the metagabbros orthogneisses and paragneisses of the connemara complex western ireland although now largely disappeared within the 400 ma old galway granite the syntectonic connemara metagabbro gneiss complex which crystallized at 490 ma arenig is the largest intrusion into the dalradian rocks it is part of widespread cambro ordovician volcanism and plutonic injection into continental crust in the appalachian caledonide orogenic belt being synchronous in crystallization with the widely obducted 490 ma ophiolites within the orogeny the peridotites and hornblende gabbros were injected broken up and shouldered aside by quartz diorite granodiorite granite and trondhjemite gneisses and it is shown that these orthogneisses are not the in situ differentiation products of the gabbro magma the hornblende in the metagabbros is mainly igneous but is partly metamorphic and replaces olivine fo 75 92 orthopyroxene en 65 92 clinopyroxene wo 48 5 en 50 39 fs 5 14 and plagioclase typically an 80 92 range an 50 96 an aureole at least 10 km wide in the sillimanite zone was imposed and cordierite garnet sillimanite dalradian hornfelses were partially melted at temperatures up to 1000 o c near to the gabbros at 4 5 1 kbar corresponding to c 18 km depth this suggests that the complex forms part of the root of a now eroded batholith of calc alkaline affinities the gabbros corresponding to the transition zone to a basic bottom which is often supposed to underlie many batholiths within the orthogneisses are sheets of paragneiss formed from dalradian metasediments which have been folded up from the floor and down into sides of the magma chamber which process could be illustrative of the means by which basic magma can intimately interact with crustal material the 18 o 16 o d h nd and sr isotope evidence and the existence of inherited zircons in the gneisses indicate that the gabbro and gneiss magmas were significantly contaminated with crustal possibly dalradian material both before and after intrusion with the lowest initial 87 sr 86 sr at 490 ma being 0 708 even in samples far removed from metasediment the metagabbros are tholeiitic to high alumina basalt in character but the gneisses have distinct calc alkaline geochemistry the chemistry igneous hornblende and highly calcic plagioclase match many arc plutons in the western usa the syntectonic nature and the ubiquitous gneissic fabric in the quartz diorites trondhjemites and granites is a consequence of early movements which were probably in part connected with the separation of the connemara massif and which culminated in slicing off the largely inverted complex and carrying it southwards on the mannin thrust which underlies the whole of connemara the complex is thus a fragment of a now disrupted cambro ordovician continental magmatic arc or continent island arc environment which can be traced along the se edge of the laurentian continent

recovering seismic displacements through combined use of 1 hz gps and strong motion accelerometers retrieving displacement from seismic acceleration records is often difficult because unknown small baseline offsets in the acceleration time series will contaminate the doubly integrated record with large quadratic errors one hertz global positioning system gps position estimates and collocated seismic data are available from the 2003 m w 8 tokachi oki hokkaido earthquake after a process of correcting for possible misorientation of the seismic sensors an inversion method is used to simultaneously solve for ground displacement with both data sets as input constraints this inversion method takes into account the presence of unknown offsets in the acceleration record and the relatively large uncertainties in the estimated 1 hz gps positions in this study 117 channels of seismic data were analyzed only 5 of the time does the static displacement retrieved from traditional baseline correction processing without gps information agree with the absolute displacement measured with 1 hz gps to within the errors of the gps data in solving simultaneously for constrained displacements that agree with both the seismic and gps data sets an optimal solution was found that included only one or two step functions in the acceleration records potential explanations for the offsets are analyzed in terms of tilt of the sensor or electronic noise for nine stations clear misorientations of the seismic sensors of more than 20 deg from the reported orientation were found for this size event the 30 sec sampled gps solutions were also a sufficient constraint for establishing the offset errors and recovering reliable displacements the results significantly extend the frequency band over which accelerometer data are reliable for source inversion studies online material plots of constrained seismograms with metadata

silicon isotope fractionation during silica precipitation from hot spring waters evidence from the geysir geothermal field iceland this study aims to explore the extent and controls of silicon isotope fractionation in hot spring systems of the geysir geothermal area iceland a setting where sinter deposits are actively formed the 30si values of dissolved silica measured in the spring water and sampling sites along outflowing streams covering a temperature range between 20 and 100 c were relatively constant around 0 2 whereas the 30si signatures of associated opaline sinters from the streambeds were between 0 1 and 4 0 becoming progressively more negative in the downstream parts of the aprons here the deposited sinters represent some of the most 30si depleted abiotically produced terrestrial materials documented to date compared to the data reported for icelandic basalts considered to be the source of the silicon the 30si values of the fluids and sinter deposits are higher and lower respectively the resulting values for apparent solid water isotope fractionation 30sisolid water decreased with decreasing temperature from ca 0 7 at 80 c to 3 7 at 20 c locally down to 4 4 this temperature relationship was reproducible in each of the investigated hot spring systems and is qualitatively consistent with recent findings in laboratory experiments on kinetic fractionation for a flowing fluid however the apparent fractionation magnitudes observed in the field are ca 2 more negative and thus significantly larger we infer that solid water silicon isotope fractionation during deposition of amorphous silica from a flowing fluid correlates inversely with temperature but is essentially a function of the precipitation rate such that the fractionation factor decreases with increasing rate as an important corollary the effective fractionation behavior during precipitation of silica from saturated solutions is a system dependent feature which should be taken into account when using silicon isotopes for paleo environmental reconstructions

