lead and bromine enrichment in eclogite facies fluids extreme fractionation during lower crustal hydration hydration reactions associated with eclogite facies metamorphism of granulites in the norwegian caledonides led to the formation of saline brines with exceptional compositions primary omphacite and garnet hosted fluid inclusions from norwegian eclogites formed by hydration of granulites contain a plethora of solid phases a total of 18 different minerals have been identified in multiphase brines and 12 of these occur at the badsholmen locality in sunnfjord fluid inclusions from this locality are characterized by a high br cl mass ratio 0 03 and extreme pb enrichment as demonstrated by the presence of pb bearing daughter minerals including galena a pb cl bearing phase and a pb cl br bearing phase the fluid compositions may reflect enrichment of elements incompatible with the silicate structure during consumption of h 2 o by eclogite forming hydration reactions pb is believed to have been scavenged from the parent granulite by the increasingly saline brine during k feldspar breakdown

plate boundary observatory and related networks gps data analysis methods and geodetic products the geodesy advancing geosciences and earthscope gage facility global positioning system gps data analysis centers produce position times series velocities and other parameters for approximately two thousand continuously operating gps receivers spanning a quadrant of earth s surface encompassing the high arctic north america and caribbean the purpose of this review is to document the methodology for generating station positions and their evolution over time and to describe the requisite tradeoffs involved with combination of results gage gps analysis involves formal merging within a kalman filter of two independent loosely constrained solutions one is based on precise point positioning produced with the gps inferred positioning system orbit analysis simulation gipsy oasis software at central washington university cwu and the other is a network solution based on phase and range double differencing produced with the gps at mit gamit software at new mexico institute of mining and technology nmt the primary products generated are the position time series that show motions relative to a north america reference frame and secular motions of the stations represented in the velocity field the position time series themselves contain a multitude of signals in addition to the secular motions co seismic and post seismic signals seasonal signals from hydrology and transient events some understood and other not yet fully explained are all evident in the time series and ready for further analysis and interpretation we explore the impact of analysis assumptions on the reference frame realization and on the final solutions and we compare within the gage solutions and with others

global sea level rise published values for the long term global mean sea level rise determined from tide gauge records exhibit considerable scatter from about 1 mm to 3 mm yr this disparity is not attributable to instrument error long term trends computed at adjacent sites often agree to within a few tenths of a millimeter per year instead the differing estimates of global sea level rise appear to be in large part due to authors using data from gauges located at convergent tectonic plate boundaries where changes of land elevation give fictitious sea level trends in addition virtually all gauges undergo subsidence or uplift due to postglacial rebound pgr from the last deglaciation at a rate comparable to or greater than the secular rise of sea level modeling pgr by the ice 3g model of tushingham and peltier 1991 and avoiding tide gauge records in areas of converging tectonic plates produces a highly consistent set of long sea level records the value for mean sea level rise obtained from a global set of 21 such stations in nine oceanic regions with an average record length of 76 years during the period 1880 1980 is 1 8 mm yr 0 1 this result provides confidence that carefully selected long tide gauge records measure the same underlying trend of sea level and that many old tide gauge records are of very high quality

itrf2014 a new release of the international terrestrial reference frame modeling nonlinear station motions for the first time in the international terrestrial reference frame itrf history the itrf2014 is generated with an enhanced modeling of nonlinear station motions including seasonal annual and semiannual signals of station positions and postseismic deformation for sites that were subject to major earthquakes using the full observation history of the four space geodetic techniques very long baseline interferometry vlbi satellite laser ranging slr global navigation satellite systems gnss and doppler orbitography and radiopositioning integrated by satellite doris the corresponding international services provided reprocessed time series weekly from slr and doris daily from gnss and 24 h session wise from vlbi of station positions and daily earth orientation parameters itrf2014 is demonstrated to be superior to past itrf releases as it precisely models the actual station trajectories leading to a more robust secular frame and site velocities the itrf2014 long term origin coincides with the earth system center of mass as sensed by slr observations collected on the two lageos satellites over the time span between 1993 0 and 2015 0 the estimated accuracy of the itrf2014 origin as reflected by the level of agreement with the itrf2008 both origins are defined by slr is at the level of less than 3 mm at epoch 2010 0 and less than 0 2 mm yr in time evolution the itrf2014 scale is defined by the arithmetic average of the implicit scales of slr and vlbi solutions as obtained by the stacking of their respective time series the resulting scale and scale rate differences between the two solutions are 1 37 0 10 ppb at epoch 2010 0 and 0 02 0 02 ppb yr while the postseismic deformation models were estimated using gnss gps data the resulting parametric models at earthquake colocation sites were applied to the station position time series of the three other techniques showing a very high level of consistency which enforces more the link between techniques within the itrf2014 frame the users should be aware that the postseismic deformation models are part of the itrf2014 products unlike the annual and semiannual signals which were estimated internally with the only purpose of enhancing the velocity field estimation of the secular frame

estimation of offsets in gps time series and application to the detection of earthquake deformation in the far field extracting geophysical signals from global positioning system gps coordinate time series is a well established practice that has led to great insights into how the earth deforms often small discontinuities are found in such time series and are traceable to either broad scale deformation i e earthquakes or discontinuities due to equipment changes and or failures estimating these offsets accurately enables the identification of coseismic deformation estimates in the former case and the removal of unwanted signals in the latter case which then allows tectonic rates to be estimated more accurately we develop a method to estimate accurately discontinuities in time series of gps positions at specified epochs based on a so called offset series the offset series are obtained by varying the amount of gps data before and after an event while estimating the offset two methods a mean and a weighted mean method are then investigated to produce the estimated discontinuity from the offset series the mean method estimates coseismic offsets without making assumptions about geophysical processes that may be present in the data i e tectonic rate seasonal variations whereas the weighted mean method includes estimating coseismic offsets with a model of these processes we investigate which approach is the most appropriate given certain lengths of available data and noise within the time series themselves for the sumatra andaman event with 4 5 yr of pre event data we show that between 2 and 3 yr of post event data are required to produce accurate offset estimates with the weighted mean method with less data the mean method should be used but the uncertainties of the estimated discontinuity are larger

ionospheric response to the initial phase of geomagnetic storms common features 1 ionospheric responses to the initial phases of three geomagnetic storms 2 5 april 2004 7 9 november 2004 and 13 16 december 2006 were compared using both ground based gps total electron content tec data and coupled magnetosphere ionosphere thermosphere cmit model simulations the onset times for these storms all occurred at local daytime in the north american sector this similarity of onset times and other factors resulted in some common features in their ionospheric response these common features include 1 enhanced tec positive response at low and middle latitudes in the daytime 2 depleted tec negative response around the geomagnetic equator in the daytime 3 a north south asymmetry in the positive response as the northern hemispheric response appeared to be more pronounced and 4 negative response at high latitudes as the storms progressed the cmit model captured most of these features analysis of model results showed that storm time enhancements in the daytime eastward electric field were the primary cause of the observed positive storm effects at low and middle latitudes as well as the negative response around the geomagnetic equator in the daytime these eastward electric field enhancements were caused by the penetration of high latitude electric fields to low latitudes during southward interplanetary magnetic field imf periods when imf bz oscillated between southward and northward direction in the initial shock phase of the storms consequently the ionosphere was lifted up at low and middle latitudes to heights where recombination was weak allowing the plasma to exist for a long period resulting in higher densities in addition the cmit model showed that high latitude negative storm responses were related to the enhancements of molecular nitrogen seen in timed global ultraviolet imager observations whereas the negative storm effects around the geomagnetic equator were not associated with thermospheric composition changes they were the result of plasma transport processes

the relationship between riverine lithium isotope composition and silicate weathering rates in iceland abstract this study presents lithium isotope and elemental data for the dissolved phase and suspended and bedload sediments of the major icelandic rivers for the dissolved phase 7li values range between 10 1 and 23 8 while river sediments display lower and much more homogeneous values 7li 3 1 4 8 close to the composition of unweathered mid ocean ridge basalt morb high 7li values are associated with high k li na li and mg li ratios in waters draining mainly old and weathered basalt catchments whereas low 7li rivers are located in younger parts of the island simple mixing between precipitation li rich hydrothermal springs and basalt weathering is unable to explain the entire range of 7li values instead a simple model of li uptake by secondary minerals associated with clay water li isotope fractionation 7li ranging from 1 to 7 5 can explain both water and sediment 7li values a negative correlation is observed between basalt chemical erosion rates and 7li measured in icelandic rivers and an empirical law is inferred comparison with literature data suggests that this relationship may be applicable at a more global scale and if confirmed could be of particular use for estimating the evolution of continental weathering preserved in marine sedimentary records however more data are now needed for rivers draining silicates typical of the continental crust in order to refine large scale modelling

