ferromanganese crusts as archives of deep water cd isotope compositions 1 the geochemistry of cd in seawater has attracted significant attention owing to the nutrient like properties of this element recent culturing studies have demonstrated that cd is a biologically important trace metal that plays a role in the sequestration of inorganic carbon this conclusion is supported by recent isotope data for cd dissolved in seawater and incorporated in cultured phytoplankton these results show that plankton features isotopically light cd while cd depleted surface waters typically exhibit complimentary heavy cd isotope compositions seawater samples from below 900 m depth display a uniform and intermediate isotope composition of e114 110cd 3 3 0 5 this study investigates whether ferromanganese fe mn crusts are robust archives of deep water cd isotope compositions to this end cd isotope data were obtained for the recent growth surfaces of 15 fe mn crusts from the atlantic pacific indian and southern oceans and two usgs fe mn reference nodules using double spike multiple collector inductively coupled plasma mass spectrometry the fe mn crusts yield a mean e114 110cd of 3 2 0 4 2 se n 14 data for all but one of the samples are identical within the analytical uncertainty of 1 1e114 110cd 2 sd to the mean deep water cd isotope value this indicates that fe mn crusts record seawater cd isotope compositions without significant isotope fractionation a single sample from the southern ocean exhibits a light cd isotope composition of e114 110cd 0 2 1 1 the origin of this signature is unclear but it may reflect variations in deep water cd isotope compositions related to differences in surface water cd utilization or long term changes in seawater e114 110cd the results suggest that time series analyses of fe mn crusts may be utilized to study changes in marine cd utilization

the δ15n of nitrate in the southern ocean consumption of nitrate in surface waters we report nitrogen isotope data for nitrate from transects of hydrocast and surface samples collected in the eastern indian and pacific sectors of the southern ocean focusing here on the data from the upper water column to study the effect of nitrate consumption by phytoplankton the 15n of nitrate increases by 1 2 from deep water into the antarctic summertime surface layer due to kinetic isotopic fractionation during nitrate uptake estimation of the nitrate uptake isotope effect from antarctic depth profiles yields values in the range of 5 6 in east indian sector and 4 5 in the east pacific sector surface transect data from the pacific sector also yield values of 4 5 the major uncertainty in the profile based estimation of the isotope effect involves the 15n of nitrate from the temperature minimum layer below the summertime antarctic surface layer which deviates significantly from the predictions of simple models of isotope fractionation for the subantarctic surface it is possible to distinguish between nitrate supplied laterally from the surface antarctic and nitrate supplied vertically from the subantarctic thermocline because of the distinctive relationships between the 15n and concentration of nitrate in these two potential sources our subantarctic samples collected during the summer and fall indicate that nitrate is supplied to the subantarctic surface largely by northward transport of antarctic surface water isotopic data from the pacific sector of the subantarctic suggest an isotope effect of 4 5 indistinguishable from the antarctic estimates in this sector

silicon isotope fractionation during nutrient utilization in the north pacific the distribution of silicon in the north pacific is controlled by the utilization of silicic acid by diatoms a process that fractionates silicon si isotopic compositions silicon isotope variations are presented for six water column profiles from the surface mixed layer down to the deep waters of the north pacific ocean although the observed si isotopic variations display an apparently simple inverse relationship with dissolved nutrient concentrations in fact they reflect mixing of surface waters undergoing active si isotope fractionation and deep waters with more uniform concentrations and isotope compositions samples from the surface of the subtropical gyre have the lowest dissolved si concentrations and heaviest si isotope compositions of marine waters measured thus far fractionation in the surface waters follows a typical rayleigh type distillation curve for a closed surface water reservoir resulting from stratification of the surface layer in the subarctic region in contrast an open system prevails within the subtropical gyre where there is significant recycling of silicic acid in the upper water column and lateral transport of silicon within surface currents for deep waters the si isotope composition distinguishes between the northern north pacific deep water npdw and the southerly derived bottom water the relatively light si isotope compositions measured from waters within the subarctic gyre provides evidence for isolation of the nutrient pool in the north pacific

the quaternary glacial history of the lahul himalaya northern india this paper presents the first glacial chronology for the lahul himalaya northern india the oldest glaciation the chandra glacial stage is represented by glacially eroded benches at altitudes greater than 4300 m above sea level this glaciation was probably of a broad valley type the second glaciation the batal glacial stage is represented by highly weathered and dissected lateral moraines which are present along the chandra valley and some of its tributaries this was an extensive valley glaciation the third major glaciation the kulti glacial stage is represented by well preserved moraines in the main tributary valleys of the chandra valley this represents a less extensive valley glaciation two minor glacial advances the sonapani i and ii are represented by small sharp crested moraines which are within a few hundred metres or few kilometres of the present day glaciers the change in style and extent of glaciation is attributed to an increase in aridity throughout the quaternary due either to global climatic change or uplift of the pir panjal mountains to the south of lahul which restricted the northward penetration of the south asian summer monsoon 1996 john wiley sons ltd

preliminary results from vertical seismic profiling of oroville microearthquake s waves seismograms recorded along a 0 5 km deep borehole in oroville ca show that ground level s wave velocity spectra at this location are a product of site effects in the 6 25 to 50 hz range studied both the cleveland hill fault through which the borehole was drilled and the rock above it contribute to a substantial loss of s wave energy in first order approximation the average apparent s wave quality factor qsa along the well is 9 across the fault zone the qsa drops to a low of 3 downhole the seismograms can readily be separated into longitudinal and transverse components particle motion diagrams show that the s arrival is made up of two differently polarized waves this splitting is possibly an effect of wave propagation in the highly cracked and probably anisotropic rock of the region

glacial enrichments of authigenic cd and u in subantarctic sediments a climatic control on the elements oceanic budget we examine the possibility that glacial increase in the areal extent of reducing sediments might have changed the oceanic cd inventory thereby decoupling cd from po4 we suggest that the precipitation of cd sulfide in suboxic sediments is the single largest sink in the oceanic cd budget and that the accumulation of authigenic cd and u is tightly coupled to the organic carbon flux into the seafloor sediments from the subantarctic ocean and the cape basin south atlantic where oxic conditions currently prevail show high accumulation rates of authigenic cd and u during glacial intervals associated with increased accumulation of organic carbon these elemental enrichments attest to more reducing conditions in glacial sediments in response to an increased flux of organic carbon a third core overlain by circumpolar deep water cpdw as are the other two cores but located south of the antarctic polar front shows an approximately inverse pattern to the subantarctic record the contrasting patterns to the north and south of the antarctic polar front suggest that higher accumulation rates of cd and u in subantarctic sediments were driven primarily by increased productivity this proposal is consistent with the hypothesis of glacial stage northward migration of the antarctic polar front and its associated belt of high siliceous productivity however the increase in authigenic cd and u glacial accumulation rates is higher than expected simply from a northward shift of the polar fronts suggesting greater partitioning of organic carbon into the sediments during glacial intervals lower oxygen content of cpdw and higher organic carbon to biogenic silica rain rate ratio during glacial stages are possible causes higher glacial productivity in the cape basin record very likely reflects enhanced coastal up welling in response to increased wind speeds we suggest that higher productivity might have doubled the areal extent of suboxic sediments during the last glacial maximum however our calculations suggest low sensitivity of seawater cd concentrations to glacial doubling of the extent of reducing sediments the model suggests that during the last 250 kyr seawater cd concentrations fluctuated only slightly between high levels about 0 66 nmol kg 1 on glacial initiations and reaching lowest values about 0 57 nmol kg 1 during glacial maxima the estimated 5 lower cd content at the last glacial maximum relative to modern levels 0 60 nmol kg 1 cannot explain the discordance between cd and 13c such as observed in the southern ocean this low sensitivity is consistent with foraminiferal data suggesting minimal change in the glacial cd mean oceanic content

