system in israel abstract this study focuses on the impact of surface reservoirs fish ponds on a multi aquifer coastal system and the relation between the aquifer and the sea the study was conducted in an israeli mediterranean coastal aquifer which includes a sandy phreatic unit and two confined calcareous sandstone units the geological description is based on 52 wells from which 33 samples were collected for stable isotope analysis and 25 samples for organic and inorganic parameters hydraulic head and chemical measurements suggest that there is an hydraulic connection between the fish ponds above the aquifer and the phreatic unit whereas the connection with the confined units is very limited the phreatic unit is characterized by a low concentration of oxygen and high concentrations of ammonium and phosphate while the confined units are characterized by higher oxygen and much lower ammonium and phosphate concentrations organic matter fluorescence was found to be a tool to distinguish the contribution of the pond waters whereby a pond water signature characterized by proteinaceous tryptophan like and typical humic matter fluorescence was found in the phreatic aquifer the phreatic unit is also isotopically enriched similar to pond waters with 18o of 1 and d of 4 6 indicating enhanced evaporation of the pond water before infiltration whereas there is a depleted isotopic composition in the confined units 18o 4 3 d 20 4 which are also om poor the phreeqc model was used for quantitative calculation of the effect of pond losses on the different units the dissolved inorganic nitrogen din in the upper unit increases downstream from the ponds toward the sea probably due to organic matter degradation suggesting contribution of din from shallow groundwater flow to the sea 87sr 86sr and mg ca in the brackish and saline groundwater of the lower confined units increase toward seawater value suggesting that the salinization process in the region is connected to seawater intrusion and not to old brine from the underlying cretaceous aquitard

new kinematic models for pacific north america motion from 3 ma to present i evidence for steady motion and biases in the nuvel 1a model we use velocities derived from 2 4 5 years of continuous gps observations at 21 sites on the pacific and north american plates along with a subset of the nuvel 1a data to examine the steadiness of pacific north america motion since 3 16 ma the transfer of baja california to the pacific plate and the magnitude of biases in the nuvel 1a estimate of pacific north america motion we find that pacific north america motion has remained steady since 3 16 ma but at rates significantly faster than predicted by nuvel 1a in the vicinity of baja california our gps derived model and recent seafloor spreading rates in the southern gulf of california both indicate that the nuvel 1a model underestimates pacific north america rates by 4 2 mm yr 1 steady pacific north america motion since 3 16 myr and increasing seafloor spreading rates since 3 58 myr in the gulf of california imply that pacific north america motion was partitioned between seafloor spreading in the gulf of california and decelerating slip along faults in or offshore from the baja peninsula

effects of source model variations on coulomb stress analyses of a multi fault intraplate earthquake sequence abstract fault models are quickly produced and iteratively improved over weeks to years following a major earthquake to characterise the dynamics of rupture evaluate the role of stress transfer and contribute to earthquake forecasting we model coulomb stress transfer cfs between the largest foreshock mw 5 4 1 year prior to first mainshock and three mw 6 1 to 6 5 earthquakes that occurred in a 12 hour period on january 22 1988 in central australia tennant creek earthquake sequence to investigate the role of static stress transfer in earthquake triggering relative to progressive source model development the effects of fault model variance are studied using cfs modelling of five different fault source model sequences 27 total models using different inputs from seismic and geospatial data some initial models do not yield positive cfs changes proximal to hypocentres but in all models preceding earthquakes generate positive cfs 0 1 bar on 10 to 30 of the forthcoming receiver fault rupture areas the most refined and data integrative model reveals cfs 0 7 to 13 bars within 2 km of impending hypocentres and large 30 to 99 areas of positive cfs when compared to global compilations of threshold cfs prior to impending ruptures average 3 71 bar median 1 bar this suggests that coulomb stress change theory adequately explains the tennant creek rupture sequence in the most refined model earthquake inter event times decrease as cfs increases suggesting that higher stress magnitudes may have more rapidly within hours triggered successive events thus accounting for some temporal aspects of this sequence cfs analyses provide a useful framework for understanding the spatiotemporal aspects of some intraplate earthquakes the progressive refinement of source models using emergent data may reduce epistemic uncertainties in the role of stress transfer that result from different model inputs approaches and results

gps and seismological constraints on active tectonics and arc continent collision in papua new guinea implications for mechanics of microplate rotations in a plate boundary zone 1 the island of new guinea is located within the deforming zone between the pacific and australian plates that converge obliquely at 110 mm yr new guinea has been fragmented into a complex array of microplates some of which rotate rapidly about nearby vertical axes we present velocities from a network of 38 global positioning system gps sites spanning much of the nation of papua new guinea png the gps derived velocities are used to explain the kinematics of major tectonic blocks in the region and the nature of strain accumulation on major faults in png we simultaneously invert gps velocities earthquake slip vectors on faults and transform orientations in the woodlark basin for the poles of rotation of the tectonic blocks and the degree of elastic strain accumulation on faults in the region the data are best explained by six distinct tectonic blocks the australian pacific south bismarck north bismarck and woodlark plates and a previously unrecognized new guinea highlands block significant portions of the ramu markham fault appear to be locked which has implications for seismic hazard determination in the markham valley region we also propose that rapid clockwise rotation of the south bismarck plate is controlled by edge forces initiated by the collision between the finisterre arc and the new guinea highlands

evidence for active subduction at the new guinea trench 1 recent seismic tomography imaging shows clear evidence for southwestward subduction along the entire length of the new guinea trench ngt in indonesia and papua new guinea viewed in conjunction with the occurrence of large mw 7 thrust earthquakes that are known to have occurred on the trench this confirms conclusions of earlier studies that the ngt is an active inter plate boundary the 650 km long slab is visible to a depth of about 300 km and subducts with a dip angle that varies from 30 at 136 e to 10 at 143 e the improved clarity of the seismic tomography in this region stems from the use of a more accurate data set of p and s wave arrival times and hypocentral locations

geochemistry of hydrothermal fluids from the pacmanus northeast pual and vienna woods hydrothermal fields manus basin papua new guinea abstract processes controlling the composition of seafloor hydrothermal fluids in silicic back arc or near arc crustal settings remain poorly constrained despite growing evidence for extensive magmatic hydrothermal activity in such environments we conducted a survey of vent fluid compositions from two contrasting sites in the manus back arc basin papua new guinea to examine the influence of variations in host rock composition and magmatic inputs both a function of arc proximity on hydrothermal fluid chemistry fluid samples were collected from felsic hosted hydrothermal vent fields located on pual ridge pacmanus and northeast ne pual near the active new britain arc and a basalt hosted vent field vienna woods located farther from the arc on the manus spreading center vienna woods fluids were characterized by relatively uniform endmember temperatures 273 285 c and major element compositions low dissolved co 2 concentrations 4 4 mmol kg and high measured ph 4 2 4 9 at 25 c temperatures and compositions were highly variable at pacmanus ne pual and a large newly discovered vent area fenway was observed to be vigorously venting boiling 358 c fluid all pacmanus fluids are characterized by negative d h 2 o values in contrast to positive values at vienna woods suggesting substantial magmatic water input to circulating fluids at pual ridge low measured ph 25 c values 2 6 2 7 high endmember co 2 up to 274 mmol kg and negative 34 s h 2 s values down to 2 7 in some vent fluids are also consistent with degassing of acid volatile species from evolved magma dissolved co 2 at pacmanus is more enriched in 13 c 4 1 to 2 3 than vienna woods 5 2 to 5 7 suggesting a contribution of slab derived carbon the mobile elements e g li k rb cs and b are also greatly enriched in pacmanus fluids reflecting increased abundances in the crust there relative to the manus spreading center variations in alkali and dissolved gas abundances with cl at pacmanus and ne pual suggest that phase separation has affected fluid chemistry despite the low temperatures of many vents in further contrast to vienna woods substantial modification of pacmanus ne pual fluids has taken place as a result of seawater ingress into the upflow zone consistently high measured mg concentrations as well as trends of increasingly non conservative so 4 behavior decreasing endmember ca cl and sr cl ratios with increased mg indicate extensive subsurface anhydrite deposition is occurring as a result of subsurface seawater entrainment decreased ph and endmember fe mn ratios in higher mg fluids indicate that the associated mixing cooling gives rise to sulfide deposition and secondary acidity production several low temperature 80 c fluids at pacmanus ne pual also show evidence for anhydrite dissolution and water rock interaction fixation of b subsequent to seawater entrainment hence the evolution of fluid compositions at pual ridge reflects the cumulative effects of water rock interaction admixing and reaction of fluids exsolved from silicic magma phase separation segregation and seawater ingress into upflow zones