present day post glacial sea level change far from the late pleistocene ice sheets implications for recent analyses of tide gauge records we examine the sensitivity of predictions of the present day rate of sea level change due to glacial isostatic adjustment gia in two regions located within the far field of the late pleistocene ice sheets europe north africa and the western pacific caribbean to variations in the mantle viscosity profile the regions considered here encompass the location of 11 of 21 sites used in a recent determination based on gia corrected tide gauge records of the global rate of secular sea level change our analysis suggests that the mean gia correction at the 11 far field sites may vary by as much as 0 5 mm yr depending on the adopted earth model and we derive a bound on the residual secular sea level rise of 1 1 to 1 6 mm yr this bound is consistent with our analysis of the tide gauge record from the u s east coast and it suggests that previous estimates of the residual sea level rise represent an upper bound

uncertainty of the 20th century sea level rise due to vertical land motion errors assessing the vertical land motion vlm at tide gauges tg is crucial to understanding global and regional mean sea level changes slc over the last century however estimating vlm with accuracy better than a few tenths of a millimeter per year is not a trivial undertaking and many factors including the reference frame uncertainty must be considered using a novel reconstruction approach and updated geodetic vlm corrections we found the terrestrial reference frame and the estimated vlm uncertainty may contribute to the global slc rate error by 0 2 mmyr 1 in addition a spurious global slc acceleration may be introduced up to 4 8 x 10 3 mmyr 2 regional slc rate and acceleration errors may be inflated by a factor 3 compared to the global the difference of vlm from two independent glacio isostatic adjustment models introduces global slc rate and acceleration biases at the level of 0 1 mmyr 1and 2 8 x 10 3 mmyr 2 increasing up to 0 5 mm yr 1 and 9 x 10 3 mmyr 2 for the regional slc errors in vlm corrections need to be budgeted when considering past and future slc scenarios

global and regional sea level change during the 20th century sea level variations prior to the launch of satellite altimeters are estimated by analyzing historic tide gauge records recently a number of groups have reconstructed sea level by applying eof techniques to fill missing observations we complement this study with alternative methods in a first step gaps in 178 records of sea level change are filled using the pattern recognition capabilities of artificial neural networks afterward satellite altimetry is used to extrapolate local sea level change to global fields patterns of sea level change are compared to prior studies global mean sea level change since 1900 is found to be 1 77 0 38 mm yr 1 on average local trends are essentially positive with the highest values found in the western tropical pacific and in the indian ocean east of madagascar where it reaches about 6 mm yr 1 regions with negative trends are spotty with a minimum value of about 2 mm yr 1 south of the aleutian islands although the acceleration found for the global mean 0 0042 0 0092 mm yr 2 is not significant local values range from 0 1 mm yr 2 in the central indian ocean to 0 1 mm yr 2 in the western tropical pacific and east of japan these extrema are associated with patterns of sea level change that differ significantly from the first half of the analyzed period i e 1900 1950 to the second half 1950 2000 we take this as an indication of long period oceanic processes that are superimposed to the general sea level rise

transient deformation in california from two decades of gps displacements implications for a three dimensional kinematic reference frame our understanding of plate boundary deformation has been enhanced by transient signals observed against the backdrop of time independent secular motions we make use of a new analysis of displacement time series from about 1 000 continuous global positioning system gps stations in california from 1999 to 2018 to distinguish tectonic and nontectonic transients from secular motion a primary objective is to define a high resolution three dimensional reference frame datum for california that can be rapidly maintained with geodetic data to accommodate both secular and time dependent motions to this end we compare the displacements to those predicted by a horizontal secular fault slip model for the region and construct displacement and strain rate fields over the past 19 years california has experienced 19 geodetically detectable earthquakes and widespread postseismic deformation we observe postseismic strain rate variations as large as 1 000 nstrain year with moment releases equivalent up to an mw6 8 earthquake we find significant secular differences up to 10 mm year with the fault slip model from the mendocino triple junction to the southern cascadia subduction zone the northern basin and range and the santa barbara channel secular vertical uplift is observed across the transverse ranges coastal ranges sierra nevada as well as large scale postseismic uplift after the 1999 mw7 1 hector mine and 2010 mw7 2 el mayor cucapah earthquakes we also identify areas of vertical land motions due to anthropogenic natural and magmatic processes finally we demonstrate the utility of the kinematic datum by improving the accuracy of high spatial resolution 12 day repeat cycle sentinel 1 interferometric synthetic aperture radar displacement and velocity maps

uncertainty estimation in regional models of long term gia uplift and sea level change an overview this work provides a comparison of four approaches that can be used to describe uncertainty in models of the long term glacial isostatic adjustment gia process the four methods range from pessimistic to optimistic representations of gia uncertainty each estimation method is applied to selected one dimensional gia model predictions and compared with vertical land motion data from global positioning system gps measurements across fennoscandia and north america the methods are evaluated relative to two main properties 1 their expected ability to separate non gia from gia signals and 2 their estimated statistical appropriateness given a specific gia model and data set for the first point non gia signals are considered isolated from the long term millennial time scale gia signal at sites where measurement and model uncertainties do not overlap across methods the frequency and accuracy with which non gia signals are separated from gia signals in gps data display both consistent similarities and disparities for the second point we compare model predictions with rates of vertical land motion and relative sea level change that have been cleaned of non gia signals to determine the most appropriate value of model uncertainty and relate the findings to the four approaches best fit inferences suggest that within deglaciation centers gia model uncertainty is up to 2 mm yr vertical land motion likewise away from the former ice sheet centers gia uncertainty for relative sea level change is inferred to be 0 3 0 5 mm yr along the u s east coast and 0 6 0 8 mm yr in the north sea

halogen contents of eclogite facies fluid inclusions and minerals caledonides western norway primary multiphase brine fluid inclusions in omphacite and garnet from low to medium temperature eclogites have been analysed for cl br i f li and so4 halogen contents and ratios provide information about trapped lower crustal fluids even though the major element na k ca contents of inclusion fluids have been modified by fluid mineral interactions and step daughter crystal formation after trapping halogens in the inclusion fluids were analysed with crush leach techniques cl br and cl i mass ratios of eclogite fluids are in the range 31 395 and 5000 33 000 respectively most fluids have a cl br ratio lower than modern seawater and a cl i ratio one order of magnitude lower than modern seawater fluids with the lowest cl br and highest cl i ratios come from an eclogite that formed by hydration of granulite facies rocks and may indicate that br and i are fractionated into hydrous minerals reconstructions indicate that the inclusion fluids originally contained 500 4000 ppm br 1 14 ppm i and 33 438 ppm li electron microprobe analyses of eclogite facies amphibole biotite phengite and apatite indicate that f and cl fractionate most strongly between phengite f cl mass ratio of 1469i1048 and fluid f cl mass ratio of 0 008 and the least between amphibole and fluid the chemical evolution of cl and br in pore fluids during hydration reactions is in many ways analogous to cl and br in seawater during evaporation the cl br ratio remains constant until the ah2o value is sufficiently lowered for cl to be removed from solution by incorporation into hydrous minerals

strain measurements and the potential for a great subduction earthquake off the coast of washington geodetic measurements of deformation in northwestern washington indicate that strain is accumulating at a rate close to that predicted by a model of the cascadia subduction zone in which the plate interface underlying the continental slope and outer continental shelf is currently locked but the remainder of the interface slips continuously presumably this locked segment will eventually rupture in a great thrust earthquake with a down dip extent greater than 100 kilometers

configuration of subducting philippine sea plate and crustal structure in the central japan region a seismic experiment with six explosive sources and 391 seismic stations was conducted in august 2001 in the central japan region the crustal velocity structure for the central part of japan and configuration of the subducting philippine sea plate were revealed a large lateral variation of the thickness of the sedimentary layer was observed and the p wave velocity values below the sedimentary layer obtained were 5 3 5 8 km s p wave velocity values for the lower part of upper crust and lower crust were estimated to be 6 0 6 4 and 6 6 6 8 km s respectively the reflected wave from the upper boundary of the subducting philippine sea plate was observed on the record sections of several shots the configuration of the subducting philippine sea slab was revealed for depths of 20 35 km the dip angle of the philippine sea plate was estimated to be 268 for a depth range of about 20 26 km below this depth the upper boundary of the subducting philippine sea plate is distorted over a depth range of 26 33 km a large variation of the reflected wave amplitude with depth along the subducting plate was observed at a depth of about 20 26 km the amplitude of the reflected wave is not large and is explained by the reflected wave at the upper boundary of the subducting oceanic crust however the reflected wave from reflection points deeper than 26 km showed a large amplitude that cannot be explained by several reliable velocity models some unique seismic structures have to be considered to explain the observed data such unique structures will provide important information to know the mechanism of inter plate earthquakes d 2004 elsevier b v all rights reserved