source parameter analysis of microearthquakes recorded around the underground gas storage in the montello collalto area southeastern alps italy abstract the study of seismic source parameters is crucial for understanding the origin of seismicity and retrieving information on the energy balance and the stress involved in earthquake rupture processes in active tectonic areas where underground industrial activities are carried out such parameters may help to understand whether earthquakes are induced triggered or natural the montello collalto area southeastern alps is located in an active tectonic environment and hosts a depleted natural reservoir used to store gas since 2012 a high quality seismic network monitors the microseismicity occurring around the underground gas storage reservoir to understand if the storage activity might induce seismicity in this paper we estimate the source parameters of low magnitude events representative of the seismicity occurring in the area surrounding the reservoir the analysis includes a preliminary removal of the site effects specifically computed within this study from all the records then using a parametric multistep inversion scheme we estimate the seismic moment the corner frequency and the static stress drop that can be set as reference for the microseismicity occurring in the study area all the investigated earthquakes show low seismic efficiency compatible with overshoot processes which is typical of natural i e tectonic earthquakes our procedure can be implemented in other tectonic regions hosting underground industrial activities to support the decisional processes related to real time monitoring

source parameters of the 15 november 1995 border town nevada earthquake sequence abstract the november 1995 border town nevada earthquake sequence occurred near the california nevada border approximately 20 km northwest of reno nevada the largest earthquake of the sequence m w 4 5 was widely felt throughout the reno sparks truckee region this event occurred on a west dipping high angle fault at a depth of 14 km and shows dip slip motion on a preferred fault plane orientation of strike n10 e dip 70 w and rake 75 we have relocated 27 aftershocks and one foreshock of the event using records from the local network and two portable digital instruments the largest aftershocks also align along a n10 e trend and define the preferred fault plane all of the aftershocks occur within a small volume with a 2 by 2 km horizontal extent and between depths of 10 and 14 km simultaneous determination of m 0 f c and is made by fitting spectra using various starting models i e initial s and based on an f 2 spectral shape m 0 ranges from 10 18 to 10 23 dyne cm for 14 events and hypocentral distances were less than 15 km we fit s wave spectra with different starting models to test the stability of s the results show that s and converged to different values depending on the starting model and the magnitude because of an attenuation source dimension trade off for example a model starting with a stress drop of 10 bars produced an average s of 27 bars and an apparent scaling breakdown below m w 3 starting the search at 50 bars produced an average s of 69 bars and no magnitude dependence we cannot resolve any breakdown in self similarity because we find plausible spectral models for all magnitudes where s is nearly constant at 60 bars seismograms of the four largest aftershocks m w 3 0 to 3 4 were deconvolved using smaller aftershocks as empirical green9s functions event radii estimated from the pulse widths yield stress drop averaging 34 bars within the range of the frequency domain results

earthquake source scaling relationships from 1 to 5 ml using seismograms recorded at 2 5 km depth the scaling relationships of earthquake sources less than about magnitude 3 have been the subject of considerable controversy over the last two decades studies of such events have shown a tendency for the constant stress drop self similarity of larger earthquakes to breakdown at small magnitudes and an apparent minimum source dimension of about 100 m has been observed other studies showed that this apparent breakdown in scaling could be an artifact of severe near surface attenuation limiting the spatial resolution of surface data in this study source parameters are determined for over 100 nearby tectonic earthquakes from recordings at a depth of 2 5 km in granite in the cajon pass scientific drill hole southern california comparison of the seismograms recorded at this depth with those at the wellhead clearly demonstrates the effect of the severe attenuation in the upper kilometers of the earth s crust source parameters are calculated by spectral modeling of three component p and s waves assuming four source models based on the brune 2 n 2 model in model l n 2 is fixed and q of p and s waves is determined to be 912 581 1433 and 1078 879 1323 respectively the numbers in parentheses are 1 standard deviation in model 2 qp qs 1000 is assumed and n is allowed to vary the 2 model is a good average for the data set but there is some real scatter supported by the data in model 3 qp qs 1000 is also assumed and 2 is constrained and in model 4 attenuation is ignored and n is allowed to vary source dimensions of less than 10m are observed for all four models 10 times smaller than the proposed minimum no breakdown in constant stress drop scaling is seen in the downhole data approximately ml 1 to 5 5 m0 109 1016 nm the ratio between radiated seismic energy estimated by integrating the velocity squared spectra with adequate signal bandwidth and seismic moment appears to decrease gradually with decreasing moment in the magnitude range 1 to 7 this is not incompatible with a constant stress drop but could result from errors in calculating energy the ratio of the s wave energy to that radiated by the p waves is about 14 after correction for attenuation this low value is consistent with the corner frequency shift of about 1 3 this corner frequency shift is observed for all four source models and therefore is interpreted as being source controlled

surface deformation and strike slip faulting controlled by dyking and host rock lithology a compendium from the krafla rift iceland abstract in the present work we have obtained a detailed complete view of surface deformation at a volcano tectonic structure belonging to the krafla fissure swarm ne iceland through the integration of field mapping and the aerial structure from motion technique asfm as well as through orthomosaics and digital surface models dsms the documented 2 5 km long deformation zone is marked by a range of features such as topographic bulging parallel extension fractures and narrow grabens affected by local floor uplift which we have explained as the effect of the northward shallow propagation of a dyke from the krafla magma chamber our lithostratigraphic field survey of the area at a 1 5000 scale indicates that major changes in the pattern of surface deformation take place across the contacts between deposits with different rheological properties the transition from very stiff lavas to softer hyaloclastites produces changes from extensional fracturing to normal faulting though the width of the deformation zone does not change we have also documented a number of ne sw left lateral and nnw sse right lateral strike slip fault zones that are rotated in clockwise and anticlockwise sense to the main nne ssw graben trend and extend outwards as much as about 17 m the graben zone terminates to the north by splitting into two strike slip fault zones these were likely generated at the front of the dyke tip during its propagation and were later on bypassed by the advancement of the dyke as the dyke entered the soft hyaloclastites propagation was slowed down and the dyke became thicker

hydrothermal scavenging at the mid atlantic ridge modification of trace element dissolved fluxes abstract we have carried out an icp ms study of the distributions of trace elements fe ca mg al mn cu zn v as cr co pb y mo ag sn cd and be in particulate material collected from the tag hydrothermal plume 26 n mid atlantic ridge to examine the extent to which fluxes of dissolved trace elements emitted from hydrothermal vent fluids are balanced by the precipitation of associated particulate phases comparison of particulate trace element distributions with particulate fe concentrations within the neutrally buoyant plume reveals that the distribution of trace elements within the plume is controlled by the following processes i co precipitation from vent fluids ii scavenging from seawater and iii preferential settling from the plume and oxidative dissolution within the water column for y and be continuous scavenging from seawater appears to be important whereas for v as and cr it appears that conditions suitable for uptake into particles may be restricted to the buoyant portion of the hydrothermal plume from a comparison of trace element fe ratios in the particles and associated mid atlantic ridge vent fluids it appears that for many elements e g cu co ag pb al cd be and zn the flux of dissolved material from vent fluids is matched closely by the precipitation of hydrothermal particulate phases of the various elements studied here hydrothermal activity only appears to act as a significant source for dissolved ca and dissolved mn