assessment of the interrill and rill contributions to total soil loss from an upland field plot abstract govers g and poesen j 1988 assessment of the interrill and rill contributions to total soil loss from an upland field plot geomorphology 1 343 354 erosion measurements were carried out on an upland field plot in the loam region of belgium the sediment being detached by splash on interrill areas is transported to the channel system mainly by interrill wash over the entire 7500 m field plot rill and gully erosion is more important than interrill erosion however the relative importance of interrill erosion varies in time and in space due to changes of the interrill surface characteristics and the activation of sidewall and gullying processes in the channel network these factors should be taken into account in a realistic rill interrill erosion model introduction at present few available field data permit the separation of rill and or gully and interrill contributions to sediment removal from arable land the scarcity of this type of field data is a major factor inhibiting the validation and fur ther development of recently developed physi cally based models describing upland erosion by water e g foster 1982 rose et al 1983 knowledge of the contribution of rill and inter rill processes to total soil loss has also some practical interest if the ratio between rill and interrill erosion were known even approxi mately it would be possible to obtain a quick estimate of total erosion by making a volumet ric recording of rill patterns plot measure

use of stable water isotopes to assess sources and influences of slope groundwater on slope failure this study employs stable oxygen and hydrogen isotopes as natural tracers to assess the headwater of a landslide next to a drainage divide and the importance of the slope s headwater in the study area the study is undertaken near wu she township in the mountains of central taiwan because a reservoir is located on the other side of the divide this study evaluates the relationship between the reservoir water and headwater of the landslide as well over a 1 year period water samples from september 2008 to september 2009 including local precipitation lp wu she reservoir s water wsrw slope groundwater sgw upper reach stream water ustw and down reach stream water dstw were analysed for deuterium d and oxygen 18o stable isotopes results indicate that wsrw is the predominant component in sgw approximately 70 of sgw originates from wsrw and 30 from lp based on a two end member mass balance mixing model for 18o the similar two end member mixing model is also employed to assess the contributions of ustw and sgw to dstw model results indicate that sgw is the major source of dstw with a contribution of about 67 accordingly about 47 of dstw sources from the wsrw in short owing to reservoir leakage wsrw contributes the greater part of both sgw and dstw plentiful wsrw in sgw threatens the stability of the slope in the divide area to avoid subsequent continuous slope failure necessary mitigation steps are required copyright 2011 john wiley sons ltd

science society and the coastal groundwater squeeze coastal zones encompass the complex interface between land and sea understanding how water and solutes move within and across this interface is essential for managing resources for society the increasingly dense human occupation of coastal zones disrupts natural groundwater flow patterns and degrades freshwater resources by both overuse and pollution this pressure results in a coastal groundwater squeeze where the thin veneers of potable freshwater are threatened by contaminant sources at the land surface and saline groundwater at depth scientific advances in the field of coastal hydrogeology have enabled responsible management of water resources and protection of important ecosystems to address the problems of the future we must continue to make scientific advances and groundwater hydrology needs to be firmly embedded in integrated coastal zone management this will require interdisciplinary scientific collaboration open communication between scientists and the public and strong partnerships with policymakers

motion of the south bismarck plate papua new guinea the absolute motion of the south bismarck plate was first estimated by tregoning et al 1998 from three site velocities estimated from global positioning system gps observations we report an improved estimate of the euler vector for this plate using site velocities derived from new gps data which include the velocity of a site located 25 km from the pole of rotation the gps velocities of madang witu jacquinot bay and finschafen can be modelled to within 3 mm yr using a single pole of rotation located at 6 75 s 147 98 e with a clockwise rotation rate of 8 11 my the known tectonic features and available geophysical data surrounding the south bismarck plate can also be explained by a rotation of the south bismarck plate about this pole

subaqueous cryptodome eruption hydrothermal activity and related seafloor morphologies on the andesitic north su volcano abstract north su is a double peaked active andesite submarine volcano located in the eastern manus basin of the bismarck sea that reaches a depth of 1154 m it hosts a vigorous and varied hydrothermal system with black and white smoker vents along with several areas of diffuse venting and deposits of native sulfur geologic mapping based on rov observations from 2006 and 2011 combined with morphologic features identified from repeated bathymetric surveys in 2002 and 2011 documents the emplacement of a volcanic cryptodome between 2006 and 2011 we use our observations and rock analyses to interpret an eruption scenario where highly viscous crystal rich andesitic magma erupted slowly into the water saturated gravel dominated slope of north su an intense fragmentation process produced abundant blocky clasts of a heterogeneous magma olivine crystals within a rhyolitic groundmass that only rarely breached through the clastic cover onto the seafloor phreatic and phreatomagmatic explosions beneath the seafloor cause mixing of juvenile and pre existing lithic clasts and produce a volcaniclastic deposit this volcaniclastic deposit consists of blocky non altered clasts next variably 1 100 altered clasts hydrothermal precipitates and crystal fragments the usually applied parameters to identify juvenile subaqueous lava fragments i e fluidal shape or chilled margin were not applicable to distinguish between pre existing non altered clasts and juvenile clasts this deposit is updomed during further injection of magma and mechanical disruption gas propelled turbulent clast recycling causes clasts to develop variably rounded shapes an abundance of blocky clasts and the lack of clasts typical for the contact of liquid lava with water is interpreted to be the result of a cooled high viscosity crystal rich magma that failed as a brittle solid upon stress the high viscosity allows the lava to form blocky and short lobes the pervasive volcaniclastic cover on north su is partly cemented by hydrothermal precipitates these hydrothermally cemented breccias crusts and single pillars show that hydrothermal circulation through a thick layer of volcaniclastic deposits can temporarily increase slope stability through precipitation and cementation

a new gps velocity field for the pacific plate part 1 constraints on plate motion intraplate deformation and the viscosity of pacific basin asthenosphere

global plate velocities from the global positioning system we have analyzed 204 days of global positioning system gps data from the global gps network spanning january 1991 through march 1996 on the basis of these gps coordinate solutions we have estimated velocities for 38 sites mostly located on the interiors of the africa antarctica australia eurasia nazca north america pacific and south america plates the uncertainties of the horizontal velocity components range from 1 2 to 5 0 mm yr with the exception of sites on the pacific and nazca plates the gps velocities agree with absolute plate model predictions within 95 confidence for most of the sites in north america antarctica and eurasia the agreement is better than 2 mm yr we find no persuasive evidence for significant vertical motions 3 standard deviations except at four sites three of these four were sites constrained to geodetic reference frame velocities the gps velocities were then used to estimate angular velocities for eight tectonic plates absolute angular velocities derived from the gps data agree with the no net rotation nnr nuvel 1a model within 95 confidence except for the pacific plate our pole of rotation for the pacific plate lies 11 5 west of the nnr nuvel 1a pole with an angular speed 10 faster our relative angular velocities agree with nuvel 1a except for some involving the pacific plate while our pacific north america angular velocity differs significantly from nuvel 1a our model and nuvel 1a predict very small differences in relative motion along the pacific north america plate boundary itself our pacific australia and pacific eurasia angular velocities are significantly faster than nuvel 1a predicting more rapid convergence at these two plate boundaries along the east pacific rise our pacific nazca angular velocity agrees in both rate and azimuth with nuvel 1a

stable isotopic characteristic of taiwan s precipitation a case study of western pacific monsoon region abstract the stable oxygen and hydrogen isotopic features of precipitation in taiwan an island located at the western pacific monsoon area are presented from nearly 3 500 samples collected during the past decade for 20 stations results demonstrate that moisture sources from diverse air masses with different isotopic signals are the main parameter in controlling the precipitation s isotope characteristics the air mass from polar continental pc region contributes the precipitation with high deuterium excess values up to 23 and relatively enriched isotope compositions e g 3 2 for 18o during the winter with prevailing northeasterly monsoon by contrast air masses from equatorial maritime em and tropical maritime tm supply the precipitation with low deuterium excess values as low as about 7 and more depleted isotope values e g 8 9 and 6 0 for 18o of tm and em respectively during the summer with prevailing southwesterly monsoon thus seasonal differences in terms of 18o d and deuterium excess values are primarily influenced by the interactions among various precipitation sources while these various air masses travel through taiwan secondary evaporation effects further modify the isotope characteristics of the inland precipitation such as raindrop evaporation reduces the deuterium excess of winter precipitation and moisture recycling increases the deuterium excess of summer precipitation the semi quantitative estimations in terms of evaluation for changes in the deuterium excess suggest that the raindrop evaporation fractions for winter precipitation range 7 to 15 and the proportions of recycling moisture in summer precipitation are less than 5 additionally the isotopic altitude gradient in terms of 18o for summer precipitation is 0 22 100 m greater than 0 17 100 m of winter precipitation the greater isotopic gradient in summer can be attributed to a higher temperature vs altitude gradient relative to winter the observed spatial and seasonal stable isotopic characteristics in taiwan s precipitation not only contribute valuable information for regional monsoon research crossing the continent ocean interface of east asia but also can serve as very useful database for local water resources management