quasi real time fault model estimation for near field tsunami forecasting based on rtk gps analysis application to the 2011 tohoku oki earthquake mw 9 0 1 real time crustal deformation monitoring is extremely important for achieving rapid understanding of actual earthquake scales because the measured permanent displacement directly gives the true earthquake size seismic moment mw information which in turn provides tsunami forecasting we have developed an algorithm to detect estimate static ground displacements due to earthquake faulting from real time kinematic gps rtk gps time series the new algorithm identifies permanent displacements by monitoring the difference of a short term average sta to a long term average lta of the gps time series we assessed the noise property and precision of the rtk gps time series with various baseline length conditions and orbits and discerned that the real time ephemerides based on the international gnss service igs are sufficient for crustal deformation monitoring with long baselines up to 1 000 km we applied the algorithm to data obtained in the 2011 off the pacific coast of tohoku earthquake mw 9 0 to test the possibility of coseismic displacement detections and further we inverted the obtained displacement fields for a fault model the inversion estimated a fault model with mw 8 7 which is close to the actual mw of 9 0 within five minutes from the origin time once the fault model is estimated tsunami waveforms can be immediately synthesized using pre computed tsunami green s functions the calculated waveforms showed good agreement with the actual tsunami observations both in arrival times and wave heights suggesting that the rtk gps data by our algorithm can provide reliable rapid tsunami forecasting that can complement existing tsunami forecasting systems based on seismic observations

very high rate 10 hz gps seismology for moderate magnitude earthquakes the case of themw6 3 l aquila central italy event accepted for publication in journal of geophysical research copyright 2010 american geophysical union

tem study of progressive alteration of igneous biotite to kaolinite throughout a weathered soil profile abstract tem characterization of progressive alteration of igneous biotite to kaolinite throughout a weathered soil profile was carried out to study the mechanisms of the reaction from biotite to kaolinite a biotite like phase with d 001 10 5 a but with a higher al si ratio and lower fe mg and k contents forms as a first intermediate alteration product of igneous biotite this phase is referred to as altered biotite two different alteration mechanisms are responsible for the altered biotite kaolinite reaction 1 reaction of one layer of altered biotite to form two layers of kaolinite and 2 transition of one layer of altered biotite to one layer of halloysite which subsequently reacted to form one layer of kaolinite metastable intermediate altered biotite and halloysite form at low temperatures where reactions are sluggish as consistent with the ostwald step rule and in direct contrast to equivalent reactions at high temperatures

mechanisms controlling the silicon isotopic compositions of river waters it has been proposed that silicon si isotopes are fractionated during weathering and biological activity leading to heavy dissolved riverine compositions in this study the first seasonal variations of stable isotope compositions of dissolved riverine si are reported and compared with concomitant changes in water chemistry four different rivers in switzerland were sampled between march 2004 and july 2005 the unique high resolution multi collector icp ms nu1700 has been used to provide simultaneous interference free measurements of 28si 29si and 30si abundances with an average limiting precision of 0 04 on 30si this precision facilitates the clarification of small temporal variations in isotope composition the average of all the data for the 40 samples is 30si 0 84 0 19 1 sd despite significant differences in catchment lithologies biomass climate total dissolved solids and weathering fluxes the averaged isotopic composition of dissolved si in each river is strikingly similar with means of 0 70 0 12 for the birs 0 95 0 22 for the saane 0 93 0 12 for the ticino and 0 79 0 19 for the verzasca however the 30si undergoes seasonal variations of up to 0 6 comparisons between 30si and physico chemical parameters such as the concentration of dissolved si and other cations the discharge of the rivers and the resulting weathering fluxes permits an understanding of the processes that control the si budget and the fate of dissolved si within these rivers the main mechanism controlling the si isotope composition of the mountainous verzasca river appears to be a two component mixing between the seepage of soil ground waters with heavier si produced by clay formation and superficial runoff associated with lighter si during high discharge events a biologically mediated fractionation can be excluded in this particular river system the other rivers display increasing complexity with increases in the proportion of forested and cultivated landscapes as well as carbonate rocks in the catchment in these instances it is impossible to resolve the extent of the isotopic fractionation and contributed flux of si contributed by biological processes as opposed to abiotic weathering the presence of seasonal variations in si isotope composition in mountainous rivers provides evidence that extreme changes in climate affect the overall composition of dissolved si delivered to the oceans the oceanic si isotope composition is very sensitive to even small changes in the riverine si isotope composition and this parameter appears to be more critical than plausible changes in the si flux therefore concurrent changes in weathering style may need to be considered when using the si isotopic compositions of diatoms sponges and radiolaria as paleoproductivity proxies

germanium silicon fractionation in a tropical granitic weathering environment abstract germanium silicon ge si ratios were determined on quartz diorite bedrock saprolite soil primary and secondary minerals phytolith soil and saprolite pore waters and spring water and stream waters in an effort to understand ge si fractionation during weathering of quartz diorite in the rio icacos watershed puerto rico the ge si ratio of the bedrock is 2 mol mol with individual primary mineral phases ranging between 0 5 and 7 mol mol the ratios in the bulk saprolite are higher 3 mol mol than values measured in the bedrock the major saprolite secondary mineral kaolinite has ge si ratios ranging between 4 8 and 6 1 mol mol the high ge si ratios in the saprolite are consistent with preferential incorporation of ge during the precipitation of kaolinite bulk shallow soils have lower ratios 1 1 1 6 mol mol primarily due to the residual accumulation of ge poor quartz ge si ratios measured on saprolite and soil pore waters reflect reactions that take place during mineral transformations at discrete depths spring water and baseflow stream waters have the lowest ge si ratios 0 27 0 47 mol mol reflecting deep initial weathering reactions resulting in the precipitation of ge enriched kaolinite at the saprolite bedrock interface mass balance calculations on saprolite require significant loss of si and al even within 1 m above the saprolite bedrock interface higher pore water ge si ratios 1 2 mol mol are consistent with partial dissolution of this ge enriched kaolinite pore water ge si ratios increase up through the saprolite and into the overlying soil but never reach the high values predicted by mass balance perhaps reflecting the influence of phytolith recycling in the shallow soil