attenuation and source parameters at deception island south shetland islands antarctica deception island is the most active volcano of the south shetland islands antarctic peninsula group experiencing eruptions in 1967 1969 and 1970 local attenuation derived from coda analysis and source parameters derived from brune s model for well located seismic events have been studied in order to complement the available geophysical information results show abnormally lowq0 values and an abnormally high frequency dependence as well as large dispersion these factors are strongly dependent on the path travelled by the seismic wave retrieved values of the source parameters stress drop seismic moment and source radius are again abnormally low compared to world wide average values for example those obtained for the oroville california aftershock series between june and september 1976 these results are consistent with some aspects of the geology of deception island such as the very high degree of fracturing and faulting and the existence of a strong hydrothermal alteration affecting most of the subaerial volcanic rocks moreover the pattern defined for the lateral variations ofq0 shows minimum values in the inner bay of the island close to the most recent eruption vents a large reduction in spectral amplitudes over a particular frequency range occurs in several observations corresponding to the path crossing the zone of highest attenuation this observation suggests the existence of a hot magmatic intrusion produced during the most recent eruption and coincides with the superficial low density mass distribution obtained from the gravimetric model and the long wave magnetic field component obtained from magnetic surveys the width of this intrusion is estimated to be about 200 m in agreement with the previous results obtained analyzing residuals of the location of seismic events

source parameters of the 1980 mammoth lakes california earthquake sequence from the more than 1500 mammoth lakes earthquakes recorded on three component digital seismographs spudich et al 1981 150 were used in an analysis of the locations mechanism and source parameters a composite fault plane solution of nine earthquakes 3 9 m 5 1 defines a right lateral strike slip mechanism on a steeply dipping nearly east west plane striking s75 e or left lateral strike slip on a nearly north south plane striking n10 e vertical cross sections of well located aftershocks indicate possibly three east west planes that coincide with the locations of the four largest earthquakes with ml 6 0 using the spectral analysis of s waves brune 1970 source parameters for 67 earthquakes were determined forty eight had magnitudes greater than or equal to 3 0 seismic moments ranged from 9 20 1018 dyn cm to 2 33 1024 dyn cm earthquakes with seismic moment greater than about 1 0 1021 dyn cm had nearly constant stress drops 50 bars earthquakes with seismic moment less than about 1 0 1021 dyn cm had stress drops that apparently decrease as seismic moment decreases

source parameters of small earthquakes recorded at 2 5 km depth cajon pass southern california implications for earthquake scaling a 2 5 km deep triaxial seismometer at cajon pass in southern california has recorded several hundred earthquakes ml4 0 occurring within the san andreas fault system at 2 5 km seismic background noise is below amplifier sensitivity and the 2 250 hz spectral range of recorded seismic motion is wider and higher than that of most natural event catalogs compared with downhole recorded motion seismic amplitudes at the surface are amplified below 10 hz and severely attenuated above 30 hz we estimate that qs is at least 1000 for wave motion at 2 5 km and below and qp is over 2000 the range of source dimensions in the downhole recorded catalog is 10 m to 70 m ml 2 0 mo 108 nm to ml 2 7 mo 1013 nm the plot of log source radius vs log moment has a straight line trend compatible with earthquake scaling at constant stress drop inferred stress drops are scattered between 1 and 500 bars there is no evidence in the catalog for the proposed minimum source dimension at 100 m when the cajon pass borehole catalog containing some of the smallest recorded natural earthquakes is combined with 800 larger events from previous studies the moment radius trend suggests that natural earthquakes are self similar over a magnitude range m 2 to 8 we suggest that inferences of minimum source dimension are more likely due to bias in bandlimited individual catalogs than to properties of the seismic crust

recessional pattern of thelu and swetvarn glaciers between 1968 and 2019 bhagirathi basin garhwal himalaya india abstract this study assesses the temporal changes of swetvarn and thelu glaciers between 1968 and 2019 in rakvarn glacial valley of bhagirathi basin here we utilized high resolution satellite images of corona kha 1968 liss iv 2012 and sentinel 2 msi 2019 along with medium resolution images of landsat tm 1990 and srtm 2000 to carry out the research work analytical viewed strongly convinced that the selected glaciers receding continuously with non homogeneous retreat rate since 1968 during 1968 to 2019 the snout of the swetvarn glacier lost 623m total length with 12 21ma 1 retreat rate while the snout of thelu glacier lost 590m total length 11 56ma 1 results further confirmed that about 16 60 glaciated area of swetvarn glacier and 24 50 glaciated area of thelu glacier also vanished completely between 1968 and 2019 during this tenure the ablation zone shows 160m upward shift for swetvarn glacier and 145m for thelu glacier respectively overall analysis explains that three climatic trends of garhwal himalayan region 1 catastrophic variation between rainfall and temperature during 1960 1990 2 gradual increase in temperature and decrease in precipitation 3 increased liquid precipitation and decreased solid precipitation highly influences the process of melting of the study region

ca isotopes in carbonate sediment and pore fluid from odp site 807a the ca2 aq calcite equilibrium fractionation factor and calcite recrystallization rates in pleistocene sediments abstract the calcium isotopic compositions 44ca of 30 high purity nannofossil ooze and chalk and 7 pore fluid samples from odp site 807a ontong java plateau are used in conjunction with numerical models to determine the equilibrium calcium isotope fractionation factor s f between calcite and dissolved ca2 and the rates of post depositional recrystallization in deep sea carbonate ooze the value of s f at equilibrium in the marine sedimentary section is 1 0000 0 0001 which is significantly different from the value 0 9987 0 0002 found in laboratory experiments of calcite precipitation and in the formation of biogenic calcite in the surface ocean we hypothesize that this fractionation factor is relevant to calcite precipitation in any system at equilibrium and that this equilibrium fractionation factor has implications for the mechanisms responsible for ca isotope fractionation during calcite precipitation we describe a steady state model that offers a unified framework for explaining ca isotope fractionation across the observed precipitation rate range of 14 orders of magnitude the model attributes ca isotope fractionation to the relative balance between the attachment and detachment fluxes at the calcite crystal surface this model represents our hypothesis for the mechanism responsible for isotope fractionation during calcite precipitation the ca isotope data provide evidence that the bulk rate of calcite recrystallization in freshly deposited carbonate ooze is 30 40 myr and decreases with age to about 2 myr in 2 3 million year old sediment the recrystallization rates determined from ca isotopes for pleistocene sediments are higher than those previously inferred from pore fluid sr concentration and are consistent with rates derived for late pleistocene siliciclastic sediments using uranium isotopes combining our results for the equilibrium fractionation factor and recrystallization rates we evaluate the effect of diagenesis on the ca isotopic composition of marine carbonates at site 807a since calcite precipitation rates in the sedimentary column are many orders of magnitude slower than laboratory experiments and the pore fluids are only slightly oversaturated with respect to calcite the isotopic composition of diagenetic calcite is likely to reflect equilibrium precipitation accordingly diagenesis produces a maximum shift in 44ca of 0 15 for site 807a sediments but will have a larger impact where sedimentation rates are low seawater circulates through the sediment pile or there are prolonged depositional hiatuses