using oxygen hydrogen and tritium isotopes to assess pond water s contribution to groundwater and local precipitation in the pediment tableland areas of northwestern taiwan summary environmental isotopes including stable hydrogen and oxygen and radioactive tritium isotopes are employed to assess groundwater sources in the taoyuan chungli tableland tct northwestern taiwan we evaluate the contribution to groundwater resources of copious ponds distributed throughout the tct results indicate that both precipitation and pond water are the end sources of proximal shallow groundwater p sgw in the tct recharge of p sgw to deep groundwater in the proximal fan region p dgw is obvious because values of p dgw are similar to those of p sgw and no barrier restricts p sgw entering p dgw however the infiltration of precipitation or pond water to shallow groundwater in the mid and distal fan regions md sgw is restricted somewhere because of impermeable confining layers overlying the md sgw in addition apart from the upstream recharge of the p sgw md sgw overlying the deep groundwater in the mid distal fan regions md dgw contributes to md dgw through barrier layer leakage between md sgw and md dgw overall values indicate that pond sourced moisture accounts for about 6 of precipitation in the studied tableland this contribution fraction is larger than that in the western plains or reservoir catchments of taiwan the calculations also indicate that precipitation and pond water respectively contribute 51 and 49 to p sgw among the 49 contribution from pond water to p sgw 46 is from direct infiltration and the remaining 3 is via the evaporation precipitation process the fractional results clearly indicate that pond water is a vital source of both local precipitation and groundwater

initial results from wing the continuous gps network in the western pacific area to investigate tectonic deformation in the western pacific a continuous gps tracking network has been established and named the western pacific integrated network of gps wing between 1995 and march 1997 we establised ten new sites data for the period july 1995 to october 1996 were analyzed together with data from international gps service for geodynamics igs global sites to estimate daily coordinates a fiducial free approach was used to obtain the most accurate baseline estimates to fix the estimated coordinates to the terrestrial reference frame the tsukuba igs site is assumed to be moving westward relative to the stable eurasian continent at 2 cm yr according to heki s 1996 estimate we find that 1 velocities of sites well within oceanic plates are in good agreement with rigid plate motion models 2 sites close to plate boundaries are all affected by the deformation at those boundaries among which back arc rifting spreading is clearly visible at the mariana and okinawa troughs 3 sites in eastern asia are moving east to east southeast relative to the stable eurasian continent suggesting long distance effects of the northward collision of india with asia

controls on back arc crustal accretion insights from the lau manus and mariana basins abstract together the lau manus and mariana basins encompass a broad range of conditions of back arc basin development marine surveys have determined the tectonic setting and reconnaissance scale geophysical and geochemical properties of the extension axes in these basins we review these data to examine crustal accretion characteristics in the back arc setting in each basin magmatism is enhanced in spreading centres near the arc volcanic front but decreases becoming deficient in axes further from the arc in the lau and manus basins the axes extend far behind the arc and develop typical mid ocean ridge mor like characteristics we propose that these variations are controlled by the subducting slab which shapes composition and flow within the mantle wedge water released from the slab lowers the mantle solidus and increases in concentration toward the volcanic arc spreading centres near the arc advect the hydrated mantle material enhancing melt production slab induced flow carries melt depleted mantle material back beneath the basin where it mixes with ambient mantle spreading centres further from the arc advect this mantle mixture and produce thinner than normal crust far from the arc spreading centres advect essentially mid ocean ridge basalt morb source mantle and their characteristics are mor like thus in addition to spreading rate effects on mantle melting that predominate at mors in back arc basins the subducting slab introduces additional systematic effects

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

assessing groundwater sources and their association with reservoir water using stable hydrogen and oxygen isotopes a case study of the taipei basin northern taiwan the purpose of this isotopic study is to identify groundwater sources in taipei basin tpb and their association with water of the feitsui reservoir ftr northern taiwan to this end water samples including precipitation catchment surface water tpb groundwater ftr water and catchment surface water of ftr were analyzed for stable hydrogen and oxygen isotope compositions 2h and 18o isotopic results support previous reports that dahan stream and xindian stream waters are the major recharge sources of tpb groundwater these recharge regions are located along the southern border of the tpb further isotopic evidence finds that water from the southern hills catchment area of the tpb also recharges tpb groundwater and most importantly indicates that tpb groundwater is highly related to ftr water however for caution s sake future comprehensive study is needed to confirm hydrological connectivity between the ftr water and tpb groundwater

erosion processes in a dune landscape along the dutch coast abstract the landscape of the dunes along the dutch coast is the result of the interaction of biological and geomorphological processes where the latter prevail new landforms are created blowouts by wind erosion and rills and accumulation footslopes by overland flow spatial extent and rate of the erosion processes have been assessed by mapping and by measuring it appears that dune sand is either sensitive to erosion by wind or erosion by water depending on the presence of organic material clean yellow sand is cohesionless and easily blown away but has no surface runoff grey sand containing organic matter on the other hand will resist wind erosion but it is waterrepellent and will be washed from slopes when rain follows a period of dry weather once the grey surface sand is removed from the surfaces by water erosion wind erosion begins in the underlying yellow sand present day geomorphological processes reshape the slopes of the original parabolic dunes wind is particularly active in summit areas where new blowouts are formed whereasoverland flow creates concave south exposed slopes the stepped surface of the north exposed slopes is due to mass movements following rabbit activity

groundwater seawater interactions off the coast of southern taiwan evidence from environmental isotopes abstract we have conducted detailed hydrochemical surveys off the pingtung plain coast sw taiwan using environmental isotope compositions d 18 o 13 c dic tritium and 14 c as the main tracers to investigate groundwater seawater interactions in the region the 18 o values of seawater in this area show significant variability with heavy isotope enrichment relatively to groundwater the d and 18 o data also confirmed that submarine groundwater discharge sgd originated from meteoric water and were mixed with seawater due to an overdraft of groundwater seawater has intruded inwardly through the offshore outcrops for both the unconfined and confined aquifers at a depth of 300 m however 18 o depleted layer is found along deep parts of kaoping canyon this result provides evidence for sgd in this region this phenomenon is also reflected in depleted 13 c dic and lower 14 c values in deep canyon water than in adjacent seawater and indicating that the discharge zone extends over a considerable distance to the offshore area 25 km based on these three parameters 18 o 13 c dic and 14 c we used two end member mixing model to estimate that fresh submarine groundwater constitute the submarine fresh groundwater contributed about 3 and the estimated submarine fresh groundwater discharge was calculated as 4 5 10 9 m 3 per year this result is comparable with groundwater annual loss in the pingtung plain as documented by the isotopic composition of the collected samples detailed results show that sgd in the pingtung coastal zone raises a potential environmental concern and provides implication for the management of groundwater resource in the region

geomorphology and natural hazards abstract natural hazards research was initiated in the 1960 s by gilbert white and his students who promulgated a research paradigm that involved assessing risk from a natural event identifying adjustments to cope with the hazard determining people s perception of the event defining the process by which people choose adjustments and estimating the effects of public policy on the choice process studies of the physical system played an important role in early research but criticismsof the paradigm resulted in a shift to a prominence of social science geomorphologists are working to fill gaps in knowledge of the physical aspects of individual hazards but use of the information by social scientists will only occur if information is presented in a format that is useful to them one format involves identifying the hazard according to seven physical parameters established by white and his colleagues magnitude frequency duration areal extent speed of onset spatial dispersion and temporal spacing geomorphic hazards are regarded as related to landscape changes that affect human systems the processes that produce the changes are rarely geomorphic in nature but are better regarded as atmospheric or hydrologic an examination of geomorphic hazards in four fields soil erosion mass movement coastal erosion and fluvial erosion demonstrates that advances in those fields may be evaluated in terms of the seven parameters geomorphologists have contributed to hazard research by focusing on the dynamics of the landforms the prediction of occurence the determination of spatial and temporal characteristics the impact of physical characteristics on people s perception and the impact of physical characteristics on adjustment formulation opportunities for geomorphologists to improve our understanding of geomorphic hazards include research into the characteristics of the events particularly with respect to predicting the occurence and increased evaluation of the impact of human activities on natural systems

