analysis of three component data from iris ida stations in the ussr abstract this paper presents results of backazimuth incidence angle and phase identification studies based on the three component polarization of 0 to 5 hz seismic signals recorded at the iris ida stations within the ussr a data set was built from the analysis of three component 3 c recordings from seismic stations at arti aru garm gar kislovodsk kiv and obninsk obn for the month of march 1989 approximately 260 events were studied at stations aru kiv and obn teleseisms dominated the sample of recordings station gar however recorded a larger set of events that included a significant number of local and regional events except for station obn all of the iris ida stations are located near major geologic structural boundaries that are characterized by significant lateral variation in the deep velocity structure these stations near boundaries show system atic deviations in estimates of backazimuth and angle of incidence at station gar both of these measurements were influenced by the structure polarization characteristics of seismic phases were studied individually for each station at stations obn and kiv the initial teleseismic p wave was characterized for the most part by prograde elliptical motion at aru and gar the motion was rectilinear regional s phases from hindu kush earthquakes recorded at gar were dominated by transverse horizontally polarized motion sh at kiv and aru lg motion was predominantly in a near horizontal plane a phase identification study was performed using discriminant analysis based on polarization parameters and frequency content two discriminants linear combinations of polarization and frequency measurements were able to separate arrival data into one of three groups of phases teleseismic p regional p and regional s at gar the first discriminant is correlated with polarization and separates arrivals with p wave characteristics from arrivals with s wave characteristics the second discriminant accentuates the differences in the frequency content of the arrivals and provides a good separation between regional and teleseismic phases backazimuth estimates were made for local regional and teleseismic events at gar and for teleseismic events at aru kiv and obn the unique structural environment of each station required that custom processing parameters be developed for each station the assumed particle motion rectilinear or elliptical used in the polarization computation the window length and the frequency band characteristic for each station were determinant factors backazimuth estimates within 25 of the theoretical value were obtained for about 70 of the events at most of the stations at gar systematic backazimuth errors caused by large lateral velocity discontinuities degraded the results corrections could be made to reduce these errors

temporal observations of a seasonal snowpack using upward looking gpr an increase of the spatial and temporal resolution of snowpack measurements in alpine or arctic regions will improve the predictability of flood and avalanche hazards and increase the spatial validity of snowpack simulation models in the winter season 2009 we installed a ground penetrating radar gpr system beneath the snowpack to measure snowpack conditions above the antennas in comparison with modulated frequency systems gpr systems consist of a much simpler technology are commercially available and therefore are cheaper the radar observed the temporal alternation of the snow height over more than 2 5 months the presented data showed that with moved antennas it is possible to record the snow height with an uncertainty of less than 8 in comparison with the probed snow depth three persistent melt crusts which formed at the snow surface and were buried by further new snow events were used as reflecting tracers to follow the snow cover evolution and to determine the strain rates of underlaying layers between adjacent measurements the height in two way travel time of each layer changed over time which is a cumulative effect of settlement and variation of wave speed in response to densification and liquid water content the infiltration of liquid water with depth during melt processes was clearly observed during one event all recorded reflections appeared in concordance with the physical principles e g in phase structure and one can assume that distinct density steps above a certain threshold result in reflections in the radargram the accuracy of the used impulse radar system in determining the snow water equivalent is in good agreement with previous studies which used continuous wave radar systems the results of this pilot study encourage further investigations with radar measurements using the described test arrangement on a daily basis for continuous destruction free monitoring of the snow cover

diagenesis and geochemistry of porites corals from papua new guinea implications for paleoclimate reconstruction coral proxy records of sea surface temperature sst and hydrological balance have become important tools in the field of tropical paleoclimatology however coral aragonite is subject to post depositional diagenetic alteration in both the marine and vadose environments to understand the impact of diagenesis on coral climate proxies two mid holocene porites corals from raised reefs on muschu island papua new guinea were analysed for sr ca 18 o and 13 c along transects from 100 aragonite to 100 calcite thin section analysis showed a characteristic vadose zone diagenetic sequence beginning with leaching of primary aragonite and fine calcite overgrowths transitional to calcite void filling and neomorphic fabric selective replacement of the coral skeleton average calcite sr ca and 18 o values were lower than those for coral aragonite decreasing from 0 0088 to 0 0021 and 5 2 to 8 1 respectively the relatively low sr ca of the secondary calcite reflects the sr ca of dissolving phases and the large difference between aragonite and calcite sr ca partition coefficients the decrease in 18 o of calcite relative to coral aragonite is a function of the 18 o of precipitation carbon isotope ratios in secondary calcite are variable though generally lower relative to aragonite ranging from 2 5 to 10 4 the variability of 13 c in secondary calcite reflects the amount of soil co 2 contributing 13 c depleted carbon to the precipitating fluids diagenesis has a greater impact on sr ca than on 18 o the calcite compositions reported here convert to sst anomalies of 115 c and 14 c respectively based on calcite sr ca compositions in this study and in the literature the sensitivity of coral sr ca sst to vadose zone calcite diagenesis is 1 1 to 1 5 c per percent calcite in contrast the rate of change in coral 18 o sst is relatively small 0 2 to 0 2 c per percent calcite we show that large shifts in 18 o reported for mid holocene and last interglacial corals with warmer than present sr ca ssts cannot be caused by calcite diagenesis low level calcite diagenesis can be detected through x ray diffraction techniques thin section analysis and high spatial resolution sampling of the coral skeleton and thus should not impede the production of accurate coral paleoclimate reconstructions copyright 2003 elsevier science ltd

source parameters for 11 earthquakes in the tien shan central asia determined by p and sh waveform inversion the tien shan mountain belt of central asia was formed in late paleozoic time and reactivated in tertiary time following the collision of india with eurasia more than 1500 km to the south to study the style and distribution of faulting occurring today in the tien shan we digitized long period world wide standard seismograph network p and sh waveforms of 11 of the largest tien shan earthquakes between 1965 and 1982 and then used a least squares inversion routine to constrain their fault plane solutions and depths four of the earthquakes occurred near the southern edge of the tien shan and two occurred in the intermontane fergana basin these earthquakes occurred at depths of 10 20 km and are associated with thrust faulting on east west to southwest northeast striking fault planes that dip moderately 35 55 the other five earthquakes in the northern tien shan were mostly deeper 15 44 km and the fault plane solutions of four of them are similar to the events farther south the exception an event on june 2 1973 probably occurred on a gently northward dipping east west striking fault plane all events occur within the basement at depths of 10 km or greater waveforms for earthquakes near the edges of the dzungarian fergana and kucha basins are fit best using velocity structures with thick sediment layers implying that sediments from these basins have been and are being underthrust beneath the neighboring mountains we examined only the relatively small mb 5 5 6 2 events after 1965 and did not study any of the largest events ms 8 that occurred in the tien shan earlier in this century still we can conclude that north south shortening is presently occurring in the tien shan with the formation of basement uplifts flanked by moderately dipping thrust faults the present day tectonics of the tien shan seem to be analogous to those of the rocky mountains in colorado wyoming and utah during the laramide orogeny in late cretaceous and early tertiary time

strontium calcium ratios in modern porites corals from the great barrier reef as a proxy for sea surface temperature calibration of the thermometer and monitoring of enso high precision sr ca ratios are reported for porites corals from davies reef at 19 s on the midshelf of the great barrier reef australia skeletal growth parameters were also determined from coral slabs using x ray photographs and densitometry measurements a calibration of the sr ca thermometer has been obtained using in situ measured sea surface temperatures which gives sr ca 10 10 48 0 01 0 0615 0 0004 t wheret is in c this calibration applies to different species of porites and a large range of annual extension and calcification rates provided sampling follows a major growth axis biases of 1 2 c have been observed in the low density margins where growth is hampered by interfering fans of corallites the analytical and the long term reproducibility of sr ca derived temperatures are both better than 0 3 c 2 coral growth parameters such as the extension rate or density generally appear to respond to environmental changes such as rainfall but do not affect the sr ca partitioning between coralline aragonite and seawater no correlation has been found between calcification rate and sr ca variations consistent with sr ca being mainly controlled by temperature in the great barrier reef the interannual variability in sst is primarily related to the el nino southern oscillation phenomenon and is typically marked by a cold anomaly during the winter preceding the mature warm phase instrumental records show that the surface waters of the coral sea around 19 s have experienced a significant cooling associated with the el ninos of 1965 1972 and 1982 1983 which the porites corals record faithfully the coral derived temperatures for the period from 1965 to 1993 show an increase of 1 3 c which has occurred mainly since 1979 this warming is larger in magnitude but consistent with the trend for the southern hemisphere land and marine temperature records which shows an increase of around 0 4 c