high frequency observations and source parameters of microearthquakes recorded at hard rock sites we have estimated the source parameters of 53 microearthquakes recorded in july 1983 which were aftershocks of the miramichi new brunswick earthquake that occurred on 9 january 1982 these events were recorded by local three component digital seismographs at 400 sps component from 2 hz velocity transducers sited directly on glacially scoured crystalline basement outcrop hypocentral distances are typically less than 5 km and the hypocenters and the seven digital seismograph stations established all lie essentially within the boundaries of a granitic pluton that encompasses the faults that ruptured during the main shock and major aftershocks the p wave velocity is typically 5 km sec at the surface and at least 6 km sec at depths greater than about 1 km the events have s wave corner frequencies in the band 10 to 40 hz and the calculated brune model seismic moments range from 1015 to 1018 dyne cm the corresponding stress drops are generally less than 1 0 bars but there is considerable evidence that the seismic source signals have been modified by propagation and or site effects the data indicate a there is a velocity discontinuity at 0 5 km depth b the top layer has strong scattering attenuating properties c some source receiver paths differentiate the propagated signal d there is a hard rock site p wave f max between 50 and 100 hz and e some hard rock sites are characterized by p wave resonance frequencies in the range 50 to 100 hz comparison of this dataset with the january 1982 new brunswick digital seismograms which were recorded at sites underlain by several meters of low velocity surface sediments suggests that some of the hard rock site phenomena listed above can be explained in terms of a layer over a half space model for microearthquakes this result implies that spectrally determined source dimension scales with site dimension thickness of the layer more generally it emphasizes that it is very difficult to accurately observe the details of seismogenic processes from the earth s surface

seismic source parameters for microearthquakes of the granada basin southern spain abstract ninety five microearthquakes of the granada basin southern spain with duration magnitudes ranging from 1 3 to 3 5 moment magnitude from 0 9 to 2 5 have been spectrally analyzed with digital recordings from ten stations of the andalusian seismic network the coda q quality factor qc assumed to be frequency dependent was used instead of q for the path correction and the q adopted was equal to 9 4 qc the k parameter for site attenuation correction had values in the range of 0 02 0 05 fourier displacement spectra were calculated for p and s waves and analyzed with respect to the source model of brune 1970 1971 spectral parameters were automatically determined by the method of snoke 1987 the seismic moment ranged from 1017 to 1020 dyne cm with average m0 p to m0 s ratio of 1 02 and the source radii spanned from 0 14 to 0 40 km with average r p to r s ratio of 1 3 the seismic energy values ranged from 1 103 to 9 107 j with p to s energy ratio from 1 to 10 for about 85 of the events whereas the static stress drop varied from 0 02 to 2 6 bar the scaling relation between the seismic moment and the stress drop indicates a decrease in stress drop with decreasing seismic moment apparent stress is linearly correlated with stress drop and have on average similar values and this points out to a partial stress drop

site response attenuation and source spectra of s waves along the guerrero mexico subduction zone acceleration spectra from nine earthquakes and up to 11 stations per earthquake are inverted to find the source spectra the site response and the quality factor q of s waves this method is applied to moderate earthquakes 4 0 0 8 hz does not follow a simple linear relation as observed in previous studies of attenuation in other regions when the source spectra are interpreted in terms of brune s model the stress drops obtained are less than 20 bars for the four larger events analyzed the site functions obtained indicate that although all the stations used are on rock the effect of the near surface geology caused important amplifications at some stations

microearthquake spectra from the anza california seismic network site response and source scaling abstract we analyzed spectra of local microearthquakes recorded by the anza california seismic network to isolate the effects of site response and to investigate the scaling of source parameters for small earthquakes spectra of microearthquakes m m o 19 dyne cm at anza have shapes characteristic of the receiver sites and are generally independent of the source region thus the site response is a major conditioner of the observed spectral shape to remove the effects of site response from the spectra of a m 3 event and isolate its source spectrum we divided by the spectra of an adjacent aftershock used as an empirical green9s function event the spectral ratios indicate that the apparent corner frequencies of small earthquakes m o 19 dyne cm observed at even the high f max stations on hard rock are much lower than the source corner frequencies the spectral ratios are consistent with stress drop remaining constant with decreasing seismic moment for events with moments as small as 10 18 dyne cm the spectral ratios display remarkable agreement between sites which showed vast differences in their original spectra indicating that the spectral division effectively removed the site response the source spectrum of the m 3 event has a high frequency spectral fall off of about 2 an apparent dependence of high frequency fall off with seismic moment in the original spectra can also be explained by the effects of site response the difference between the p and s wave corner frequencies and high frequency roll offs in the observed spectra for these events is the result of the site response and is not a source property the shapes of the spectra of microearthquakes at anza can largely be explained by attenuation at shallow depth with a frequency independent q for some sites near surface resonances are also apparent in the spectra of microearthquakes it is indicated by t values determined for each site that q p q s for the shallow low q layer further evidence of low near surface q is observed in the anomalous spectra of an unusually shallow earthquake source depth 1 km in the network the spectra from this shallow event are depleted in high frequency energy at most stations relative to those of deeper events this observation can be explained by a low q surficial zone for stations of the network situated on alluvium this low q layer has a maximum thickness of about 3 km and maximum p and s wave q values of 30 to 50

source attenuation and site parameters of the 1997 umbria marche seismic sequence from the inversion of p wave spectra a comparison between constant qp and frequency dependent qp models 1 the attenuation of p waves the site responses and the source parameters seismic moment corner frequency source dimension of 490 seismic events that occurred during the 1997 colfiorito umbria marche seismic sequence have been inferred from the inversion of p wave velocity spectra the boatwright source model has been assumed to model the source spectra a global nonlinear inversion scheme was developed to avoid any a priori selection of the initial qp and the corner frequency to establish if a frequency dependent qp model fits the data better than a constant qp model two inversion results have been compared application of the akaike information criterion indicates that the constant qp model represents the best compromise between model simplicity and data misfit the station qp values are small in the range of 50 to 200 a one dimensional qp model is obtained by back projecting the inverted t our results indicate both well defined near site attenuation effects at some sites and heterogeneity in the inelastic properties of the crust with the exception of the amplification response at five seismic stations most of the recording sites did not show amplification peaks at particular frequencies the stress drop clearly increases as a function of the seismic moment which indicates a deviation from self similarity whereas it does not show an increase with depth probably owing to the effects of fluid pressurization in the crust a stress drop of about 39 mpa is inferred the relationship between the seismic moment and the local magnitude for p waves has been calibrated

source scaling of microearthquakes at mt etna volcano and in the calabrian arc southern italy microearthquake data recorded at mt etna volcano and in the calabrian arc southern italy have been used to study the scaling of the main source parameters after correction of the p wave displacement spectra for both path attenuation and the site amplification effects an inverse method has been applied to compute spectral parameters low frequency spectral level corner frequency and high frequency roll off results show that seismic moments m0 range from ca 1016 to 1021 dyne cm at mt etna and from ca 1017 to 1020 dyne cm in southern calabria corner frequencies range from ca 3 to 15 hz in both areas we found that the stress drop decreases from ca 100 to few bars with decreasing seismic moment a simple brune source model is not able to explain the source scaling because the typical fall off observed at higher frequencies 3 as an average is larger than that of brune s theory furthermore the relation between the seismic moment and the corner frequency points to a scaling law behaving as m0 c 4 5 and m0 c 3 6 on average at mt etna and in southern calabria respectively and higher for smaller events in both areas therefore the cube law m0 3 generally accepted for large earthquakes does not hold true for the analysed microearthquakes neither for those which occur along the tectonic structures of southern calabria or along those hosting the roots of the feeding system of the largest european volcano