a time varying 3 d displacement model of the 5 9 year westward motion and its applications for the global navigation satellite system positions and velocities

crustal deformation during 1994 1998 due to oblique continental collision in the central southern alps new zealand and implications for seismic potential of the alpine fault the positions of 115 ground marks in a 150 100 km area of oblique continental collision in the central southern alps new zealand have been measured by global positioning system gps two to four times between 1994 and 1998 contemporary velocity and strain rate fields derived from these observations are largely invariant along the northeasterly strike of the mountains and alpine fault across strike more than 60 of the strain occurs within a band from 5 km nw to 20 km se of the alpine fault but significant strain continues at least a further 60 km se to near the edge of the southern alps foothills projections of the fault parallel and fault normal components of velocity onto an alpine faultnormal profile show that about 85 of the nuvel 1a model relative plate motion is observed within the gps network the surface displacements in the high strain rate region are well fit by a model in which stable slip or shearing is occurring at 50 70 of the relative plate rate in a region deeper than about 5 8 km on the down dip extension of the se dipping alpine fault material shallower than this is behaving elastically and thus storing elastic strain in the region of the alpine fault the longer wavelength displacements can be modeled either as distributed deformation beneath the southern alps or by localization of elastic strain around the upper end of a discrete nw dipping fault or shear zone that is slipping stably below about 30 km depth and would outcrop near the se boundary of the mountains if extrapolated to the surface strain determined from a small scale survey network crossing the alpine fault indicates no significant near surface aseismic fault slip on the central alpine fault over the past 25 years our results are consistent with independent geological evidence that the central section of the alpine fault is capable of producing large to great earthquakes

using hydrogen oxygen and tritium isotopes to identify the hydrological factors contributing to landslides in a mountainous area central taiwan over a 1 year period 343 samples including precipitation creek pond and groundwater were collected from june 2003 to may 2004 analyses were performed for stable oxygen and hydrogen isotope compositions selected samples were also analyzed for tritium the goal was to identify possible hydrologic factors contributing to a severe landslide in the li shan area central taiwan the isotope characteristics indicate that groundwater from fu shou shan farm located up slope from the landslide area is a major source for slope groundwater in addition to precipitation the groundwater is mainly recharged by pond water at fu shou shan farm according to the calculation of a two end member equation with 18o the contribution of farm groundwater to slope groundwater is significantly higher than that of precipitation up to a factor of five the estimated drainage efficiency of the existing system is only 23 draining off the slope groundwater in the up slope region to decrease farm groundwater flow into the slope area is a feasible strategy to effectively reduce the risk of landslide

plate motions slab dynamics and back arc deformation back arc extension or compression is often related to a particular behavior of the slab dip change and or forward backward migration with respect to the upper plate slabs act either passively when anchored in the deep mantle whereas back arc deformation accommodates the backward or forward motion of the upper plate with respect to the trench or actively when slab pull increasing with slab age forces the trench to rollback in addition to these two mechanisms i e slab anchor and slab rollback numerous observations support the existence of dynamic mantle flow that can exert an overpressure on one side of the slab causing its forward or rearward migration with respect to the arc based on a compilation of upper plate absolute motion trench absolute motion back arc deformation rate upper plate strain regime and slab age for all oceanic subduction zones excluding any kind of collision with continents arcs or plateaus we have examined how the combined effects of these parameters can account for the observed back arc deformations our main results are 1 a global correlation exists between upper plate absolute motion and back arc deformation i e back arc extension when upper plate retreats and vice versa 2 there are as many advancing trenches as retreating ones with trench motion globally limited to 50 mm y 1 furthermore there is no positive correlation between trench retreat and slab age and 3 upper plate absolute motion often fails to explain the back arc deformation rates and the trench motions observed at several subduction zones as tonga new hebrides sandwich or ryukyu we propose that the trench migration of these subduction zones are on the influence of mantle flows we conclude that spontaneous trench rollback related to slab pull is negligible with respect to upper plate motion back arc deformation regime is mostly controlled by the upper plate absolute motion relative to a partly anchored slab trench motion is limited to 50 mm y 1 even if locally mantle flows force slab to move

using h and o isotopic data for estimating the relative contributions of rainy and dry season precipitation to groundwater example from cheju island korea abstract a comparison of deuterium excess or d values of precipitation and groundwater at cheju island korea indicates that unlike in many temperate climates precipitation during the whole year contributes to groundwater recharge this in turn suggests that evapotranspiration effects are minimal consistent with the fact that the island contains highly permeable volcanic rocks overlain by thin soils this hypothesis is contrary to current water budget models that ascribe a significant role to evapotranspiration processes three coastal springs and several streams and ponds throughout the island have enriched 18 o and d values that plot off the local meteoric water line and have relatively high cl concentrations this relationship is suggestive of seawater mixing for the coastal springs and evaporation for the streams and ponds this database thus provides a useful means for evaluation of groundwater resources of the island

geologic setting of pacmanus hydrothermal area high resolution mapping and in situ observations abstract this study presents a systematic analysis and interpretation of autonomous underwater vehicle based microbathymetry combined with remotely operated vehicle rov video recordings rock analyses and temperature measurements within the pacmanus hydrothermal area located on pual ridge in the bismarck sea of eastern manus basin the data obtained during research cruise magellan 06 and so 216 provides a framework for understanding the relationship between the volcanism tectonism and hydrothermal activity pacmanus is a submarine felsic vocanically hosted hydrothermal area that hosts multiple vent fields located within several hundred meters of one another but with different fluid chemistries vent temperatures and morphologies the total area of hydrothermal activity is estimated to be 20 279 m2 the microbathymetry maps combined with the rov video observations allow for precise high resolution mapping estimates of the areal extents of hydrothermal activity we find the distribution of hydrothermal fields in the pacmanus area is primarily controlled by volcanic features that include lava domes thick and massive blocky lava flows breccias and feeder dykes spatial variation in the permeability of local volcanic facies appears to control the distribution of venting within a field we define a three stage chronological sequence for the volcanic evolution of the pacmanus based on lava flow morphology sediment cover and lava sio2 concentration in stage 1 sparsely to moderately porphyritic dacite lavas 68 69 8 wt sio2 erupted to form domes or cryptodomes in stage 2 aphyric lava with slightly lower sio2 concentrations 67 2 67 9 wt sio2 formed jumbled and pillowed lava flows in the most recent phase stage 3 massive blocky lavas with 69 to 72 5 wt sio2 were erupted through multiple vents constructing a volcanic ridge identified as the pacmanus neovolcanic zone the transition between these stages may be gradual and related to progressive heating of a silicic magma following a recharge event of hot mantle derived melts

the groundwater recharge regime of some slightly metamorphosed neoproterozoic sedimentary rocks an application of natural environmental tracers isotope data of precipitation and groundwater in parts of the voltaian basin in northern ghana were used to explain the groundwater recharge regime in the area groundwater recharge is an important parameter in the development of a decision support system for the management and efficient utilization of groundwater resources in the area it is therefore important to establish the processes and sources of groundwater recharge 18o and 2h data for local precipitation suggest enrichment relative to the global meteoric water line gmwl and indicate that precipitation takes place at a relative humidity less than 100 the groundwater data plot on an evaporation line with a slope of 5 suggesting a high degree of evaporative enrichment of the precipitation in the process of vertical infiltration and percolation through the unsaturated zone into the saturated zone this finding is consistent with the observation of high evapotranspiration rates in the area and ties in with the fact that significant clay fraction in the unsaturated zone limits vertical percolation and thus exposes the percolating rainwater to the effects of high temperatures and low humidities resulting in high evapotranspiration rates groundwater recharge estimates from the chloride mass balance cmb method suggest recharge in the range of 1 8 32 of the annual average precipitation in the form of rainfall the highest rates are associated with areas where open wells encourage significant amount of groundwater recharge from precipitation in the area in the northern parts of the study area groundwater recharge is lower than 12 the recharge so computed through the application of the cmb methodology takes on a spatial distribution akin to the converse of the spatial pattern of both 18o and 2h in the area as such the locations of the highest recharge are associated with the most depleted values of the two isotopes this observation is consistent with the assertion that low vertical hydraulic conductivities slow down vertical percolation of precipitation down to the groundwater water the percolating precipitation water thus gets enriched in the heavier isotopes through high evapotranspiration rates at the same time the amount of water that finally reaches the water table is considerably reduced copyright 2013 john wiley sons ltd