two dimensional x ray diffraction as a tool for the rapid nondestructive detection of low calcite quantities in aragonitic corals paleoclimate reconstructions based on reef corals require precise detection of diagenetic alteration secondary calcite can significantly affect paleotemperature reconstructions at very low amounts of 1 x ray powder diffraction is routinely used to detect diagenetic calcite in aragonitic corals this procedure has its limitations as single powder samples might not represent the entire coral heterogeneity a conventional and a 2 d x ray diffractometer were calibrated with gravimetric powder standards of high and low magnesium calcite 0 3 to 25 calcite calcite contents 1 can be recognized with both diffractometer setups based on the peak area of the calcite 104 reflection an advantage of 2 d xrd over convenient 1 d xrd methods is the nondestructive and rapid detection of calcite with relatively high spatial resolution directly on coral slabs the calcite detection performance of the 2 d xrd setup was tested on thin sections from fossil porites sp samples that based on powder xrd measurements showed 1 calcite quantification of calcite contents for these thin sections based on 2 d xrd and digital image analysis showed very similar results this enables spot measurements with diameters of 4 mm as well as systematic line scans along potential tracks previous to geochemical proxy sampling in this way areas affected by diagenetic calcite can be avoided and alternative sampling tracks can be defined alternatively individual sampling positions that show dubious proxy results can later be checked for the presence of calcite the presented calibration and quantification method can be transferred to any 2 d x ray diffractometer

analysis of historical seismograms root mean square lg magnitudes yields and depths of explosions at the semipalatinsk test range summary magnitudes mb lg based on rms amplitudes of lg waves recorded at nine internal soviet stations for 83 underground nuclear explosions at the semipalatinsk test range were analysed network magnitudes based on a combination of station magnitudes were formed as weighted averages over the station magnitudes after adjusting for variations among station magnitudes in scaling with source strength combining the station magnitudes into network magnitudes although the number of stations was small less than six appeared to reduce scatter in magnitude yield relations the correlation between network mb lg and announced explosion yields was very high and mb lg closely approximated simple proportionality with the logarithm of yield throughout the yield interval 2 165 kt the error of misfit was about 0 04 magnitude units excluding data for the explosion of 1972 august 16 8 kt at 139m the yield of which appeared high compared to mb lg the close correlation between network mb lg and explosion yield together with the fact that several of the explosions were not at scaled depths indicates that mb lg may not be critically dependent on depth of burial at least for depth ranges within a factor of two

the strontium magnesium and sodium composition of recent scleractinian coral skeletons as standards for palaeoenvironmental analysis to establish standards for the palaeoenvironmental interpretation of scleractinian coral bearing strata the geochemistry of the three major trace element constituents of living scleractinian coral skeletons is discussed in relation to possible controls on their concentrations experiments were conducted in which the sr ca and mg ca ratios of the seawater were altered and the resultant change in skeletal composition monitored the partition coefficient of strontium ksr was shown to be linear ranging from approximately half to over ten times the normal seawater sr ca ratio increases in the magnesium concentration of seawater decreased ksr growth rates were increased through the addition of calcium and strontium but decreased by magnesium the sodium and magnesium contents of the skeleton were unaffected by their seawater concentrations relative to calcium or strontium magnesium however was affected by growth while sodium by salinity

chronological control of coral records using luminescent lines and evidence for non stationary enso teleconnections in northeast australia eight multicentury porites coral cores were used to develop a 373 year chronology by cross dating techniques adapted from dendrochronology characteristic patterns of distinct luminescent lines within the coral skeletons were matched between coral cores from inshore and mid shelf reefs in the central great barrier reef australia skeleton plots of luminescent banding were produced for each core and combined into a master chronology back to ad 1615 in addition to improving dating control the luminescence master chronology provides a proxy for burdekin river runoff and queensland summer rainfall variations in the magnitude of the correlation between the luminescence master and the mann et al 2000 nino3 sea surface temperature reconstruction provides insights into the long term stability of el nino southern oscillation enso telecon nections burdekin river runoff was significantly inversely related to enso variability for much of the period from the ad 1650s to 1800 suggesting that enso related te

evaluation of the effect of diagenetic cements on element ca ratios in aragonitic early miocene 16ma caribbean corals implications for deep time palaeo environmental reconstructions abstract early miocene corals siderastrea conferta and montastraea limbata from the paraguana peninsula venezuela and a modern coral s radians from bermuda were examined in order to quantitatively assess the effect of skeletal preservation on element ca proxies used for palaeo environmental reconstructions the biostratigraphic age burdigalian of the corals was confirmed via sr isotope stratigraphy to 16 5 0 4 ma light and scanning electron microscopy revealed the presence of aragonite and calcite cements in both fossil and modern corals but brucite cements were found only in the modern coral cement distribution is very heterogeneous resulting in zones of excellent preservation juxtaposed with less well preserved regions in both modern and fossil coral oil filled pore spaces were noted in the fossil specimens targeted la icpms depth profile analyses showed significant differences in sr ca mg ca b ca ba ca and u ca in aragonite and calcite cements compared to primary skeletal aragonite increased sr ca and decreased mg ca ratios were found in aragonite cements compared to skeletal aragonite whereas in calcite cements these trends were reversed b ca ratios were lower in both aragonite and calcite cements compared to primary aragonite estimates of the effect of 1 contamination by aragonite cements on coral sr ca mg ca b ca and u ca palaeo sea surface temperature reconstructions for the fossil corals produced anomalies of 1 2 c 0 2 c 0 3 c and 0 1 c respectively similar percentage calcite cement contamination produced temperature anomalies of 1 7 c 2 7 c 0 3 c and 0 1 c because of both highly elevated and depleted ba ca signatures in aragonite and calcite cements respectively care has to be exercised when reconstructing past flood or upwelling events from fossil corals when using targeted spatially resolved analysis well preserved early miocene corals may overall yield reliable deep time palaeo proxy information in much the same way as commonly utilised holo pleistocene corals

extending the radiocarbon calibration beyond 26 000 years before present using fossil corals fossil coral is an excellent archive to extend the radiocarbon 14c calibration beyond tree ring records however published coral data older than 26 000 years before present are too disparate for practical calibration we propose an explanation for these discrepancies trace amounts of secondary calcite and organic matter in fossil corals shift the 14c ages toward younger ages in a series of acid leaching experiments to simulate the standard cleaning procedure prior to 14c analysis we measure up to a 300 enrichment of diagenetic calcite in corals due to the solubility differences between calcite and aragonite in model calculations we show the 14c age offsets produced by acid leaching could be hundreds to thousands of years when typical amounts of calcite are present in samples we demonstrate the necessity and our ability to detect 0 2 calcite in aragonite by x ray diffraction and apply 0 2 calcite as our a priori criterion for our coral samples the estimated age offsets of samples with 0 2 calcite fall within the reported analytical uncertainty of 14c dating in addition we present 14c results from an extended hydrogen peroxide h2o2 pretreatment for coral samples to remove organic matter our data show that treated samples yield consistent or older 14c dates compared to non treated samples these rigorous but necessary screening and cleaning techniques provide precise reproducible and accurate radiocarbon calibration data

seismic event detection and source location using single station three component data the seismic event detection and source location scheme presented in this paper uses single station seismic data to analyze seismic events to detect events the detection scheme combines the signals on the horizontal components in a manner analogous to beam steering once an event is detected the location scheme estimates the location of the source with respect to the receiver by estimating the polarization direction of the pn phase the range estimate is then obtained from the relative timing of different phases

regional seismic event location with a sparse network application to eastern kazakhstan ussr three component data from a sparse three station seismic network in eastern kazakhstan surrounding the soviet nuclear test site have been analyzed to determine location estimates for regional events recorded by two or three stations included among these events are the september 1987 chemical explosions whose locations are known locations are calculated using arrival times of p and s phases and arrival azimuths from first p location uncertainties are estimated using a combination of a priori and a posteriori data uncertainties a layered p wave velocity model adapted from soviet deep seismic sounding surveys is employed for calculating travel times and two s models are tried location results for the chemical explosions are excellent even if only two stations are used absolute location errors are less than 10 km and estimated 90 confidence uncertainties are only a few kilometers the data are also adequate to determine correctly their depth i e focus at the surface the other regional events include numerous suspected mine blasts and two earthquakes from the tien shan the calculated locations of the latter events agree well with a teleseismic location for one of them falling within a belt of regular seismic activity nearly all of the presumed blasts can be associated with mapped mines and we have been able to identify the source areas for two sets of blasts in high resolution satellite images before and after photographs allow us to identify specific active mines our location estimates agree quite well with the observed active mines

