ferromanganese oxide deposits from the central pacific ocean i encrustations from the line islands archipelago abstract chemical and mineralogical analyses of a well controlled suite of ferromanganese encrustations from the line islands archipelago central pacific suggest that they represent purely hydrogenous deposits i e they have formed through the slow accumulation of trace metal enriched oxides directly from the water column mineralogically they consist predominantly of mno2 and amorphous feoohxh2o compositionally they are similar to mno2 nodules from adjoining basinal areas but are enriched in both mn mean 20 4 max 29 3 and co mean 0 55 max 1 57 mno2 is the most important trace metal bearing phase strong associations are noted between it and co mo ni zn and cd whilst only be is associated specifically with feooh v sr and pb are partitioned between the authigenic oxide phases whilst ti most probably occurs as tio2xh2o cu is contained in both aluminosilicate contaminant phases and fe oxide phases these relations are considered to reflect the differing scavenging behaviour of mn and fe oxides in the water column crusts from 1 2 km are enriched in mn and the mn related elements and exhibit higher mn fe ratios than deeper crusts which are compositionally constant the higher mn fe ratios may result from a supply of mn from continental borderland sediments at these depths which is transported horizontally by advective diffusive processes since manganophile elements are enriched relative to mn in the 1 2 km crusts it is considered that the supply of mn is scavenged by existing oxides is oxidised and effectively occludes them a higher proportion of oxide particles thus exhibit mn oxide scavenging properties in the 1 2 km depth zone the increased vertical flux of mn resulting from the supply at 1 2 km is not reflected by higher mn fe ratios in deeper crusts so that the vertical flux of oxides is not simply related to the standing crop the mn fe ratios of the crusts thus reflect the composition of suspended oxides at similar depths

geyser preplay and eruption in a laboratory model with a bubble trap article i nfo boiling eruption conduit preplay we present visual observations and temperature measurements from a laboratory model of a geyser our model incorporates a bubble trap a zone in which vapor can accumulate in the geyser s subsurface plumbing in a ver tical conduit connected to a basal chamber analogous features have been identified at several natural geysers weobserve threetypesof eruptions 1 rising bubblesejecta smallvolume of liquidina weak spout smallerup tion 2 boilingoccursintheconduitabovethebubbletrap mediumeruption and3 boilingoccursinthecon duitandchamber large eruption inthelasttwocases boilingintheconduitcausesarapidhydrostaticpressure dropthatallows for the rise anderuptionofliquidwaterina vigorousspout boiling initiatesatdepth rather than propagating downward from the surface in a single eruption cycle multiple small eruptions precede every medium and large eruption at least one eruption cycle that culminates in a medium eruption i e a quiescent period followed by a series of small eruptions leading up to a medium eruption precedes every eruption cycle thatculminatesinalarge eruption we findthatthe transferof fluidwithhighenthalpytotheupperconduitdur ingsmallandmediumeruptionsisnecessarytoheattheupperconduitandpreparethesystemforthefullboiling required for a large eruption the placement of the bubble trap midway up the conduit allows for more efficient heatingoftheupperconduit ourmodelprovidesinsightintotheinfluenceofconduitgeometryoneruptionstyle and the importance of heat transfer by smaller events in preparing the geyser system for eruption

geometry of geyser plumbing inferred from ground deformation author s ardid a vera e kelly c manga m munoz saez c maksymowicz a ortega culaciati f abstract 2019 american geophysical union all rights reserved broadband seismic data were recorded on the ground surface around an exceptionally regular eruptive system geyser el jefe in the el tatio geyser field chile we identify two stages in the eruption recharge and discharge characterized by a radial expansion and contraction respectively of the surface around the geyser we model the deformation with spherical sources that vary in size location and pressure constrained by pressure observations inside the conduit that are highly correlated with deformation signals we find that in order to fit the data the subsurface pressure sources must be laterally offset from the geyser vent during the recharge phase and that they must migrate upward toward the vent during the eruption phase this pattern is consistent with models in which ascending fluids accumulate and then are released from a bubble trap that is horizontally offset from the shallow conduit of the geyser

nd and pb isotope time series from atlantic ferromanganese crusts implications for changes in provenance and paleocirculation over the last 8 myr high resolution nd and pb isotope time series for the last 8 myr are reported for four atlantic ferromanganese crusts dated by 10be 9be chronology these are compared to new high resolution and high precision pb isotope time series and recently published nd isotope time series for two previously studied crusts from the nw atlantic ocean these records allow a more detailed examination of atlantic deepwater variability over the time period of intensification of northern hemisphere glaciation nhg changes in the pb isotope time series started after 3 ma but were most dramatic over the last 1 8 myr coinciding with changes of pb isotopes in the arctic ocean this latter change post dates the intensification of nhg at 3 1 to 2 5 ma and reflects an increase in the input of material eroded from the archean shield of canada and greenland shifts in nd and pb isotope compositions in a crust from the blake plateau occur before 5 ma and most prominent at 8 ma suggest that water masses from either the pacific or southern ocean influenced the isotope composition of this crust the relatively high end values around 8 ma recorded by the blake plateau crust are explained by a contribution of eastward flowing pacific water through the panama gateway into the caribbean sea this high end signal decreased between 8 and 5 ma suggesting that the supply of pacific water into the caribbean became restricted this is earlier than the caribbean seawater salinity increase at 4 2 ma deduced from 18o data and may indicate that there was only a surface water connection between the caribbean and pacific between 5 and 4 2 ma the closure of the panama gateway to intermediate and deep water exchange 200 m depth apparently occurred much earlier than the intensification of northern hemisphere glaciation at 3 1 2 5 ma and cannot therefore have been a direct cause of this climatic change but may as recently argued only have been a necessary precondition

estimating growth rates of ferromanganese nodules from chemical compositions implications for nodule formation processes abstract using available information on the accretion rates and the bulk chemical compositions of oceanic ferromanganese nodules it can be shown that the accumulation rate of manganese is proportional to the square of the accumulation rate of iron this relationship has been used to derive an equation that predicts nodule growth rates from their chemical compositions the equation accurately predicts growth rates up to about 50 mm 10 6 yr but yields incorrect rates for faster growing concretions from this relationship nodules underneath water of high primary productivity grow most rapidly and accumulate transition metals most rapidly however nodules from regions of highest primary productivity do not have the highest concentrations of nickel and copper reduction of manganese within the sediment column and remobilization of a fraction to the surface sediments adds manganese to nodules without substantially augmenting the supply of other transition elements the addition of remobilized manganese to the nodule dilutes the concentrations of nickel copper and iron even though their rates of accumulation are also high

relative location of microseismicity abstractapplying the two point paraxial ray tracing we develop a technique for relative location of microseismic events our technique assumes the availability of a perforation shot or an already located microseismic event termed the master for which the paraxial ray tracing has been performed the ray tracing output for the master makes it possible to compute the relative locations of adjacent microseismic events as many as a data set contains with an efficient algorithm that requires no additional ray tracing and reduces to solving a series of simple low dimensional and well behaved optimization problems the relative event location approach discussed in our paper is especially well suited for surface microseismic monitoring because the high accuracy of the paraxial ray approximation in the directions orthogonal to the reference rays typically spanning the stimulated horizons for surface microseismic geometries ensures the calculation of precise event hypocenters at appreciable distances from th

deep fault plane geometry inferred from multiplet relative relocation beneath the south flank of kilauea dense microearthquake swarms occur in the upper south flank of kilauea providing multiplets composed of hundreds of events the similarity of their waveforms and the quality of the data have been sufficient to provide accurate relative relocations of their hypocenters a simple and efficient method has been developed which allowed the relative relocation of more than 250 events with an average precision of about 50 m horizontally and 75 m vertically relocation of these events greatly improves the definition of the seismic image of the fault that generates them indeed relative relocations define a plane dipping about 6 northward although corresponding absolute locations are widely dispersed in the swarm a composite focal mechanism built from events providing a correct spatial sampling of the multiplet also gives a well constrained northward dip of about 5 to the near horizontal plane this technique thus collapses the clouds of hypocenters of single event locations to a plane coinciding with the slip plane revealed by previous focal mechanism studies we cannot conclude that all south flank earthquakes collapse to a single plane there may locally be several planes perhaps with different dips and depths throughout the south flank volume the 6 northward dipping plane we found is too steep to represent the overall flexure of the oceanic crust under the load of the island of hawaii this plane is probably an important feature that characterizes the basal slip layer below the upper south flank of kilauea volcano differences in seismicity rate and surface deformations between the upper and lower south flank could be related to the geometry of this deep fault plane the present work illustrates how high precision relative relocations of similar events in dense swarms combined with the analysis of geodetic measurements can help to describe deep fault plane geometry systematic selection and extensive relative relocation of similar earthquakes could be attempted in other well instrumented highly seismic areas to provide reliable basic information especially useful for understanding of earthquake generation processes

variations in the fine scale composition of a central pacific ferromanganese crust paleoceanographic implications a 47 to 60 mm thick fe mn crust from horizon guyot water depth 1800 1780 m central pacific was used to evaluate the potential of crusts as recorders of neogene paleoceanographic and paleoclimatic conditions the chemical composition was determined by microprobe for 16 elements from a polished thin section three analyses were made per millimeter and averaged to give the composition of each millimeter the age of the crust was determined by measuring the strontium isotope composition of the crust and comparing it with the tertiary seawater curve the crust represents 18 5 m y of growth of fe and mn oxyhydroxides the crust is composed of alternating botryoidal and laminated layers the botryoidal layers formed during the same time intervals that widespread neogene deep sea hiatuses were forming in bottom sediments the botryoidal layers represent growth during times of intensified deepwater flow whereas the laminated intervals represent more quiescent conditions the correspondence between the botryoidal layers and the neogene hiatuses is so strong that we were able to choose a variable growth rate model over a constant growth rate model for the crust chemical changes in the crust take two forms the first is represented by broad changes in the composition defined chiefly by fourth order polynomial fits to the chemical profiles of each element with depth in the crust the second is high frequency changes in composition the broader changes occurred primarily at about 15 11 5 7 4 6 4 5 2 and 4 6 ma which may correlate with major changes in paleoceanographic circulation and development of ice caps at the poles the periods of the high frequency changes may reflect climatic changes that resulted from orbital forcing these high frequency changes may correspond to the high order eccentricity periods of 3 47 2 04 and 1 31 m y