a hydrochemical study of hungtsaiping landslide area nantou taiwan the hungtsaiping landslide was triggered by the chi chi earthquake mw 7 6 which occurred on september 20 1999 near the town of chi chi in nantou county in central taiwan the purpose of this study is to understand the relationship between geochemical characteristics and the landslide in the hungtsaiping area water samples were collected from springs creeks ponds groundwater and the yonglu stream once every month from may 2008 to may 2009 oxygen and hydrogen stable isotopes ionic concentrations electrical conductivities and ph values were analyzed the results show that the ionic concentrations display a significant spatial variation for instance calcium and magnesium bicarbonate rich water was found on the top and the middle part of the slope in addition sodium bicarbonate rich water with exceptionally high sulfate concentration was found on the foot of the slope the sulfate content decreased with increasing elevation along the slope finally a conceptual model was established by summarizing the hydrogeochemical analyses after a scientific understanding of the mechanism of the hungtsaiping landslide all of the analytical information can be integrated for hazard prevention in the future

using stable hydrogen and oxygen isotopes to reveal monsoonal and related hydrological effects on meteoric water in the western pacific monsoon region a case study of the ilan region northeastern taiwan abstract this study analyzes the isotopic compositions 2h and 18o of meteoric waters including precipitation and stream water to reveal what major hydrological processes affect the hydrological regime of the ilan region northeastern taiwan the isotopic results indicate monsoonal flows as the fundamental factors affecting studied precipitation and stream water summer precipitation sourced from southerly air mass exhibits lower and deuterium excess de values than winter precipitation sourced from northerly air masses the 18o and de values are respectively 7 7 and 8 for summer precipitation and 3 3 and 24 for winter precipitation furthermore semi quantitative estimations using de evidence indicate that summertime southerly air masses generally contribute more to stream water than wintertime northerly air mass flows approximately 54 vs 46 however the contribution fractions are controlled by the orientation of catchments to the windward side of respective monsoonal flows northern catchments located on the windward side of southerly air masses receive about 60 of their water from precipitation condensed from the southerly air masses and 40 from the northerly air masses by comparison southern catchments located on the windward side of northerly air masses receive about 59 of their water from northerly air masses and 41 from southerly air masses additionally catchment effect induced from value is notable in stream basins with high elevations but this is not related to catchment sizes besides this altitude effect which is determined in terms of 18o values was derived using data from four precipitation stations of northern taiwan it ranges from 2 5 to 3 0 per 100 m depending on the season moreover based on the de evidence secondary evaporation effects are apparent with moisture recycling influencing inland summer precipitation and raindrop evaporation influencing inland winter precipitation

motion and rigidity of the pacific plate and implications for plate boundary deformation 1 using up to 11 years of data from a global network of global positioning system gps stations including 12 stations well distributed across the pacific plate we derive present day euler vectors for the pacific plate more precisely than has previously been possible from space geodetic data after rejecting on statistical grounds the velocity of one station on each of the pacific and north american plates we find that the quality of fit of the horizontal velocities of 11 pacific plate pa stations to the best fitting pa euler vector is similar to the fit of 11 australian plate au velocities to the au euler vector and 20 better than the fit of nine north american plate na velocities to the na euler vector the velocities of stations on the pacific and australian plates each fit a rigid plate model with an rms residual of 0 4 mm yr while the north american velocities fit a rigid plate model with an rms velocity of 0 6 mm yr our best fitting pa au relative euler vector is located 170 km southeast of the nuvel 1a pole but is not significantly different at the 95 confidence level it is also close 70 km in position and 3 in rate to a pole derived from transform faults identified from satellite altimetry suggesting that the vector has not changed significantly over the past 3 myr our relative euler vector is also consistent with all known geological and geodetic evidence concerning the au pa plate boundary through new zealand the gps sites offshore of southern california are presently moving 4 5 1 mm yr relative to predicted pacific velocity with their residual velocities in approximately the opposite direction to pa na relative motion likewise the easternmost sites in south island new zealand are moving 3 1 mm yr relative to predicted pacific velocity with the residuals in approximately the opposite direction to pa au relative motion these velocity residuals are in the same sense as predicted by elastic strain accumulation on known plate boundary faults but are of a significantly higher magnitude in both southern california and new zealand implying that the plate boundary zones in both regions are wider than previously believed index terms 1206 geodesy and gravity crustal movements interplate 8155 1208 geodesy and gravity crustal movements intraplate 8110 1243 geodesy and gravity space geodetic surveys 8158 tectonophysics evolution of the earth plate motions present and recent 3040 8159 tectonophysics evolution of the earth rheology crust and lithosphere keywords pacific plate motion plate rigidity plate boundary deformation

plate motion and crustal deformation estimated with geodetic data from the global positioning system we use geodetic data taken over four years with the global positioning system gps to estimate 1 motion between six major plates and 2 motion relative to these plates of ten sites in plate boundary zones the degree of consistency between geodetic velocities and rigid plates requires the one dimensional standard errors in horizontal velocities to be 2 mm yr each of the 15 angular velocities describing motion between plate pairs that we estimate with gps differs insignificantly from the corresponding angular velocity in global plate motion model nuvel 1a which averages motion over the past 3 m y the motion of the pacific plate relative to both the eurasian and north american plates is observed to be faster than predicted by nuvel 1a supporting the inference from very long baseline interferometry vlbi that motion of the pacific plate has sped up over the past few m y the eurasia north america pole of rotation is estimated to be north of nuvel 1a consistent with the independent hypothesis that the pole has recently migrated northward across northeast asia to near the lena river delta victoria which lies above the main thrust at the cascadia subduction zone moves relative to the interior of the overriding plate at 30 of the velocity of the subducting plate reinforcing the conclusion that the thrust there is locked beneath the continental shelf and slope

no net rotation model of current plate velocities incorporating plate motion model nuvel 1 we present nnr nuvel1 a model of plate velocities relative to the unique reference frame defined by requiring no net rotation of the lithosphere while constraining relative plate velocities to equal those in global plate motion model nuvel 1 demets et al 1990 differences between nnr nuvel1 and no net rotation plate motion model am0 2 minster and jordan 1978 are as large as 15 mm yr in nnr nuvel1 the pacific plate rotates in a right handed sense relative to the no net rotation reference frame at 0 67 m y about 63 s 107 e this rotation nearly parallels but is 32 slower than the pacific hotspot euler vector of hs2 nuvel1 which is a global model of plate hotspot velocities constrained to consistency with nuvel 1 gripp and gordon 1990 at hawaii the pacific plate moves relative to the no net rotation reference frame at 70 mm yr which is 25 mm yr slower than the pacific plate moves relative to the hotspots differences between nnr nuvel1 and hs2 nuvel1 are described completely by a right handed rotation of 0 33 m y about 49 s 65 e the 99 confidence ellipsoids for plate hotspot motion in model hs2 nuvel1 exclude the corresponding euler vectors from model nnr nuvell thus the no net rotation reference frame differs significantly from the hotspot reference frame if the difference between reference frames is caused by motion of the hotspots relative to a mean mantle reference frame then hotspots beneath the pacific plate move with coherent motion towards the east southeast alternatively the difference between reference frames may show that the uniform drag no net torque reference frame which is kinematically equivalent to the no net rotation reference frame is based on a dynamically incorrect premise possible exceptions to the assumption of uniform drag include a net torque on the lithosphere due to attached subducting slabs and greater resistance to plate motion beneath continents than beneath oceans