the effects of attenuation and site response on the spectra of microearthquakes in the northeastern caribbean abstract the spectra of microearthquakes recorded by a seismic network in the northeastern caribbean were analyzed to determine the effects of attenuation and site response on these spectra the ratios of the spectral amplitudes at 5 and 20 hz were measured for several earthquakes at different distances from a fixed receiver to estimate q for p and s waves in the crust and upper mantle the average q p determined from three stations was 380 for epicentral distances between 40 and 200 km the average q s determined from two stations was estimated at 400 spectra of earthquakes closer than 40 km to one station indicate that a high q path q 800 exists for these short distances in the island arc platform the near equivalence of q p and q s observed in this study of the upper lithosphere contrasts with estimates of anderson et al 1965 that q p 9 4 q s in the asthenosphere this finding that q p is approximately equal to q s suggests that the attenuation mechanism in the upper lithosphere differs from that in the asthenosphere the spectra of nearby microearthquakes unaffected by crustal attenuation display corner frequencies which are uniform despite large differences in the seismic moments of the events the corner frequencies of these spectra appear to be characteristic of the receiver site and insensitive to the location and moment of the earthquakes at one station the s wave corner frequency of a nearby blast was identical to the corner frequency of a magnitude 4 8 earthquake derived from the record of a strong motion accelerograph at the same site

spectral analysis of earthquakes in the 1989 mammoth mountain swarm near long valley california abstract the 1989 earthquake swarm beneath mammoth mountain near long valley california was unique for the area because of the occurrence of low frequency and unusual mixed frequency events at the time of the swarm a computer based earthquake detection system with near real time location and spectral fitting capabilities was operational at long valley this system detected over 1500 earthquakes during the swarm about 64 of the events had a high frequency content 4 to 8 hz 34 had a medium frequency content

terrain changes caused by the 15 17 june 2013 heavy rainfall in the garhwal himalaya india a case study of alaknanda and mandakini basins abstract exceptional early high monsoon rains between 15 and 17 june 2013 combined with discharge from snowmelt water caused widespread floods in every major river of the garhwal himalaya this catastrophic event triggered widespread landslides and devastation in the region affecting the movement of the people that led to stranding of pilgrims in various pilgrimage routes this event caused many casualties and irreparable damage to the infrastructures and property in the garhwal himalaya a large volume of debris was deposited in kedarnath town 3 9 10 6 m 3 and a huge amount of debris was removed from rambara and surrounding areas 2 6 10 8 m 3 the study also found that villages like lambaghar bhyundar alaknanda river valley and rambara mandakini river valley were completely washed away leaving no trace of earlier settlement govindghat and pulna villages in the alaknanda river valley were also badly damaged approximately 0 3 10 6 and 0 72 10 6 m 3 of debris was deposited respectively similarly in the mandakini valley kedarnath and sonprayag towns were also badly damaged and 3 9 10 6 and 1 4 10 6 m 3 of debris was deposited in the area respectively simultaneously the moraine dammed chorabari lake breached releasing 6 1 10 5 m 3 of water with an average rate of 1429 m 3 s discharge of lake the towns of pandukeshwar in the alaknanda valley and gaurikund in the mandakini valley were partially damaged however no evidence of such magnitude of destruction was reported from the yamuna river valley during the same period this catastrophic event changed the landscape in many parts of uttarakhand making the whole region more fragile and vulnerable a disaster of such magnitude was perhaps not witnessed by the region for at least the last 100 years

inversion of source parameters and site effects from strong ground motion records using genetic algorithms the low frequency flat levels and corner frequencies of the aftershocks of the kobe earthquake together with the site effects of the recording stations are inverted by using genetic algorithms all records were corrected by the quality factor q of propagation path and for each aftershock a different omega squared model was assumed such that the low frequency flat levels and corner frequencies would minimize the standard deviation of the site effects at all stations it was observed that site effects for rock sites showed significant amplification at high frequencies this amplification was found to correlate with spectral ratios of records located at 70 m depth and at the surface for one of the stations after estimating the seismic moment and the stress drop it was observed that the relation of the seismic moment m0 versus the corner frequency fo followed the scaling law m0 fo 3 large values of stress drop were found around asperities on the fault zone and at depth

seismic imaging of the site response using microearthquake recordings part ii application to the swabian jura southwest germany seismic network the subsurface site structure of the swabian jura southwest germany seismic network has been modeled from the inversion of locally recorded sh wave microearthquake seismograms the observed records have been deconvolved from the effects of apparent source pulse broadening due to the combined influence of frequency bandlimited source signals absorption peg leg multiple reflections and the recording system following the procedure of scherbaum and stoll 1985 corresponding pseudo reflection seismograms were calculated based on the kunetz claerbout relation for sh waves and inverted using a levison recursion algorithm the final structural models have been optimized in terms of numbers of layers and depth resolution using ferber s 1985 noise stabilization technique the resulting impedance models for the swabian jura southwest germany seismic network show some strongly correlated reflectors in the uppermost layers which are well understood in terms of the local stratigraphy the comparison of the inverted impedance model hsn with the p wave velocity log from a nearby exploration drilling trochtelfingen beb shows a high degree of similarity of the dominating reflectors down to a depth of several hundred meters as a consequence the coda generating process for the early part of the coda of the observed swabian jura microearthquake seismograms wood anderson magnitude mwa 3 0 can be completely interpreted as an effect of the local subsurface structure

is climate change responsible for changing landslide activity in high mountains climate change manifested by an increase in mean minimum and maximum temperatures and by more intense rainstorms is becoming more evident in many regions an important consequence of these changes may be an increase in landslides in high mountains more research however is necessary to detect changes in landslide magnitude and frequency related to contemporary climate particularly in alpine regions hosting glaciers permafrost and snow these regions not only are sensitive to changes in both temperature and precipitation but are also areas in which landslides are ubiquitous even under a stable climate we analyze a series of catastrophic slope failures that occurred in the mountains of europe the americas and the caucasus since the end of the 1990s we distinguish between rock and ice avalanches debris flows from de glaciated areas and landslides that involve dynamic interactions with glacial and river processes analysis of these events indicates several important controls on slope stability in high mountains including the non linear response of firn and ice to warming three dimensional warming of subsurface bedrock and its relation to site geology de glaciation accompanied by exposure of new sediment and combined short term effects of precipitation and temperature based on several case studies we propose that the following mechanisms can significantly alter landslide magnitude and frequency and thus hazard under warming conditions 1 positive feedbacks acting on mass movement processes that after an initial climatic stimulus may evolve independently of climate change 2 threshold behavior and tipping points in geomorphic systems 3 storage of sediment and ice involving important lag time effects