bubble collapse as the source of tremor at old faithful geyser old faithful geyser yellowstone was used as a natural laboratory for fluid flow induced seismic activity pressure measurements within the geyser s water column obtained simultaneously with seismic measurements on the surface demonstrated that the tremor observed at old faithful results from impulsive events in the geyser tremor intensity is controlled by the rate of occurrence of these impulsive events there is no resonance observed within the water column the impulsive events are modeled by a collapse of a spherical bubble including the effects of residual non condensible gas and damping the pressure data can be explained by a collapse of a 5 cm radius bubble driven by a pressure difference of p 0 3 10 5 pa and effective viscosity e 0 04 m 2 s using a quasi static geyser model we treat the individual bubble collapses as cooling events that occur when the water column reaches a critical temperature their rate of occurrence is controlled by the heating rate dt dt of the water column as a result the intensity of the hydrothermal and seismic activities is determined by the heat and mass input rate into the geyser it is demonstrated that a sharp widening of the conduit can cause the number of events per unit time to drop as observed while the water level is still rising and heat is being input and thus the tremor intensity can be modulated by variations in the conduit shape

strontium isotopic compositions and paleoceanographic implication of fossil manganese nodules in dsdp odp cores leg 1 126 abstract strontium isotopic compositions of acetic acid hoac leachate fractions of eight manganese oxide deposits from the modern seafloor and of twenty one buried manganese nodules from cretaceous to recent sediments in dsdp odp cores were measured 87sr 86sr ratios of hoac leachates in all modern seafloor manganese oxides of various origins are identical with present seawater the 87sr 86sr ratios of the hoac leachates of buried nodules from dsdp odp cores are significantly lower than those of nodules from the modern seafloor and are mostly identical with coeval seawater values estimated from the age of associated sediments it is suggested that the buried nodules in dsdp odp cores are not artifacts transported from the present seafloor during the drilling process but are in situ fossil deposits from the past deep sea floor during cretaceous to quaternary periods the formation of deep sea fossil nodules prior to the formation of antarctic bottom water aabw indicates that the circulation of oxygenated deep seawaters have activately deposited manganese oxides since the eocene epoch or earlier

researching the earth and a few of its neighbors during my career our knowledge of erupting geysers and volcanoes in the solar system has exploded in this prefatory i tell how i became fascinated with high speed processes through studying meteorite impact dynamics and then how my initial idea of studying old faithful geyser as a volcanic analog led me to work not only on the dynamics of eruption of mount st helens in 1980 but also on geysers erupting on io a fiery satellite of jupiter triton a frigid satellite of neptune and enceladus an active satellite of saturn unforeseeably the study of these events also led to work on mineral thermodynamics and the hydraulics and geomorphic evolution of rapids in the grand canyon this is a narrative not a formal review article but the reader can find references in the related resources section to explore topics in more detail

eruptions at lone star geyser yellowstone national park usa 1 energetics and eruption dynamics 1 geysers provide a natural laboratory to study multiphase eruptive processes we present results from a 4 day experiment at lone star geyser in yellowstone national park usa we simultaneously measured water discharge acoustic emissions infrared intensity and visible and infrared video to quantify the energetics and dynamics of eruptions occurring approximately every 3 h we define four phases in the eruption cycle 1 a 28 3 min phase with liquid and steam fountaining with maximum jet velocities of 16 28 m s 1 steam mass fraction of less than 0 01 intermittently choked flow and flow oscillations with periods increasing from 20 to 40 s are coincident with a decrease in jet velocity and an increase of steam fraction 2 a 26 8 min posteruption relaxation phase with no discharge from the vent infrared ir and acoustic power oscillations gliding between 30 and 40 s 3 a 59 13 min recharge period during which the geyser is quiescent and progressively refills and 4 a 69 14 min preplay period characterized by a series of 5 10 min long pulses of steam small volumes of liquid water discharge and 50

the source scanning algorithm mapping the distribution of seismic sources in time and space summary we introduce a new method which we call the source scanning algorithm ssa for imaging the distribution of seismic sources in both time and space using trial locations and origin times the method calculates the brightness function by summing the absolute amplitudes observed at all stations at their respective predicted arrival times the spatial and temporal distribution of sources is then identified by a systematic search throughout the model space and time for the maximum brightness the greatest advantages of this method are that 1 it exploits waveform information both arrival times and relative amplitudes without the need to calculate highfrequency synthetic seismograms and 2 it requires neither pre assembled phase picking data nor any a priori assumptions about the source geometry a series of tests using synthetic data have shown that this method is robust and can faithfully recover the input source configuration to within 1 grid interval finally we demonstrate the value of the algorithm by locating a typical tremor event with emergent waveforms that occurred during the recent episodic tremor and slip ets sequence in the northern cascadia subduction zone

nd sr isotopic and ree constraints on the genesis of hydrothermal manganese crusts in the galapagos manganese oxide crusts from the galapagos spreading centre interpreted to be of hydrothermal origin have nd isotopic compositions and rare earth element ree concentrations that approach seawater values as the age increases numerous authors1 2 have cited hydrothermal processes along the mid oceanic ridges to explain the composition of metalliferous sediments other authors believe that these sediments whether now located on a ridge axis or in some deep were derived from hydrothermal activity near ridges and were modified during removal from these ridges3 6 nd and sr isotopic compositions as well as concentrations of ree and cu ni and co in hydrothermal mn crusts of different ages from the galapagos spreading area were determined to provide new information regarding the problem of the alteration behaviour with time of oceanic sediments our data suggest that hydrothermal crusts react with seawater and ultimately acquire the trace element characteristics of hydrogeneous crusts

magnitude bias in the great basin and its implications for explosion magnitude versus yield estimates comparison of teleseismic p wave delays in the vicinity of the central nevada test site in hot creek valley nevada with p delay data over a wider region in the great basin shows that upper mantle speeds under hot creek valley stations are higher than the average for the great basin as a whole but lower than those beneath pahute mesa these observations indicate that the caldera complex in hot creek valley may have a high speed root similar to that proposed to exist beneath the silent canyon caldera at pahute mesa however the hot creek valley anomaly is not as strong as the pahute mesa anomaly these high speed upper mantle structures cause defocusing for outgoing rays resulting in a shadow zone at the distance range corresponding to many european stations the shadow zone caused by the pahute mesa structure is much more pronounced and consequently magnitudes of pahute mesa explosions can be underestimated relative to the magnitude of hot creek valley explosions of similar yield when magnitude versus yield relationships developed using pahute mesa data are applied to other areas such as hot creek valley they can result in a biased estimate of yield

in situ observations of old faithful geyser in a series of experiments from 1983 to 1993 four probes were carefully lowered into old faithful geyser yellowstone national park wyoming at different times these probes variously recorded pressure temperature time conditions to nearly 22 m depth and video probes showed the conduit geometry and processes of recharge to 13 m depth temperatures recorded were within experimental error the same as those recorded in 1942 with a peak bottom temperature t of 118 c processes observed include fog formation in the upper levels of the conduit owing to wind and entrainment of cool air bank storage of hot water that splashes to high levels cools and recharges recharge of cooler ground water into the conduit superheated steam expansion into the conduit t 129 5 c periodic temperature fluctuations and exsolution of bubbles of noncondensable gas which we propose are co 2

measuring pressure in the source region for geysers geyser valley kamchatka abstract liquid water and steam that erupt at geysers are provided from deeper reservoirs whose location geometry and pressure are in general poorly known here we report measurements at two geysers from a field experiment in geyser valley kamchatka designed to measure pressure in the reservoir providing water to the geysers water level in the geyser conduit was controlled and the recharge to the geyser conduit was measured by monitoring the discharge needed to maintain the controlled water level recharge is not constant but depends on water level in the geyser from the relationship between water level in the conduit and recharge to the conduit we can estimate the hydraulic head in the reservoir that supplies water to the geyser hydraulic head in the two studied reservoirs is within a couple of meters of the elevation of the geyser vents and the adjacent rivers pressures in the reservoirs are low enough that the reservoirs should not be prone to hydrothermal explosions and explain why flooding of geysers in geyser valley terminated their eruptions

comparison of migration based location and detection methods for microseismic events microseismic monitoring in the oil and gas industry commonly uses migration based methods to locate very weak microseismic events the objective of this study is to compare the most popular migration based methods on a synthetic dataset that simulates a strike slip source mechanism event with a low signal to noise ratio recorded by surface receivers vertical components the results show the significance of accounting for the known source mechanism in the event detection and location procedures for detection and location without such a correction the ability to detect weak events is reduced we show both numerically and theoretically that neglecting the source mechanism by using only absolute values of the amplitudes reduces noise suppression during stacking and consequently limits the possibility to retrieve weak microseismic events on the other hand even a simple correction to the data polarization used with otherwise ineffective methods can significantly improve detections and locations a simple stacking of the data with a polarization correction provided clear event detection and location but even better results were obtained for those data combined with methods that are based on semblance and cross correlation

the origin of harmonic tremor at old faithful geyser volcanic tremor the seismic signal which is often associated with eruptions is among the least understood phenomena in seismology large variations in the physical properties of volcanic rocks and fluids along with the complex geological structure make it difficult to obtain reliable source models old faithful geyser yellowstone national park was chosen as a laboratory for studying fluid flow induced seismicity the geyser s cyclic behavior on an hourly time scale and its accessibility make it suitable for a detailed study of seismic behavior between eruptions simultaneously with underwater pressure measurements inside the geyser we observe that sharp pressure pulses inside the water column attributed to steam bubble collapse are followed by distinct seismic events with a sharp onset and a harmonic horizontal motion whose frequency varies spatially but not temporally a superposition of these events creates the appearance of continuous harmonic tremor since the pressure in the water column exhibits no sign of resonance the harmonic motion must be caused by elastic waves reverberating in the solid medium a near surface soft layer is demonstrated to be a possible elastic model the harmonic tremor observed at old faithful seems analogous to some examples of shallow volcanic tremor