geochemical evolution and timescale of seawater intrusion into the coastal aquifer of israel this study is an attempt to quantify the geochemical processes and the timescale of seawater intrusion into a coastal aquifer from changes in the major ionic composition of the water and the natural distribution of the cosmogenic isotopes 14c and 3h for that purpose we sampled saline and brackish groundwaters from the israeli coastal aquifer a multilayer sampler mls was used to obtain very high resolution 10 cm profiles across the fresh saline water interface fsi the chemical and stable isotope data revealed three distinct water types end members that are located in different zones on the route to the coastal aquifer 1 slightly modified mediterranean seawater sws 2 slightly diluted with up to 20 fresh groundwater saline groundwater sds and 3 fresh groundwater fgw the sws samples generally show an excess of total alkalinity and total dissolved inorganic carbon dic and a depletion of 13cdic and 14cdic with respect to normal seawater indicating that anaerobic oxidation of organic matter is the first diagenetic reaction that affects seawater during its penetration into the bottom sediments sds waters appear when sws is slightly diluted gain ca2 and sr2 and is depleted in k suggesting that the main processes that transform sws into sds are slight dilution with fresh groundwater and cation exchange at the fresh saline water interface sds generally shows conservative mixing with fgw inspection of chemical data from coastal aquifers around the world indicates that intensive ion exchange in slightly diluted saline groundwater is a globally important phenomenon of seawater intrusion most of our saline groundwater samples contain substantial amounts of 3h suggesting that penetration of mediterranean seawater and its inland travel to a distance of 50 100 m onshore occurred 15 30 yr ago this is supported by the 14cdic mass balance that explains the relatively low 14cdic activities in the sds as influenced by diagenesis and not by simple radioactive decay

one hundred years of earthquake recording in australia abstract a comprehensive new catalog of australian earthquakes has been compiled and used to review the seismicity of australia the catalog contains 27 000 events of which 17 000 are considered to be mainshocks the catalog is complete for all australian events with a magnitude greater than m l 5 5 since 1910 m l 5 since 1960 m l 4 since 1970 and m l 3 5 since 1980 it is complete for events in southern australia above m l 3 5 since 1965 and m l 2 since 1980 before the development of local magnitude scales for australia around 1990 the richter magnitude scale was generally used at 600 km a typical hypocentral distance for much of australia the richter formula overestimates magnitude by around 0 5 units thus the results in the catalogs before and after the early 1990s are potentially discrepant most well located australian earthquakes are in the southern areas of the continent where the seismometer density is greatest in general the location uncertainty of australian earthquakes is high only 60 of events are located with an uncertainty of 10 km or less this percentage is smaller for earthquakes before 1980 and before 1960 very few events were located to within 10 km the hypocentral depths of australian earthquakes range mostly between 8 and 18 km except for the southwest corner of the continent where they are typically shallower than 5 km the seismicity in some areas of australia has been steady for at least 100 yr including the southeast corner the flinders ranges and the northwest corner in contrast seismicity in the southwest corner jumped by at least a factor of 6 in the 1940s and has been steady since then much of the rest of australia is characterized by episodic seismicity these episodes begin with a period of high activity lasting 1 10 yr and they are normally associated with a large m 6 earthquake following the large earthquake there is often a period of moderate activity lasting from a few years to several decades before and after each episode is a quiescent period of low activity lasting 0 1 10 ka during which the seismicity is more than an order of magnitude lower than during the period of high activity frequency magnitude relations were calculated using events since 1970 from the new catalog gutenberg richter a and b values were calculated on an 85 km grid and maps of the probability of an earthquake of m 4 9 occurring per year were derived these results are very similar to the global seismic hazard assessment program gshap map for australia the results were used to define four large 20 000 km 2 seismogenic zones fig 1 there are also several other small zones some of which appear to reflect recent episodes while others appear to be long lived the expected number of earthquakes m 5 and m 6 strain rate and deformation rate is given for the four large zones the remainder of australia and the whole australian continent the combined estimates of strain using seismic global positioning system gps and satellite laser ranging slr data suggest east west compressive deformation across southern australia of 0 65 2 0 mm per year likely to be in the 0 5 1 0 mm per year range

biogeochemical processes in infiltration basins and their impact on the recharging effluent the soil aquifer treatment sat system of the shafdan plant israel abstract soil aquifer treatment sat systems utilize infiltration basins for recharging pre treated effluent into the aquifer for water quality improvement the present research focuses on the diurnal and seasonal variations of oxygen carbon and nitrogen species in the infiltration basins and in the uppermost vadose zone for determining the impact of different environmental conditions on the composition of the infiltrating effluent the study was conducted in one of the infiltration basins of the dan region sewage reclamation project shafdan israel solar radiation and aeration were recognized to be the two main factors controlling the chemical composition of the effluent within the basin and the uppermost vadose zone the effluent entering the basin show initial enrichment with dissolved oxygen do due to gas exchange caused by injection through the inlet fountain and turbulence during basin filling the do ph and dissolved inorganic carbon dic fluctuate diurnally as a result of intense in basin daylight photosynthesis and nighttime respiration do and ph increase during day and decrease during night and the dic shows an opposite behavior the daylight net primary production was 240 mol l 1 d 1 and the diurnal respiration rate was 430 mol l 1 d 1 assuming that the nighttime respiration rate is constant over a whole diurnal cycle the gross primary production during daylight was 450 mol l 1 d 1 dissolved organic carbon doc and inorganic nitrogen species nh 4 no 3 varied significantly in the uppermost vadose zone however neither the vadose zone nor the basin showed diurnal fluctuations it appears that chemical variations between three sampling campaigns conducted in different seasons stemmed mainly from the efficiency of basin aeration that resulted from changes in basin s operation regime and local environmental conditions the results of this study lead to the following basin management recommendations 1 keeping short flooding and drying cycles and allowing complete basin desiccation before the next flooding and 2 flooding the basin during daytime starting at dawn to maximize oxygen production and minimize infiltration during nighttime following these routines would result in higher redox potential of the infiltrating effluent

active low angle normal faulting in the woodlark extensional province papua new guinea a physical model 1 in eastern papua new guinea the seismicity geomorphology and results of seismic reflection profiling drilling and structural geological analysis reveal a zone of active low angle normal faulting the only clear known active example of this process worldwide this woodlark extensional province is 250 km long in the east west direction located within the continental crust to the south of the solomon sea ocean basin it adjoins the young oceanic spreading center farther east in the woodlark basin and since 4 ma has accommodated northward extension at rates of in excess of 10 mm yr 1 on low angle normal faults that are rooted to the north this geometry and the region s earlier history are assessed in the light of modern ideas for the mechanics of low angle normal faulting to derive a working hypothesis for the existence of this process in this region the extension in the woodlark extensional province and oceanic spreading in the woodlark basin are thus interpreted as consequences of the slab pull force due to northward subduction of the solomon sea floor which has caused the small solomon sea plate to separate from the australian plate it is suggested that this plate geometry developed by 6 5 ma following the ending of southward subduction of the solomon sea floor beneath what is now the woodlark extensional province the double thickness of lithosphere that formerly existed locally cooled the continental crust making it brittle to the moho following the end of this subduction the base of the continental lithosphere became progressively exposed to the asthenosphere causing dramatic heating of the overlying continental crust this resulted in transient thermal disequilibrium inducing transient horizontal lower crustal flow the shear tractions imparted on the base of the brittle layer by such flow combined with the stress components that develop after some of the lower crust has flowed from beneath a locality requiring it to be supported laterally rather than from below will rotate the principal axes of the stress tensor sufficiently to enable low angle normal faults to form and it is estimated that this sense of deformation was initiated around 4 ma the geometry of this study region means that this process will create north dipping low angle normal faults as are observed this scheme can also account for a great deal of other observational evidence including the available thermochronologic evidence and the observed vertical crustal motions to explain this instance of active low angle normal faulting thus requires knowledge of its relationship to earlier subduction and of effects of temperature dependent changes to continental crustal rheology in crust that was initially cold

modelling the erosional susceptibility of catchments in terms of energy summary basically the paper proposes to consider catchments as functional units in which geomorphic work generally results from combined effects of erosion by water and by mass movements or from a combination of erosion by wind by runoff and by mass movements therefore a measure of the erosional susceptibility e s of catchments introduces the gravitational potential beside the kinetic energy of the eroding agents furthermore expressions of e s stress the impact of the spatial distribution of erosion as a much differentiating factor for future research it is recommended to look after timedependent variations of e s for representative drainage basins