the potential of high rate gps for strong ground motion assessment abstract we show that high rate global positioning system gps can have a vital role to play in near real time monitoring of potentially destructive earthquakes we do this by investigating the potential of gps in recording strong ground motions from earthquakes in switzerland and japan the study uses finite fault stochastic ground motion simulation based on fourier amplitude spectra and duration models previously developed for both countries allowing comparisons in terms of both fourier and time domain characteristics here the peak ground velocity pgv we find that earthquakes of magnitude m w 5 8 can be recorded by gps in real time at 10 km distance that is their fourier spectrum exceeds the noise of the instruments enough to be used in strong motion seismology postprocessing of gps time series lowers the noise and can improve the minimum observable magnitude by 0 1 0 2 as gps receivers can record at higher rates 10 hz we investigate which sampling rate is sufficient to optimally record earthquake signals and conclude that a minimum sampling rate of 5 hz is recommended this is driven by recording events at short distances below 10 km for magnitude 6 events and below 30 km for magnitude 7 events furthermore the maximum ground velocity derived from gps is compared with the actual pgv for synthetic signals from the stochastic simulations and the 2008 m w 6 9 iwate earthquake the proposed model confirmed by synthetic and empirical data shows that a reliable estimate of pgv for events of about magnitude 7 and greater can be basically retrieved by gps in real time and could be included for instance in shakemaps for aiding postevent disaster management

chemical weathering in a tropical watershed luquillo mountains puerto rico ii rate and mechanism of biotite weathering abstract samples of soil saprolite bedrock and porewater from a lower montane wet forest the luquillo experimental forest lef in puerto rico were studied to investigate the rates and mechanisms of biotite weathering the soil profile at the top of a ridge in the rio icacos watershed consists of a 50 100 cm thick layer of unstructured soil above a 600 800 cm thick saprolite developed on quartz diorite the only minerals present in significant concentration within the soil and saprolite are biotite quartz kaolinite and iron oxides biotite is the only primary silicate releasing significant k and mg to porewaters although biotite in samples of the quartz diorite bedrock is extensively chloritized chlorite is almost entirely absent in the saprolite phyllosilicates phyllosilicate grains are present as 200 1000 m wide books below about 50 cm depth x ray diffraction xrd and electron microprobe analyses indicate that the phyllosilicate grains contain a core of biotite surrounded by variable amounts of kaolinite lattice fringe images under transmission electron microscope tem show single layers of biotite altering to two layers of kaolinite suggesting dissolution of biotite and precipitation of kaolinite at discrete boundaries some single 14 a layers are also observed in the biotite under tem the degree of kaolinitization of individual phyllosilicate grains as observed by tem decreases with depth in the saprolite this tem work is the first such microstructural evidence of epitaxial growth of kaolinite onto biotite during alteration in low temperature environments the rate of release of mg in the profile calculated as a flux through the soil normalized per watershed land area is approximately 500 mol hectare 1 yr 1 1 6 10 9 molmg msoil 2 s 1 this rate is similar to the flux estimated from mg discharge out the rio icacos 1000 mol hectare 1 yr 1 or 3 5 10 9 molmg msoil 2 s 1 indicating that scaling up from the soil to the watershed is possible for mg release the rate of mg release from biotite normalized to brunauer emmett teller bet surface area is calculated using a mass balance equation which includes the density and volume of phyllosilicate grains porewater chemistry and flux and soil porosity the mean rates of biotite weathering calculated from k and mg release rates are approximately 6 and 11 10 16 molbiotite mbiotite 2 s 1 respectively significantly slower than laboratory rates 10 12 to 10 11 molbiotite mbiotite 2 s 1 the discrepancy in scaling down from the soil to the laboratory is probably explained by 1 differences in weathering mechanism between the two environments 2 higher solute concentrations in soil porewaters 3 loss of reactive surface area of biotite in the saprolite due to kaolinite and iron oxide coatings and or 4 unaccounted for heterogeneities in flow path through the soil

gps seismology application to the 2002 mw 7 9 denali fault earthquake abstract the 2002 denali fault alaska earthquake m w 7 9 caused one or more components of most broadband seismometers in western canada to clip yet did not trigger strong motion instruments thus leaving a substantial gap in the seismic record of this event however the large amplitude surface waves generated by this event were well recorded by the global positioning system gps in the same region out to epicentral distances of more than 3000 km in this article we explore the capabilities of gps seismology specifically how the relative strengths of gps and seismic data sets can be exploited in order to more effectively study earthquake source characteristics and wave propagation effects high rate 1 hz gps data from 23 stations throughout western north america have been analyzed to derive displacement waveforms for this event and the impact of instrumentation gps receiver model and error reduction strategy modified sidereal and spatial filtering on the noise characteristics of displacement time series at each gps site was assessed after applying error reduction methods to gps displacements the final average noise floors of 0 5 cm in the horizontal and 1 5 cm in the vertical indicate that large dynamic displacements are observable by gps we validate the gps displacements by comparing broadband seismic recordings integrated to displacement with gps recordings for four effectively colocated sets of instruments we show excellent agreement between the unclipped seismic and gps recordings of the surface waves from the denali earthquake over the period range of 10 50 sec and for ground displacements exceeding about 1 0 cm thus a large gps displacement data set is now available for western north america an area where records of this event were previously missing or incomplete the final gps seismograms are archived at incorporated research institutions for seismology iris for public use in future studies of the 2002 denali earthquake