seismic response of the fractured and faulted granite of soultz sous forets france to 5 km deep massive water injections summary the european enhanced geothermal system egs formerly hot dry rock hdr programme of soultz sous foris organized around three wells drilled to a depth of about 5000 m hydraulic stimulations were performed in the wells in 2000 gpk2 well 2003 gpk3 well and 2004 and 2005 gpk4 well the stimulation of gpk2 induced more than 700 seismic events with a magnitude greater than 1 0 the seismicity depicts a dense homogeneous cloud without any apparent structure medium size earthquakes represent more than 80 per cent of the cumulative seismic moment the b value of the gutenberg and richter law is larger than 1 2 the injectivity has been increased by a factor 20 these characteristics indicate that the stimulation reactivated a 3 d dense network of fractures the stimulation of gpk3 induced only about 250 events with a magnitude greater than 1 0 but with a greater proportion of large events up to 2 9 the hypocentres form clear structures identified as large faults the b value is about 0 9 and the large events m 2 0 account for the greater part of the cumulative seismic moment the injectivity of the well which was already high before the stimulation remained unchanged the stimulation of gpk4 was achieved in two stages this stimulation produced even less induced events making the interpretation difficult the differences between the seismic response of gpk2 and gpk3 are due to the presence of large faults cut by gpk3 or in its close vicinity and reached by the injected water once a seismic event occurs on a fault a sequence of earthquakes is triggered and the seismicity behaves for a large part independent of the injected flow rate the stimulations also show some evidence that creeping could be a major source of deformation if not the main one the future egs programme will have to drill wells in zones free of large faults to avoid poor hydraulic performance and inconvenience to the population

age determinations and growth rates of pacific ferromanganese deposits using strontium isotopes abstract 87 sr 86 sr ratios trace element and ree compositions and textural characteristics were determined for three hydrogenetic fe mn crusts one hydrothermal deposit and two mixed hydrothermalhydrogenetic crusts from the pacific the sr isotope data are compared to the sr seawater curve for the cenozoic to determine the ages and growth rates of the crusts the 87 sr 86 sr in the crusts does not increase monotonically with depth as expected if the sr were solely derived from seawater and perfectly preserved since deposition this indicates post depositional exchange of sr or heterogeneous sources for the sr originally contained in the crusts textures of hydrogenetic crusts generally correlate with sr isotopic variations the highest porosity intervals commonly exhibit the highest 87 sr 86 sr ratios indicating exchange with younger seawater intervals with the lowest porosity commonly have lower 87 sr 86 sr and may preserve the original sr isotopic ratios minimum ages of crust growth inception were calculated from dense low porosity intervals growth of the hydrogenetic crusts began at or after 23 ma although their substrates are cretaceous estimated average growth rates of the three hydrogenetic crusts vary between 0 9 and 2 7 mm ma consistent with published rates determined by other techniques within the marshall islands crust growth rates for individual layers varied greatly between 1 0 and 5 4 mm ma for one crust very low 87 sr 86 sr ratios occurred in detrital rich intervals hydrothermal fe mn oxide from the active lau basin back arc spreading axis valu fa ridge has an 87 sr 86 sr ratio with a predominantly seawater signature 87 sr 86 sr 0 709196 indicating a maximum age of 0 9 ma one crust from an off axis seamount west of gorda ridge may have begun precipitating hydrogenetically at 0 5 ma 0 709211 and had increasing hydrothermal or volcanic input in the top half of the crust indicated by a significantly lower 87 sr 86 sr ratio 0 709052

transport and release of transition elements during early diagenesis sequential leaching of sediments from manop sites m and h part i ph 5 acetic acid leach sediments from manop sites m and h in the eastern tropical pacific ocean can be partitioned into operationally defined phases by means of a sequential leach procedure this paper reports the results of the first leach in the sequence an acetic acid solution buffered as p h 5 with sodium acetate this leach is designed to remove carbonate bound and sorbed cations the only cation bound in a consistent ratio to calcium in the carbonate is strontium the molar ratio is 2 10 3 in contrast transition metals are sorbed onto the surfaces of other sedimentary particles the proportions sorbed range from 2 to 10 of the total manganese about 10 of the total nickel and copper and less than 1 of the total iron the pool of sorbed metals in surface sediments is sufficiently large and the rate of biological stirring is sufficiently rapid for this metal reservoir potentially to dominate the porewater reservoir in supplying metals to ferromanganese nodules a simple model for nodule growth based upon transfer of metals through this reservoir suggests that only 1 of the sedimentary sorbed metals within a radius of 2 to 9 cm is required to support typical nodule growth rates

an experimental study of the role of subsurface plumbing on geothermal discharge in order to better understand the diverse discharge styles and eruption intervals observed at geothermal features we performed three series of laboratory experiments with differing plumbing geometries a single straight conduit that connects a hot water bath flask to a vent funnel can originate geyser like periodic eruptions continuous discharge like a boiling spring and fumarole like steam discharge depending on the conduit length and radius the balance between the heat loss from the conduit walls and the heat supplied from the bottom determines whether and where water can condense which in turn controls discharge style next we connected the conduit to a cold water reservoir through a branch simulating the inflow from an external water source colder water located at a higher place than a branching point can flow into the conduit to stop the boiling in the flask controlling the periodicity of the eruption when an additional branch is connected to a second cold water reservoir the two cold reservoirs can interact our experiments show that branching allows new processes to occur such as recharge of colder water and escape of steam from side channels leading to greater variation in discharge styles and eruption intervals this model is consistent with the fact that eruption duration is not controlled by emptying reservoirs we show how differences in plumbing geometries can explain various discharge styles and eruption intervals observed in el tatio chile and yellowstone usa this article is protected by copyright all rights reserved

locating sources of volcanic tremor and emergent events by seismic triangulation application to arenal volcano costa rica 1 we address the issue of locating the sources of volcanic tremor and emergent events with a method requiring a limited amount of equipment a network of several triangular seismic antennas made of vertical sensors is used the slowness vectors are estimated at each array on a sliding window by inverting the time delays between the sensors calculated with the cross spectral method a probabilistic approach is adopted whereby each measure and its error are represented by a probability density function pdf a weighted summation of the pdfs is carried out in which the stable directions of propagation are enhanced the effects of the structural heterogeneities are taken into account by introducing an additional error associated to a robust hyperbolic secant sech type pdf the resulting pdfs of the back azimuth are combined to calculate a pdf of the source location the maximum likelihood of this pdf is taken as an estimate of the source position and its spread is characterized by a covariance analysis data from an experiment carried out at arenal volcano costa rica with four arrays are analyzed the precision and robustness of the method are tested by exploring the influence of the array configuration and other parameters the mean standard deviation on the position of the sources is 600 m for the tremor and 400 m for the explosions and long period lp events several tremors explosions and lp events are analyzed and their sources located the seismogenic zone is located in a 600 m radius area centered on the active crater

high resolution stratigraphy with strontium isotopes the isotopic ratio of strontium 87 to strontium 86 shows no detectable variation in present day ocean water but changes slowly over millions of years the strontium contained in carbonate shells of marine organisms records the ratio of strontium 87 to strontium 86 of the oceans at the time that the shells form sedimentary rocks composed of accumulated fossil carbonate shells can be dated and correlated with the use of high precision measurements of the ratio of strontium 87 to strontium 86 with a resolution that is similar to that of other techniques used in age correlation this method may prove valuable for many geological paleontological paleooceanographic and geochemical problems

growth of a manganese nodule from peru basin a radiochemical anatomy abstract attempts have been made to study the entire growth history of a manganese nodule from the northern part of peru basin in the pacific using radiochemical profiles of 230 th 232 th 227 th 230 th and 10 be 9 be combined with the observations on fe mn contents and textural variation the radiochemical data indicate that the nodule grew more or less concentrically throughout most of its existence since it formed 1 5 my ago receiving mn from both bottom water and pore water this condition appeared to have changed about 180 ky ago when the growth became asymmetric in that the top and bottom sides became fixed in their relative positions on the sea floor since then the bottom side accreted with a fast rate of close to 200 mm my apparently fueled by the supply of diagenetically remobilized mn in pore water from the sediment substrate in the meantime the top side accumulated at about 6 mm my a value which is in the normal range for deep sea nodules having their mn supplied from the hydrogenous source

calcareous nannofossil biostratigraphic dating of a ferromanganese crust from schumann seamount abstract calcareous nannofossil biostratigraphy was employed to determine the age and growth rates of the different layers within ferromanganese crusts from schumann seamount 200 miles north of the island of kauai hawaii this work is part of a study to reconstruct the paleoceanographic history of crusts using various geochemical indicators the methods are based on the identification of coccolith imprints not actual coccolith remains age constraints on the time span of a particular horizon are defined either 1 by the presence of a species which was extant for only a limited geological time interval or 2 by the presence of two organisms whose time ranges overlapped age resolution is optimized by short time ranges or narrow overlaps in the crust studied there was considerable inter horizon variability in the preservation of coccolith imprints in imprint abundance and in species diversity some of the crust layers examined were narrowly constrained temporally 1 4 myr while others were less so 10 myr our results indicate that the minimum age for the interval at 27 mm depth is at least eocene this is the maximum age many believe any crust can be the position of this interval however is only about one half of the way through the crust while the data support previous estimates of average crust growth rates 0 5 mm myr the actual apparent growth rate appears to have varied by an order of magnitude 0 1 to 2 mm myr

effects of phosphatization on the geochemical and mineralogical composition of marine ferromanganese crusts most hydrogenetic ferromanganese crusts in the central pacific consist of two growth generations a phosphatized older growth generation that is impregnated with carbonate fluorapatite cfa and a younger non phosphatized growth generation geochemical and mineralogical investigations of non phosphatized and phosphatized crust layers revealed significant differences that are not simply dilution effects by cfa certain elements are depleted in old crusts compared to young crusts in the order si fe al ti co mn pb others like ni zn cu y and rees rare earth elements are mostly enriched suboxic conditions in the phosphate rich water of the oxygen minimum zone that infiltrated the crusts caused a partial redissolution of crust phases resulting in mobilization of associated elements a partial recrystallization of more stable phases and a secondary input of nutrient type elements the frequent occurrence of todorokite in phosphatized crust layers indicates that mn mobilized from the vernadite crust phase was partially recrystallized as todorokite which is more stable under suboxic conditions incorporating ni cu and zn into the crystal lattice but rejecting co other metals like pb y and rees probably form stable phosphate phases in phosphatized crusts our investigations emphasize that under the influence of phosphatization diagenetic remobilization and reorganization in fe mn crusts took place in contrast to non phosphatized crusts the older phosphatized crust generation no longer represents a complete primary crust precipitate therefore young non phosphatized and old phosphatized crust generations should be considered as two different sample types with respect to geochemical composition mineralogy and evolution we also suggest that most methods for age determination like the 87sr86sr isotopic dating method or co chronometry cannot be used for phosphatized crusts without caution