dayside midlatitude ionospheric response to storm time electric fields a case study for 7 september 2002 1 with the storm of 7 8 september 2002 as a study case we demonstrate that an ionospheric model driven by a suitable storm time convection electric field can reproduce the f region dayside density enhancements associated with the ionospheric storm positive phase the ionospheric model in this case is the utah state university time dependent ionospheric model tdim the electric field model is the university of michigan s hot electron and ion drift integrator heidi extensive ground truth is available throughout the study period from two independent sources ground based vertical tec and ionosonde stations our simulation results are in good agreement with these observations we address the question of what is the source of the high density plasma that is seen during the positive storm phase and show that in this case a magnetospheric electric field with an eastward component that penetrates to midlatitudes increases local production on the dayside to a degree that is sufficient to account for the storm time density increases that have been observed

source mechanism of a very long period event at mt ontake central japan response of a hydrothermal system to magma intrusion beneath the summit abstract a very long period vlp volcanic event which occurred on 25 january 2007 beneath mt ontake central japan was recorded by nearby broadband seismometers as well as the japanese nationwide hi net and f net seismic networks the vlp waveforms show a pulse like shape with a duration of approximately 1 min the vlp event was accompanied by a burst sequence of long period lp events we carried out waveform inversion to determine the source mechanism and location of the vlp event our analysis indicates volumetric changes in an inclined crack seismic moment of 10 14 nm at the vlp source which is located at 0 6 km above sea level beneath the summit of mt ontake and above dikes determined from gps data the source time functions of the vlp event showed a pulse like triangular shape indicating inflation followed by deflation of the crack at the source we interpreted the result of the waveform inversion as follows gases released from the intruded magma heated an aquifer system beneath the summit of mt ontake a break of unstable superheated water in a hydrothermal crack in the system caused vaporization of water and associated crack inflation which was followed by discharge of steam from the crack resulting in its collapse these processes caused the vlp event which may have been a precursor of a small phreatic eruption that occurred in late march 2007

helium 3 emission related to volcanic activity the helium 3 helium 4 ratio in bubbling gases from ten hot springs located around mount ontake an active volcano in central japan ranges from 1 71 r sub atm 1 71 times the atmospheric ratio of 1 40 x 10 sup 6 to 6 15 r sub atm the value of the ratio decreases with distance from the central cone of the volcano such a tendency may be a characteristic of helium 3 emission in volcanic areas and suggests more primitive helium 3 is carried with fluid flowing through a conduit during volcanic activity 6 references 1 figure 1 table

noise in gps displacement measurements from southern california and southern nevada 1 time series of position changes estimated from data from 236 continuously recording gps receivers operating in southern california and southern nevada are evaluated for noise models that characterize their temporal correlations the lengths of the time series range between 3 5 and 10 years after adjusting these data for postseismic deformation offsets and annual periodicities i find that about one half of the time series have temporal correlations that are categorized as either flicker or random walk noise the remaining time series can be best categorized as either a combination of flicker and random walk power law noise first order gauss markov plus random walk noise or power law plus broadband seasonal noise a variety of geodetic monuments are used in southern california and nevada including deeply braced designs cement piers pins drilled in outcrop and buildings when i evaluate the noise for each time series in terms of an estimate of the standard error in velocity i find that the sites with the smallest errors are those located in nevada using deeply braced monuments sites that are installed within regions of active pumping both for groundwater and oil had the largest standard errors in velocity comparison of monument stability as measured by standard error in rate with average annual rainfall nearby indicates a marginally significant correlation in addition even though regional filtering removed much of the common mode signals in these time series there still remains a common mode seasonal signal which can and should be removed

experiments in reconstructing twentieth century sea levels abstract one approach to reconstructing historical sea level from the relatively sparse tide gauge network is to employ empirical orthogonal functions eofs as interpolatory spatial basis functions the eofs are determined from independent global data generally sea surface heights from either satellite altimetry or a numerical ocean model the problem is revisited here for sea level since 1900 a new approach to handling the tide gauge datum problem by direct solution offers possible advantages over the method of integrating sea level differences with the potential of eventually adjusting datums into the global terrestrial reference frame the resulting time series of global mean sea levels appears fairly insensitive to the adopted set of eofs in contrast charts of regional sea level anomalies and trends are very sensitive to the adopted set of eofs especially for the sparser network of gauges in the early 20th century the reconstructions appear especially suspect before 1950 in the tropical pacific while this limits some applications of the sea level reconstructions the sensitivity does appear adequately captured by formal uncertainties all our solutions show regional trends over the past five decades to be fairly uniform throughout the global ocean in contrast to trends observed over the shorter altimeter era consistent with several previous estimates the global sea level rise since 1900 is 1 70 0 26 mm yr 1 the global trend since 1995 exceeds 3 mm yr 1 which is consistent with altimeter measurements but this large trend was possibly also reached between 1935 and 1950

an experimental study of alteration of oceanic crust and terrigenous sediments at moderate temperatures 51 to 350 c insights as to chemical processes in near shore ridge flank hydrothermal systems studies of hydrothermal circulation within partly buried basement on the eastern flank of the juan de fuca ridge jfr have shown that ridge flank geochemical fluxes are potentially important for the global budgets of some elements there are major uncertainties in these flux calculations however because the composition of these basement fluids is strongly dependent on temperature and because they may be modified by interaction with the overlying terrigenous sediments either by diffusive exchange with basement or during upwelling to the seafloor to better understand the nature and temperature control of basalt fluid and sediment fluid reactions at the jfr flank we have conducted laboratory experiments between 51 and 350 c and at 400 bars pressure k rb and si are leached from basalt between 150 and 351 c and sr and u are taken up the direction of exchange of li and ca with basalt varies with temperature li and sr are removed from fluid at 150 c but isotope studies show that there is simultaneous release of both elements from basalt indicating that uptake is controlled by the formation of secondary minerals moreover our experiments confirm that sr isotope exchange with oceanic crust occurs at moderate temperature and is not confined to high temperature axial hydrothermal systems our data and field data from the jdr flank indicate that uptake of u into basalt at moderate temperature could remove between 9 9 and 15 106 mol u yr 1 from the oceans this is higher than a recent estimate based on measurements of u in altered ocean crust 5 7 3 3 106 mol yr 1 which concords with arguments that the element heat ratios of jdr flank fluids are too large to be representative of average global flank fluids k ca sr ba li si and b are leached from terrigenous sediments between 51 and 350 c and u is taken up cs and rb are removed from the fluid below 100 c and leached from the sediment at higher temperature sr isotope data show that sr is preferentially mobilised from volcanic components within terrigenous sediments which may lead to an overestimation of the ridge flank sr isotope flux at the jdr if there is exchange of sediment pore fluids with basement

lithium and strontium isotopic systematics of waters around ontake volcano japan implications for deep seated fluids and earthquake swarms abstract since 1976 earthquake swarms have occurred beneath the southeast flank of ontake volcano in central japan electrical conductivity surveys have shown that these earthquake swarms are associated with the upwelling of deep seated fluid to investigate the nature of the deep seated fluid we analyzed 7 li 6 li and 87 sr 86 sr ratios of water samples collected from springs and wells around ontake volcano in 2000 2003 2005 2007 and 2009 the li and sr isotopic compositions of these water samples are largely explained by binary component mixing between near surface meteoric water and non surface fluid at each sampling site on the basis of their cl li and cl sr ratios we singled out water samples whose li and sr isotopic ratios were minimally affected by meteoric water contamination to represent non surface fluids the li and sr isotopic compositions of most ontake non surface fluids except for samples from the earthquake swarm region can be explained as the result of volcanic fluids reacting with basement rocks where they acquired upper crustal signatures we attribute the fluid associated with the region of earthquake swarms to the lower crust beneath the study area