rock and stiff soil site amplification dependency on vs30 and kappa κ0 abstract a ground motion prediction equation gmpe specific to rock and stiff soil sites is derived using seismic motion recorded on high v s 30 sites in japan this gmpe applies to events with 4 5 m w 6 9 and v s 30 ranging from 500 to 1500 m s stiff soil to rock sites the empirical site coefficients obtained and the comparison with the simulated site functions show that seismic motion on rock and stiff soil sites does not depend only on v s 30 but also on the high frequency attenuation site properties 0 the effects of the site specific 0 on site amplification are analyzed using stochastic simulations with the need to take into account both of these parameters for rock site adjustments adding the site specific 0 into the gmpes thus appears to be essential in future work the rock site stochastic ground motion simulations show that the site specific 0 controls the frequency corresponding to the maximum response spectral acceleration f amp 1 this observation is used to link the peak of the response spectral shape to 0 in this specific japanese dataset and then to add the effects of high frequency attenuation into the previous gmpe from the peak ground acceleration and up to periods of 0 2 s the inclusion of 0 allows the observed bias to be corrected for the intraevent residuals and thus reduces sigma however this 0 determination is limited to a minimum number of rock site records with m w 4 5 and to distances of less than 50 km

a first look at the distribution of the stable isotopes of silicon in natural waters the first data on the distribution of the stable isotopes of silicon in marine and freshwater systems are reported both marine and riverine 30si are more positive than 30si of igneous rocks suggesting isotopic fractionation during weathering and clay formation and or biomineralization the 30si value for dissolved silicic acid from several ocean basins is 1 1 0 3 n 69 more positive values are found in surface waters due to discrimination against 30si during biogenic opal formation by diatoms the deep pacific ocean is depleted in 30si relative to the deep atlantic by roughly 0 4 30si of riverine dissolved silicon averages 0 8 0 3 n 8 the biologic fractionation of silicon isotopes coupled with effects associated with thermohaline circulation appears to play a significant role in controlling the distribution of silicon isotopes in the sea the average 30si value of inputs of silicon to the ocean most likely falls between 0 3 and 0 9 and that of the outputs falls between 0 9 to 1 9 probably in the neighborhood of 1 0

sr isotopes as a tracer of weathering processes and dust inputs in a tropical granitoid watershed luquillo mountains puerto rico abstract sr isotope data from soils water and atmospheric inputs in a small tropical granitoid watershed in the luquillo mountains of puerto rico constrain soil mineral development weathering fluxes and atmospheric deposition this study provides new information on pedogenic processes and geochemical fluxes that is not apparent in watershed mass balances based on major elements alone 87sr 86sr data reveal that saharan mineral aerosol dust contributes significantly to atmospheric inputs watershed scale sr isotope mass balance calculations indicate that the dust deposition flux for the watershed is 2100 700 mg cm 2 ka 1 nd isotope analyses of soil and saprolite samples provide independent evidence for the presence of saharan dust in the regolith watershed scale sr isotope mass balance calculations are used to calculate the overall short term chemical denudation velocity for the watershed which agrees well with previous denudation rate estimates based on major element chemistry and cosmogenic nuclides the dissolved streamwater sr flux is dominated by weathering of plagioclase and hornblende and partial weathering of biotite in the saprock zone a steep gradient in regolith porewater 87sr 86sr ratio with depth from 0 70635 to as high as 0 71395 reflects the transition from primary mineral derived sr to a combination of residual biotite derived sr and atmospherically derived sr near the surface and allows multiple origins of kaolinite to be identified

natural variations of δ30si ratios during progressive basalt weathering hawaiian islands abstract silicon stable isotopes can be used to trace the biogeochemical pathways of si as it moves from its continental sources to its sink in ocean sediments along the way si is incorporated into clay minerals taken up by plants where it forms plant opal and leached into rivers the major land to ocean conduit compared to igneous rocks the waters that drain continents are enriched in heavy si isotopes but the mechanisms that control fractionation have not been elucidated we studied si isotope fractionation along a 4 million yr basaltic soil chronosequence on the hawaiian islands using the natural context of these samples in combination with laboratory experiments we demonstrate that the isotopic composition of dissolved si in weathering systems is determined by the combined effects of rock disintegration clay mineral neosynthesis and si biocycling weathering preferentially releases 28si into solution whereas secondary mineral formation preferentially removes 28si from solution in humid environments leached soils have lost large amounts of this soluble si thus creating a net loss of 30si from the entire soil system as soils develop and greater fractions of si reside in neoformed clay minerals 30sibulk soil values change progressively toward more negative values basalt 30si values are about 0 5 but older soils have 30si values up to 2 5 the difference between the solid and solution 30si values remains more or less constant with progressive weathering and therefore soil water from older soils has a more negative 30si composition in the upper horizons of the hawaiian soils this weathering driven 30si shift is modified by the addition of unweathered primary minerals via dust carrying 30si values of about 0 5 and by biocycling of si via plants producing negative 30si values in phytoliths and positive 30si values in soil solutions derived from upper horizons due to the high concentrations of dissolved si in these near surface layers rivers have more positive 30si values than predicted based on the weathering status of the lower horizons when combined with published 30si values from large rivers worldwide we find that the results from hawaii point to weathering control of si isotopes delivered to the oceans and thus to an important continent ocean linkage that warrants further investigation