joint location and source mechanism inversion of microseismic events benchmarking on seismicity induced by hydraulic fracturing summary seismic monitoring can greatly benefit from imaging events with a low signal to noise ratio snr as the number of the events with a low signal grows exponentially one way to detect weaker events is improvement of a snr by migration type stacking of waveforms from multiple stations we have developed a new method of location of seismic events that involves stackingofseismicphasesandamplitudesalongdiffractiontraveltimecurvestosuppressnoise and detect seismic events with a snr lower than that on individual receivers the stacking includes polarity correction based on a simultaneous seismic moment tensor inversion and detection algorithm on the stack function we applied this method to locate microseismicity induced by hydraulic fracturing first we calibrated the velocity model by locating perforation shots at known locations then we processed 3 d of data from microseismic monitoring of shale stimulation and benchmarked migration type locations of the largest events that were manually located the detected and located events induced by hydraulic fracturing in this case study are mostly shear events forming narrow bands along the maximum horizontal stress direction approximately 100 m above the injection intervals the proposed technique is fully automated and feasible for real time seismic monitoring

introduction to microseismic source mechanisms microseismic events are very weak earthquakes that occur at very small spatial scales microseismic events can result from natural forces such as tectonic motions natural seismicity or they can be induced by man made changes to the natural stress strain conditions in the earth induced seismicity there is a growing awareness that fluid injection into or fluid withdrawal from the earth s subsurface e g oil gas production geothermal energy production waste fluid disposal which changes the pore pressure stress and strain conditions in the rock can induce microseismic events and might eventually lead to larger felt seismic events see the june 2015 tle special section on injection induced seismicity

ferromanganese crusts from necker ridge horizon guyot and s p lee guyot geological considerations abstract necker ridge horizon guyot and s p lee guyot in the central pacific were sampled seismically surveyed and photographed by bottom cameras in order to better understand the distribution origin and evolution of ferromanganese crusts necker ridge is over 600 km long with a rugged crest pods of sediment to 146 m thick slopes that average 12 to 20 and debris aprons that cover some of the lower flanks substrate lithologies are mostly hyaloclastite volcaniclastic breccia and minor alkalic basalt horizon guyot 300 km long and 75 km wide is capped by at least 160 m of sediment which buries stepped terraces substrate lithologies are similar to those on necker ridge although previous workers sampled much tholeiitic basalt on horizon s p lee guyot 125 km long and 80 km wide is capped by at least 300 m of sediment and contains talus aprons along its lower flanks ferromanganese encrusted rocks were recovered in every dredge and are thickest on necker ridge crust thicknesses average about 2 5 1 5 and 0 8 cm for necker horizon and s p lee respectively crusts range from smooth or porous surfaces to knobby and botryoidal the entire crust is laminated however two distinct layers commonly exist separated by a paper thin layer of phosphorite the dominant mineral of all crusts is vernadite mno 2 while quartz feldspar apatite and in three rocks todorokite are minor phases quartz and feldspar decrease with decreasing latitude of occurrence and is suggested to be related to eolian input on the average apatite also increases within the crusts with decreasing latitude of occurrence which may be related to high biological productivity in the zone of equatorial upwelling phosphorite substrates are more abundant on necker ridge and s p lee guyot than they are on horizon guyot seamount ferromanganese nodules are distinct from abyssal nodules in their chemistry and internal structure

time reverse modeling of low frequency microtremors application to hydrocarbon reservoir localization 1 time reverse modeling is applied to synthetic and real low frequency microtremors measured at the earth surface with synchronized seismometers in contrast to previous time reverse applications no single event or first arrival time identification is applied for microtremor localization synthetic low frequency microtremors are numerically generated within a small underground area and modeled with a finite difference algorithm simulating two dimensional elastic wave propagation time reverse modeling using synthetic microtremors shows that small underground source areas can be accurately located different source characteristics which emit mainly p waves or s waves vertically influence the localization accuracy time reverse modeling is applied to two real microtremor data sets acquired 16 months apart above known oil reservoirs nearby voitsdorf austria to investigate whether spectral anomalies observed above the reservoirs originate from the reservoirs time reverse modeling indicates that low frequency microtremor signals originate from the reservoir locations and provides a possible method for reservoir localization

sr and nd isotopic variations in ferromanganese crusts from the central pacific implications for age and source provenance abstract isotopic analyses of two hydrogenetic ferromanganese fe mn crusts from volcanic edifices in the central pacific ocean reveal systematic variations in 87 sr 86 sr and 143 nd 144 nd with both ratios decreasing as a function of depth into the fe mn crusts leaching experiments suggest that sr in the crusts is contained in at least two discrete sites a loosely bound sr dominated by modern marine sr is removed by leaching with a 10 percent acetic acid solution the 87 sr 86 sr ratio of the residue is significantly less than the 87 sr 86 sr ratio of the unleached material the sr isotope ratios of leached samples are compared with the temporal variation in seawater to provide ages for layers within the fe mn crusts these data suggest that the oldest crust layers began to accrete in the early to middle miocene correlated to the 87 sr 86 sr variations 143 nd 144 nd ratios suggest that the nd isotope composition of central pacific ocean seawater also changed systematically over this time interval or that the fe mn crusts simply incorporated nd from various parts of an isotopieally heterogeneous ocean as the crusts were carried along with the oceanic plate in contrast to the layered ferromanganese crust the phosphatized volcaniclastic substrates have sr and nd isotope compositions that are consistent with their volcanic origin

investigation of induced microseismicity at valhall using the life of field seismic array here we use data from the life of field seismic lofs surface array in conjunction with a migration style approach to locate microseismic events in valhall field during 6 5 hours of hydraulic fracturing we identify an event distribution that extends roughly 300 m vertically and 200 m horizontally with sources both within the chalk layer containing the reservoir and the overburden however the temporal distribution of the events is not consistent with the induced fracturing extending into the overburden instead the synchronous increase in event activity with downhole pressure could be interpreted as evidence that elastic wavefronts originating from well activity trigger movement on faults where the in situ stress is very close to that required for failure

enhanced hydrothermal processes at the new born lusi eruptive system indonesia abstract little is known about the processes taking place in new born hydrothermal systems we investigate the eruptive activity of lusi a sediment hosted hydrothermal system active since 2006 in east java indonesia we show that superimposed on the regular geysering activity lusi features periods of enhanced hydrothermal processes during which boiling mud breccia is violently discharged from the eruptive vents this results in sudden flooding lasting from several minutes to several hours and featuring almost instantaneous temperature peaks i e from 35 c to more than 65 c in less than 2 min such activity here named hydrothermal waves is marked by high frequency seismic radiations and is distinguished by sharp peaks of ch4 and co2 concentrations in the erupted fluids this suggests fluids upwelling from at least tents of meters below the near surface the injection into the shallow plumbing system of ch4 and co2 rich batches of fluids may promote instabilities in the mud breccia column leading to the hydrothermal waves our findings provide key insights into the deep charging dynamics of a new born hydrothermal system and highlight the effects imposed by subtle variations in fluid chemistry changes at depth

extraction of phase and group velocities from ambient surface noise in a patch array configuration abstractwe have investigated the use of ambient noise data to extract phase and group velocities from surface noise sources in a microseismic monitoring context the data were continuously recorded on 44 patch arrays with an interpatch distance on the order of 1 km typically a patch array design consists of a few tens of patches each containing 48 strings of 12 single vertical component geophones densely distributed within the patch area the specificity of the patch array design allows seismic analysis at two different scales within each patch highly coherent signals at small distances provide phase information at high frequency up to 10 hz from which surface wave phase velocities can be extracted between the pairs of patches surface wave group velocity maps can be built using correctly identified and localized surface noise sources the technique can be generalized to every patch pair using different noise sources identified at the surface we note that the incoherent but localized noise sourc

video observations inside conduits of erupting geysers in kamchatka russia and their geological framework implications for the geyser mechanism several models have been proposed to explain periodic eruptions of geysers in essence the models all use two principally different types of geyser plumbing confi gurations dealing with two different physical mechanisms here we present data on direct video observations of interior conduit systems for four erupting geysers in geyser valley kamchatka russia the video footage reveals highly contorted water fi lled conduits that periodically discharge voluminous parcels of steam bubbles during eruptions these observations do not favor the models that use the most popular long vertical conduit type of plumbing where eruptions are caused by sudden fl ashing of superheated water into steam in contrast our data fi t the models using the less explored type of plumbing where pressurized steam gradually accumulates in an underground cavity bubble trap and periodically erupts through a water fi lled highly contorted conduit with the confi guration of an inverted siphon hydrodynamic calculations show that such a plumbing confi guration produces periodic eruptions when the volume of the bubble trap exceeds the volume of the conduit connecting it to the ground surface conduits of the studied geysers were developed from erosion by ascending geothermal water in landslide deposits chaotic internal structures of the deposits facilitated the formation of conduit systems with highly contorted confi gurations of the bubble trap type we suggest that geyser fi elds are rare on earth because they require the combination of hydrothermal discharge and geological formations having specifi c mechanical properties and structures that facilitate the generation of highly contorted conduits

long period long duration seismic events during hydraulic stimulation of shale and tight gas reservoirs part 1 waveform characteristics abstractlong period long duration lpld seismic events are relatively low amplitude signals that have been observed during hydraulic fracturing in several shale gas and tight gas reservoirs these events are similar in appearance to tectonic tremor sequences observed in subduction zones and transform fault boundaries lpld events are predominantly composed of s waves but weaker p waves have also been identified in some cases microearthquakes are observed during the events based on the similarity with tectonic tremors and our observations of several impulsive s wave arrivals within the lpld events we interpret the lpld events as resulting from the superposition of slow shear slip events on relatively large faults most large lpld waveforms appear to start as a relatively slower low amplitude precursor lacking clear impulsive arrivals we estimate the energy carried by the larger lpld events to be 1000 times greater than a mw 2 microseismic event that is typical of the events that occur during hyd