lithium and strontium isotopic systematics in playas in nevada usa constraints on the origin of lithium lithium rich brine in playas is a major raw material for lithium production recently lithium isotopic ratios 7li have been identified as a tool for investigating water rock interactions thus to constrain the origin of lithium in playas by the use of its isotopes we conducted leaching experiments on various lacustrine sediment and evaporite deposit samples collected from playas in nevada usa we determined lithium and strontium isotopic ratios and contents and trace element contents of the leachate estimated the initial 7li values in the water flowing into the playas and examined the origin of lithium in playas by comparison with 7li values of the possible sources in samples from the playas 7li values show some variation reflecting differences both in isotopic fractionation during mineral formation and in initial 7li value in water flowing into each playa however all 7li values in this study are much lower than those in river water and groundwater samples from around the world but they are close to those of volcanic rocks considering the temperature dependence of lithium isotopic fractionation between solid and fluid these results indicate that the lithium concentrated in playas in nevada was supplied mainly through high temperature water rock interaction associated with local hydrothermal activity and not directly by low temperature weathering of surface materials this study which is the first to report lithium isotopic compositions in playas demonstrates that 7li may be a useful tracer for determining the origin of lithium and evaluating its accumulation processes in playas

a new global mode of earth deformation seasonal cycle detected we have detected a global mode of earth deformation that is predicted by theory precise positioning of global positioning system sites distributed worldwide reveals that during february to march the northern hemisphere compresses and the southern hemisphere expands such that sites near the north pole move downward by 3 0 millimeters and sites near the equator are pulled northward by 1 5 millimeters the opposite pattern of deformation occurs during august to september we identify this pattern as the degree one spherical harmonic response of an elastic earth to increased winter loading of soil moisture snow cover and atmosphere data inversion shows the load moment s trajectory as a great circle traversing the continents peaking at 6 9 1022 kilogram meters near the north pole in winter indicating interhemispheric mass exchange of 1 0 1016 0 2 1016 kilograms

extent and duration of the 2003 cascadia slow earthquake 1 inversion of continuous gps measurements from the pacific northwest show the 2003 cascadia slow earthquake to be among the largest of ten transients recognized here twelve stations bracketing slow slip indicate transient slip propagated bi directionally from initiation in the southern puget basin reaching 300 km along strike over a period of seven weeks this event produced for the first time resolvable vertical subsidence and horizontal displacement reaching six mm in southern washington state inverted for non negative thrust slip a maximum of 3 8 cm of slip is inferred centered at 28 km depth near the sharp arch in the subducting juan de fuca plate nearly all slip lies shallower than 38 km inverted slip shows a total moment release equal to mw 6 6 and a high degree of spatial localization rather than near uniform slip this suggests rupture concentrated along asperities holds for slow earthquakes as well as conventional events

composition of fluids in the lower crust inferred from metamorphic salt in lower crustal rocks knowledge of the rheological properties of the lower crust and the metamorphic processes that operate there is important for our understanding of orogenic processes and granite genesis the rheological properties critically depend on whether fluids are present in the lower crust1 2 and if present on their composition3 4 5 6 fluid inclusion7 8 9 and phase equilibria4 10 studies of lower crustal granulites have shown that fluids with low water activities due to the presence of dissolved components such as ch4 n2 co co2 and chlorides 11 are present at least episodically in the lower crust here we report the occurrence of a solid salt solution nacl kcl found together with chlorine rich amphibole and biotite in lower crustal granulites a desiccation mechanism explains how salt and chlorine rich minerals formed from an originally water rich fluid through a short lived series of hydration reactions in the granulites during which chlorine was progressively enriched in the fluid consequently it would appear that fluid was present in the lower crust in only small amounts and was not stable over geologically long periods of time leading to the conclusion that the lower crust is devoid of a free fluid phase during most of its history

the lithium isotopic composition of waters of the mono basin california mono lake a major closed basin alkaline salt lake in eastern california derives its water from a mixture of creeks and springs with the former providing in excess of 75 of the total the li isotopic composition of lake water has not varied significantly over a 4 year meromictic period 7li 19 5 springs are isotopically distinct groundwater springs and seeps carry water enriched in isotopically heavy li whereas thermal springs supply isotopically light 7li 50 of the li to the lake 2 the li budget is sensitively balanced on small thermal spring contributions 3 of the total spring inflow and 3 the residence time of li in the lake is 28 ka other great basin closed lakes have variable li isotopic compositions 7li from 16 7 to 23 7 all of which differ significantly from those of several major lakes and seawater homogeneously 32

temperature dependent isotopic fractionation of lithium between clinopyroxene and high pressure hydrous fluids the fractionation of lithium isotopes between synthetic spodumene as representative of li bearing clinopyroxene and cl and oh bearing aqueous fluids was experimentally determined between 500 and 900 c at 2 0 gpa in all the experiments 7li was preferentially partitioned into the fluid the fractionation is temperature dependent and approximated by the equation 7li clinopyroxene fluid 4 61 1 000 t k 2 48 r 2 0 86 significant li isotopic fractionation of about 1 0 exists even at high temperatures of 900 c using neutral and weakly basic fluids revealed that the amount of fractionation is not different the li isotopic fractionation between altered basalt and hot spring water 350 c in natural samples is in good agreement with our experimentally determined fractionation curve the data confirm earlier speculations drawn from the li isotopic record of dehydrated metamorphic rocks that fluids expelled from a dehydrating slab carry heavier li into the mantle wedge and that a light li component is introduced into the deeper mantle li and li isotopes are redistributed among wedge minerals as fluids travel across the wedge into hotter regions of arc magma production this modifies the li isotopic characteristics of slab derived fluids erasing their source memory and explains the absence of cross arc variations of li isotopes in arc basalts

interseismic uplift rates for western oregon and along strike variation in locking on the cascadia subduction zone 1 we quantify the spatial pattern of uplift rate in western oregon and northernmost california using tidal and leveling records to better understand the pattern of interseismic locking on the cascadia subduction zone we extend relative sea level time series of the six primary noaa tide gauges to include all observations from 1925 to 2006 previously unidentified bench mark instability biases portions of tidal records by 1 6 mm a 1 before correction we determine precise relative uplift rates at the six tidal sites with an adjustment that includes rates of differenced time series as additional constraints our analysis of national geodetic survey leveling data between tide gauges corrects errors in 1941 leveling and 184 secondary ties double the number of highest quality uplift rate estimates relative uplift rates from leveling are adjusted to the tidal rates accounting for uncertainties in both data types tidal and leveling uplift rates agree within error for all but one of the coastal segments where we infer systematic leveling error affects the 1988 line uplift rates are made absolute using an interval and location specific geocentric sea level rise rate of 2 3 0 2 mm a 1 total propagated one sigma errors for the absolute uplift rates of bench marks are 0 4 mm a 1 along strike changes in uplift rate near 45 n and 42 8 n require two distinct changes in locking depth as inferred from elastic dislocation modeling the along strike changes in locking on this portion of the cascadia subduction zone interface correlate to the western and southern extent of the mafic siletzia block in the fore arc

seismic velocity structure of the crust beneath the japan islands abstract more than 13 000 arrival times of 562 local shallow earthquakes selected from the japan university network earthquake catalog are used to investigate the seismic velocity structure of the crust beneath the japan islands we simultaneously determined the hypocenter parameters p and s wave station corrections and depth distributions of the conrad and moho discontinuities beneath the whole of the japan islands by applying an inversion method the p and s wave station corrections show similar distribution patterns they are negative relatively late arrivals of seismic waves in hokkaido and positive relatively early arrivals of seismic waves in western japan in eastern honshu they are positive along the coast of the pacific ocean and negative in the land area and along the coast of the japan sea the conrad discontinuity is located at a depth range from 12 to 22 km in hokkaido the conrad is shallow in the eastern pan and becomes deep toward the west in ne honshu the conrad is deep beneath the land area and becomes shallow toward the surrounding seas in western japan the conrad is shallow in the northern part and becomes deep toward the south the moho is located in a depth range from 25 to 40 km in hokkaido the moho has the shape of a circular cone with a maximum depth of 36 km in most parts of the japan islands the moho is deep beneath the land area and becomes shallow toward the surrounding seas the moho is deepest up to 40 km beneath the central part of the chubu district