cadmium isotope fractionation in seawater a signature of biological activity investigations of cadmium isotope variations in the oceans may provide new insights into the factors that control the marine distribution and cycling of this element here we present the results of cd isotope and concentration analyses for 22 seawater samples from the atlantic southern pacific and arctic oceans the results reveal for the first time large and well resolved cd isotope fractionations in the marine environment the majority of the seawater samples display an inverse relationship between dissolved cd contents and isotope compositions which range from e114 110cd 3 0 5 for cd rich waters 0 8 1 0 nmol kg to e114 110cd 38 6 for surface water with a cd concentration of only 0 003 nmol kg all e114 110cd data are reported relative to the jmc cd munster standard this suggests that the cd isotope variations reflect kinetic isotope effects that are generated during closed system uptake of dissolved seawater cd by phytoplankton a few samples do not follow this trend as they exhibit extremely low cd contents 0 008 nmol kg and nearly un fractionated cd isotope compositions such complexities which are not revealed by concentration data alone require that the cd distribution at the respective sites was affected by additional processes such as water mass mixing atmospheric inputs of cd and or adsorption uniform isotope compositions of e114 110cd 3 3 0 5 1 s d were determined for seawater from 900 m depth despite of cd concentrations that display the expected increase along the global deep water pathway from the atlantic 0 3 nmol kg to the pacific ocean 0 9 nmol kg this indicates that the biomass which is remineralized in the deeper ocean is also characterized by a very constant cd isotope composition this observation is in accord with the interpretation that the cd distribution in surface waters is primarily governed by rayleigh fractionation during near quantitative uptake of dissolved seawater cd

source parameters of microearthquakes at mount st helens usa summary we estimate the source parameters for a selection of microearthquakes that occurred at mount st helens in the period 1995 1998 excluding the activity of 2004 september this time period includes the most intense episode of earthquake activity since the last dome building eruption in 1986 october 200 seismograms were processed to obtain seismic moments source radii stress drops and average fault slip the source parameters were determined from the spectral analysis of p waves after correction for attenuation and site effects in particular p wave quality qp and site s factors have been previously calculated in the frequency ranges 2 7 hz and 18 30 hz because it was impossible to perform corrections for qp and s over the whole spectrum we applied a new approach based on the notion of holed spectrum to estimate spectral parameters the term holed spectrum indicates a spectrum lacking corrected spectral amplitude values at certain frequencies we carried out a statistical study to verify that dealing with the holed spectrum does not lead to significant differences in the estimates of spectral parameters we also investigated the dependence of spectral parameters low frequency level corner frequency and high frequency decay on the bandwidth of spectral hole and defined the threshold values for three different spectral models displacement holed spectra corrected by attenuation and site response are then used to determine spectral parameters in order to calculate seismic source parameters seismic moments range from 1017 to 1019 dyne cm source dimensions from 100 to 350 m and average fault slip from 0 003 to 0 1 cm self similarity seems to break down in that stress drops are very low 0 1 1 bars we postulate that seismicity is associated with a brittle shear failure mechanism occurring in a highly heterogeneous material under a relatively low stress regime

contemporary glacier retreat triggers a rapid landslide response great aletsch glacier switzerland the destabilization and catastrophic failure of landslides triggered by retreating glaciers is an expected outcome of global climate change and poses a significant threat to inhabitants of glaciated mountain valleys around the globe of particular importance are the formation of landslide dammed lakes outburst floods and related sediment entrainment based on field observations and remote sensing of a deep seated landslide located at the present day terminus of the great aletsch glacier we show that the spatiotemporal response of the landslide to glacier retreat is rapid occurring within a decade our observations uniquely capture the critical period of increase in slope deformations onset of failure and show that measured displacements at the crown and toe regions of the landslide demonstrate a feedback mechanism between glacier ice reduction and response of the entire landslide body these observations shed new light on the geomorphological processes of landslide response in paraglacial environments which were previously understood to occur over significantly longer time periods

an assessment procedure for glacial hazards in the swiss alps glacial hazards such as ice avalanches glacial lake outburst floods and debris flows have caused severe damage in populated mountain regions such as the swiss alps assessment of such hazards mus

source parameters estimated from the aftershocks of the 1997 umbria marche italy seismic sequence we derived the source parameters of 563 aftershocks 1 4 m l 4 5 of the 1997 umbria marche seismic sequence by analyzing three component digital recordings of a temporary network and developed a local magnitude scale using the whole available data set more than 25 000 waveforms from synthetic wood anderson seismograms then considering a subnetwork composed of nine portable stations more than 12 000 earthquake spectra were corrected for the near surface attenuation parameter k and the path attenuation the corrected spectra were used to compute the seismic moment the source radius and stress drop assuming an 2 brune source model we calculate the relationship log m 17 46 1 12 m l between seismic moment and local magnitude for the studied area the source dimension versus seismic moment relationship did not show any breakdown in the similarity of the rupture process even when events of magnitude less than 2 2 the threshold value for the completeness of the considered catalog were considered the average stress drop obtained analyzing the s wave spectra was 38 10 bar and the source dimension ranged between about 40 and 500 m

study of temporal response 1976 2019 and associated mass movement event during 2017 of meru glacier bhagirathi valley garhwal himalaya india abstract impact of climate change on glaciers brings the favorable conditions of lakes formation within glacier moraines these lakes may produce outburst floods and transport the huge amount of debris debris flow in downstream settlements the present study addresses the current knowledge on mass movement activity occurred in the gangotri glacier area garhwal himalaya uttarakhand temporal response terminus retreat and frontal area loss of meru glacier during 1976 2019 using the images of landsat mss 1976 tm 1990 2011 etm 2001 oli 2019 and event of intense mass movement occurred along meru glacier during 2017 is assessed our estimations clearly reveals that the meru glacier is retreating continuously since 1976 with inconsistent rate considering the time span 1976 1990 1990 2001 2001 2011 2011 2019 the terminus receded with 12 42 m y 1 7 72 m y 1 6 00 m y 1 11 50 m y 1 and vacated the frontal area at the rate of 2330 70 m2 y 1 2185 88 m2 y 1 1425 18 m2 y 1 1452 66 m2 y 1 respectively field observations and high resolution imagery of liss iv suggest that the lower area of meru glacier experienced the event of intense mass movement in july 2017 this event breached the continuity of left morainic wall of bhagirathi valley this mass movement event influenced the initial course of bhagirathi river 1559 m length and also modified the morphology of the gaumukh region the precipitation data from indian meteorological department imd and satellite images of different years suggest that the multiple factors such as intense precipitation large amount of sediment transport from the upper reaches to lower area slope failure collapse of frontal part of meru glacier were the main causative factors for this event

estimation of source parameters of local earthquakes originated in shillong mikir plateau and its adjoining region of northeastern india abstract we estimate the source parameters seismic moment source radius stress drop and source displacement and scaling laws for local earthquakes that occurred in the shillong mikir plateau assam valley and arunachal himalaya in northeast india during 2001 2008 the source parameters were determined using the spectral analysis of p waves from the vertical component seismograms after correction for attenuation seismic moments are observed within the range from 9 51 10 12 to stress drop ranges from 4 10 5 to 9 10 7 pa for the brune model and 7 10 5 to 1 10 8 pa for the madariaga model seismic events in this study are prominent with an average stress drop of 0 1 10 mpa the effect of site geology may be a contributing factor for such a variation in stress drop source dimensions are however found to be smaller within the major part of the plateau it is suggested that local earthquakes in the region are associated with a brittle shear failure mechanism on fault segments and or the presence of weakened zones and earthquakes are triggered by low deviatoric stress empirical relations between m w m l and m 0 m l are developed leading to the future prediction of calibration coefficients for the local earthquakes in the shillong mikir plateau and its adjoining region online material tables of source parameters