rupture processes of the 2004 chuetsu mid niigata prefecture earthquake japan a series of events in a complex fault system 1 we relocated the hypocenters of the 2004 chuetsu earthquake sequence niigata japan using the double difference method the distribution of aftershocks reveals a complex fault system consisting of five different fault planes inversions of strong motion records for the five major events within the sequence indicate that the mainshock mw 6 6 and the largest aftershock mw 6 3 occurred on parallel wnw dipping fault planes the zones of large slip asperities of these two events are located near the hypocenters in contrast the three other large earthquakes mw 5 9 5 7 and 5 9 occurred on east dipping fault planes oriented perpendicular to the fault plane of the mainshock we used slip distributions deduced from waveform inversions to estimate the coulomb failure stress changes that occurred immediately prior to each event cff values were positive at the hypocenters and within the asperities of the major aftershocks these results suggest that stress changes resulting from individual earthquakes led directly to the occurrence of subsequent earthquakes within the complex fault system

modeling the rupture process of the 2003 september 25 tokachi oki hokkaido earthquake using 1 hz gps data received 10 september 2004 accepted 3 october 2004 published 3 november 2004 1 high rategpshasthepotentialtorecoverbothdynamic and static displacements accurately we analyze 1 hz gps data recorded during the 2003 tokachi oki earthquake the 1 hz gps displacement waveforms show good agreement with integrated accelerometer records except for low frequency noise that are inherently present in integrated seismic records the gps waveforms were inverted to model the spatio temporal evolution of the fault slip during the rupture the slip is found to propagate downdip in the subduction zone with largest moment release 50 km northwest of the hypocenter the region of largest slip agrees in general with traditional seismic studies indicating that 1 hz gps can be used for finite fault studies the 1 hz gps slip model shows clearer contrast with afterslip distributions than those inferred from strong motion data possibly because 1 hz gps is more sensitive to cumulative slip distribution index terms 1294 geodesy and gravity instruments and techniques 7209 seismology earthquake dynamics and mechanics 7212 seismology earthquake ground motions and engineering citation miyazaki s k m larson k choi k hikima k koketsu p bodin j haase g emore and a yamagiwa 2004 modeling the rupture process of the 2003 september 25 tokachi oki hokkaido earthquake using 1 hz gps data geophys res lett 31 l21603 doi 10 1029 2004gl021457

δ30si systematics in a granitic saprolite puerto rico granite weathering and clay mineral formation impart distinct and interpretable stable si isotope 30 si signatures to their solid and aqueous products within a saprolite clay minerals have 30 si values 2 0 more negative than their parent mineral and the 30 si signature of the bulk solid is determined by the ratio of primary to secondary minerals mineral specific weathering reactions predominate at different depths driving changes in differing 30 si pore water values at the bedrock saprolite interface dissolution of plagioclase and hornblende creates 30 si pore water signatures more positive than granite by up to 1 2 these reactions are the main contributor of si to stream water and determine its 30 si value throughout the saprolite biotite weathering releases si to pore waters but kaolinite overgrowth formation modulates its contribution to pore water si the influence of biotite on 30 si pore water is greatest near the bedrock where biotite derived si mixes with bulk pore water prior to kaolinite formation higher in the saprolite biotite grains have become more isolated by kaolinite overgrowth which consumes biotite derived si that would otherwise influence 30 si pore water because of this isolation which shifts the dominant source of pore water si from biotite to quartz 30 si pore water values are more negative than granite by up to 1 3 near the top of the saprolite

detection of ground motions using high rate gps time series monitoring surface deformation in real time help at planning and protecting infrastructures and populations manage sensitive production i e seveso type and mitigate long term consequences of modifications implemented we present rt shake an algorithm developed to detect ground motions associated with landslides sub surface collapses subsidences earthquakes or rock falls rt shake detects first transient changes in individual gps time series before investigating for spatial correlation s of observations made at neighbouring gps sites and eventually issue a motion warning in order to assess our algorithm on fast seconds to minute large from 1cm to meters and spatially consistent surface motions we use the 1hz geonet gnss network data of the tohoku oki mw9 0 2011 as a test scenario we show the delay of detection of seismic wave arrival by gps records is of 10 seconds with respect to an identical analysis based on strong motion data and this time delay depends on the level of the time variable noise nevertheless based on the analysis of the gps network noise level and ground motion stochastic model we show that rt shake can narrow the range of earthquake magnitude by setting a lower threshold of detected earthquakes to mw6 5 7 if associated with a real time automatic earthquake location system

long period surface motion of the multi patch mw9 0 tohoku oki earthquake we show that it is possible to capture the oscillatory ground motion induced by the tohoku oki event for periods ranging from 3 to 100s using precise point positioning ppp we find that the ground motions of the sedimentary basins of japan were large respectively 0 15m s and 0 15m s2 for velocity and acceleration even for periods larger than 3s we compare geodetic observables with a ground motion prediction equation gmpe designed for japan seismicity and find that the spectral acceleration sa is well estimated for periods larger than 3s and distances ranging from 100 to 500km at last through the analysis of the displacement attenuation plots we show that the 2011 tohoku oki event is likely composed of multiple rupture patches as suggested before by time reversal inversions of seismic data