characterizing and minimizing the effects of noise in tide gauge time series relative and geocentric sea level rise around australia we quantify the rate of sea level rise around the australian continent from an analysis of tide gauge and global positioning system gps data sets to estimate the underlying linear rates of sea level change in the presence of significant interannual and decadal variability treated here as noise we adopt and extend a novel network adjustment approach we simultaneously estimate time correlated noise as well as linear model parameters and realistic uncertainties from sea level time series at individual gauges as well as from time series differences computed between pairs of gauges the noise content at individual gauges is consistent with a combination of white and time correlated noise we find that the noise in time series from the western coast of australia is best described by a first order gauss markov model whereas east coast stations generally exhibit lower levels of time correlated noise that is better described by a power law process these findings suggest several decades of monthly tide gauge data are needed to reduce rate uncertainties to 1 for undifferenced single site time series with typical noise characteristics our subsequent adjustment strategy exploits the more precise differential rates estimated from differenced time series from pairs of tide gauges to estimate rates among the network of 43 tide gauges that passed a stability analysis we estimate relative sea level rates over three temporal windows 1900 2011 1966 2011 and 1993 2011 accounting for covariance between time series the resultant adjustment reduces the rate uncertainty across individual gauges and partially mitigates the need for century scale time series at all sites in the network our adjustment reveals a spatially coherent pattern of sea level rise around the coastline with the highest rates in northern australia over the time periods beginning in 1900 1966 and 1993 we find weighted average rates of sea level rise of 1 4 0 6 1 7 0 6 and 4 6 0 8mmyr 1 respectively while the temporal pattern of the rate estimates is consistent with acceleration in sea level rise it may not be significant as the uncertainties for the shorter analysis periods may not capture the full range of temporal variation analysis of the available continuous gps records that have been collected within 80 km of australian tide gauges suggests that rates of vertical crustal motion are generally low with the majority of sites showing motion statistically insignificant from zero a notable exception is the significant component of vertical land motion that contributes to the rapid rate of relative sea level change 4mmyr 1 at the hillarys site in the perth area this corresponds to crustal subsidence that we estimate in our gps analysis at a rate of 3 1 0 7mmyr 1 and appears linked to groundwater withdrawal uncertainties on the rates of vertical displacement at gps sites collected over a decade are similar to what we measure in several decades of tide gauge data our results motivate continued observations of relative sea level using tide gauges maintained with high accuracy terrestrial and continuous co located satellite based surveying

gps constraints on 34 slow slip events within the cascadia subduction zone 1997 2005 1 refinements to gps analyses in which we factor geodetic time series to better estimate both reference frames and transient deformation resolve 34 slow slip events located throughout the cascadia subduction zone from 1997 through 2005 timing of transient onset is determined with wavelet transformation of geodetic time series thirty continuous stations are included in this study ranging from northern california to southwestern british columbia our improvements in analysis better resolve the largest creep events and also identify many smaller events at 48 5 n latitude a 14 month average recurrence interval has been observed over eight events since 1997 farther north along vancouver island a host of smaller events with a distinct 14 month periodicity also occurs in southern washington state some of the largest transient displacements are observed but lack any obvious periodicity in their recurrence along central oregon an 18 month recurrence is evident while in northern california an 11 month periodicity continues through 2005 we invert gps offsets of the 12 best recorded events for thrust slip along the plate interface using a cross validation scheme to derive optimal smoothing parameters these 12 events have equivalent moment magnitudes between 6 3 and 6 8 and have 2 3 cm of slip unlike other subduction zones no long duration events are observed and cumulative surface deformation is consistently less than 0 6 cm the many newly resolved smaller transient events in cascadia show that slow slip events occur frequently with gps best capturing only the largest events it is likely that slow slip events occur more frequently at levels not detectable with gps

periodic slow earthquakes from the cascadia subduction zone continuous geodetic measurements from convergent margins have shown that deep transient creep events can release large amounts of strain energy without detectable seismic shaking and they are thus known as slow or silent earthquakes because subduction zones generate the largest earthquakes

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

great geomagnetic storm of 9 november 1991 association with a disappearing solar filament 1 we attribute the great geomagnetic storm on 8 10 november 1991 to a large scale eruption that encompassed the disappearance of a 25 solar filament in the southern solar hemisphere the resultant soft x ray arcade spanned 90 of solar longitude the rapid growth of an active region lying at one end of the x ray arcade appears to have triggered the eruption this is the largest geomagnetic storm yet associated with the eruption of a quiescent filament the minimum hourly dst value of 354 nt on 9 november 1991 compares with a minimum dst value of 161 nt for the largest 27 day recurrent coronal hole storm observed from 1972 to 2005 and the minimum 559 nt value observed during the flare associated storm of 14 march 1989 the greatest magnetic storm recorded during the space age overall the november 1991 storm ranks 15th on a list of dst storms from 1905 to 2004 surpassing in intensity such well known storms as 14 july 1982 310 nt and 15 july 2000 317 nt we used the cliver et al and gopalswamy et al empirical models of coronal mass ejection propagation in the solar wind to provide consistency checks on the eruption storm association

solar and interplanetary sources of major geomagnetic storms dst 100 nt during 1996 2005 1 we present the results of an investigation of the sequence of events from the sun to the earth that ultimately led to the 88 major geomagnetic storms defined by minimum dst 100 nt that occurred during 1996 2005 the results are achieved through cooperative efforts that originated at the living with a star lws coordinated dataanalysis workshop cdaw held at george mason university in march 2005 on the basis of careful examination of the complete array of solar and in situ solar wind observations we have identified and characterized for each major geomagnetic storm the overall solar interplanetary solar ip source type the time velocity and angular width of the source coronal mass ejection cme the type and heliographic location of the solar source region the structure of the transient solar wind flow with the storm driving component specified the arrival time of shock disturbance and the start and ending times of the corresponding ip cme icme the storm driving component which possesses a prolonged and enhanced southward magnetic field bs may be an icme the sheath of shocked plasma sh upstream of an icme a corotating interaction region cir or a combination of these structures we classify the solar ip sources into three broad types 1 s type in which the storm is associated with a single icme and a single cme at the sun 2 m type in which the storm is associated with a complex solar wind flow produced by multiple interacting icmes arising from multiple halo cmes launched from the sun in a short period 3 c type in which the storm is associated with a cir formed at the leading edge of a high speed stream originating from a solar coronal hole ch for the 88 major storms the s type m type and c type events number 53 60 24 27 and 11 13 respectively for the 85 events for which the surface source regions could be investigated 54 63 of the storms originated in solar active regions 11 13 in quiet sun regions associated with quiescent filaments or filament channels and 11 13 were associated with coronal holes remarkably nine 11 cme driven events showed no sign of eruptive features on the surface or in the low corona e g no flare no coronal dimming and no loop arcade etc even though all the available solar observations in a suitable time period were carefully examined thus while it is generally true that a major geomagnetic storm is more likely to be driven by a frontside fast halo cme associated with a major flare our study indicates a broad distribution of source properties the implications of the results for space weather forecasting are briefly discussed

lithium isotope fractionation between li bearing staurolite li mica and aqueous fluids an experimental study abstract we determined the lithium isotope fractionation between synthetic li staurolite and aqueous fluids containing excess licl or lioh at 3 5 gpa between 670 and 880 c and between li mica and similar fluids at 2 0 gpa and 300 to 500 c in all experiments for the system li staurolite fluid 7 li was weakly partitioned into li staurolite whereas for li mica fluid 7 li preferentially fractionated into the fluid the difference in the li isotope fractionation behaviour results from different li coordination in staurolite li 4 and mica li 6 for the system li mica fluid fractionation is about half as large along the same t range as for spodumene fluid wunder b meixner a romer r l heinrich w 2006 t dependent isotopic fractionation of lithium between clinopyroxene and high pressure hydrous fluids contrib mineral petrol 151 112 120 this behaviour is consistent with differences in the bonding strengths of the li octahedra in li mica and spodumene subduction and concomitant dehydration of metabasic oceanic crust containing chlorite and clinopyroxene with li in six fold coordination releases fluids enriched in li and 7 li into the fore arc and arc mantle and thus introduces a light li component into the deeper mantle ongoing dehydration and li loss along the subduction path produces fluids with increasingly lower li concentrations and lighter lithium isotope compositions however as staurolite is the most important carrier of li in metapelitic assemblages the inverse fractionation of li isotopes relative to fluids enables staurolite to transport high li concentrations in combination with an isotopic composition enriched in 7 li into the mantle thus depending on the li contents and li isotope signature of the protolite breakdown of li bearing staurolite at high p and t can release fluids with high li contents and isotopically heavy li into the deep mantle wedge