isotopic fractionation of cadmium into calcite abstract cadmium mimics the distribution of the macronutrient phosphate in the oceans and has uses as a palaeoproxy of past ocean circulation and nutrient utilization isotopic analyses of dissolved cd in modern seawater show potential as a new tool for disentangling phytoplankton utilization of cd from abiotic processes such as ocean mixing extending this information into the past requires the cd isotope signal to be captured and faithfully preserved in a suitable sedimentary archive however the role that environmental factors such as temperature may play in controlling cd isotope fractionation into such archives has not been assessed to this end we have performed controlled inorganic caco3 precipitation experiments in artificial seawater solutions we grew calcite under different precipitation rates temperatures salinities and ambient mg2 before measuring cd isotopic compositions by double spike mc icpms we find that the isotopic fractionation factor for cd into calcite c a c o 3 c d aq in seawater is always less than one i e light isotopes of cd are preferred in calcite the fractionation factor has a value of 0 99955 0 00012 and shows no response to temperature mg2 or precipitation rate across the range studied the constancy of this fractionation in seawater suggests that marine calcites may provide a record of the local seawater composition without the need to correct for effects due to environmental variables we also performed caco3 growth in freshwater and in contrast to calcite precipitated from artificial seawater solutions no isotopic offset was recorded between the growth solution and calcite c a c o 3 c d aq 1 0000 0 0001 cadmium isotope fractionation during calcite growth can be explained by a kinetic isotope effect during the largely unidirectional incorporation of cd at the mineral surface further the rate of cd uptake and isotopic fractionation can be modulated by increased ion blocking of crystal surface sites at high salinity the fractionation of cd isotopes observed during precipitation of calcite has the same direction and similar magnitude to that implicated for cd removal from the surface ocean by seawater measurements however flux calculations show that caco3 precipitation is unlikely to play a significant role in setting the cd isotope composition in seawater compared to cd utilization in phytoplankton soft tissue marine carbonates therefore record seawater cd isotope chemistry with potential as a palaeoceanographic proxy rather than drive oceanic cd isotope compositions

combination of srtm3 and repeat aster data for deriving alpine glacier flow velocities in the bhutan himalaya abstract the present study evaluates the fusion of dems from the advanced spaceborne thermal emission and reflection radiometer aster instrument and the shuttle radar topography mission srtm the study area consists of high elevation glaciers draining through the rough topography of the bhutan himalayas it turns out that the aster derived and srtm3 dems have similar accuracy over the study area but the srtm3 dem contains less gross errors however for rough topography large sections of the srtm3 dem contain no data we therefore compile a combined srtm3 aster dem from this final composite master dem we produce repeat aster orthoimages from which we evaluate the dem quality and derive glacier surface velocities through image matching the glacier tongues north of the himalayan main ridge which enter the tibet plateau show maximum surface velocities in the order of 100 200 m year 1 in contrast the ice within the glacier tongues south of the main ridge flows with a few tens of meters per year these findings have a number of implications among others for glacier dynamics glacier response to climate change glacier lake development or glacial erosion the study indicates that space based remote sensing can provide new insights into the magnitude of selected surface processes and feedback mechanisms that govern mountain geodynamics

magma system recharge of mount st helens from precise relative hypocenter location of microearthquakes 1 four hundred forty seven well recorded earthquakes at mount st helens during the late 1990s are relocated with high precision using a combination of a cross correlation technique and then a procedure to obtain a one dimensional velocity structure solution together with station corrections the resulting high resolution pattern of the spatial temporal evolution of the earthquake activity along with focal mechanisms of events provide additional evidence for the presence of a magma reservoir in the depth range 5 5 10 km connected to the surface by a thin vertical conduit moreover the distribution of the events below 5 5 km yielded a much clearer view of the structures that generate the seismicity at that depth some of the deeper events occur along a sequence of faults under the influence of a radial stress field however a large number of the events occur on a nne ssw striking steeply dipping fault with slip consistent with magma being periodically injected into a truncated dike on the northwest side of this fault

present and future states of himalaya and karakoram glaciers a complete glacier inventory of the himalaya and karakoram h k has been created by merging records from the chinese glacier inventory several regional inventories produced by the international centre for integrated mountain development kathmandu nepal and partial inventories from the geological survey of india the only remaining gap the indian part of kashmir has been filled by a reconnaissance inventory based on soviet military maps at 1 200 000 scale representing the late 1970s it contains records for 3526 glaciers covering 9584 km 2 the new h k inventory contains records and outlines for 20 812 glaciers covering 43 178 km 2 the extent of ice in the karakoram is slightly less than in the himalaya but the karakoram glaciers are on average twice as thick 160 m as against 80 m a glacier by glacier analysis relying on estimates of mass balance for the entire mountain range and on an extension of the often used volume area scaling relation suggests that up to about one fifth of the glaciers present in 1985 may have disappeared already if mass loss were to remain constant at the average rate for 1975 2008 from 3000 to 13 000 more glaciers might disappear by 2035 if mass loss were to continue to accelerate as inferred for 1985 2008 only a few thousand to a few hundred glaciers might remain in 2035 total area and total mass would each decrease by about one half constant rate assumption or three quarters constant trend assumption these projections which are uncertain and neglect some possibly important mitigating controls such as variable extents of debris cover and the feedback due to retreat to higher elevations demonstrate the need for more complete analyses to inform public perceptions of and policy decisions relating to the health of h k glaciers

spatio temporal fluctuations over chorabari glacier garhwal himalaya india between 1976 and 2017 abstract the current research work deals with the health of chorabari glacier between 1976 and 2017 using multi spectral and multi dated satellite data series of landsat mss tm and etm and resourcesat ii liss iv result closely reveals that the studied glacier receding continuously with inconsistent rate for the last 41 years and rate of receding dominates significantly after 2012 it lost 306 43 61 m total length 7 46 1 48 m a 1 0 074 km2 frontal area 0 0018 km2 a 1 0 31 km2 24 glaciated area 0 007 km2 a 1 0 015 km3 32 60 glaciated volume the upward migration of sla snow line altitude from 5265 m to 5290 m also suggests that the melting process were prevailing during the study tenure an existence of supra glacial lakes and its successive growth over the surface of chorabari glacier further justifies that the temperature of the surroundings has increased significantly and influences the melting process as well the melting process between 1976 and 1990 of the studied glacier directly influenced by the frequent episodes of precipitation and temperature anomalies of central himalayan region during 1960 1990 while the melting process after 1990 is directly influenced by the increase in average mean temperature and decrease in average mean precipitation of garhwal himalayan region the tree ring data of garhwal himalaya region also well matches the precipitation data of imd indian meteorological department the overall analysis explains that the chorabari glacier is retreating continuously since 1976

lack of a significant temperature influence on the incorporation of cd into benthic foraminiferal tests 1 benthic foraminiferal cd ca is an important proxy for seawater paleonutrient concentrations and therefore deep ocean paleocirculation although previous work suggests that the incorporation of cd into benthic foraminiferal calcite is insensitive to temperature at least one species of planktonic foraminifer appears to be strongly influenced the present study provides a closer look at the relationship between benthic cd partition coefficients and temperature using new and previously published data from the bahama banks neither calcitic taxa nor the aragonitic hoeglundina elegans exhibits any consistent changes in partition coefficients over the range 4 to 18 c