two major cenozoic episodes of phosphogenesis recorded in equatorial pacific seamount deposits seamount phosphorites have been recognized since the 1950s but this is the first study to provide an in depth exploration of the origin and history of these widespread deposits representative samples from equatorial pacific cretaceous seamounts were analyzed for chemical mineralogical and stable isotope compositions the phosphorites occur in a wide variety of forms but most commonly carbonate fluorapatite cfa replaced middle eocene and older carbonate sediment in a deep water environment 1000 m element ratios distinguish seamount phosphorites from continental margin plateau and insular phosphorites uranium and thorium contents are low and total rare earth element ree contents are generally high ree ratios and shale normalized patterns demonstrate that the rees and host cfa were derived from seawater strontium isotopic compositions compared with inferred cenozoic seawater curves define two major episodes of cenozoic phosphatization late eocene early oligocene 39 34 ma and late oligocene early miocene 27 21 ma three minor events are also indicated the major episodes occurred at times of climate transition the first from a nonglacial to glacial earth and the second from a predominantly glacial to warm earth the paleoceanographic conditions that existed at those times initiated and sustained development of phosphorite by accumulation of dissolved phosphorus in the deep sea during relatively stable climatic conditions when oceanic circulation was sluggish fluctuations in climate sealevel and upwelling that accompanied the climate transitions may have driven cycles of enrichment and depletion of the deep sea phosphorus reservoir as temperature gradients in the oceans increased antarctic glaciation expanded and oceanic circulation and upwelling intensified expansion and intensification of the oxygen minimum zone may have increased the capacity for midwater storage of phosphorus supplied by dynamic upwelling around seamounts however the bottom waters never became anoxic during the phosphogenic episodes fluctuations in the ccd and lysocline co2 fluxes and changes in bottom water circulation and temperatures may have bathed the seamount carbonates in more corrosive waters which coupled with increased supplies of dissolved phosphorus promoted replacement processes the late eocene early oligocene phosphogenic episode recorded in seamount deposits is not matched by large phosphorite deposits in the geologic record whereas the late oligocene early miocene episode and middle miocene event are matched by large deposits distributed globally the seamount phosphorites are exposed at the surface of the seamounts and have been for most of the neogene and oligocene the phosphorites do not show signs of etching that would indicate substantial undersaturation of seawater phosphate with respect to cfa mass balance calculations indicate that about 5 4 19 1012 g of p2o5 are locked up in equatorial pacific seamount phosphorites that amount is equivalent to about 2 7 years of the present annual input from rivers

self potential and passive seismic monitoring of hydrothermal activity a case study at iodine pool waimangu geothermal valley new zealand abstract iodine geyser located in the waimangu geothermal valley new zealand has been studied by both passive electrical and seismic methods the activity of the geyser was monitored at various distances from the vent using self potential method the self potential signals display cyclic negative variations with respect to a baseline drawn when the geyser is quiet the minimum in the self potential signals coincides with the maximum overflow we provide a numerical model able to explain both the polarity and magnitude of the observed signal this model is based on the fluctuations of the hydraulic head in the conduit of the geyser the divergence of the streaming current density is created at the interface between the pipe and the surrounding rock passive seismic experiments were used to localize ambient noise sources these signals have been processed with the so called matched field processing technique mfp a dominant source emerged from this processing that we characterized in range and depth with a good accuracy

multiscale matched field processing for noise source localization in exploration geophysics abstractin the study we investigate the use of ambient noise data to locate microseismic sources at the exploration scale we develop a multiscale matched field processing mfp approach to localize seismic sources at frequencies below 10 hz an application to an actual data set acquired over a hydrocarbon field is presented to determine the reliability of the mfp procedure the data used were continuously recorded over five days at a total of 397 stations on a 1 km per side square seismic network the mfp results show 1 a dominant and stable surface source associated with human activities road and exploration platforms around the reservoir and 2 weaker sources at depth below the seismic network that are related to the injection extraction process

strontium neodymium and lead isotope variations of authigenic and silicate sediment components from the late cenozoic arctic ocean implications for sediment provenance and the source of trace metals in seawater proven ance changes of silicate sediment deposited during the late cenozoic 5 0 ma on the alpha ridge central arctic ocean are determined from variations in strontium lead and neodymium isotope compositions whereas strontium and lead isotope compositions are relatively invariant from 5 to 1 7 ma end values start to increase at 3 ma subsequently s7sr 86sr and 2 6pb z 4pb ratios progressively increase and end values progressively decrease from 1 7 ma to the present day from these isotope variations three different endmember compositions for sediment source regions are defined the two endmember compositions defined by sediment that was deposited by sea ice from 5 to 1 7 ma are consistent with a significant component being derived from the east siberian shelf the progressive change in isotope compositions from 1 7 to 0 ma correlates with an increase in coarse detritus deposited by icebergs over this time period the isotope data are consistent with a progressive increase in the proportion of sediment that was deposited in the central arctic ocean since 1 7 ma having been derived from the northern canada or queen elizabeth island region changes in the strontium neodymium and lead isotope compositions of arctic seawater are determined by analyzing the oxide fractions of fe mn micronodules strontium isotope compositions of the microno dule oxide fractions are similar to published late cenozoic seawater data and indicate that 97 of the sr is seawater derived but minute contributions of sr from silicate detritus prohibit using the hydrogenous fractions for chronostratigraphic purposes neodymium and lead isotope compositions of the micronodule oxide fractions which reflect those of arctic seawater follow the isotope variations of the silicate components throughout the late cenozoic these relations indicate that river water can not be the primary source of rare earth elements and pb to the dissolved reservoir in arctic seawater and that ice rafted detritus by dissolution or exchange processes is an important source of trace elements to seawater in ice covered oceans copyright 1997 elsevier science ltd

eruption dynamics of co2 driven cold water geysers crystal tenmile geysers in utah and chimayo geyser in new mexico abstract the co 2 bubble volume fraction eruption velocity flash depth and mass emission of co 2 were determined from multiple wellbore co 2 driven cold water geysers crystal and tenmile geysers in utah and chimayo geyser in new mexico at shallow depths the bubble volume fraction ranges from 0 to 0 8 eruption velocities range from 2 to 20 m s and flash depths are predominately shallow ranging from 5 to 40 m below the surface annual emission of co 2 is estimated to be 4 77 1 92 10 3 6 17 1 73 10 1 6 54 0 57 10 1 t yr for crystal tenmile and chimayo geysers respectively these estimates are coherent with burnside et al 2013 showing that the rate of co 2 leakage from wellbores is greater than fault parallel or diffuse co 2 leakage the geyser plumbing geometry consists of a vertical wellbore which allows for the upward migration of co 2 rich fluids due to artesian conditions the positive feedback system of a co 2 driven eruption occurs within the well active inflow of co 2 into the regional aquifers through faulted bedrock allows geysering to persist for decades crystal geyser erupts for over 24 h at a time highlighting the potential for a wellbore in a natural environment to reach relatively steady state high velocity discharge mitigating high velocity co 2 driven discharge from wellbores will however be easier than mitigating diffuse leakage from faults or into groundwater systems

geochemical constraints on the formation of late cenozoic ferromanganese micronodules from the central arctic ocean in order to determine geochemical compositions of late cenozoic arctic seawater oxide fractions were chemically separated from 15 samples of hand picked ferromanganese micronodules 50 300 pm the success of the chemical separation is indicated by the fact that 97 of the sr in the oxide fraction is seawater derived rare earth element ree abundances of the arctic micronodule oxide fractions are much lower than those of bulk fe mn nodules from other ocean basins of the world e g 33 vs 145 ppm nd but the arctic oxides are enriched in ce relative to nd ce nd 2 2 f 0 5 and have convex upward shale normalized ree patterns ndn gdn 0 61 f 0 06 gdn ybn 1 5 0 2 ndn yb 0 9 f 0 2 typical of other hydrogenous and diagenetic marine fe mn oxides bulk sediment samples from the central arctic ocean have ree abundances and patterns that are characteristic of those of post archean shale non detrital fractions calcite oxide coatings of recent arctic foraminifera have ree abundances and patterns similar to those of recent foraminifera from the atlantic ocean electron microprobe analyses n 178 of transition elements in 29 arctic fe mn micronodules from five different stratigraphic intervals of late cenozoic sediment indicate that oxide accretion occurred as a result of hydrogenetic and diagenetic processes close to the sediment seawater interface transition element ratios suggest that no oxide accretion occurred during transitions from oxic to suboxic diagenetic conditions only k is correlated with si and al and ratios of these elements suggest that they are associated with illite or phillipsite ca and mg are correlated with mn which indicates variable substitution of these elements from seawater into the manganate phase the geochemical characteristics of arctic fe mn micronodules indicate that the rees of the oxide fractions were ultimately derived from seawater however because of minute contributions of sr from siliciclastic detritus during diagenesis or during the chemical leaching procedure sr isotope compositions of the oxide fractions cannot be used to trace temporal changes in the sr sr ratio of arctic seawater or to improve the chronostratigraphy 0 1997 elsevier science b v kevwords 87sr 86sr arctic ocean ferromanganese nodules marine sediments rare earth elements

delineating complex spatiotemporal distribution of earthquake aftershocks an improved source scanning algorithm summary conventional earthquake location methods depend critically on the correct identification of seismic phases and their arrival times from seismograms accurate phase picking is particularly difficult for aftershocks that occur closely in time and space mostly because of the ambiguity of correlating the same phase at different stations in this study we introduce an improved source scanning algorithm issa for the purpose of delineating the complex distribution of aftershocks without time consuming and labour intensive phase picking procedures the improvements include the application of a ground motion analyser to separate p and s waves the automatic adjustment of time windows for brightness calculation based on the scanning resolution and a modified brightness function to combine constraints from multiple phases synthetic experiments simulating a challenging scenario are conducted to demonstrate the robustness of the issa the method is applied to a field data set selected from the ocean bottom seismograph records of an offshore aftershock sequence southwest of taiwan although visual inspection of the seismograms is ambiguous our issa analysis clearly delineates two events that can best explain the observed waveform pattern

dissolved gases in hydrothermal phreatic and geyser eruptions at yellowstone national park usa multiphase and multicomponent fluid flow in the shallow continental crust plays a significant role in a variety of processes over a broad range of temperatures and pressures the presence of dissolved gases in aqueous fluids reduces the liquid stability field toward lower temperatures and enhances the explosivity potential with respect to pure water therefore in areas where magma is actively degassing into a hydrothermal system gas rich aqueous fluids can exert a major control on geothermal energy production can be propellants in hazardous hydrothermal phreatic eruptions and can modulate the dynamics of geyser eruptions we collected pressurized samples of thermal water that preserved dissolved gases in conjunction with precise temperature measurements with depth in research well y 7 maximum depth of 70 1 m casing to 31 m and five thermal pools maximum depth of 11 3 m in the upper geyser basin of yellowstone national park usa based on the dissolved gas concentrations we demonstrate that co 2 mainly derived from magma and n 2 from air saturated meteoric water reduce the near surface saturation temperature consistent with some previous observations in geyser conduits thermodynamic calculations suggest that the dissolved co 2 and n 2 modulate the dynamics of geyser eruptions and are likely triggers of hydrothermal eruptions when recharged into shallow reservoirs at high concentrations therefore monitoring changes in gas emission rate and composition in areas with neutral and alkaline chlorine thermal features could provide important information on the natural resources geysers and hazards eruptions in these areas