lithium and its isotopes in major world rivers implications for weathering and the oceanic budget abstract the outstanding problem in the lithium geochemical cycle is the lack of an isotopic mass balance in the ocean the 6li compositions of fresh basalts 4 the hydrothermal fluids derived from them average 9 and seawater significantly heavier at 32 are well understood but only very sparse river input data are available for li mass balance calculations in an attempt to rectify the situation we have measured the lithium concentrations and isotopic compositions of major world rivers draining representative geological terrains this helps both to constrain the river endmember and to understand the behavior of lithium isotopes in the continental weathering environment fluvial isotopic compositions display a very large range 6 0 to 32 2 there is no definitive relationship between 6li and lithology but in general rivers draining marine evaporites are 20 to 22 carbonates 26 to 32 black shales 26 shields 6 6 to 19 and mixed siliceous terrains 6 to 28 the flow weighted mean concentration of the measured rivers is 215 nm at 23 this updated riverine 6li value responsible for 30 of the global riverine discharge does not solve the isotopic imbalance if the measured li concentrations and isotopic compositions are representative of all rivers the presence of a yet unidentified sink with a higher fractionation factor 1 023 than determined for low temperature basalt alteration 1 019 is required for an isotopic steady state of li in the ocean authigenic clays are a possible candidate as clays are known to be enriched in both lithium and in the light isotope preferentially alternatively the hydrothermal flux must be much less than half of that estimated by the 3he inventory and the oceanic budgets for 87sr 86sr and mg the relationship of 6li to the major ions and 87sr 86sr suggests that the important processes affecting river dissolved lithium isotopic compositions are fractionation between solution and secondary minerals and thus the intensity of weathering

two step development of geomagnetic storms using the dst index more than 1200 geomagnetic storms from weak to intense spanning over three solar cycles have been examined statistically interplanetary magnetic field imf and solar wind data have also been used in the study it is found that for more than 50 of intense magnetic storms the main phase undergoes a two step growth in the ring current that is before the ring current has decayed significantly to the prestorm level anew major particle injection occurs leading to a further development of the ring current and making dst decrease a second time thus intense magnetic storms may often be the result of two closely spaced moderate storms the corresponding signature in the interplanetary medium is the arrival of double structured southward imf at the magnetosphere

crustal uplift and sea level rise in northern cascadia from gps absolute gravity and tide gauge data we combine data from nine gps absolute gravity and tide gauge stations to estimate the relation between sea level rise vertical motion and solid earth processes in the pacific northwest gps vertical velocities in itrf2000 and absolute gravity rates are well correlated with a gradient of 0 2 0 1 gal mm 1 but show a significant offset of 0 53 0 30 gal yr 1 2 2 1 3 mm yr 1 95 confidence tide gauge and gps data indicate a northeast pacific regional sea level rise of 1 7 0 5 mm yr 1 aligned to itrf2000 or an unlikely regional sea level fall of 0 5 0 5 mm yr 1 aligned to absolute gravity although we cannot rule out a bias in the gps reference frame alignment our results suggest a possible absolute gravity bias by a long period mass increase from an unknown near surface or deep seated source the impact of such a mass increase on gravity vertical motion and sea level remains to be defined

subduction of the philippine sea plate beneath southwestern japan slab geometry and its relationship to arc magmatism 1 we carry out high resolution three dimensional seismic tomography of the crust and upper mantle beneath southwestern sw japan using arrival time data obtained from the nationwide seismograph network the tomographic images provide new insights into the configuration of the philippine sea slab and arc magmatism the results confirm the existence of an aseismic portion of the philippine sea slab at greater depths beyond the seismic portion the philippine sea slab is subducting aseismically down to at least a depth of 200 km in chubu 60 80 km in kinki and 60 km in chugoku and is subducting seismically to depths of 150 200 km in kyushu in the chubu district it is subducting seismically at a shallow dip and then bends downward beneath the volcanic area whereas in the kinki district it is subducting subhorizontally as far as the japan sea the differences in the slab geometry between adjacent regions correlate with the differences in volcanic activity suggesting the importance of the geometry of the philippine sea slab on arc magmatism our tomographic images further imply subduction of the philippine sea slab down to a depth of around 70 km northwest of the izu peninsula the philippine sea slab in that region might have split into western and eastern parts separated by a slab tear and collided with the pacific slab at depths of 150 200 km

effect of annual signals on geodetic velocity 1 our analysis of global positioning system gps site coordinates in a global reference frame shows annual variation with typical amplitudes of 2 mm for horizontal and 4 mm for vertical with some sites at twice these amplitudes power spectrum analysis confirms that gps time series also contain significant power at annual harmonic frequencies with spectral indices 1 2 which indicates the presence of repeating signals van dam et al 2001 showed that a major annual component is induced by hydrological and atmospheric loading unless accounted for we show that annual signals can significantly bias estimation of site velocities intended for high accuracy purposes such as plate tectonics and reference frames for such applications annual and semiannual sinusoidal signals should be estimated simultaneously with site velocity and initial position we have developed a model to calculate the level of bias in published velocities that do not account for annual signals simultaneous estimation might not be necessary beyond 4 5 years as the velocity bias rapidly becomes negligible minimum velocity bias is theoretically predicted at integer plus half years as confirmed by tests with real data below 2 5 years the velocity bias can become unacceptably large and simultaneous estimation does not necessarily improve velocity estimates which rapidly become unstable due to correlated parameters we recommend that 2 5 years be adopted as a standard minimum data span for velocity solutions intended for tectonic interpretation or reference frame production and that we be skeptical of geophysical interpretations of velocities derived using shorter data spans

rates of sea level change over the past century in a geocentric reference frame 1 the results from a carefully implemented gps analysis using a strategy adapted to determine accurate vertical station velocities are presented the stochastic properties of our globally distributed gps position time series were inferred allowing the computation of reliable velocity uncertainties most uncertainties were several times smaller than the 1 3 mm yr global sea level change and hence the vertical velocities could be applied to correct the long tide gauge records for land motion the sea level trends obtained in the itrf2005 reference frame are more consistent than in the itrf2000 or corrected for glacial isostatic adjustment gia model predictions both on the global and the regional scale leading to a reconciled global rate of geocentric sea level rise of 1 61 0 19mm yr over the past century in good agreement with the most recent estimates

estimates of the regional distribution of sea level rise over the 1950 2000 period abstract topex poseidon satellite altimeter data are used to estimate global empirical orthogonal functions that are then combined with historical tide gauge data to estimate monthly distributions of large scale sea level variability and change over the period 1950 2000 the reconstruction is an attempt to narrow the current broad range of sea level rise estimates to identify any pattern of regional sea level rise and to determine any variation in the rate of sea level rise over the 51 yr period the computed rate of global averaged sea level rise from the reconstructed monthly time series is 1 8 0 3 mm yr 1 with the decadal variability in the computed global mean sea level it is not possible to detect a significant increase in the rate of sea level rise over the period 1950 2000 a regional pattern of sea level rise is identified the maximum sea level rise is in the eastern off equatorial pacific and there is a minimum along the equator in the western pacific and in the eastern indian ocean a g

kar age determination of late quaternary volcanic rocks using the mass fractionation correction procedure application to the younger ontake volcano central japan abstract we propose an age derivation procedure for the k ar dating method to be applied to late quaternary volcanic rocks of low to medium k 2 o content whose k ar ages calculated by the conventional derivation procedure provide insufficient age information in this procedure which we call the mass fractionation correction procedure mfcp the initial 40 ar 36 ar ratios of the samples are estimated from the stable 38 ar 36 ar ratios determined by the unspiked technique assuming that the initial argon isotope ratios of all the samples should lie on a theoretical mass fractionation line of argon in the atmosphere to examine the usefulness of the mfcp systematic k ar age determinations using this procedure were made on volcanic rocks from the stratigraphically well known younger ontake volcano in central japan which has erupted repeatedly over the past 100 ka the k ar ages determined for these volcanics by this procedure generally have analytical uncertainties within 25 1 level and are consistent with the volcanostratigraphy exceptions were the large phenocrysts in pumice fall deposits these may contain significant amounts of excess 40 ar and we considered them to be unsuitable for accurate k ar age determinations of young volcanic rocks in the cases of lava flows which underlie a widespread fallout tephra the k ar ages determined by the mfcp were consistent with the 14 c age of the tephra 21 22 ka