magnesium isotopic composition of submarine vent fluids from arc and back arc hydrothermal systems in the western pacific abstract seafloor hydrothermal systems are important sinks for mg as their concentration in high temperature hydrothermal vent fluids decreases to near zero through the formation of secondary minerals however the problem of mass balance still persists regarding the global sink for mg via sub seafloor high temperature hydrothermal reactions in this study we measured isotopic compositions of mg in high temperature hydrothermal vent fluids from 5 arc and back arc systems in the western pacific this was done to better understand mg behavior during hydrothermal circulation and to quantify the oceanic mg cycle the samples with significantly low mg concentrations showed 26mg depletion due to mg fractionation and mg fixation during hydrothermal circulation addition of mg to the permeable sub seafloor during venting is the probable reason for the isotopic variation of mg the vent fluids return flux with lighter mg isotopic compositions contain much smaller amounts of mg than seawater this confirms that the high temperature hydrothermal sinks have a less significant effect on the oceanic mg isotopic composition based on the simple steady state equations and low temperature hydrothermal sinks of 26mg 0 25 to 0 00 of 26mg 7 26 of the riverine mg input is presumed to be removed through the high temperature sink this estimate is lower than that proposed by mottl and wheat 1994 which was 10 40 thus other mg sinks such as the low temperature hydrothermal sink and or the dolomite sink need to be considered

identification of groundwater sources of a local scale creep slope using environmental stable isotopes as tracers summary water plays an important role for slope stability and typically consists of local precipitation lp and original slope groundwater osgw high amount of the osgw leads the slope groundwater sgw easily to exceed the critical level that causes slope failure in a heavy raining event this study was to verify the source and significance of the osgw for a creep slope adjoining a hydropower plant northern taiwan by an environmental stable isotope approach isotope results indicate that the source of the osgw derived from leaking of the water transporting system of the power plant the leaking fraction in the sgw is as high as 70 80 high leaking component in the sgw indicates that the leaking water rather than local precipitation is the crucial factor for the mass movement of the creep slope since the mass movement poses a potential threat to the hydropower plant safety the most important measure for the remedial project is to perform a comprehensive check and repair the leak of the water transporting system

estimation of current plate motions in papua new guinea from global positioning system observations plate tectonic motions have been estimated in papua new guinea from a 20 station network of global positioning system sites that has been observed over five campaigns from 1990 to 1996 the present velocities of the sites are consistent with geological models in which the south bismarck woodlark and solomon sea plates form the principal tectonic elements between the pacific and australian plates in this region active spreading is observed on the woodlark basin spreading centre but at a rate that is about half the rate determined from magnetic reversals the other major motions observed are subduction on the new britain trench seafloor spreading across the bismarck sea seismic lineation convergence across the ramu markham fault and left lateral strike slip across the papuan peninsula these motions are consistent with a 8 2 myr 1 clockwise rotation of the south bismarck plate about a pole in the huon gulf and a rotation of the woodlark plate away from the australian plate second order deformation may also be occurring in particular manus island and northern new ireland may be moving northward relative to the pacific plate at 5 8 mm yr 1 significant at the 95 but not at the 99 confidence level which may suggest the existence of a north bismarck plate

tracking the australian plate motion through the cenozoic constraints from 40ar 39ar geochronology here we use geochronology of australian intraplate volcanoes to construct a high resolution plate velocity record and to explore how tectonic events in the southwest pacific may have influenced plate motion nine samples from five volcanoes yield ages from 33 6 0 5 to 27 3 0 4 ma and when combined with published ages from 30 to 16 ma show that the rate of volcanic migration was not constant instead the results indicate distinct changes in australian plate motion fast northward velocities 61 8 and 57 4 km ma prevailed from 34 to 30 0 5 and from 23 to 16 0 5 ma respectively with distinct reductions to 20 10 and 22 5 km ma from 30 to 29 0 5 ma and from 26 to 23 0 5 ma these velocity reductions are concurrent with tectonic collisions in new guinea and ontong java respectively interspersed between the periods of sluggish motion is a brief 29 26 0 5 ma burst of atypically fast northward plate movement of 100 20 km ma we evaluate potential mechanisms for this atypically fast velocity including catastrophic slab penetration into the lower mantle thermomechanical erosion of the lithosphere and plume push forces none are appropriate this period of fast motion was however coincident with a major southward propagating slab tear that developed along the northeastern plate margin following partial jamming of subduction and ophiolite obduction in new caledonia although it is unclear whether such an event can play a role in driving fast plate motion numerical or analogue models may help address this question key points we determine nine 40ar 39ar ages from five cenozoic volcanoes in australia slow velocities correlate with new guinea and ontong java collisions anomalously fast velocity of 100 20 km ma is identified from 29 26 ma

the dynamic relationship between ground water and the columbia river using deuterium and oxygen 18 as tracers abstract deuterium and oxygen 18 were used as natural tracers to investigate the hydraulic relationship between the columbia river and the blue lake gravel aquifer near portland oregon a time series of stable isotope data collected from surface and ground waters during a march 1990 aquifer test confirms that the river and aquifer are hydraulically connected calculations based on simple mixing show that the river contributed 40 50 of the yield of three wells after 5 6 days of pumping data collected during august 1990 show that the river contributed 65 80 of the yield of one well after 22 days of pumping and indicate that the contribution of the river was still increasing

the de ploey erosional susceptibility model for catchments es abstract this article is based on an unpublished manuscript by the late prof dr jan de ploey it focusses on the erosional susceptibility of catchments in terms of total energy input by the meteorological factors water and wind e s model the form and the universal character of the basic expression of the erosional susceptibility are explained applications of the model are illustrated for different processes such as landsliding and debris flows gullying creep and rill interrill combinations characteristic e s values exist for these processes also e s values vary in regions with differing pedo botanical characteristics and land use the difference between e s values for single storm events and longer periods are related to the magnitude frequency distribution of erosive activities and allow in many cases an assessment of the age of erosion phenomena and an estimation of the recurrence period of extreme single events

crustal motion in indonesia from global positioning system measurements terrestrial reference frame 2000 we compute poles of rotation for the australia eurasia and pacific plates based on our analysis of the global gps data we find that regional tectonics is dominated by the interaction of four discrete rotating blocks spanning significant areas of the sunda shelf the south banda arc the bird s head region of new guinea and east sulawesi the largest the sunda shelf block ssh is estimated to be moving 6 3 mm yr se relative to eurasia the south banda block sbb rotates clockwise relative to both the ssh and australia plate resulting in 15 8 mm yr of motion across the timor trough and 60 3 mm yr of shortening across the flores sea southern new guinea forms part of the australia plate from which the bird s head block bhb moves rapidly wsw subducting beneath the seram trough the east sulawesi block rotates clockwise about a nearby axis with respect to the sunda shelf thereby transferring east west shortening between the pacific and eurasia plates into north south shortening across the north sulawesi trench except for the sunda shelf the crustal blocks are all experiencing significant internal deformation in this respect crustal motion in those regions does not fit the microplate tectonics model index terms 1206 geodesy and gravity crustal movements interplate 8155 1243 geodesy and gravity space geodetic surveys 8150 tectonophysics plate boundary general 3040 8158 tectonophysics plate motions present and recent 3040 9320 information related to geographic region asia keywords crustal motion indonesia tectonics gps current plate motions southeast asia

rotations in the actively colliding finisterre arc terrane paleomagnetic constraints on plio pleistocene evolution of the south bismarck microplate northeastern papua new guinea abstract we report paleomagnetic results from 12 plio pleistocene localities in the actively colliding finisterre arc terrane of northeastern papua new guinea png calcareous hemipelagic cover rocks possess a stable syn collisional remagnetization indicating a clockwise rotation of the colliding terrane through about 40 in post miocene time a decrease in paleomagnetic declination anomalies as a function of along strike distance in the finisterre arc terrane analyzed by our preferred model of a linear remagnetization and a migrating euler pole suggests an average rotation rate of 8 ma 1 in good agreement with the instantaneous rate from global positioning system geodesy thus we propose that this rotation results from a coherent rigid body rotation of the finisterre terrane rather than from sequential docking of independently colliding blocks of the terrane moreover we conclude that these paleomagnetic declinations result mainly from south bismarck plate motion and not decoupled rotation of the crustal terrane independent of the underlying lithosphere we examine models of a syn collisional remagnetization with both fixed and migrating euler poles of south bismarck australia plate relative motion and suggest that the euler pole describing south bismarck plate motion has migrated southwestward to its present location on the collision suture in response to the propagating collision this plate kinematic model agrees with the variability in depth of the seismogenic slab beneath the collision zone our best fit model of pole migration describes south bismarck australia relative motion producing a highly oblique collision in its early stages with the finisterre arc terrane converging along a left lateral ramu markham suture gradually changing to the nearly orthogonal convergence observed today