a review of modern coral δ18o and δ14c proxy records abstract this paper is a review of published modern coral 18 o and 14 c isotopic records that are at least 30 and 20 years long respectively the data are presented to show basin scale trends in both of these proxy records on decadal to centennial timescales the goal was to qualitatively integrate the general inter annual to centennial timescale variability revealed in these data as well as the statistical and modeling output results that have been produced using these coral records while many review papers typically include a representative subset of the data available this review aims to include as much of the available data as possible in general coral 18 o records show a long term warming and or freshening throughout the tropical oceans and agree with the noaa extended reconstruction sea surface temperature 2 ersst on decadal timescales in the western pacific it is most likely a freshening of the seawater 18 o that dominates the signal el nino southern oscillation enso variability dominates most 18 o records either by varying local seawater temperature or salinity depending on the regional oceanography climatology outside of the pacific enso affects seawater temperature and salinity via atmospheric or oceanic teleconnections post bomb coral 14 c records collectively show that the uptake of 14 c has been greatest in gyre water fed sites followed in descending order by western boundary current areas equatorial upwelling regions and eastern tropical pacific upwelling sites these surface water 14 c values indicate the proportion of surface water and or the residence time of water at the surface at a given location and can be used to model water mass mixing rates such models have only begun to be run and show that the amount of eastern pacific water entering the central south pacific increases during el ninos and that the indonesian throughflow is supplied year round by the north pacific comparing ocean circulation models with coral 14 c modelled circulation enables researchers to explore the mechanisms that drive seawater 14 c variability and fine tune their models in addition our comparison between the rate of coral 14 c increase between 1960 and 1970 and total anthropogenic co 2 uptake rates show general agreement demonstrating the value of coral records in understanding past carbon fluxes overall coral 18 o and 14 c proxy records represent natural archives of seawater conditions and are critical for studying the natural variability in local and regional patterns within and teleconnection patterns between the tropics extra tropics temperate and polar regions on intra annual to centennial timescales

infrasound detection of large mining blasts in kazakstan we describe infrasonic observations recorded since october 1997 at the kurchatov observatory in kazakstan from large mining blasts in kazakstan and siberia seismic signals are regularly recorded on a 21 element cross array from events located at the ekibastuz mine 250 km nw of kurchatov however associated infrasonic detections are infrequent and appear to be seasonal with maximum numbers of detections occurring during november to january raytracing through model atmosphere temperature and wind profiles predicts enhanced infrasound reception during the winter months when the prevailing stratospheric winds blow towards kurchatov in addition raytracing confirms that the first infrasound arrivals at kurchatov propagate through the troposphere and are followed some 50 70 s later by a stratospheric arrival

images of diagenetic textures in porites corals from papua new guinea and indonesia diagenesis is now recognized as a potentially major source of error in paleoclimatic reconstructions from fossil and modern coral geochemical records key to avoiding spurious results caused by diagenesis is thorough screening of coral material prior to geochemical analysis in this data brief we present color images from thin sections of fossil and modern porites corals and demonstrate the effectiveness of thin sections in detecting low levels of diagenesis the images presented here cover a range of coral preservation levels from pristine aragonite to 100 calcite we particularly focus on samples containing around 1 diagenetic material a level known to create artifacts in key climate parameters such as sea surface temperature and close to the detection limits of other screening methods such as x ray diffraction xrd a qualitative scheme is also presented to rate the degree of diagenesis in a coral where xrd results are not available or where secondary aragonite is present overall this collection of images is designed as a starting point in combination with other techniques to assist in identifying and screening corals for diagenesis

local earthquake relative location by digital records abstract an analysis has been carried out on digital seismograms collected by the national telemetered network for earthquake sequences occurring in central italy during april may 1984 comparison of seismograms has shown that events can conveniently be considered in groups having similar wave forms inside such groups data referring to pairs of events recorded by the same station have rather high correlation coefficients using techniques based on cross correlation we have estimated small time delays between first arrivals for pairs of events and obtained a relative location for such events the preliminary results show that events belonging to the same group of wave forms are generally located close together

high frequency seismic observations in eastern kazakhstan ussr with emphasis on chemical explosion experiments two temporary three station seismic networks deploying surface and 100 m borehole high frequency seismometers of the order of 200 km from the kazakh test site in the ussr and the nevada test site in the united states are discussed with emphasis on chemical explosion experiments seismograms attained from the detonation of three buried explosions 10 t 20 t 10 t in eastern kazakhstan at distances between 156 and 637 km are examined in the frequency band of 1 80 hz observed signal to noise s n ratios were high reaching a maximum of 400 for pg waves and 200 for lg waves good signal to noise levels persisted to high frequencies s n 2 at about 50 hz for lg waves about 250 km from the source and at about 14 hz at 680 km distance for pg waves s n 2 at about 50 hz 270 km from the source shapes of displacement amplitude spectra were similar characterized by a broad maximum in signal to noise levels between 4 8 hz and a decay at higher frequencies e g above 10 hz of about f 3 5 f 4 1 for lg waves and f 3 1 f 4 5 for pg unconnected for distance magnitudes estimated from lg time domain amplitudes for the 10 t explosion are between 2 8 and 3 3 depending on the magnitude relation used spectral characteristics are used to put some constraint on lg q pg q is poorly constrained by the data a similar experiment in southern nevada showed much lower pg and lg signal to noise levels above 1 hz although kazakh and nevada absolute noise levels are comparable

calcite filled borings in the most recently deposited skeleton in live collected porites scleractinia implications for trace element archives abstract skeletons of the scleractinian coral porites are widely utilized as archives of geochemical proxies for among other things sea surface temperature in paleoclimate studies here we document live collected porites lobata specimens wherein as much as 60 of the most recently deposited skeletal aragonite i e the part of the skeleton that projects into the layer of living polyps and thus is still in direct contact with living coral tissue has been bored and replaced by calcite cement calcite and aragonite were identified in situ using raman microspectroscopy the boring filling calcite cement has significantly different trace element ratios sr ca mmol mol 6 3 1 4 mg ca mmol mol 12 0 5 1 than the host coral skeletal aragonite sr ca mmol mol 9 9 1 3 mg ca mmol mol 4 5 2 3 the borings appear to have been excavated by a coccoid cyanobacterium that dissolved aragonite at one end and induced calcite precipitation at the other end as it migrated through the coral skeleton boring activity and cement precipitation occurred concomitantly with coral skeleton growth thus replacing skeletal aragonite that was only days to weeks old in some cases although the cement filled borings were observed in only 20 of sampled corals their occurrence in some of the most recently produced coral skeleton suggests that any corallum could contain such cements irrespective of the coral s subsequent diagenetic history in other words pristine skeletal aragonite was not preserved in parts of some corals for even a few weeks although not well documented in coral skeletons microbes that concomitantly excavate carbonate while inducing cement precipitation in their borings may be common in the ubiquitous communities that carry out micritization of carbonate grains in shallow carbonate settings thus such phenomena may be widespread and failure to recognize even very small quantities of early cement filled borings in corals used for paleoclimate studies could compromise high resolution paleotemperature reconstructions the inability to predict the occurrence of cement filled borings in coralla combined with the difficulty in recognizing them on polished blocks highlights the great care that must be taken in vetting samples both for bulk and microanalysis of geochemistry

sst artifacts in coral proxy records produced by early marine diagenesis in a modern coral from rabaul papua new guinea 1 we investigated the effects of early marine diagenesis on the skeletal geochemistry of a porites coral collected live offshore of rabaul papua new guinea the lowermost 14 cm of the 1 9 m coral core contains physical evidence of alteration which is clearly visible in x radiograph sem and petrography images abrupt and significant increases in coral 18o and sr ca and decreases in coral mg ca occur at the transition from unaltered to altered skeleton all of which imply significant sst cooling if the altered nature of the coral skeleton went unrecognized screening for the effects of early marine diagenesis should become a standard procedure in coral climate studies

impact of skeletal dissolution and secondary aragonite on trace element and isotopic climate proxies in porites corals restricted zones of recent dissolution and secondary aragonite infilling were identified in a coral core collected in 1986 from a living massive porites colony from the central great barrier reef australia secondary aragonite needles 20 m long cover skeletal surfaces deposited from 1972 to late 1974 and increase bulk density by 10 dissolution is observed above this zone whereas older skeleton is pristine we investigate the impact of both types of early marine diagenesis on skeletal geochemistry and coral paleoclimate reconstructions by comparison with similar records from eight contemporary porites colonies collected at nearby reefs secondary aragonite overgrowth causes anomalies in skeletal density mg ca sr ca u ca o and c the secondary aragonite is consistently associated with a cool temperature anomaly for each of the sea surface temperature sst proxies o sst 1 6 c sr ca sst 1 7 c mg ca sst 1 9 c u ca sst 2 8 c dissolution through incongruent leaching also causes cool sst artifacts but only for trace element ratios mg ca sst 1 2 c sr ca sst 1 2 c u ca sst 2 1 c the sequence of preference with respect to dissolution of coral skeleton in seawater is mg ca sr u rigorous screening of coral material for paleoclimate reconstructions is therefore necessary to detect both dissolution and the presence of secondary minerals the excellent agreement between apparent sst anomalies generated by different modes of diagenesis means that replication of tracers within a single coral cannot be used to validate climate proxy interpretations poor replication of records between different coral colonies however provides a strong indication of nonclimatic artifacts such as dissolution and secondary aragonite copyright 2007 by the american geophysical union