major geomagnetic storms dst 100 nt generated by corotating interaction regions 1 seventy nine major geomagnetic storms minimum dst 100 nt observed in 1996 to 2004 were the focus of a living with a star coordinated data analysis workshop cdaw in march 2005 in nine cases the storm driver appears to have been purely a corotating interaction region cir without any contribution from coronal mass ejection related material interplanetary coronal mass ejections icmes these storms were generated by structures within cirs located both before and or after the stream interface that included persistently southward magnetic fields for intervals of several hours we compare their geomagnetic effects with those of 159 cirs observed during 1996 2005 the major storms form the extreme tail of a continuous distribution of cir geoeffectiveness which peaks at dst 40 nt but is subject to a prominent seasonal variation of 40 nt which is ordered by the spring and fall equinoxes and the solar wind magnetic field direction toward or away from the sun the o brien and mcpherron 2000 equations which estimate dst by integrating the incident solar wind electric field and incorporating a ring current loss term largely account for the variation in storm size they tend to underestimate the size of the larger cir associated storms by dst 20 nt this suggests that injection into the ring current may be more efficient than expected in such storms four of the nine major storms in 1996 2004 occurred during a period of less than three solar rotations in september to november 2002 also the time of maximum mean imf and solar magnetic field intensity during the current solar cycle the maximum cir storm strength found in our sample of events plus additional 23 probable cir associated dst 100 nt storms in 1972 1995 is dst 161 nt this is consistent with the maximum storm strength dst 180 nt expected from the o brien and mcpherron equations for the typical range of solar wind electric fields associated with cirs this suggests that cirs alone are unlikely to generate geomagnetic storms that exceed these levels

alteration of the oceanic crust implications for geochemical cycles of lithium and boron abstract fresh tholeiitic basalt glass has been reacted with seawater at 150 c water rock mass ratio of 10 and fresh diabase has been reacted with a na k ca cl fluid at 375 c water rock mass ratios of 1 2 and 5 to understand better the role of temperature basalt composition and water rock mass ratio on the direction and magnitude of b and li exchange during basalt alteration at 150 c slight but nevertheless significant amounts of b and li were removed from seawater and incorporated into a dominantly smectite alteration phase at 375 c however b and li were leached from basalt b behaved as a soluble element and attained concentrations in solution limited only by the b concentration in basalt and the water rock mass ratio li however was less mobile for example at water rock mass ratios of 1 2 and 5 the percent of li leached from basalt was 58 70 and 92 respectively this suggests some mineralogic control on li mobility during hydrothermal alteration of basalt especially at low water rock mass ratios in general these results as well as those for b are consistent with the temperature dependent chemistry of altered seafloor basalt and the chemistry of ridge crest hydrothermal fluids based on the distribution and chemistry of products of seafloor weathering low 150 c and high temperature hydrothermal alteration of basalt and the chemistry of ridge crest hydrothermal fluids it was estimated that alteration of the oceanic crust is a li source for seawater this is not true for b however since the hot spring flux estimated for b is balanced by low temperature basalt alteration these data coupled with b and li flux estimates for other processes e g continental weathering clay mineral adsorption authigenic silicate formation and formation of siliceous skeletal material yield new insight into the b and li geochemical cycles calculations performed here indicate relatively good agreement between the magnitude of b and li sources and sinks the geochemical cycle of b however may be affected by serpentinization of mantle derived peridotite in oceanic fracture zones serpentinites are conspicuously enriched in b and if the b source for these rocks is seawater then an additional b sink exists which must be integrated into the b geochemical cycle however until more data are available in terms of areal extent of serpentinization serpentite chemistry and isotopic composition the importance of b in these rocks with respect to the b geochemical cycle remains speculative at best

effects of magnetic clouds on the occurrence of geomagnetic storms the first 4 years of wind 1 we investigate geomagnetic activity associated with magnetic clouds as well as some aspects of the clouds magnetic field structure e g magnetic field distributions of the clouds thirty four magnetic cloud events observed by wind over the years 1995 1998 are investigated in this study magnetic clouds are a principal source of strong long lasting interplanetary negative bz fields in solar magnetospheric coordinates and hence are a major source of geomagnetic activity dst 50 nt the region just upstream of a cloud may be a significant source of southward fields instead of or as well as the cloud itself we call this upstream region a sheath if it is bounded by a shock or a pressure pulse and the cloud this study helps to identify the major sources regions of southward bz following shock passages or within the magnetic clouds that are most dominant in the generation of geomagnetic storms it is found that a geomagnetic storm can be induced by 1 a sheath 2 the leading i e front part region of a cloud 3 the trailing part of a cloud and 4 both sheath and cloud regions because of this complexity a storm with a multistep main phase can occur the related occurrence percentages of storms were 17 6 six events 44 1 15 events 5 9 two events and 20 6 seven events and the averaged storm intensities minimum dst were 60 85 92 and 58 nt respectively for the remaining four events 11 8 there were no storms the occurrence timing of storm intensity is highly correlated with the occurrence timing of minimum bz maximum vbs or for a magnetic cloud with the field rotating from southward to northward

application of sr isotopes to geochemical mapping and provenance analysis the case of aichi prefecture central japan abstract geochemical maps expressing areal distributions of chemical elements in the earth s land surface have been published in several countries in relation to various global environment issues the authors have applied a radiogenic isotope ratio 87 sr 86 sr to geochemical mapping in order to understand the geological origin transportation and dispersion system of chemical elements in the earth s land surface the sr isotope ratio is a useful tracer for distinguishing the geological origin of surficial deposits especially in areas where surface exposure of bedrocks is low because it is not significantly altered by the processes of weathering and transportation most bedrocks in the japanese islands are covered by plants soils and urban areas in this study 142 of 1219 stream sediments 87 sr 86 sr values and the above average presence of granitic rocks in the study area compared with the surface exposure of the japan arc the first factor controlling the distribution of sr isotope ratios is the bedrock distributed around the sampling points regional variation in the 87 sr 86 sr value shows that it is higher in the western and southeastern parts where sedimentary rocks and metamorphic rocks are distributed and that it is lower mainly in the central part where granitic rocks are distributed the 87 rb 86 sr 87 sr 86 sr plot for stream sediments more clearly reveals the differences and similarities of bedrocks in some locations the distribution of sr isotope ratios does not correspond to that of bedrocks on the geological map one reason is the existence of unmapped bedrock for example small intrusive masses of granite the other is fluvial transportation and dispersion the distribution of the isotope ratios suggests that some stream sediments include surficial deposits from a few km upstream application of the sr isotope ratio to geochemical mapping is useful for revealing both the distribution of unexposed bedrocks and the transportation of surficial deposits information on unexposed bedrocks will be expected to contribute to the improvement of geological mapping

downstream and seasonal changes of lithium isotope ratios in the ganges brahmaputra river system the li isotope ratio 7li is expected to be a useful tracer of silicate weathering in river and groundwater systems which is an important contributor to the seawater compositional changes that accompany the evolution of the earth s surface environment to obtain accurate estimates of continental li fluxes to the ocean we determined 7li values of dissolved li in the lower ganges brahmaputra river system in both the dry and rainy seasons and in deep groundwater in the bengal basin dissolved li and 7li values in the lower reaches of the rivers 0 04 0 66 mol kg 1 and 19 1 to 34 2 respectively were predominantly derived from silicate weathering as is the case in the upper parts of these rivers we observed large changes in 7li over a distance of more than 1000 km downstream that were due mainly to rayleigh type removal of li from river water extremely high li concentrations 1 15 1 67 mol kg 1 and low 7li values 5 1 to 11 6 in groundwater samples indicate congruent isotope leaching and dissolution of silicate minerals in the deep aquifer where the water residence time is long in the rainy season li concentrations and 7li values were lower than in the dry season owing to the shorter residence time of river water and the substantial input of local subsurface flow through lowland alluvium these results suggest that accurate estimation of continental li fluxes to the ocean should take account of downstream and seasonal changes as well as aquifer depth variations in 7li values

southern california permanent gps geodetic array error analysis of daily position estimates and site velocities we analyze time series of daily positions estimated from data collected by 10 continuously monitoring global positioning system gps sites in southern california during the 19 month period between the june 28 1992 mw 7 3 landers and january 17 1994 mw 6 7 northridge earthquakes each time series exhibits a linear tectonic signal and significant colored noise spectral power at frequencies in the range 5 yr 1 to 0 5 d 1 is dominated by white noise or possibly fractal white noise and is several orders of magnitude higher than what would be expected from random walk noise in this short period range attributed by others to geodetic monument motions estimating a single slope for the time series power spectra suggests fractal white noise processes with spectral indices of about 0 4 site velocity uncertainties assuming this fractal white noise model are 2 4 times larger than uncertainties obtained assuming a purely white noise model a combination white noise plus flicker noise spectral index of 1 model also fits the data and suggests that the velocity uncertainties should be 3 6 times larger than for the white noise model we cannot adequately distinguish between these two noise models nor can we rule out the possibility of a random walk signal at the lowest frequencies these questions await the analysis of longer time series in any case reducing the magnitude of low frequency colored noise is critical and appears to be best accomplished by building sites with deeply anchored and braced monuments otherwise rate uncertainties estimated from continuous gps measurements may not be improved significantly compared to those estimated from infrequent campaign mode measurements