spatial variation of groundwater arsenic distribution in the chianan plain sw taiwan role of local hydrogeological factors and geothermal sources summary we present here major ion trace element stable and radioisotope data based on forty six groundwater samples collected from various locations along few selected profiles across the chianan plain southwestern taiwan including the area affected by well known blackfoot disease manifested by peripheral vascular gangrene the objective of the study was to understand the role of local hydrogeology in terms of spatial variation of arsenic concentration in groundwater wells of the entire chianan plain and the foothill belt of the central mountain range an attempt has also been made to assess the contribution of nearby geothermal sources to the arsenic budget in groundwater of the chianan plain our study shows a gradual increase in all major and trace ion concentrations including total arsenic from foothill belt arsenic median 4 g l range 0 667 6 g l sample number n 16 to coastal zones arsenic median 42 74 g l range 0 14 348 6 g l n 15 of the plain inverse geochemical modeling shows that ca may be exchanged on clays and that the degree of the exchange increases from the foothill to the coastal zones inverse geochemical modeling further suggests that the oxidation of organic matter ch2o required in various east west profiles across the plain to balance the total bicarbonate concentration and co2 input from organic matters significantly increases from the foothill to the coastal zones with transfer coefficients ranging from 1 55 10 2 to 1 69 10 5 mol l high concentrations of tritium mean 1 33 0 11 tu n 4 in foothill groundwater and low concentration of tritium in groundwater of central zone suggest gradually increasing water rock interaction from the foothill to the coastal part few elevated arsenic median 171 8 g l maximum 667 60 g l minimum 24 g l n 6 hotspots are identified in the foothill belt available lithologs and aquifer test data suggest that the presence of impermeable clay around those pockets possibly inhibits vertical and lateral flushing of the aquifer and aids strong water rock interactions subsequently leading to release of arsenic into groundwater using oxygen isotope and chloride mass balance method we estimated that geothermal sources can recharge a maximum of 4 of groundwater in proximal aquifers and contribute

back arc basin basalt systematics the mariana east scotia lau and manus back arc basins babs have spreading rates that vary from slow 100 mm yr and extension axes located from 10 to 400 km behind their island arcs axial lava compositions from these babs indicate melting of mid ocean ridge basalt morb like sources in proportion to the amount added of previously depleted water rich arc like components the arc like end members are characterized by low na ti and fe and by high h2o and ba la the morb like end members have the opposite traits comparisons between basins show that the least hydrous compositions follow global morb systematics and an inverse correlation between na8 and fe8 this is interpreted as a positive correlation between the average degree and pressure of mantle melting that reflects regional variations in mantle potential temperatures lau manus hotter than mariana scotia this interpretation accords with numerical model predictions that faster subduction induced advection will maintain a hotter mantle wedge the primary compositional trends within each bab a positive correlation between fe8 na8 and ti8 and their inverse correlation with h2o 8 and ba la are controlled by variations in water content melt extraction and enrichments imposed by slab and mantle wedge processes systematic axial depth as a proxy for crustal production variations with distance from the island arc indicate that compositional controls on melting dominate over spreading rate hydrous fluxing enhances decompression melting allowing depleted mantle sources just behind the island arc to melt extensively producing shallow spreading axes flow of enriched mantle components around the ends of slabs may augment this process in transform bounded back arcs such as the east scotia basin the re circulation by mantle wedge corner flow to the spreading axes of mantle previously depleted by both arc and spreading melt extraction can explain the greater depths and thinner crust of the east lau spreading center manus southern rifts and mariana trough and the very depleted lavas of east scotia segments e8 e9 the crust becomes mid ocean ridge mor like where the spreading axes further away from the island arc and subducted slab entrain dominantly fertile mantle

large scale present day plate boundary deformations in the eastern hemisphere determined from vlbi data implications for plate tectonics and indian ocean growth the dynamics of the planet earth are manifestations of diverse plate tectonic processes which have been occurring since the archean period of the earth s evolution and continue to deform the plate boundaries very long baseline interferometry vlbi is an efficient space geodetic method that enables precise measurement of plate motion and associated deformations we analyze here vlbi measurements made during a period of approximately three decades at five locations on the eastern hemisphere of the globe which are geographically distributed over five continents plates around the indian ocean computed rate of change of baseline length show the deformation pattern and its rate at the boundaries between the major tectonic plates constituting the eastern hemisphere of the earth the african nubian and antarctic plates are moving apart at 13 5 mm year which is mostly attributed to spreading of the south west indian ridge similarly spreading of 59 0 mm year is observed for the south east indian ridge that separates the antarctic and australian plates shortening at the rate of 3 9 mm year is estimated across the subduction boundary between africa nubia and eurasia similar convergence is evident between the australian and sunda blocks of the eurasian plate the associated deformation of 54 8 mm year seems to be chiefly accommodated along the banda arc system where the australian plate is subducting under the sunda block vlbi sites within the eurasian plate wettzell in germany and seshan on the south china block are moving apart at 3 6 mm year this relative motion between locations on the same plate is interpreted as a result of the deformation process along a large strike slip fault which is identified as the western boundary of the south china block expansion of the indian ocean at 91 5 m2 year is also estimated from the rate of deformation estimated within the five baselines studied here from the hurst exponent values which are indicators of the future trend of time series data we predict deceleration of the various tectonic processes occurring at present

seismotectonics of taiwan abstract high quality seismicity data and focal mechanism solutions obtained during 1973 1983 by the permanent taiwan telemetered seismographic network and several temporary local seismographic networks are used for a detailed study of the seismotectonics of the taiwan area seismicity distribution in southern taiwan clearly reveals an east dipping benioff zone which has a thickness of about 30 km and begins to deepen along 121 e at a dip angle of 55 60 the leading edge of this benioff zone reaches a depth of about 180 km between 21 n and 22 n but tapers off to a shallower depth of about 100 km from 22 n to 23 n the presence of this seismic zone implies that subduction of the south china sea plate under the philippine sea plate extends from luzon northward to about 23 n the position of the northern boundary of the south china sea plate as tentatively defined according to the seismicity distribution passes through southern taiwan from the offshore area in the taiwan strait west of kaohsiung in an east northeast direction to the taitung area where a triple junction probably lies seismicity is found to disappear abruptly below a certain depth in many parts of taiwan this phenomenon may be attributed to the frictional to quasiplastic transition in the crust or upper mantle comparison of shallow seismicity with surface faults and fractures shows that all areas of active shallow seismicity are marked by densely developed faults and fractures however the converse is not necessarily true this may be partly due to the relatively short duration of seismicity data and partly due to excessive weakening of some of the severely faulted and fractured areas finally focal mechanism solutions for west central taiwan and the kuangfu fuli area in eastern taiwan predominantly show a maximum horizontal compression in the se nw direction which can be related to collision between the eurasian and philippine sea plates however focal mechanism solutions for both the hualien area in eastern taiwan and the tainan area in southwestern taiwan show remarkable irregularities which may result from local tectonic complexities

geochemistry of hot springs at the susu knolls hydrothermal field eastern manus basin advanced argillic alteration and vent fluid acidity abstract susu knolls is an area of ongoing magmatic activity and recent volcanism located in the back arc spreading environment of the manus basin in the bismarck sea papua new guinea in 2006 hydrothermal fluids were collected from three areas of submarine hot spring venting and analyzed for the chemical and isotopic composition of major and trace species fluids were characterized by temperatures that varied from 226 325 c and formed grey to black smoke as they mixed with bottom seawater the compositions of seawater derived vent fluids are regulated by the relative contributions of fluid rock and fluid sediment interaction phase separation and the addition of volatiles from magmatic degassing in addition to phase separation leaching of cl from felsic rocks that compose the lithosphere in back arc environments may produce cl concentrations in excess of seawater values the measured ph25 c of susu knolls smoker fluids varied from 1 5 3 7 a range that includes values substantially more acidic than typically observed in fluids at mid ocean ridge spreading centers late stage addition of magmatic volatiles in the shallow seafloor is directly responsible for the most acidic fluids ph25 c values below 2 in contrast the acidity of vent fluids characterized by ph25 c values between 2 and 3 is not the direct result of the direct addition of magmatically derived acidic species instead the ph of these fluids likely reflects reaction with rocks that were previously altered by highly acidic magmatic fluids to an advanced argillic alteration assemblage containing quartz illite pyrophyllite anhydrite alunite in hydrothermal upflow zones fluids that do not react with advanced argillic alteration assemblages during upflow have measured ph25 c values between 3 and 4