improving confidence in ferromanganese crust age models a composite geochemical approach abstract accurate age models for marine ferromanganese fe mn crusts are essential to understand paleoceanographic changes and variations in local environmental factors affecting crust growth rate and their lateral continuity however no absolute method exists for dating these deposits beyond the age of 10 myr which requires the combination of a number of approaches here we present a composite age model for a 15 cm thick fe mn crust sample obtained by unique core drilling using a remotely operated vehicle at a water depth of 1130 m on the summit of tropic seamount in the north east atlantic the age model is based on cross validation of laser ablation u pb dating co chronometry and os isotopes these enable robust calibration of the age depth model using the bayesian statistical modelling of markov chain monte carlo mcmc simulations the results show that this fe mn crust commenced growth in the late cretaceous between 73 and 77 ma and grew at a rate between 1 and 24 mm myr averaging 4 mm myr the phosphatised carbonate substrate capping tropic seamount and underlying most of the fe mn crusts yields a u pb age of 84 4 myr and provides the upper age limit for the model less radiogenic excursions of 188os 187os in the vertical profile through the crust permit the identification of key inflection points in the os isotope seawater curve at the eocene oligocene and cretaceous paleogene transitions growth rates estimated from the empirical co chronometer are combined with the age envelope defined by the os data and used to validate the mcmc simulations the model identifies five hiatuses that occurred during the pliocene 2 5 1 9 5 3 1 7 ma early miocene 16 1 27 2 ma oligocene 29 2 32 1 ma eocene 41 2 52 0 6 ma and the late paleocene 55 1 59 1 4 ma a major phosphatisation event affecting the fe mn core can be dated to the late eocene 38 1 2 ma which coincides with a recorded change in the global oceanic system from warm and sluggish circulation to cold and vigorous thermohaline driven meridional overturn at the onset of antarctic glaciation

rupture geometry from high precision relative hypocentre locations of microearthquake clusters summary in 1987 two microearthquake sequences with a duration of about a week each and consisting of 37 and 46 events respectively occurred in the upper crust below the jura mountains of northern switzerland the seismograms within each sequence exhibit a high degree of similarity indicating tight clustering of hypocentres and similar focal mechanisms using a cross correlation technique applied to the seismograms in the time domain together with a new least squares adjustment procedure it was possible to determine relative hypocentre locations of the earthquakes in each cluster with a precision of a few tens of metres the results show that hypocentres of events with the same focal mechanism lie on a plane which coincides exactly with one of the nodal planes of the fault plane solution and that consequently swarm like sequences of similar earthquakes are due to repeated slip on the same fault in one case slip occurred as right lateral motion on a steeply dipping plane striking in wnw ese direction whereas the other case corresponds to left lateral slip on two almost vertical planes striking roughly n s in 1988 an additional earthquake triplet occurred on a wnw ese oriented normal fault nearby all three mechanisms are consistent with a general nnw sse oriented direction of maximum crustal shortening and a corresponding wsw ene oriented extension repeated slip on the same fault is indicative of a large degree of heterogeneity and of short term temporal variability of both frictional resistance and stress distribution on the fault an explanation for the occurrence of such swarm like seismic activity in terms of barriers or asperities would require that shear stress on the unbroken patches increase from one event to the next since however the overall shear stress would be expected to decrease as a consequence of the stress released in each event a more plausible mechanism involves pore pressure fluctuations caused by fluids under suprahydrostatic pressures migrating upward through pre existing zones of weakness in the crust

detailed record of the neogene sr isotopic evolution of seawater from dsdp site 590b a detailed study of strontium isotope variations in neogene marine carbonate sediments from deep sea drilling project site 590b using techniques that allow the 87sr 86sr ratio to be determined to better than 0 00001 gives a high resolution record of the sr isotopic evolution of seawater the data show that the rate of change of the marine 87sr 86sr ratio has varied significantly even on time scales as short as 1 m y periods of particularly rapid growth appear to follow major marine regressions and probably reflect an increase in the delivery of radiogenic sr from the continents coupled with a decreased submarine carbonate dissolution rate greater carbonate compensation depth periods of relatively slowly changing 87sr 86sr follow major marine transgressions on the basis of correlations with the marine oxygen isotope record and the times of major continental glacier growth it is inferred that the effects of sea level variations are modified by climatic factors that affect the intensity of continental weathering and runoff the effects of sea floor generation rate variations are not discernible for the neogene the maximum attainable stratigraphic resolution using sr isotopes is between 0 1 and 2 m y for this time period

time reversal location of glacial earthquakes in 2003 ekstrom et al reported the detection and location of a new class of earthquakes occurring in the polar regions of the earth the proposed source mechanism involves large and sudden sliding motions of glaciers which gave the name glacial earthquakes to these events in this study we localize some of these earthquakes with a time reversal mirror trm algorithm which contrary to ordinary back projection methods does not involve testing each possible source location in trm localization an earthquake is located on the basis of only one 3 d spectral element simulation of seismic wave propagation by using the full complexity of recorded data as simultaneous time reversed sources we show that on the basis of this approach even glacial earthquakes with a faint signal can be correctly localized and that the pattern of the time reversed wavefield is coherent with the motion of glaciers down their valley

the plumbing of old faithful geyser revealed by hydrothermal tremor 1 old faithful geyser in yellowstone national park usa has attracted numerous scientific investigations for over two centuries to better understand its geological structure the physics of its eruptions and the controls of its intermittency using data acquired with a seismic array in 1992 we track the sources of hydrothermal tremor produced by boiling and cavitation inside the geyser the location of seismic sources identifies a previously unknown lateral cavity at 15 m below the surface on the sw side of the vent and connected to the conduit this reservoir is activated at the beginning of each geyser eruption cycle and plays a major role in the oscillatory behavior of the water level in the conduit before each eruption

143nd 144nd in pacific ferromanganese encrustations and nodules abstract 143 nd 144 nd ratios have been measured in fe mn encrustations and nodules taken from a wide area of the pacific and over a large depth range over much of the pacific e nd 0 values fall between 2 5 and 5 0 similar to values for nd presently dissolved at mid depth in the pacific deposits forming within the realm of antarctic bottom water aabw are distinctly less radiogenic e nd 0 6 0 to 7 5 and appear to have sampled nd both from ambient aabw e nd 0 8 5 and from higher in the water column e nd 0 0 3 to 4 5 samples drilled from 50 to 65 mm within one crust are chemically and isotopically distinct from surface layers of the same crust the isotope values suggest that the mid depth pacific may have previously exhibited a less radiogenic nd isotope signal than that presently observed

rare earth elements and neodymium isotopes in ferromanganese oxide coatings of cenozoic foraminifera from the atlantic ocean abstract an evaluation has been made of the method of establishing the ree contents and patterns and nd isotopic compositions of sea water over cenozoic time from their record in the femn oxide coatings of foraminiferal calcite using 0 60 ma samples from the rio grande rise dsdp site 357 it has been established that the ree contents of the coatings are generally similar to those of recent samples however in the cenozoic samples the surface coatings have been diagenetically modified under suboxic conditions resulting in a distinctly different ree pattern although the original 143 nd 144 nd ratios appear to have been preserved the nd isotopic curve for cenozoic sea water in the s atlantic shows clear temporal trends although these are not so extreme as to show 143 nd 144 nd ratios outside the range observed in modem sea water with the principal exception of the oldest samples there is an approximate inverse relationship between the nd and sr isotopic compositions of the foraminifera it is suggested that the changes reflect both global changes in the relative proportions of nd and sr derived from continental input and from the weathering of volcanic debris together with short term and local variations to which the sr curve is insensitive reflecting the different response times of the two elements to changes in oceanic input functions the nd isotope curve appears to be a potentially useful tracer of ocean palaeochemistry

locating hydrothermal acoustic sources at old faithful geyser using matched field processing in 1992 a large and dense array of geophones was placed around the geyser vent of old faithful in the yellowstone national park to determine the origin of the seismic hydrothermal noise recorded at the surface of the geyser and to understand its dynamics old faithful geyser ofg is a small scale hydrothermal system where a two phase flow mixture erupts every 40 to 100 min in a high continuous vertical jet using matched field processing mfp techniques on 10 min long signal we localize the source of the seismic pulses recorded at the surface of the geyser several mfp approaches are compared in this study the frequency incoherent and frequency coherent approach as well as the linear bartlett processing and the non linear minimum variance distorsionless response mvdr processing the different mfp techniques used give the same source position with better focalization in the case of the mvdr processing the retrieved source position corresponds to the geyser conduit at a depth of 12 m and the localization is in good agreement with in situ measurements made at old faithful in past studies

cenozoic accumulation history of a pacific ferromanganese crust to investigate the growth rates and absolute time stratigraphy of marine hydrogenetic ferromanganese encrustations we performed 10be profiling and co chronometry of crustal layers as well as 87sr86sr and 18o analysis of phosphatised limestone francolite within a 9 5 cm thick ferromanganese crust from schumann seamount in the hawaiian archipelago together with microfossil stratigraphy our results indicate that some seamount crusts greatly exceed the commonly accepted miocene maximum age in this case probably approaching the cretaceous age of the seamount in addition to the unconformity at the crust substrate boundary at least eight major disconformities are indicated in the schumann seamount crust which probably represent depositional hiatuses or episodes of crust erosion three of the six upper disconformities can be placed at the plio pleistocene middle miocene and paleocene eocene based on 10be microfossil and co chronometer evidence 87sr86sr and 18o values of purified francolite from an inclusion rich layer between the depths of 44 and 49 mm suggest apparent ages that approach those of eocene late paleocene microfossils reported in overlying layers whereas francolite vein infillings in the lower part of the crust and in the basaltic substrate yield values that if interpreted as ages of phosphatization suggest a minimum oligocene age paleotracking suggests the phosphogenesis observed here and on other central pacific seamounts could not have resulted from upwelling enhanced productivity associated with equatorial divergence if the oligocene and middle miocene isotopic ages reported here and elsewhere are correct however a maximum late paleocene age for the phosphogenesis consistent with the stratigraphy would place these seamounts within 10 n of the equator paleotracking also suggests northeast tradewind transport of aluminosilicates in the cenozoic in agreement with other evidence for the antiquity of this ferromanganese crust