silicon isotope compositions of dissolved silicon and suspended matter in the yangtze river china abstract silicon isotope compositions of main channel samples of the yangtze river were systematically investigated along with their chemical compositions the concentration of suspended matter in the yangtze river tends to decrease from the upper reaches to the lower reaches corresponding to settling of the sediments in the lakes and reservoirs due to reduction of the velocity of water flow the silica contents of suspended matter vary from 52 1 to 56 9 and their 30si values vary from 0 to 0 7 both similar to those of shales from the upper to lower reaches the silica contents of suspended matter tend to increase whilst their 30si values tend to decrease both trends reflect the increase of clay minerals and decrease of carbonates in suspended matter the concentrations of dissolved silicon vary from 97 to 121 mol l and their 30si values vary over a wide range from 0 7 to 3 4 from the upper to lower reaches dissolved silica concentrations tend to decrease and their 30si values tend to increase these trends mainly reflect the change of chemical and isotopic characteristics of the tributaries from the upper to lower reaches the major factors responsible for these changes may be the high meteoric precipitation and significant silicon absorption by grass in wetlands and rice in paddy fields in drainage areas of the middle and lower reaches there is no correlation between 30si of dissolved silicon and that of suspended matter the 30sidiss spm values vary over a wide range of 1 0 3 7 indicating that 1 they are out of isotopic equilibrium 2 dissolved silicon and the associated suspended matter do not belong to one physico chemical system and 3 isotopic exchange rate between them is very slow the 30si value of dissolved silicon output from the yangtze river to the east sea is estimated to be 3 0 much higher than the values reported for the amazon and congo rivers this increases the 30si range of dissolved silicon in the world s rivers from 0 4 1 2 to 0 4 3 4

using 1 hz gps data to measure deformations caused by the denali fault earthquake the 3 november 2002 moment magnitude 7 9 denali fault earthquake generated large permanent surface displacements in alaska and large amplitude surface waves throughout western north america we find good agreement between strong ground motion records integrated to displacement and 1 hertz global positioning system gps position estimates collected 140 kilometers from the earthquake epicenter one hertz gps receivers also detected seismic surface waves 750 to 3800 kilometers from the epicenter whereas these waves saturated many of the seismicinstruments in the same region high frequency gps increases the dynamic range and frequency bandwidth of ground motion observations providing another tool for studying earthquake processes

the shallow plumbing system of stromboli island as imaged from 1 hz instantaneous gps positions 1 the stromboli volcano aeolian islands italy erupted suddenly on 28 december 2002 after a 17 year period of typically persistent but moderate eruptive activity followed two days later by a tsunamigenic landslide on its nw flank sciara del fuoco felt in the coastal areas of southern italy three continuous gps stations were quickly deployed near the volcano s rim sampling at 1 hz with instantaneous positions computed relative to a fourth station on its flank we report on two deformation episodes a vent migration on 16 17 february 2003 caused significant displacements at only one site and contributed to the decision not to issue a warning of an impending tsunamigenic landslide the second episode on 5 april 2003 a paroxystic explosion from the summit crater allowed us to model for the first time with geodetic data the shallow magma chambers that give rise to strombolian explosive activity

5hz gps seismology of the el mayor cucapah earthquake estimating the earthquake focal mechanism summary high rate 5hz gps records observed in the near field following the magnitude 7 2 el mayor cucapah earthquake that occurred in northern mexico on 2010 april 4 are compared with broad band seismograms the high rate gps displacement records are consistent with the twice integrated strong motion seismic records in the near field where broad band seismograms are clipped due to strong shaking agreement degrades at distances greater than about 150 km from the epicentre where displacement amplitudes approach the noise level of gps seismograms using high rate gps data the focal mechanism of the main shock is estimated and is shown to be consistent with teleseismic estimates the result is seen as confirmation that high rate gps observed at near field stations can be applied together with teleseismic seismometers to yield better information about earthquake rupture properties and parameters

the effects of weathering variability and anthropogenic pressures upon silicon cycling in an intertropical watershed tana river kenya abstract we present the first study of the si isotopic composition of dry season river waters from the tana river kenya data encompasses the entire river basin with samples collected from headwaters to the estuary thereby capturing a salinity gradient in the headwaters the isotopic signature is affected by climate as a result of its control on soil drainage and weathering the 30 si signatures in the basin range from 0 69 up to 2 23 signatures are clearly affected by dams an increase in 30 si ratios of 0 54 and a decrease in the dissolved si dsi concentration by 41 were observed downstream of the masinga dam the largest of a succession of 5 hydroelectric dams this reduction in si load is most likely due to increased diatom productivity as the corresponding change in 30 si signature is consistent with the known fractionation by these organisms the 30 si composition of waters entering the estuary is ca 2 and dsi concentrations are 349 m in the estuary the dsi concentrations decrease linearly following the salinity while the 30 si ratio remains stable indicating the absence of processes affecting the dsi pool for the studied range of salinity

centroid moment tensor inversions using high rate gps waveforms displacement time series recorded by global positioning system gps receivers are a new type of near field waveformobservation of the seismic source we have developed an inversion method which enables the recovery of an earthquake s mechanism and centroid coordinates from such data our approach is identical to that of the classical centroid moment tensor cmt algorithm except that we forward model the seismic wavefield using a method that is amenable to the efficient computation of synthetic gps seismograms and their partial derivatives we demonstrate the validity of our approach by calculating cmt solutions using 1 hz gps data for two recent earthquakes in japan these results are in good agreement with independently determined source models of these events with wider availability of data we envisage the cmt algorithm providing a tool for the systematic inversion of gps waveforms as is already the case for teleseismic data furthermore this general inversion method could equally be applied to other near field earthquake observations such as those made using accelerometers