origins of lithium in submarine mud volcano fluid in the nankai accretionary wedge abstract to investigate fluid regimes in the nankai accretionary wedge we estimated the temperatures of lithium li reservoirs from the li isotope ratio 7li 6li in fluids recovered from kumano mud volcano no 5 kmv 5 in the nankai forearc basin the 7li 6li ratios in the kmv 5 fluids are among the lightest reported from submarine mud volcanoes the estimated li reservoir temperatures 310 c at maximum were significantly higher than the smectite to illite conversion temperature 60 150 c whereas the temperature of fluid from the deeper nankai decollement was estimated to be 150 c at maximum data obtained from previous conductivity surveys across the trench suggest that there are two fluid reservoirs associated with distinct dehydration processes in the nankai subduction zone from these results we inferred that the discontinuous mud diapirism in the kumano forearc basin results from the periodic injection of deep seated fluid accumulated in the corner of the serpentinized forearc mantle wedge that travels upward via a thrust fault the intermittent upwelling of deep seated fluid from the nankai accretionary wedge due to periodic breaches of a low permeability barrier above the fluid reservoir may be associated with seismogenic fault activity

effects of pore fluid pressure and tectonic stress on diverse seismic activities around the mt ontake volcano central japan abstract to understand the effects of pore fluid pressure and tectonic stress in generating diverse seismicity we deployed 11 temporary seismic stations around an active volcano mt ontake in central japan during the summers of 2009 2011 we obtained well constrained focal mechanism solutions from the seismic data recorded at the temporary stations and permanent stations located within 50 km around mt ontake we estimated the 3 d pore fluid pressure field taking into consideration spatial changes in the tectonic stress pattern by applying the method of focal mechanism tomography to the dataset we found overpressurized fluid reservoirs with a peak of 100 150 mpa at depths between 5 and 12 km in the southeast and east flanks of mt ontake this region has experienced earthquake swarm activity since 1976 many seismic events concentrated at the edge of the overpressurized fluid reservoirs where pore fluid pressure gradients are steep this indicates that a large amount of fluid flow would trigger seismic events by decreasing fault strength caused by an increase in pore fluid pressures many small events m

helium and carbon isotope systematics at ontake volcano japan we have measured chemical compositions he ne ratios and he and c isotopic compositions of 47 gas samples collected from crater fumaroles and hot springs associated with ontake volcano japan geographical and temporal variations of chemical compositions 3he 4he ratios and 13c values of co2 are reported here between 1981 and 1993 3he 4he ratios decreased with increasing distance from the central cone of the volcano while 13c values increased with the distance magmatic he and co2 are probably carried by a fluid flowing through the volcanic edifice and are diluted by crustal he and co2 a negative correlation of 3he 4he ratios and 13c values suggests two component mixing between magmatic and crustal end members at the sampling sites close to the fault formed by a m6 8 earthquake that occurred in september 1984 3he 4he ratios have increased significantly with time from 1984 to 1993 while except for three sites close to the fault no systematic change of 13c values is found on the other hand he and c isotopes have been constant at the sites distant from the fault the temporal variations of 3he 4he ratios may be related to the recent reactivation of ontake volcano

post seismic hydrochemical changes in regional groundwater flow systems in response to the 2016 mw 7 0 kumamoto earthquake abstract an understanding of the detailed mechanisms and processes of hydrochemical changes in regional groundwater flow systems in response to large earthquakes has been hindered because of a lack of spatiotemporal datasets to describe these changes to clarify these issues we documented hydrochemical changes observed during the 2016 mw 7 0 kumamoto crustal earthquake using a large amount of analytical records for an area of ca 945 km2 from 139 wells for 82 measured parameters spatiotemporal distribution patterns of these changes were characterized based on a factor notation calculated using a 10 year data trend our results suggest that alteration of hydrogeological properties i e seismic rupturing coseismic mountain water release and release of soil pore waters caused changes in hydrochemical signatures at the regional scale most prominently reflected in elevated dissolved si diluted cl and increased co2 and organic compounds contents other hydrochemical anomalies detected at the local scale were induced by deep fluid upwelling and liquefaction this study identified the combined mechanisms and processes that generate the overall water chemistry changes in active groundwater flow systems in kumamoto our results provide new insights into coseismic hydrochemical changes that could be applied to other aquifer systems and importantly the use of groundwater resources during and after disasters

global scale observations of ionospheric convection during geomagnetic storms 1 the global effects on the ionosphere during periods of intense geomagnetic activity associated with geomagnetic storms are investigated using the super dual auroral radar network superdarn the influence of the main and recovery phases of geomagnetic storms on ionospheric properties such as backscatter occurrence rates velocity distributions and convection patterns are presented the evolution of magnetosphere and ionosphere parameters during the storms did not depend on the origin of the storm e g a coronal mass ejection or a corotating interaction region instead there was a continuum of response to the intensity of the driver for example we found a clear relationship between the most negative value of the southward component of the interplanetary magnetic field imf bz and the most negative value of the sym h index which marks the end of the main phase of a storm this is one of the first superposed epoch studies that analyzes the sunward antisunward line of sight velocity as a function of magnetic local time for geomagnetic storms of various intensities in the noon sector before and during the main phase of the storms the superdarn radars recorded faster antisunward ionospheric plasma drifts together with a significant increase in the number of ionospheric echoes this is consistent with the expected increase in soft particle precipitation in the noon sector and with the reconnection electric field that occurs when the imf bz is strongly negative as is the case during the main phase of storms the superdarn echo occurrence in the noon sector returned to prestorm values early in the recovery phase the overall response was similar in the midnight sector except that the peak echo occurrence for the most intense storms was limited to a narrower time interval centered on the end of the main phase there were reductions in the strong antisunward flows near local midnight observed during the main phase and early in the recovery phase particularly for the intense storm class strong electric fields are applied in the nightside ionosphere during storms and the decameter structures from which superdarn scatter are more easily produced however in regions of energetic auroral precipitation and after a long exposure to strong electric fields there is often a reduction in superdarn echoes due to absorption or changes in radio wave propagation

a silent slip event on the deeper cascadia subduction interface continuous global positioning system sites in southwestern british columbia canada and northwestern washington state usa have been moving landward as a result of the locked state of the cascadia subduction fault offshore in the summer of 1999 a cluster of seven sites briefly reversed their direction of motion no seismicity was associated with this event the sudden displacements are best explained by 2 centimeters of aseismic slip over a 50 kilometer by 300 kilometer area on the subduction interface downdip from the seismogenic zone a rupture equivalent to an earthquake of moment magnitude 6 7 this provides evidence that slip of the hotter plastic part of the subduction interface and hence stress loading of the megathrust earthquake zone can occur in discrete pulses

assessing the impact of vertical land motion on twentieth century global mean sea level estimates near global and continuous measurements from satellite altimetry have provided accurate estimates of global mean sea level in the past two decades extending these estimates further into the past is a challenge using the historical tide gauge records not only is sampling nonuniform in both space and time but tide gauges are also affected by vertical land motion vlm that creates a relative sea level change not representative of ocean variability to allow for comparisons to the satellite altimetry estimated global mean sea level gmsl typically the tide gauges are corrected using glacial isostatic adjustment gia models this approach however does not correct other sources of vlm that remain in the tide gauge record here we compare global positioning system gps vlm estimates at the tide gauge locations to vlm estimates from gia models and assess the influence of non gia related vlm on gmsl estimates we find that the tide gauges on average are experiencing positive vlm i e uplift after removing the known effect of gia resulting in an increase of 0 24 0 08 mm yr 1 in gmsl trend estimates from 1900 to present when using gps based corrections while this result is likely dependent on the subset of tide gauges used and the actual corrections used it does suggest that non gia vlm plays a significant role in twentieth century estimates of gmsl given the relatively short gps records used to obtain these vlm estimates we also estimate the uncertainty in the gmsl trend that results from limited knowledge of non gia related vlm