seychelles coral record of changes in sea surface temperature bimodality in the western indian ocean from the mid holocene to the present we report fossil coral records from the seychelles comprising individual time slices of 14 20 sclerochronological years between 2 and 6 2 kyr bp to reconstruct changes in the seasonal cycle of western indian ocean sea surface temperature sst compared to the present 1990 2003 these reconstructions allowed us to link changes in the sst bimodality to orbital changes which were causing a reorganization of the seasonal insolation pattern our results reveal the lowest seasonal sst range in the mid holocene 6 2 5 2 kyr bp and around 2 kyr bp while the highest range is observed around 4 6 kyr bp and between 1990 and 2003 the season of maximum temperature shifts from austral spring september to november to austral autumn march to may following changes in seasonal insolation over the past 6 kyr however the changes in sst bimodality do not linearly follow the insolation seasonality for example the 5 2 and 6 2 kyr bp corals show only subtle sst differences in austral spring and autumn we use paleoclimate simulations of a fully coupled atmosphere ocean general circulation model to compare with proxy data for the mid holocene around 6 kyr bp the model results show that in the mid holocene the austral winter and spring seasons in the western indian ocean were warmer while austral summer was cooler this is qualitatively consistent with the coral data from 6 2 to 5 2 kyr bp which shows a similar reduction in the seasonal amplitude compared to the present day however the pattern of the seasonal sst cycle in the model appears to follow the changes in insolation more directly than indicated by the corals our results highlight the importance of ocean atmosphere interactions for indian ocean sst seasonality throughout the holocene in order to understand holocene climate variability in the countries surrounding the indian ocean we need a much more comprehensive analysis of seasonally resolved archives from the tropical indian ocean insolation data alone only provides an incomplete picture

aragonite cycles diagenesis caught in the act organic biomarker and nannofossil assemblages are used in combination with sedimentary petrology to identify the role of diagenesis for the formation of a rhythmic calcareous succession a record from the early pliocene of the maldives ocean drilling program odp leg 115 is presented containing precession and eccentricity cycles expressed as variable aragonite content additional sub milankovitch cycles are caused by rhythmic precipitation of calcite cement in the lower part of the interval comparison with palaeo productivity indicators nannofossils chlorin total organic carbon suggests that cementation occurs preferentially in intervals characterized by increasing or decreasing productivity the coupled variability in productivity and carbonate diagenesis is attributed to the effect of organic matter degradation in the sediment the observed combination of primary and diagenetic factors hampers the interpretation of the cyclicity on milankovitch and sub milankovitch scales diagenetically stable proxies for palaeo productivity such as nannofossil assemblage data were used to distinguish between palaeoclimate and diagenetic influences

large scale characteristics of the distribution of blowing snow sublimation to consider the large scale characteristics of blowing snow sublimation and its importance in the hydrological cycle in the cryosphere we investigated the sublimation of blowing snow particles on a global scale using the global datasets of the european centre for medium range weather forecasts ecmwf re analysis data and the international satellite land surface climatology project islscp initiative i data for 1987 the sublimation fluxes of blowing snow particles were estimated globally with 2 58 resolution at 6 hour intervals we found that the sublimation of blowing snow particles occurs more widely in the northern hemisphere than in the southern hemisphere does not increase monotonously with latitude and becomes more active in the polar coast regions and highlands although the annual mean sublimation fluxes of the northern and southern hemispheres are almost equal in addition we confirmed the characteristic seasonal changes in the area of sublimation in the northern hemisphere although we need to incorporate continuous parameters from systematic ground based studies of the structure of blowing snow in specific fields to reduce uncertainty regarding the characteristics of blowing snow our results point to a need to review the current understanding of the hydrological cycle

teleseismic location techniques and their application to earthquake clusters in the south central pacific abstract improved methods for single and multiple event hypocenter determinations are developed and applied to the problem of locating earthquake clusters in the south central pacific ocean bayesian statistical methods are used to incorporate a priori information about arrival time variance into the derivation of hypocenter confidence ellipsoids permitting a more realistic calculation of critical parameters in the case where the number of stations is small the diagonal elements of certain projection operators called data importances by minster et al 1974 are used to evaluate network balance the hypocentroid of an event cluster is defined to be the average location of events within the cluster and the deviations of individual hypocenters from the hypocentroid are called cluster vectors the problem of estimating the cluster vectors can be decoupled from the problem of estimating the hypocentroid by a simple but fundamental mathematical result here termed the hypocentroidal decomposition theorem the algorithm based on this analysis appears to have many advantages over other published methods for multiple event location both in its efficient use of available information and its computational speed the application of this method to three clusters of shallow intraplate seismicity in the south central pacific designated regions a b and c demonstrates that the seismicity within each cluster is very localized the rms lengths of the cluster vectors for each group of epicenters are estimated to be only 9 6 and 12 km respectively estimates of the epicentroids are

studies of high frequency seismic noise in eastern kazakhstan abstract three seismographic stations have been established in the region of the principal underground nuclear weapons test site in the republic of kazakhstan in the soviet union instrumentation includes both surface and borehole seismometers with a bandwidth of 100 hz and a system dynamic range of 180 db power spectra of the regional ambient ground acceleration peak between 4 and 6 hz and are on average frequency independent above 10 hz where levels are approximately equal to 10 15 to 10 16 m sec 2 2 hz 1 kazakh noise levels are roughly equivalent to those observed by the regional seismic test network between 1 and 20 hz and about 10 to 20 db higher than the very low noise model for lajitas texas in the same band noise observed by the borehole sensors is about 10 db less than that observed by the surface instruments above about 20 hz under low wind conditions at two of the three kazakh sites borehole improvement is greater under high winds the third kazakh site karasu is characterized by much higher surface noise levels 15 to 20 db higher than the borehole levels from 4 to 40 hz under both low or high wind conditions which is attributed to amplification by local site conditions and the exposed terrain power spectra of individual runs of ambient vertical ground acceleration measured down the borehole show that high frequency slopes between 10 and 80 hz vary between f 0 60 and f 0 22 depending on wind and site conditions

upper mantle structure beneath central eurasia using a source array of nuclear explosions and waveforms at regional distances we have observed very consistent broadband regional three component p waveforms from a set of 11 explosions that occurred at the former soviet test site in kazakhstan during 1988 and 1989 and have modeled most of the prominent features in these waveforms to determine upper mantle structure beneath central eurasia using a subset of events as a source array we have identified four consistent arrivals during the first 15 s of p waves recorded at the soviet incorporated research institutions for seismology iris stations arti aru d 1500 km and garm gar d 1380 km these arrivals show consistent variations in frequency content relative timing and amplitudes from event to event despite a range in source magnitude mb between 4 9 and 6 1 we have also identified consistent features in p waveforms of these events recorded at obninsk obn d 2880 km we argue that most of the prominent features in these waveforms can be explained by reflections at or refractions near discontinuities or large velocity gradients in the upper mantle we show that a model with discontinuities of approximately 3 0 and 6 5 near 200 km and 400 km respectively produces a better fit to the broadband data at aru and gar than previous models for this region this model also produces a good match to waveforms recorded at obn and noress however this model is not unique for example we show that it is also possible to produce similar waveforms by replacing the 200 km discontinuity with a large notch shaped low velocity zone between approximately 100 and 140 km based on reflectivity synthetics we suggest that additional data especially from distances less than 1000 km should indicate which of these models is more accurate although our models are not unique our observations do constrain the following features 1 there must be reflectors between about 140 and 200 km and near 400 km depth in the upper mantle to explain the large secondary arrivals at both aru and gar 2 based on the relative size of some of the secondary arrivals at aru and gar the discontinuity near 400 km must be large however it cannot be much greater than about 6 5 because there is no evidence in our data of a reflection from 400 km at obn 3 the relatively small amplitude of the first arrivals at both aru and gar suggests that either the gradient in the uppermost mantle is very small or that a shallow low velocity zone is present comparison of our results with other upper mantle studies shows that the central eurasian upper mantle is similar to the upper mantle of the central and eastern united states