coseismic fault zone deformation revealed with differential lidar examples from japanese mw 7 intraplate earthquakes abstract we use two recent japanese earthquakes to demonstrate the rich potential as well as some of the challenges of differencing repeat airborne light detection and ranging lidar topographic data to measure coseismic fault zone deformation we focus on densely vegetated sections of the 14 june 2008 iwate miyagi m w 6 9 and 11 april 2011 fukushima hamadori m w 7 1 earthquake ruptures each covered by 2 m resolution pre event and 1 m resolution post event bare earth digital terrain models dtms obtained from commercial lidar providers three dimensional displacements and rotations were extracted from these datasets using an adaptation of the iterative closest point icp algorithm these displacements remain coherent close to surface fault breaks as well as within dense forest despite intervals of 2 years iwate miyagi and 4 years fukushima hamadori encompassed by the lidar scenes differential lidar analysis is thus complementary to interferometric synthetic aperture radar insar and sub pixel correlation techniques which often break down under conditions of long time intervals dense vegetation or steep displacement gradients although the icp displacements are much noisier than overlapping insar line of sight displacements they still provide powerful constraints on near surface fault slip in the fukushima hamadori case near fault displacements and rotations are consistent with decreased primary fault slip at very shallow depths of a few tens of meters helping to account for the large along strike heterogeneity in surface offsets observed in the field this displacement field also captures long wavelength deformation resulting from the 11 march 2011 tohoku great earthquake

denudation rates determined from the accumulation of in situ produced 10be in the luquillo experimental forest puerto rico we present a simple method for estimation of long term mean denudation rates using in situ produced cosmogenic 10be in fluvial sediments procedures are discussed to account for the effects of soil bioturbation mass wasting and attenuation of cosmic rays by biomass and by local topography our analyses of 10be in quartz from bedrock outcrops soils mass wasting sites and riverine sediment from the icacos river basin in the luquillo experimental forest puerto rico are used to characterize denudation for major landform elements in that basin the 10be concentration of a discharge weighted average of size classes of river sediment corresponds to a long term average denudation of 43 m ma 1 consistent with mass balance results

real time gnss seismology using a single receiver summary high rate gnss has attracted increasing attention and numerous applications in geohazard monitoring and early warning in this paper we investigate three current existing singlereceiver approaches for real time gnss seismology comparing their observation models for equivalence andassessingtheimpactofmainerrorcomponents weproposesomerefinements to the variometric approach and especially consider compensating the geometry error component by using the accurate initial coordinates before the earthquake to eliminate the drift trend in the integrated coseismic displacements after careful corrections of satellite ephemeris ionospheric delay tropospheric delay and geometry errors the refined variometric approach andthetemporalpointpositioning tpp methodhaveequivalentmathematicalmodelwiththe converged precise point positioning ppp we evaluated the precision of the variometric and tpp approaches with various error correction schemes and duration time using numerous data sets and demonstrated that few centimetres accuracy of coseismic displacements is achievable even for 20 min interval we applied these single receiver approaches to process 1 hz gps data collected from the tohoku oki earthquake mw 9 0 2011 march 11 in japan to capture coseismic displacement and further inverted the obtained displacement fields for fault slip distribution and moment magnitude comparisons of the results obtained using the refined variometric approach and tpp as well as the converged ppp displayed very good consistence both in coseismic displacements within few centimetres and in the slip distribution patterns and moment magnitudes

chemical weathering in a tropical watershed luquillo mountains puerto rico i long term versus short term weathering fluxes abstract the pristine rio icacos watershed in the luquillo mountains in eastern puerto rico has the fastest documented weathering rate of silicate rocks on the earth s surface a regolith propagation rate of 58 m ma 1 calculated from iso volumetric saprolite formation from quartz diorite is comparable to the estimated denudation rate 25 50 ma 1 but is an order of magnitude faster than the global average weathering rate 6 ma 1 weathering occurs in two distinct environments plagioclase and hornblende react at the saprock interface and biotite and quartz weather in the overlying thick saprolitic regolith these environments produce distinctly different water chemistries with k mg and si increasing linearly with depth in saprolite porewaters and with stream waters dominated by ca na and si such differences are atypical of less intense weathering in temperate watersheds porewater chemistry in the shallow regolith is controlled by closed system recycling of inorganic nutrients such as k long term elemental fluxes through the regolith e g si 1 7 10 8 moles m 2 s 1 are calculated from mass losses based on changes in porosity and chemistry between the regolith and bedrock and from the age of the regolith surface 200 ma mass losses attributed to solute fluxes are determined using a step wise infiltration model which calculates mineral inputs to the shallow and deep saprolite porewaters and to stream water pressure heads decrease with depth in the shallow regolith 2 03 m h2o m 1 indicating that both increasing capillary tension and graviometric potential control porewater infiltration interpolation of experimental hydraulic conductivities produces an infiltration rate of 1 m yr 1 at average field moisture saturation which is comparable with libr tracer tests and with base discharge from the watershed short term weathering fluxes calculated from solute chemistries and infiltration rates e g si 1 4 10 8 moles m 2 s 1 are compared to watershed flux rates e g si 2 7 10 8 moles m 2 s 1 consistency between three independently determined sets of weathering fluxes imply that possible changes in precipitation temperature and vegetation over the last several hundred thousand years have not significantly impacted weathering rates in the luquillo mountains of puerto rico this has important ramifications for tropical environments and global climate change