migration by extrapolation of time dependent boundary values migration of an observed zero offset wavefield can be performed as the solution of a boundary value problem in which the data are extrapolated backward in time this concept is implemented through a finite difference solution of the two dimensional acoustic wave equation all depths are imaged simultaneously at time 0 the imaging condition and all dips right up to vertical are correctly migrated numerical examples illustrate this technique in both constant and variable velocity media

analysis of near source contributions to early p wave coda for underground explosions i waveform complexity a data set of more than 1600 teleseismic short period p waves from 46 nuclear explosions is analyzed to establish near source contributions to the first 15 sec of the p signals the near source components are isolated by event to event comparisons of first cycle magnitudes rms amplitudes in the first 5 and next 10 sec of the wave forms and energy temporal centroid measurements events from the nevada amchitka and novaya zemlya test sites are analyzed separately to characterize overall source region variations event averaged waveform complexity variations between explosions within a given site are tested for dependence on source strength burial depth location within the site and tectonic release azimuthal patterns of the individual event complexity anomalies are used to discriminate between possible near source influences for events at pahute mesa a strong azimuthal amplitude pattern in both the direct p waves and the p coda for all of the events is produced principally by deep mantle variations defocusing by a high velocity anomaly in the crust and uppermost mantle beneath the site has a stronger effect on the direct p signals than on the early p coda resulting in a systematic spatially varying relative pattern

evolution of nd and pb isotopes in central pacific seawater from ferromanganese crusts abstract hydrogenetic ferromanganese crusts incorporate elements from ambient seawater during their growth on seamounts by analysing nd pb and be isotope profiles within crusts it is possible to reconstruct seawater tracer histories depth profiles of 10be 9be ratios in three pacific ferromanganese crusts have been used to obtain growth rates which are between 1 4 and 3 8 mm ma nd and pb isotopes provide intact records of isotopic variations in pacific seawater over the last 20 ma or more there were only small changes in pb isotope composition in the last 20 ma this indicates a constant pb composition for the erosional sources and suggests further that erosional nd inputs may have been uniform too end values vary considerably with time and most probably reflect changes in ocean circulation the end values of the crusts not only vary as a function of age but also as a function of water depth from 25 to 0 ma crust va13 2 from 4 8 km water depth has a similar pattern of end variation to the two shallower crusts from 1 8 and 2 3 km but about 1 0 to 1 5 units more negative this suggests that end stratification in pacific seawater as demonstrated for the present day has been maintained for at least 20 ma each crust shows a decrease in end from 3 5 ma to the present which is interpreted in terms of an increase in the nadw component present in the pacific from 10 to 3 5 ma ago the crusts show an increase in end this suggests a decreasing role for a deep water source with end less than circum pacific sources in this regard the panamanian gateway restriction from 10 ma with final closure at 3 5 ma may have played an important role in reducing access of atlantic derived nd to the pacific

the fascinating and complex dynamics of geyser eruptions geysers episodically erupt liquid and vapor despite two centuries of scientific study basic questions persist why do geysers exist what determines eruption intervals durations and heights what initiates eruptions through monitoring eruption intervals analyzing geophysical data taking measurements within geyser conduits performing numerical simulations and constructing laboratory models some of these questions have been addressed geysers are uncommon because they require a combination of abundant water recharge magmatism and rhyolite flows to supply heat and silica and large fractures and cavities overlain by low permeability materials to trap rising multiphase and multicomponent fluids eruptions are driven by the conversion of thermal to kinetic energy during decompression larger and deeper cavities permit larger eruptions and promote regularity by isolating water from weather variations the ejection velocity may be limited by the speed of sound of the liquid vapor mixture

an evaluation of strontium isotopic dating of ferromanganese oxides in a marine hydrogenous ferromanganese crust abstract in order to assess the utility of dating marine hydrogenous ferromanganese crusts with strontium isotopes we conducted a series of leaching experiments on samples selected from several stratigraphic layers of a well preserved 9 5 cm thick crust from the pacific ocean initially using a method similar to that of previous studies acetic acid leached residues of twelve subsamples were leached with hcl and the leachates analyzed for their isotopic composition the results did not make stratigraphic sense so we carried out two sequences of more detailed leaches on subsamples from four layers representing the chemical and textural spectrum observed in the crust in one sequence mineral specific leaches were selected for optimal extraction of strontium associated with the respective manganese and iron oxide phases the main compositional endmembers within ferromanganese crusts strontium isotopic ratios for these leaches were compared with those from the other sequence involving acetic acid plus hcl leaches on the same material residues remaining at the end of each leaching sequence were also analyzed it is evident from the results that hcl extracts strontium associated with both phosphatic material and aluminosilicate detritus present within the ferromanganese layers 87 sr 86 sr ratios obtained on the manganese oxides indicate that the strontium within the oxides exchanges with seawater strontium throughout the history of the deposit regardless of the porosity of the layer assuming that this crust is representative of other marine hydrogenous crusts strontium isotopes appear to be of little value for the direct dating of ferromanganese oxide deposits

sm nd in marine carbonates and phosphates implications for nd isotopes in seawater and crustal ages this study explores the possibility of establishing nd isotopic variations in seawater over geologic time calcite aragonite and apatite are examined as possible phases recording seawater values of nd modern biogenic and inorganically precipitated calcite and aragonite from marine environments were found to have nd concentrations of from 0 2 to 70 ppb showing that primary marine caco 3 contains little ree and that nd ca is not greatly enhanced relative to seawater during carbonate precipitation very young marine limestone and dolomite containing no continental detritus have 200 ppb nd all the carbonates are lree enriched 0 16 sm nd 0 45 modern and very young atlantic and pacific carbonates have nd in the range of shallow atlantic and pacific seawater respectively implying that they derive their ree from local seawater the nd in well preserved carbonate fossils is 4 10 4 ppb much greater than in their modern counterparts but like the high values found for carbonates in other studies we believe the high ree contents at the 500 ppb level in some detritusfree carbonates are due to ree rich fe hydroxide in on the carbonate in favorable cases such material may record seawater nd values however introduction of extraneous ree may obscure the original isotopic composition of pure caco 3 because of its very low intrinsic primary ree abundance modern biogenic apatite is also shown to have very low ree content 150 ppb nd but appears to quickly scavenge ree from seawater inorganically precipitated apatite from phosphorites has high concentrations of seawater derived ree young phosphorite apatite from the atlantic and pacific oceans has nd in the range of the seawater from these oceans older apatite samples of similar age from different localities bordering common oceans record similar values of nd t sedimentary apatite has sr t values in good agreement with the curves for 87 sr 86 sr of seawater as a function of time individual conodonts from a single formation yield the same sr t and nd t other workers have shown that sedimentary apatite preserves seawater ree patterns these characteristics suggest that sedimentary apatite can be used to determine nd t in ancient seawater the seawater values so inferred range between 1 7 and 8 9 over the last 700 my and lie in the range of modern seawater showing no evidence for drastic changes high values of seawater nd t in the triassic and latest precambrian may correlate with the breakup of large continental landmasses the initial nd t 15 0 of a 2 ae old phosphorite implies the presence of 1 5 ae old continental crust at 2 ae ago the approach outlined here can be used to constrain the age of the exposed crust as a function of time

magnetostratigraphy of hydrogenetic manganese crusts from northwestern pacific seamounts abstract fine scale dating is crucial to understanding the growth and environments of formation of marine manganese deposits the paleomagnetic method of dating of manganese nodules and crusts has been attempted but with no success so far we measured remanent magnetization rm on up to 75 mm thick hydrogenetic crusts at intervals of 2 5 mm after mineralogical and chemical examination careful separation and alternative field demagnetization stable sharp rm and well correlated polarity change patterns between four samples made it possible to identify the pliocene quaternary magnetic chrons in them these data show that the three crusts have grown continuously at rates of 14 17 mm m y since the early pliocene this is three or four times faster than those for central pacific seamount hydrogenetic crusts estimates of growth rate based on determination of co flux are within this range magnetostratigraphy therefore appears to be a powerful method for dating hydrogenetic manganese crusts when supported by conventional dating methods these results encourage finer scale investigations which promise more detailed paleoceanographic reconstruction

structure of the earth mantle and core the deep interior structure of the earth has been extensively analyzed using a wide variety of seismic phases and techniques during the last four years most studies have emphasized quantitative three dimensional mapping of the lateral velocity heterogeneity of the mantle and core these aspherical velocity variations are believed to be direct manifestations of thermal and compositional heterogeneity associated with convective processes a first generation of global models for the lateral velocity variations in the deep earth has been produced providing tantalizing images of large scale structures suggestive of a non steady state thermal convection system the upper 400 km of the mantle has the strongest lateral velocity variations of up to 10 for shear velocity surface wave analyses that do not require a priori regionalizations have demonstrated that there is a strong association between surface tectonic provinces and the uppermost mantle velocity variations thus the thermal and convective state of the upper 200 km of the mantle can be reliably interpreted in the context of plate tectonics the upper mantle models support the contention that continents have deep roots with differences in velocity structure from oceanic and active tectonic regions extending as deep as 400 km very long wavelength lateral velocity variations of a few percent have been detected in the transition zone at depths from 400 to 670 km as well as throughout the lower mantle these deep seated variations have little correspondence to surface tectonics and efforts to interpret their nature are just beginning the lowermost 200 km of the mantle d region has lateral velocity fluctuations comparable to those in the upper mantle and evidence has been presented for the presence of a sizable velocity discontinuity at the top of the d layer a combined thermal and compositional boundary layer roughly mirroring the lithosphere is a likely explanation for this anomalous zone the core mantle boundary appears to have significant 10 km long wavelength topography presumably sustained by dynamic stresses from deep mantle convection the inner core may have strong lateral heterogeneity or axially symmetric anisotropy suggesting a complex thermal and compositional state significant progress has been made in characterizing the frequency dependence of anelastic attenuation in the mantle in the short period body wave band models for teleseismic p wave attenuation operators have converged with t values of 0 7 1 0 s appropriate at 1 hz and t values of 0 4 0 6 s appropriate at 4 hz regional variations of attenuation are slowly being mapped out as well