early marine diagenesis in corals and geochemical consequences for paleoceanographic reconstructions detecting the potential geochemical consequences of early marine diagenesis is essential for establishing the validity of past climate reconstructions from coral we present coral skeletal 18o and sr ca data for two long coral cores spanning 1839 1994 ad at ningaloo reef western australia one of which includes significant secondary precipitation of marine inorganic aragonite long term trends in reconstructed sea surface temperatures ssts for the well preserved coral correlate strongly with instrumental sst records spanning the 20th century in contrast the 18o and sr ca for the diagenetically altered coral give identical cool sst anomalies of 4 5 c as a consequence of the addition of secondary aragonite enriched in 18o and sr our results indicate that cross checking of paleoclimate reconstructions with two supposedly independent paleothermometers may not be valid and that coral records showing cooler ssts in the past need to be interpreted with caution furthermore modern coral records with long term trends in 18o indicating recent warming and freshening of the ocean can be potentially explained by early marine diagenesis

observations of blowing snow at the south pole 1 observations of blowing snow from visual observers records as well as ground based infrared and lidar measurements at south pole station are analyzed to obtain the first climatology of blowing snow over the antarctic plateau occurrence frequencies of blowing snow wind direction and speed during blowing snow events typical snow layer heights as well as optical depths are determined blowing snow is recorded in roughly one third of the visual observations and occurs under a narrow range of wind directions blowing snow layers are usually less than 400 m in thickness but can exceed 1000 m during blowing snow conditions these near surface layers are apparent in lidar backscatter profiles these layers emit radiances similar to those from optically thin clouds frequently seen over the antarctic plateau because the near surface blowing snow layers are frequently present they are a factor in space borne laser altimetry and other satellite remote sensing

crustal structure in eastern kazakh u s s r from teleseismic receiver functions broadband receiver functions determined from teleseismic p waveforms recorded at two seismic stations in eastern kazakh u s s r are inverted for the vertical velocity structure beneath the stations the detailed broadband receiver functions are obtained by stacking source equalized radial components of teleseismic p waveforms a time domain inversion of the radial receiver function is used to determine the structure assuming a crustal model parameterized by flat lying homogeneous layers the general features of the inversion results are a complex shallow crust velocities less than 6 km s in the upper crust a high velocity 6 9 7 5 km s lower crust and a moho that varies between 47 and 57 km depth these results compare favorably with a composite velocity model from deep seismic sounding data but show lower velocities in the upper crust and higher velocities in the lower crust the results indicate that the crust in this region is relatively uniform however the nature and depth of the moho changes significantly across the region the receiver function inversion structure for the kazakh sites is similar to a published receiver function structure for a site on the canadian shield

palaeoenvironmental records from fossil corals the effects of submarine diagenesis on temperature and climate estimates the geochemistry of coral skeletons may reflect seawater conditions at the time of deposition and the analysis of fossil skeletons offers a method to reconstruct past climate however the precipitation of cements in the primary coral skeleton during diagenesis may significantly affect bulk skeletal geochemistry we used secondary ion mass spectrometry sims to measure sr mg b u and ba concentrations in primary coral aragonite and aragonite and calcite cements in fossil porites corals from submerged reefs around the hawaiian islands cement and primary coral geochemistry were significantly different in all corals we estimate the effects of cement inclusion on climate estimates from drilled coral samples which combine cements and primary coral aragonite secondary 1 calcite or not vert similar2 aragonite cement contamination significantly affects sr ca sst estimates by 1 c and 0 4 to 0 9 c respectively cement inclusion also significantly affects mg ca b ca and u ca sst estimates in some corals x ray diffraction xrd will not detect secondary aragonite cements and significant calcite contamination may be below the limit of detection not vert similar1 of the technique thorough petrographic examination of fossils is therefore essential to confirm that they are pristine before bulk drilled samples are analysed to confirm that the geochemistry of the original coral structures is not affected by the precipitation of cements in adjacent pore spaces we analysed the primary coral aragonite in cemented and uncemented areas of the skeleton sr ca b ca and u ca of primary coral aragonite is not affected by the presence of cements in adjacent interskeletal pore spaces i e the coral structures maintain their original composition and selective sims analysis of these structures offers a route to the reconstruction of accurate ssts from altered coral skeletons however mg ca and ba ca of primary coral aragonite are significantly higher in parts of skeletons infilled with high mg calcite cement we hypothesise this reflects cement infilling of intraskeletal pore spaces in the primary coral structure

the puzzling presence of calcite in skeletons of modern solitary corals from the mediterranean sea the skeleton of scleractinian corals is commonly believed to be composed entirely of aragonite due to the current mg ca molar ratio of seawater which thermodynamically favours the deposition of this polymorph of calcium carbonate caco3 however some studies have shown that other forms of caco3 such as calcite can be present in significant amount 1 20 inside tropical coral skeletons significantly impacting paleo reconstructions of sst or other environmental parameters based on geochemical proxies this study aims at investigating for the first time 1 the skeletal composition of two mediterranean solitary corals the azooxanthellate leptopsammia pruvoti and the zooxanthellate balanophyllia europaea across their life cycle 2 the distribution of the different caco3 forms inside skeletons and 3 their implications in paleoclimatology the origin of the different forms of caco3 observed inside studied coral skeletons and their relationships with the species habitat and ecological strategies are also discussed caco3 composition of l pruvoti and b europaea was investigated at six sites located along the italian coasts skeleton composition was studied by means of x ray powder diffraction and fourier transform infrared spectroscopy a significant amount of calcite 1 23 was found in more than 90 of the studied coral skeletons in addition to aragonite this calcite was preferentially located in the basal and intermediate areas than at the oral pole of coral skeletons calcite was also mainly located in the epitheca that covered the exposed parts of the coral in its aboral region interestingly in b europaea the calcite content was negatively correlated with skeleton size age the presence of calcite in scleractinian corals may result from different mechanisms 1 corals may biologically precipitate calcite crystals at their early stages in order to insure their settlement on the substrate of fixation especially in surgy environments 2 calcite presence may result from skeletons of other calcifying organisms such as crustose coralline algae and or 3 calcite may result from the infilling of galleries of boring microorganisms which are known to colonize coral skeletons we suggest that more than one of the above mentioned processes are involved

event location at any distance using seismic data from a single three component station this paper demonstrates the usefulness of a novel technique for analysis of single site three component seismogram records for reliable epicenter determinations for even small seismic events at any distance parameters that may be extracted by this technique are p phase identifications in terms of x 2 probabilities and the associated slowness vectors using data from short period and broadband seismometers installed in the new noress norway array single site event locations are demonstrated azimuth estimates are found directly from the slowness vector while epicenter distance estimates are derived from differential arrival times between pn pg sn and lg sg simultaneous inversion for crustal model and hypocenter data indicate a crustal thickness beneath noress of 33 5 km if sn and or lg are well recorded focal depth estimates are often accurate to within a few kilometers locating teleseisms is problematic since secondary phases are not fully readily identifiable and hence distance can be estimated only by conversion of the measured apparent phase velocity for distances out to approximately 1000 km event location errors as compared to network solutions seldom exceed 50 km and are due mainly to errors in azimuth estimates with sn phases available focal depth errors appear to be of the order of 4 km for teleseismic p waves short period location errors occasionally exceeded 7 and were due mainly to poor distance estimates using broadband records from relatively strong events location errors were about 1 further refinements seem feasible by using seismicity information and or recognition of stationarity in the p wave decomposition pattern for events within the same region at least in certain cases such approaches reflect genuine location refinements as demonstrated

diagenesis in live corals from the gulf of aqaba i the effect on paleo oceanography tracers abstract the effect of early diagenesis on trace element abundance in coral skeleton was studied in live coral heads porites from the nature reserve reef nrr elat gulf of aqaba northern red sea petrography of the corals shows diagenetic features of dissolution recrystallization and secondary aragonite precipitation pore filling which are most extensive in the oldest part of the coral coral porewaters were extracted with a special setup and were analyzed for chemical composition the total alkalinity and sr deficit in pore water as compared to reef water is consistent with both precipitation of secondary aragonite and recrystallization of primary skeleton the present rate constant of pore filling by secondary aragonite was estimated by a water replacement experiment to be 0 0015 y 1 which equals to pore filling rate of 1 5 0 3 kg aragonite per year the corals show clear seasonal fluctuations in sr ca ratios that are interpreted as reflecting changes in sea surface temperature sst yet the secondary aragonite is characterized by a significantly higher sr ca ratio than the average ratio in primary aragonite thus measuring a mixed sample of pristine and secondary aragonite may produce erroneous about 2 c lower sst estimates by the sr ca thermometers it appears that the sr ca ratio a major proxy for paleo environmental marine studies is sensitive to subtle pore filling and replacement of the original coral matrix by secondary aragonite in the marine environment