slip history of the 2003 san simeon earthquake constrained by combining 1 hz gps strong motion and teleseismic data 1 the slip history of the 2003 san simeon earthquake is constrained by combining strong motion and teleseismic data along with gps static offsets and 1 hz gps observations comparisons of a 1 hz gps time series and a co located strong motion data are in very good agreement demonstrating a new application of gps the inversion results for this event indicate that the rupture initiated at a depth of 8 5 km and propagated southeastwards with a speed 3 0 km sec with rake vectors forming a fan structure around the hypocenter we obtained a peak slip of 2 8 m and total seismic moment of 6 2 10 18 nm we interpret the slip distribution as indicating that the hanging wall rotates relative to the footwall around the hypocenter in a sense that appears consistent with the shape of the mapped fault trace index terms 1242 geodesy and gravity seismic deformations 7205 7212 seismology earthquake ground motions and engineering 8123 tectonophysics dynamics seismotectonics citation ji c k m larson y tan k w hudnut and k choi 2004 slip history of the 2003 san simeon earthquake constrained by combining 1 hz gps strong motion and teleseismic data geophys res lett 31 l17608 doi 10 1029 2004gl020448

ability of 1 hz gps data to infer the source process of a medium sized earthquake the case of the 2008 iwate miyagi nairiku japan earthquake 1 we demonstrate the ability of 1 hz global positioning system gps data to infer a medium sized m6 class earthquake source process through an inversion study of the 2008 iwate miyagi nairiku japan earthquake m 6 9 1 hz gps waveforms for this earthquake are compared and show good agreement with strong motion waveforms ground motions are well recorded at a sufficient number of gps stations in and around source region allowing us to perform waveform inversion using 1 hz gps data only the 1 hz gps inversion result shows fairly good agreement with a joint inversion of geodetic and strong motion data such as the seismic moment mw 6 9 cumulative slip distribution and rupture propagation such agreements demonstrate that 1 hz gps is able to infer the dynamic features of the rupture process as well as permanent or static slip even for a m6 class medium sized earthquake

numerically stable computation of complete synthetic seismograms including the static displacement in plane layered media summary we present a new method for calculating dynamic and static displacements arising from a buried point source in a plane layered isotropic elastic half space we avoid the problem of the loss of precision in solutions for p sv wave motion by integrating a system of minor vector equations with solutions constructed from pairs of solutions to the equations of motion in the frequency wavenumber domain the resulting algorithm is efficient and numerically stable at zero frequency and at high frequencies and thus can be used to compute complete synthetic seismograms that include the static offset for the special case of the static deformation of a homogeneous half space we show that our results are equivalent to formulae that are often currently used in the geodetic community an advantage of our method is that a single algorithm can be used to model both seismological and geodetic measurements of ground motion we illustrate one seismological application of our method using continuous global positioning system gps data obtained for a recent earthquake seismograms calculated in a realistic layered crustal model emulate the observed dynamic and static displacements well if the calculation is only carried out at 0 hz we obtain an image of the static surface deformation and thus our method also has potential applications in the modelling of coseismic surface displacements measured with for example synthetic aperture radar interferometry

investigation of in situ weathering of quartz diorite bedrock in the rio icacos basin luquillo experimental forest puerto rico abstract the rio icacos basin in puerto rico is the site of the highest measured chemical solute fluxes for a catchment on granodiorite this is partly attributable to high annual rainfall 4300 mm high average temperature 23 c and moderate relief the bulk of these fluxes is contributed by dissolution of plagioclase and amphiboles in zones of partially weathered rock 0 5 1 5 m thick underlying saprolite these zones are characterized by systems of onion skin rindlets each 3 10 cm thick in which porosity development is dominated by weathering of plagioclase to kaolinite fe bearing aluminosilicate minerals hornblende augite and biotite persist in the weathered rock after plagioclase has weathered to completion but hornblende and augite disappear between the porous rindlet systems and saprolite a new watershed scale solute mass balance corroborates earlier studies and yields an overall reaction stoichiometry that closely resembles complete weathering of the rock except quartz and biotite to kaolinite and fe3 oxides our findings indicate that steady state assumptions are reasonable and useful in studying weathering at this site estimated steady state sediment yields based on net solute fluxes and average bedrock composition of 3 24 10 9 to 3 60 10 9 kg m 2 s 1 are smaller than measured values indicating that sediment generation is currently accelerated with respect to steady state however sediment generation has recently been closer to steady state since weathering within the rindlet systems occurs on multiple fronts moving upward and downward two new steady state conceptual models are developed to account for 1 multiple parallel weathering fronts and 2 differential rates of advance of weathering fronts due to porosity development based on these models in situ weathering rates for plagioclase at two sample locations of 2 7 10 15 and 5 0 10 15 mol na g 1 s 1 are calculated values comparable to bet surface area normalized rates of 2 7 10 16 to 5 0 10 15 mol na m 2 s 1

simulations of long period ground motions from a large earthquake using finite rupture modeling and the ambient seismic field long period ground motions generated by large earthquakes slowly attenuate with distance and can be significantly amplified by local velocity structures even at large distances we take advantage of the wave propagation information carried by the ambient seismic field to simulate the long period ground motions of the 2008 mw 6 9 iwate miyagi nairiku earthquake which occurred in the tohoku region japan we extract green s functions between pairs of stations by regarding seismometers located in the vicinity of the mainshock fault plane as virtual sources and others as receivers we calibrate the amplitude of the extracted green s functions using records of a mw 5 0 aftershock with a reverse faulting focal mechanism similar to that of the mainshock we use scaling relations between small and large earthquakes to construct several finite fault models that are used together with the extracted green s functions to simulate the ground motions of the mainshock among the different models a uniform finite source model with a rupture velocity of 1 95 km s combined with the green s functions extracted using one virtual source station located at the center of the fault plane yields the best fit between the simulated and observed long period ground motions this study demonstrates the potential of the ambient seismic field combined with finite source modeling to assess the seismic hazard related to long period ground motions that could be generated by forthcoming large earthquakes