evidence of tectonic release from underground nuclear explosions in long period s waves the sh waves from 21 underground nuclear explosions at pahute mesa nts were used to investigate tectonic release the equivalent double couple representation of the tectonic release which was constrained by waveform modeling and the polarity of sp is very similar for all the explosions the average orientation is a right lateral strike slip fault trending n15 w seismic moments were determined on the basis of comparisons with two western united states strike slip earthquakes benham has the largest tectonic release moment 5 6 10 24 dyne cm and stilton 0 1 10 24 dyne cm the smallest of the events studied in general the seismic moments increase with the size of the explosion but the location of the explosion relative to previous explosions can strongly affect the tectonic release the pahute mesa events can be separated into two populations 1 events which are well separated 4 km from previous explosions and 2 those events which are close 4 km to previous explosions those events which are close to previous explosions show a marked decrease in tectonic release a least squares fit of seismic moment to event size as determined from the world wide average ab amplitude shows that the two populations are approximately parallel but offset the fact that the trends remain separated even at small yields e g pipkin and scotch suggests that for pahute mesa there is not a threshold for tectonic release since spatial position gives the best separation of high and low tectonic release events a volume model is favored for the source mechanism the preferred model is motion on a system of faults and joints

southward shift of the intertropical convergence zone in the western pacific during the late tertiary evidence from ferromanganese crusts on seamounts west of the marshall islands 1 hydrogenetic ferromanganese crusts were dredged from four seamounts in the western pacific osm7 osm2 lomilik and lemkein aligned in a nw se direction parallel to pacific plate movement the crusts consist of four well defined layers with distinct textural and geochemical properties the topmost layer 1 is relatively enriched in mn co ni and mo compared to the underlying layer 2 which is relatively enriched in al ti k and rb and cu zn and excess ba textural and geochemical properties of layer 2 suggest growth conditions under high biogenic and detrital flux such conditions are met in the equatorial pacific i e between the intertropical convergence zone itcz and equatorial high productivity zone layer 2 likely formed when each seamount was beneath the equatorial pacific along its back track path on the other hand layer 1 probably started to grow after seamounts moved northwest from the itcz this interpretation is consistent with the thickness of layer 1 across the four crusts which increases to the northwest ages of the layer 1 layer 2 boundary in each crust a potential proxy for northern margin of the itcz also increase to the northwest at 17 11 8 and 5 ma for osm7 osm2 lomilik and lemkein respectively assuming pacific plate motion of 0 3 myr the seamounts were located at 12 n 11 n 9 n and 8 n at the time of boundary formation this result suggests that the north edge of the itcz has shifted south since the middle miocene in the western pacific which agrees with information from the eastern pacific

changes in erosion and ocean circulation recorded in the hf isotopic compositions of north atlantic and indian ocean ferromanganese crusts abstract high resolution hf isotopic records are presented for hydrogenetic fe mn crusts from the north atlantic and indian oceans bm1969 from the western north atlantic has previously been shown to record systematically decreasing nd isotopic compositions from about 60 to 4 ma at which time both show a rapid decrease to unradiogenic nd composition thought to be related to the increasing influence of nadw or glaciation in the northern hemisphere during the oligocene north atlantic hf became progressively less radiogenic until in the mid miocene 15 ma it reached 1 it then shifted gradually back to an hf value of 3 at 4 ma since when it has decreased rapidly to about 1 at the present day the observed shifts in the hf isotopic composition were probably caused by variation in intensity of erosion as glaciation progressed in the northern hemisphere ferromanganese crusts ss663 and 109d are from about 5500 m depth in the indian ocean and are now separated by 2300 km across the mid indian ridge they display similar trends in hf isotopic composition from 20 to 5 ma with the more northern crust having a composition that is consistently more radiogenic by 2 hf units paradoxically during the last 20 ma the hf isotopic compositions of the two crusts have converged despite increased separation and subsidence relative to the ridge a correlatable negative excursion at 5 ma in the two records may reflect a short term increase in erosion caused by the activation of the himalayan main central thrust changes to unradiogenic hf in the central indian ocean after 5 ma may alternatively have been caused by the expanding influence of nadw into the mid indian basin via circum antarctic deep water or a reduction of pacific flow through the indonesian gateway in either case these results illustrate the utility of the hf isotope system as a tracer of paleoceanographic changes capable of responding to subtle changes in erosional regime not readily resolved using other isotope systems

using 234u 238u to assess diffusion rates of isotope tracers in ferromanganese crusts abstract ferromanganese crusts record seawater isotope history for several elements useful for paleoceanography interpreting crust isotope profiles however requires an assessment of the rate of diffusion of each element within the crust we address this issue using u and th isotope profiles coupled with concentration measurements of some trace elements whose isotopes are often measured in crusts a depth profile of 230thxs 234u for a north atlantic crust alv539 yields a growth rate of 3 05 mm myr consistent with an existing 10be 9be record but the growth rate implied by a 234u 238u profile in the same crust is 6 times faster due to diffusion of u in the crust the difference between the observed 234u 238u profile and that expected from 230thxs 234u enables the effective diffusivity of u to be calculated as 1 2 10 6 cm2 year recalculated literature data indicate that other crusts have diffusivities which range down to 4 7 10 8 cm2 yr this variation is to be expected given the range of porosity observed for ferromanganese crusts concentration measurements of various elements in the surface layer of the crust provide relative distribution coefficients for each element between seawater and crust these distribution coefficients enable the effective diffusivity of each element to be calculated by comparison with the diffusivity of u such diffusivities are assessed for crust alv539 and give a first indication of the expected preservation of isotope signals in ferromanganese crusts li os and sr have diffusivities of 2 10 4 3 10 5 and 2 10 5 cm2 year respectively and diffusion is expected to be sufficiently fast that crusts will not accurately preserve past seawater compositions th nd pb and be have diffusivities less than 10 9 cm2 year and are highly immobile in crusts a reassuring result for th and be crust chronologies and for nd and pb isotope tracing of past water masses using crusts hf has a diffusivity of 3 10 8 in alv539 fast enough to perturb but not destroy its isotope history for studies of hf in this and other crusts diffusion should therefore be considered measuring u isotope profiles provides a potential way of assessing such diffusion for hf or for other elements with relatively low distribution coefficients into ferromanganese crusts

seismicity at old faithful geyser an isolated source of geothermal noise and possible analogue of volcanic seismicity abstract old faithful geyser in yellowstone national park u s a is a relatively isolated source of seismic noise and exhibits seismic behavior similar to that observed at many volcanoes including bubblequakes that resemble b type earthquakes harmonic tremor before and during eruptions and periods of seismic quiet prior to eruptions although old faithful differs from volcanoes in that the conduit is continuously open that rock fracturing is not a process responsible for seismicity and that the erupting fluid is inviscid h2o rather than viscous magma there are also remarkable similarities in the problems of heat and mass recharge to the system in the eruption dynamics and in the seismicity water rises irregularly into the immediate reservoir of old faithful as recharge occurs a fact that suggests that there are two enlarged storage regions one between 18 and 22 m the base of the immediate reservoir and one between about 10 and 12 m depth transport of heat from hot water or steam entering at the base of the recharging water column into cooler overlying water occurs by migration of steam bubbles upward and their collapse in the cooler water and by episodes of convective overturn an eruption occurs when the temperature of the near surface water exceeds the boiling point if the entire water column is sufficiently close to the boiling curve that the propagation of pressure release waves rarefactions down the column can bring the liquid water onto the boiling curve the process of conversion of the liquid water in the conduit at the onset of an eruption into a two phase liquid vapor mixture takes on the order of 30 s the seismicity is directly related to the sequence of filling and heating during the recharge cycle and to the fluid mechanics of the eruption short 0 2 0 3 s monochromatic high frequency events 20 60 hz resembling unsustained harmonic tremor and in some instances b type volcanic earthquakes occur when exploding or imploding bubbles of steam cause transient vibrations of the fluid column the frequency of the events is determined by the length of the water column and the speed of sound of the fluid in the conduit when these events occur damping is controlled by the characteristic and hydraulic impedances which depend on the above parameters as well as on the recharge rate of the fluid two periods of reduced seismicity of a few tens of seconds to nearly a minute in duration occur during the recharge cycle apparently when the water rises rapidly through the narrow regions of the conduit causing a sudden pressure increase that temporarily suppresses steam bubble formation a period of decreased seismicity also precedes preplay or an eruption this appears to be the time when rising steam bubbles move into a zone of boiling that is acoustically decoupled from the wall of the conduit because of the acoustic impedance mismatch between boiling water c 10 3 g cm 2 s 1 and rock c 3 10 5 g cm 2 s 1 sustained harmonic tremor occurs during the first one to one and a half minutes of an eruption of old faithful but is not detectable in the succeeding minutes of the eruption the eruption tremor is caused by hydraulic transients propagating within a sublayer of unvesiculated water that underlies the erupting two phase liquid vapor mixture the resonant frequencies of the fluid column decrease to about 1 hz when all of the water in the conduit has been converted to a water steam mixture surges are observed in the flow at this frequency but the resonance has not been detected seismically possibly because the two phase erupting fluid is seismically decoupled from the rock on which seismometers are placed if old faithful is an analogue for volcanic seismicity this study shows that because the frequency of tremor depends on the acoustic properties of the fluid and on conduit dimensions both properties must be considered in analysis of tremor in volcanic regions because magma sound speed can vary over nearly two orders of magnitude as it changes from an undersaturated liquid into a saturated two phase mixture tremor frequency might vary by this magnitude and very broad band seismographs may be required if tremor is to be monitored as magma goes from an undersaturated liquid to a vesiculated froth cessation of fluid induced seismicity may indicate that the processes that drive the transients cease but it is also possible that the processes that drive the transients continue but the fluid properties change so that the fluid becomes acoustically decoupled from the rock on which seismometers are placed

hydraulic fractures how far can they go the maximum reported height of an upward propagating hydraulic fracture from several thousand fracturing operations in the marcellus barnett woodford eagle ford and niobrara shale usa is 588 m of the 1170 natural hydraulic fracture pipes imaged with three dimensional seismic data offshore of west africa and mid norway it is 1106 m based on these empirical data the probability of a stimulated and natural hydraulic fracture extending vertically 350 m is 1 and 33 respectively constraining the probability of stimulating unusually tall hydraulic fractures in sedimentary rocks is extremely important as an evidence base for decisions on the safe vertical separation between the depth of stimulation and rock strata not intended for penetration