hypocenter constraint with regional seismic data a theoretical analysis for the natural resources defense council network in kazakhstan ussr source depth and epicenter determination remains a simple but key method for discrimination between earthquakes and nuclear explosions at near regional distances a variety of secondary body wave arrivals can be observed that may be useful for constraining source depth and epicenter in this paper we study the source location problem using regional arrival time and arrival azimuth data from a sparse seismic network a theoretical analysis of the source location inverse problem provides estimates of the stability and uncertainty of the solution for a particular suite of data as a function of epicenter and depth as well as evaluating the importance of each datum to the solution an empirical analysis with actual data complements the theoretical analysis our approach is applied to the three station natural resources defense council soviet academy of sciences network in kazakhstan the theoretical analysis indicates that reasonable constraint on depth and epicenter is possible whenever three distinct phases p pn pg pzp and pmp or equivalent s phases are observed at two or three stations our theoretical analysis for two station locations shows that the epicenter constraints are extremely poor for sources along the line passing through the two observing stations the use of arrival azimuth in two station locations results in improvement in epicenter constraint for events occurring in the vicinity of the line connecting the two stations but there is no significant improvement elsewhere an empirical analysis of data from two of the september 1987 chemical explosions and data from an explosion in an active mining area supports the theoretical analysis showing that two station locations both epicenter and depth are quite reliable furthermore the theoretical analysis also indicates that even with data from a single observing station satisfactory results are obtained if three or more phases plus arrival azimuth are available

tracking the extent of the south pacific convergence zone since the early 1600s 1 the south pacific convergence zone spcz is the largest and most persistent spur of the intertropical convergence zone at the southeastern edge of the spcz near 170 w and 15 20 s a surface ocean salinity frontal zone exists that separates fresher western pacific warm pool water from saltier and cooler waters in the east this salinity front is known to shift east and west with the phase of the el nino southern oscillation we have generated subannually resolved and replicated coral oxygen isotopic time series from fiji 17 s 179 e and rarotonga 21 5 s 160 w that have recorded interannual displacements of the salinity front over the last 380 years and also indicate that at lower frequencies the decadal mean position of the salinity front and eastern extent of the spcz has shifted east west through 10 to 20 of longitude three times during this interval the most recent and largest shift began in the mid 1800s as the salinity front progressively moved eastward and salinity decreased at both sites our results suggest that sea surface salinity at these sites is now at the lowest levels recorded and is evidence for an unprecedented expansion of the spcz since the mid 1800s the expansion of the spcz implies a gradual change in the south pacific to more la nina like long term mean conditions this observation is consistent with the ocean thermostat mechanism for the pacific coupled ocean atmosphere system whereby exogenous heating of the atmosphere would result in greater warming in the western pacific and a greater east west surface temperature gradient components 8034 words 7 figures 2 tables

optical properties of blowing snow calc ulation procedures are developed and results shown for the exact calculation of extinction and meteorological visual range using the blowin g snow mass in the atmosp here and particle radius results of the calculations show i for monochromatic radiation geometrical optics approx imations of the extin ction efficiency are found to provide results of only moderate accuracy in calculating the extinction of radiation by a single particle 2 for broad band radiation the geomet rical optics appro ximation is sufficiently accurate for many single particle measurement instru ments and appli cations except in the infra red band where mie theory should be used 3 for typical blowing s now particle size dist ributions the shape parameter of the distribution of particle radii and the mean particle radius are very important in broa d band extinction and visua l range modelling estimates of blowing snow quantities from broad band extinction measurements or visual range from blowin g snow quantities should address the shape and mean value of the snow particle radius distribution

seismic geomorphology and growth architecture of a miocene barrier reef browse basin nw australia abstract the cenozoic succession of browse basin is characterized by a carbonate system that developed from a non tropical ramp in eocene lower miocene times to a tropical rimmed platform in the middle miocene the evolution of the platform was unraveled through the interpretation of the seismic geomorphology and borehole data of the middle miocene tropical reef system the first reef structures developed during the early middle miocene as narrow linear reef belts with an oblique orientation with respect to shelf strike direction subsequently they prograded toward the platform margin to form a barrier reef with a minimum length of 40 km the barrier reef itself comprises three distinct ridges separated by progradational steps the second and third step are separated by a karstified horizon which is interpreted to represent the global sea level fall shortly before the serravallian tortonian boundary the following third ridge formed in a slightly downstepped position during the sea level lowstand and initial transgressive phase further sea level rise during the early tortonian first drowned the barrier reef system and subsequently also the patch reefs and relic atolls that had established in a backstepped position in the platform interior the similar evolution of the browse basin reef system and other contemporaneous carbonate systems indicates a strong impact of eustatic sea level changes relatively large subsidence rates in the study area possibly augmented the eustatic sea level rise in the tortonian and hence contributed to the drowning of the reef system however the initiation and final demise of the reef system was also governed by global and regional climate variations the first seismically defined reefs developed simultaneous to a maximum in the transport capacity of the indonesian throughflow which brings warm low salinity waters to the north west shelf reef drowning followed the restriction of this seaway close to the middle to early miocene boundary this near closure of the indonesian seaway possibly led to a regional amplification of the global middle to late miocene cooling trend and hampered the potential of the reef system to keep up with the rising sea level

shear waves in lithosphere studies on the territory of the u s s r abstract thousands of kilometers of dss profiles were compiled with three component stations in the u s s r the results showed that the usual shots in holes or water basins normally create not only p waves but shear waves as well the most favourable condition for their generation is the presence of a sharp seismic boundary near the source for example the basement surface the s wave field as a rule contains all the types of reflected and refracted waves that are found in the p field the difference is in lower frequencies they are lower by one third somewhat higher intensity and greater variability of amplitudes of shear waves when recording the s waves the major information is obtained from the velocity relation v p v s with depth and laterally it reveals that three major factors are affecting this relation the degree of rock fissuring the composition of rocks and the temperatures at depth reduction of fissuring with depth i e with greater distances from the source results in an overall drop of as the composition of the uppermost crust changes the urals increases in blocks composed of basic rocks this value shows little changes on the baltic and ukrainian shields on the siberian platform first increases with depth from 1 71 up to 1 76 probably due to the dilatancy effect and then it decreases to values less than 1 7 in the lower crust and upper mantle in western siberia grows with depth reaching 1 79 in the lower crust it is somewhat reduced in the mantle but still above 1 7 this can be ascribed apparently to a higher temperature regime of the lower crust in western siberia in many regions a splitting of the shear waves of different polarization is observed due to velocity anisotropy this was found for the first refracted waves in the urals and for reflected waves from the m boundary on the siberian platform in both cases anisotropy is associated with the crust on the ukrainian and baltic shields the difference in the velocities of sh and sv waves was not recorded

rapid estimation of earthquake source parameters from pattern analysis of waveforms recorded at a single three component broadband station port vila vanuatu the present study deals with rapid automatic estimation of some earthquake parameters location focal depth and magnitude in a region of rather high seismic activity in quasi real time through the analysis of incoming broadband records the method can be applied in particular in poorly instrumented countries with high seismic risk potential it can also be applied when the analysis of a very important flow of data requires rapid sophisticated preferably automatic data processing the method requires as a minimum a three component broadband seismographic station and a sufficiently populated database that is an instrument operating for a time long enough to have accumulated an appropriate data set used to construct the knowledge base the more extensive the knowledge base the better the accuracy of the method we proceed in several steps first applying the spars algorithm to the only vertical component available waveforms are classified according to the source location taken from national earthquake information center neic catalog it results in the sorting out of a subset of waveforms events which will not be included in the knowledge base second each element of the knowledge base is validated according to the epicentral distance with respect to the reference station and eventually the azimuth of the corresponding source third new input waveforms are analyzed and compared with one or more elements of the knowledge base to estimate their source location and size the method can be used to search for doublets or multiplets if multiplets are found their location and focal depth can be determined by using a fuzzy event relocation method we have tested the capability of the proposed algorithms processing broadband waveforms collected during four and half years at the geoscope broadband station pvc operated by institut de recherche pour le developpement formerly orstom ird at port vila vanuatu among 650 events recorded at this station 254 ones meeting a good criterion of quality have been sorted the results show that in a range of distances up to 1000 km the method is capable of yielding in a very short time the location of the input event the accuracy depending on the local density of known events in the vicinity we also obtain a reliable estimation of the energy by measuring the maximum surface wave or s wave amplitude related to the classical magnitude msz

optimal backazimuth estimation for three component recordings of regional seismic events augmenting travel time data with backazimuth information can improve regional seismic event locations for which only a few recording stations are available this study examines the achievable accuracy of backazimuths derived from 164 regional short period p waves recorded at regional seismic test network rstn stations the data represent 62 events with a good distribution of distance azimuth and signal to noise ratio snr at each of four rstn stations using preliminary determination of epicenter locations to generate reference backazimuths we examine the effects of computational method signal window length frequency content and snr on rstn backazimuth estimates the variety of geologic environments at the receivers also allows assessment of the effect of receiver structure on backazimuth estimation our results indicate that regional three component recordings can produce useful backazimuths more than 75 per cent of the records yield backazimuths within 20 of the correct value when reasonable parameters are used the accuracy of the calculated backazimuths does vary with the receiver however rstn stations in new york and ontario located in precambrian terranes produce very accurate backazimuths for snrs greater than 5 db at the south dakota and tennessee stations located in sedimentary rocks complicated receiver structure is the controlling factor in backazimuth estimation propagational complexities at the south dakota site preclude recovery of reasonable backazimuth values poor statistics are obtained for all parameter combinations at the tennessee site backazimuth accuracy depends strongly on the computational method used in general the choice of frequency band is important and varies by stations while the length of the signal window is less critical if the problematic south dakota records are excluded we achieve an rms backazimuth error of about 6 for recordings with snr above 10 db while a single optimized choice of parameters produces good results for the 164 record data set a further 5 to 10 per cent improvement can be achieved if the parameters are customized on a station by station basis

seismic evidence for an ancient rift beneath the cumberland plateau tennessee a detailed analysis of broadband teleseismic p waveforms broadband receiver functions developed from teleseismic p waveforms recorded on the midperiod passband of regional seismic test network station rscp are inverted for vertical velocity structure beneath the cumberland plateau tennessee the detailed broadband receiver functions are obtained by stacking source equalizd horizontal components of teleseismic p waveforms the resulting receiver functions are most sensitive to the shear velocity structure near the station a time domain inversion routine utilizes the radial receiver function to determine this structure assuming a crustal model parameterized by many thin flat lying homogeneous layers lateral changes in structure are identified by examining azimuthal variations in the vertical structure the results reveal significant rapid lateral changes in the midcrustal structure beneath the station that are interpreted in relation to the origin of the east continent gravity high located northeast of rscp the results from events arriving from the northeast show a high velocity midcrustal layer not present in results from the southeast azimuth this velocity structure can be shown to support the idea that this feature is part of a keweenawan rift system another interesting feature of the derived velocity models is the indication that the crust mantle boundary beneath the cumberland plateau is a thick probably laminated transition zonemore between the depths of 40 and 55 km a result consistent with interpretations of early refraction work in the area less

radiocarbon calibration curve spanning 0 to 50 000 years bp based on paired 230 th 234 u 238 u and 14 c dates on pristine corals abstract radiocarbon dating is the most widely used dating technique in the world recent advances in accelerator mass spectrometry ams and sample preparation techniques have reduced the sample size requirements by a factor of 1000 and decreased the measurement time from weeks to minutes today it is estimated that more than 90 percent of all measurements made on accelerator mass spectrometers are for radiocarbon age dates the production of 14 c in the atmosphere varies through time due to changes in the earth s geomagnetic field intensity and in its concentration which is regulated by the carbon cycle as a result of these two variables a radiocarbon age is not equivalent to a calendar age four decades of joint research by the dendrochronology and radiocarbon communities have produced a radiocarbon calibration data set of remarkable precision and accuracy extending from the present to approximately 12 000 calendar years before present this paper presents high precision paired 230 th 234 u 238 u and 14 c age determinations on pristine coral samples that enable us to extend the radiocarbon calibration curve from 12 000 to 50 000 years before present we developed a statistical model to properly estimate sample age conversion from radiocarbon years to calendar years taking full account of combined errors in input ages and calibration uncertainties our radiocarbon calibration program is publicly accessible at http www radiocarbon ldeo columbia edu along with full documentation of the samples data and our statistical calibration model

determining snow water equivalent by acoustic sounding the possibility of determining snow water equivalent swe by the use of an acoustic impulse was assessed at two field locations in saskatchewan and british columbia canada these sites represent cold windswept prairie and temperate deep mountain snowcovers a continuous frequency swept acoustic wave was sent into the snowpack and received signal processing was then subsequently used to estimate the depth and density of each snow layer by a recursive relationship involving frequency modulated continuous wave fmcw radar and seismological techniques from this method it is also shown that the tortuosity of snow can be estimated data collected by gravimetric sampling was used as comparison to the swe values determined by the use of acoustic sounding the results showed that for the saskatchewan sites the correlation between the measured and the modeled values of swe was 0 86 whereas at the british columbia sites the correlation was 0 78 the difference in the correlations was interpreted as being due to additional acoustic measurement error at the british columbia sites caused by higher liquid water contents and more layers in the snowpack the measured and the modeled swe for saskatchewan snowpacks with high liquid water contents were found to be weakly associated with correlations of 0 30 the acoustically determined values of tortuosity were close to unity 1 which is in agreement with the values characteristic of snow as a porous substance further research is necessary to determine whether this technique can be applied to snow in other environmental conditions copyright 2007 john wiley sons ltd

snow particle characteristics in the saltation layer shadowgraphy was employed to study snow saltation in boundary layer wind tunnel experiments with fresh naturally deposited snow the shadowgraphy method allowed for a temporally and spatially high resolution investigation of snow particle characteristics within a measurement area of up to 50 mm x 50 mm snow particle size and number characteristics and their variation with height in the saltation layer were analysed the following observations and findings were made for the saltation layer 1 the particle number decreases exponentially with height 2 the mean particle diameter is fairly constant with a very slight tendency to decrease with height 3 the maximum particle diameter decreases linearly with height and 4 the snow particle size distribution can be adequately described by gamma probability density functions the shape and scale parameters of the gamma distribution were found to vary systematically though only slightly with height over ground and between experiments with different snowpack characteristics

the time frequency characteristics of quarry blasts and calibration explosions recorded in kazakhstan ussr summary in this paper we consider two fundamentally different processes that can be responsible for the organization of energy in seismic coda into discrete time independent frequency bands one process involves the resonance of energy in low velocity horizons and the other requires the interaction of time offset wavefields produced by subevents within multiple event mine explosions ripple fired quarry blasts we examined data collected by high frequency seismometers in kazakhstan ussr and observed regular time independent spectral modulations in coda resulting from events strongly suspected to be soviet quarry blasts but not in the coda from single event calibration explosions detonated at similar ranges we conclude these modulations are a source effect and due to ripple firing this modulation is independent of the source receiver azimuth and we infer that the spatial array of subshots in each event must be small we demonstrate that simple linear superposition theory can be used to reproduce effectively the spectral modulation observed in real quarry blasts on the basis of these observations we attempt to discriminate between the two types of events using a spectral pattern based algorithm that seeks time independent features we consider the detrimental effect that resonant energy in low velocity horizons can have on the successful application of our algorithm

effect of early marine diagenesis on coral reconstructions of surface ocean 13c 12c and carbonate saturation state recent research suggests that future decreases in the carbonate saturation state of surface seawater associated with the projected build up of atmospheric co2 could cause a global decline in coral reef building capacity whether significant reductions in coral calcification are underway is a matter of considerable debate multicentury records of skeletal calcification extracted from massive corals have the potential to reconstruct the progressive effect of anthropogenic changes in carbonate saturation on coral reefs however early marine aragonite cements are commonly precipitated from pore waters in the basal portions of massive coral skeletons and if undetected could result in apparent nonlinear reductions in coral calcification toward the present to address this issue we present records of coral skeletal density extension rate calcification rate 13c and 18o for well preserved and diagenetically altered coral cores spanning 1830 1994 a d at ningaloo reef marine park western australia the record for the pristine coral shows no significant decrease in skeletal density or 13c indicative of anthropogenic changes in carbonate saturation state or 13c of surface seawater oceanic suess effect in contrast progressive addition of early marine inorganic aragonite toward the base of the altered coral produces an apparent 25 decrease in skeletal density toward the present which misleadingly matches the nonlinear twentieth century decrease in coral calcification predicted by recent modeling and experimental studies in addition the diagenetic aragonite is enriched in 13c relative to coral aragonite resulting in a nonlinear decrease in 13c toward the present that mimics the decrease in 13c expected from the oceanic suess effect taken together these diagenetic changes in skeletal density and 13c could be misinterpreted to reflect changes in surface ocean carbonate saturation state driven by the twentieth century build up of atmospheric co2 copyright 2004 by the american geophysical union

back analysis of drifting snow measurements over an instrumented mountainous site the nemo numerical model of drifting snow whose general outlines are presented in this paper is based on a physical model for saltation and turbulent diffusion the model needs a set of input parameters including fall velocity threshold shear velocity shear velocity mass concentration and roughness which are obtained from empirical formulae and wind speed measured at a given height to better determine the required field data in an alpine context our experimental site col du lac blanc 2700 m a s l french alps was first equipped with one anemometer and blowing snow acoustic sensors which proved not to be accurate enough for research purposes in the current state of development even though a new calibration curve was used we therefore set up a snow particle counter and we returned to the traditional robust mechanical traps and a 10 m mast with six anemometers two temperature sensors and a depth sensor to better determine friction velocity and aerodynamic roughness based on the studied drifting snow events we conclude 1 the proportionality of the aerodynamic roughness to the square of the friction velocity was confirmed but with a varying proportionality ratio depending on the snowdrift event 2 values of s u f were relatively well approximated by empirical formulae from data originating from antarctica and 3 snowdrift concentration profiles obtained by pomeroy s semi empirical formulae for the saltation layer coupled with a theoretical approach for the diffusion layer overestimated the concentration profiles for the studied blowing snow event

azimuth estimation capabilities of the arcess regional seismic array abstract the effect of local geology and noise conditions on the performance of a small regional array is investigated by comparing the regional p n backazimuth estimation capabilities of the arcess array in northern norway to the noress array a broadband frequency wavenumber estimator was used to calculate backazimuths from the p n arrival for each of 203 regional events recorded at arcess while varying element spacing frequency band and time window most of the errors in backazimuth are less than 20 when appropriate parameter combinations are used and mean backazimuth errors are close to zero the best results are obtained using a 13 element configuration that has a 1 4 km aperture and a maximum station spacing of about 600 m with the 13 element configuration and the data filtered to include frequencies between 3 and 10 hz the mean errors for the 203 event data set are less than 0 9 and s d are as small as 16 9 there are differences seen in the backazimuth estimation capabilities of arcess and noress with specific parameter combinations the larger aperture configurations 10 and 17 elements have smaller means at arcess although the precision is about the same the estimates using unfiltered data at arcess are poor because of local noise conditions that increase the level of background noise at low frequencies overall the precision is better at noress but both regional arrays have the best results using the 13 element configuration and filtering the data in the middle frequency range 3 to 10 hz other factors investigated include snr and source region backazimuth estimation statistics improve if only events with 5 db of snr are included in the data set at both arcess and noress the mean errors move closer to zero and standard deviations decrease the differences between the two arrays are not as pronounced there are some path effects from different source regions around the arcess array however combinations of small aperture configurations and middle 3 to 10 hz frequency bands work well for events over the entire distance range of 30 to 1200 km arcess and noress have similar backazimuth estimation capabilities even though there are differences in the local geology and noise conditions because a 13 element configuration produces reliable results for both arrays it would be reasonable to reduce the number of elements in a regional array this in turn will reduce the costs associated with building and deploying small regional arrays

post glacial evolution of the indo pacific warm pool and el nino southern oscillation recent research has revealed new insights into the temperature size and variability of the indo pacific warm pool ipwp and the nature of the el nino southern oscillation enso since the last glacial maximum lgm sea surface temperature sst reconstructions from foraminiferal mg ca alkenone and revised coral sr ca palaeothermometry agree that ssts in the ipwp during the lgm were similar to 3degreesc cooler than at present in the central portion of the ipwf the rapid post glacial rise in sst led the deglaciation by similar to 3000 years to produce near modern ssts by the early holocene in contrast further west and north post glacial shifts in ssts in the south china and sulu seas are synchronous with abrupt climate changes in the north atlantic new evidence for the nature of the little ice age in the tropics has been obtained from a 420 year record of coral sr ca and 6180 from the great barrier reef australia this indicates that ssts and salinity were higher in the 18th century than in the 20th century the results suggest that the tropical pacific played a role as a source region of water vapour during the global expansion of little ice age glaciers the onset of modern enso periodicities is identified by palaeo enso records throughout the tropical pacific region similar to 5000 years ago with an abrupt increase in enso magnitude similar to 3000 years ago individual enso events recorded by corals reveal that the precipitation response to el nino temperature anomalies was subdued in the mid holocene the apparent non linear onset of enso in the late holocene appears to reflect abruptly enhanced interaction between the southern oscillation and the pacific intertropical convergence zone comparisons of precipitation variability recorded by great barrier reef corals with enso indices for the last 350 years confirms that non stationarity of enso teleconnections is a natural characteristic of modern climate c 2003 elsevier ltd and inqua all rights reserved

frequency dependent attenuation in eastern kazakhstan and implications for seismic detection thresholds in the soviet union abstract the frequency dependent attenuation of regional seismic phases recorded by three stations near the nuclear explosion test site in eastern kazakhstan is estimated by inverting spectra from 21 events with magnitudes between 2 3 and 4 6 at distances between 200 and 1300 km the pn spectra are inverted between 1 and 10 hz and the lg spectra are inverted between 0 5 and 2 5 hz the motivation for this study is that previous estimates of detection capability in the soviet union are based on data recorded in other regions eastern north america and scandinavia and therefore have large uncertainty the data recently recorded in eastern kazakhstan provide an excellent opportunity to compare regional wave propagation and noise characteristics at these sites to conditions assumed in previous detection capability simulations it is found that attenuation in eastern kazakhstan is not much different from attenuation in scandinavia but it is greater than attenuation in eastern north america this implies that estimates of detection thresholds that assume attenuation like that observed in eastern north america will be lower than estimates of detection thresholds that assume attenuation like that observed in eastern kazakhstan or scandinavia however it is not known how well data recorded in eastern kazakhstan represent conditions in other areas of the soviet union

location performance of a sparse regional network a key element in successful seismic verification of a nuclear test ban treaty is the capability of a sparse network of seismic stations to accurately locate regional events we have investigated the regional location accuracy of the regional seismic test network rstn a five element three component network in eastern north america using 62 events varying in size from magnitude 3 0 to 5 1 applying an algorithm which allows inclusion of back azimuth estimates as well as travel times we determined a median location error of 23 km for the data set relative to the pde locations considering the large station spacing 1500 km and a few data used in the locations 2 to 4 stations the rstn location accuracy is remarkably good the results imply that a widely spaced network of single three component stations could reliably locate regional seismic events copyright american geophysical union 1989

diagenesis of fossil coral skeletons correlation between trace elements textures and 234 u 238 u a comparative study of pleistocene fossil coral skeletons and of modern coral skeletons was carried out using petrographie and trace element analyses on a suite of pleistocene samples that had previously been studied for 234 u 230 th and u 230 th ages chen et al 1991 evidence of a range of diagenetic changes can be recognized by optical om and scanning electron microscopy sem the normal texture exhibited by modern corals under om consists of fine needles of aragonite forming a radial fibrous pattern around a central dark line center of calcification this pattern can also be seen in many fossil corals in most cases the central dark line partially disappears during diagenesis the radialfibrous pattern is obscured and there is a distinct coarsening of the radial fabric of aragonite to unoriented platy or equant aragonite crystals sem images show diagenetic textures ranging from dense structureless images of the coralline matrix with sharp boundaries at the septa walls to the development of 1 a patchy distribution of dissolution micropores partially filled with aragonite fibers in the matrix 2 aragonite needles coming from selvages in the septa walls which radiate into the septa voids using an electron microprobe and sem concentrations of na s sr and mg were measured no other trace elements were detected na s and mg contents of the matrix the fibrous micropores and radiating needles are highly variable and well correlated high concentrations of na s and mg were found in modern living corals with lower concentrations in fossil corals and fibrous micropores and the lowest value in the radiating needles the reason for the correlations of na s and mg and crystal chemistry and the response to diagenesis of these trace elements is not understood the average concentrations of na s and mg for each sample when plotted against the whole coral initial 234 u are generally correlated chen et al 1991 as all these diagenetic changes involve the recrystallization and deposition of aragonite we infer that the geologic site of diagenesis both for forming the secondary aragonitic phases and for the enhancement of the 234 u content in the fossil corals was the marine environment it is possible that the textural and na s and mg trace element contents of fossil corals be used to ascertain the reliability of fossil coral skeletons for u 230 th dating the basic problem of identifying a priori unaltered coral skeletons for 230 th dating is not yet resolved

wavefield decomposition using ml probabilities in modelling single site 3 component records summary this paper presents a new approach to the analysis of three component digital seismograms earlier approaches used techniques such as principal components to estimate particlemotion using models of p and s waves in this paper the maximum likelihood ml estimator is preferred because this allows the use of x2 probabilities to test whether energy of a specific wave type p s love or rayleigh is present in addition this analysis allows the joint estimation of azimuth of approach and in cases of p and sv waves also apparent angle of incidence and hence information on apparent velocity for a single three component seismogram the covariance matrix provides only six independent observations thus restricting analysis to rather simple wave models the technique works satisfactorily for p waves whereas shear and surface wave models sometimes prove cumbersome to handle due to correlation between radial and transverse components reflecting complex propagation characteristics in inhomogeneous media this technique has been tested on synthetic data and in such cases works perfectly for all wave types an important aspect of this work has been the visual display of the probability and velocity information as functions of time and azimuth displaying the data in this form provides information on the ray path in a manner similar to analysis performed by seismic arrays practical examples on a variety of siesmic data are given to illustrate the viability of the technique the data cover a broad spectrum of frequencies and applications from broad band teleseismic data 1 hz regional seismic data 10 40 hz seismic profiling data 125 hz and vsp 500 hz recordings