seismic imaging of the site response using microearthquake recordings part i method abstract microearthquake signals from widely distributed geographical regions have been noticed repeatedly to be strongly affected by local site effects the corresponding seismograms contain important information on the individual propagation path a single station inversion method is presented which allows the imaging of the subsurface impedance structure from locally recorded sh waves records the technique is based on the kunetz claerbout equation which in its original form states the relationship between the transmission response and the reflection response for p waves in a horizontally layered medium and vertical incidence claerbout 1968 by adapting claerbout9s formulation to the transmission problem for sh waves under oblique incidence microearthquake recordings can be used to calculate corresponding pseudo reflection seismograms which in turn can be inverted for the impedance structure by exploiting levinson recursion limitations in the high frequency content of the signals due to the combined effects of absorption recording system and bandlimited source signals as well as the influence of noise drastically reduce the resolutional power of the inversion procedure a number of different deconvolution techniques have been tested with synthetic seismograms for the applicability to reduce these effects good results have been obtained with the blind deconvolution technique of scherbaum and stoll 1985 utilizing the minimum phase property of the green9s function from the analysis of synthetic data it can be expected that for realistic source receiver situations and short period recording systems the main reflectors down to a depth of several hundreds of meters could be resolved

source parameters path attenuation and site effects from strong motion recordings of the wenchuan aftershocks 2008 2013 using a non parametric generalized inversion technique

observations of hard rock site effects abstract differences were measured in seismograms recorded at eight proximate hardrock sites five in tunnels and three on outcrops on hills tunnel sites affected the amplitude of incident signals by as much as a factor of three at frequencies inversely proportional to the depth of the site into the tunnel for example the maximum effect of a site 12 m deep was at 25 hz while that of a site 85 m deep was at 11 hz most of the observed tunnel effects could be explained in terms of interference between the incident and surface reflected waves rock outcrop sites on hills affected the amplitude of incident signals by as much as a factor of eight at frequencies inversely proportional to the dimension of the hill and more for horizontally than for vertically polarized signals hard rock site effects typically varied by no more than a factor of three for input signals from different earthquakes having widely different azimuth and incident angles

attenuation of short period seismic waves at mt vesuvius italy we analysed short period seismograms from about 250 very local events recorded by a network of high dynamic range short period seismic stations deployed on mt vesuvius to estimate the site corrected short period seismic attenuation we calculated qc 1 the inverse of the quality factor for coda waves for short lapse times 12 s and qp 1 and qs 1 the inverse of the direct body wave quality factors for p and s waves follow ing shallow ray paths we used the single scattering assumption to fit the amplitude envelopes of the coda at different frequency bands obtaining a qc 1 slowly varying with frequency similar to values measured for other volcanoes at the same lapse time site corrected qp 1 and qs 1 were estimated using the frequency decay method for both p and s waves in two frequency bands 1 6 hz and 15 24 hz results show that qp 1 is 0 028 in both frequency bands and qs 1 is 0 015 and 0 017 at low and high frequencies respectively almost independent of the frequency and that the value of qp 1 is about twice that of qs 1 as measured worldwide a check was made by measuring the broadening of the first p wave pulse with station source distance finding qp 1 0 024 using the independent estimates of qc 1 and qs 1 we separated the intrinsic from the scattering quality factor at mt vesuvius obtaining a high scattering and a low intrinsi c q 1 as already observed for other volcanoes this result confirms the hypothesis of the predominant role of the scattering phenomena with respect to the intrinsic dissipation in the seismogram formation for volcanic earthquakes

attenuation and source parameters of shallow microearthquakes at mt etna volcano italy we estimated the attenuation laws of high frequency seismic waves in the shallow crust depth 5 km and earthquake source parameters by using a se lected data set of 320 shallow events 2 6 md 4 2 recorded at mt etna volcano during the last two flank eruptions occurring in 2001 and 2002 2003 the quality factor q was estimated from spectra of p and s waves for 24 stations of the local permanent network by applying a spectral ratio technique the results show varia tions in both qp and qs as a function of frequency according to the power law q q0f n with n ranging between 0 3 and 1 3 for p waves and between 0 2 and 0 9 for s waves as typical of volcanic environments strong azimuthal variations of qp were also found suggesting the presence of local strong lateral heterogeneities and or of fluid filled cracked volumes after correction for attenuation we estimated the source parameters seismic moment source radius and stress drop of a subset of 66 shallow events under the assumption of a circular dislocation the estimated seismic moments m0 range from 10 13 to 10 15 n m the source radii r are confined between 100 and 1000 m and stress drop dr ranges between 0 2 mpa and about 4 mpa combining the source parameters obtained in this study with those calculated by pataneet al 1997 for an old data set of smaller microearthquakes 10 9 m0 10 14 n m recorded in the same area we re evaluated the scaling relationship between seismic moment m 0 and corner frequency f c for the earthquakes with m 0 ranging between 10 13 and 10 15 n m we confirm that microearthquakes at mt etna seem not to obey a

cd in planktonic and benthic foraminiferal shells determined by thermal ionisation mass spectrometry a highly sensitive method for cd determination in foraminiferal shells by isotope dilution tims has been developed and applied to 1 a more detailed reconstruction of seawater cd depth profiles for the north atlantic in the holocene and at the last glacial maximum lgm 2 the analysis of cd ca in individual benthic foraminifera shells and 3 determination of cd ca in holocene and glacial planktonic foraminifera although ca has a high first ionization potential through chemical separation of cd from the ca and optimization of the loading technique it is possible to analyze routine sized samples 10 benthics with a reproducibility in cd ca of 0 0025 micro mol mol between replicate picks from a single sample the blank of the method is 1 1 pg permitting analysis of individual benthics and of planktonic foraminifera the seawater cd reconstruction for the lgm is consistent with previous work but also suggests that depths 2 500 m were ventilated by a northern source of nutrient depleted deep water on the western side of the mid atlantic ridge individual benthic cd ca ratios show interspecimen variability which is averaged in routine analysis of multiple specimens planktonic cd ca from n atlantic cores shows interspecific differences between globigerina bulloides and neogloboquadrina pachyderma and holocene lgmmore contrasts which offers potential for use of planktonic cd ca as a palaeochemical tracer less

the 1998 earthquake sequence south of long valley caldera california hints of magmatic involvement a significant episode of seismic and geodetic unrest took place at long valley caldera california beginning in the summer of 1997 activity through late may of 1998 was concentrated in and around the south moat and the south margin of the resurgent dome the sierran nevada block snb region to the south southeast remained relatively quiet until a m 5 1 event occurred there on 9 june 1998 ut a second m 5 1 event followed on 15 july ut both events were followed by appreciable aftershock sequences an additional distinct burst of activity began on 1 august 1998 the number of events in the august sequence over the first week or two was similar to the aftershock sequence of the 15 july 1998 m 5 1 event but the later sequence was not associated with any events larger than m 4 3 all of the summer 1998 snb activity was considered tectonic rather than magmatic in general the snb is considered an unlikely location for future eruptions however the august sequence an aftershock sequence without a mainshock is suggestive of a strain event larger than the cumulative seismotectonic strain release moreover a careful examination of waveforms from the august sequence reveals a small handful of events whose spectral signature is strikingly harmonic we investigate the waveforms of these events using spectral autocorrelation and empirical green s function techniques and conclude that they were most likely associated with a fluid controlled source our observations suggest that there may have been some degree of magma or magma derived fluid involvement in the 1998 snb sequence

source parameters of the 23 april 1992 m 6 1 joshua tree california earthquake and its aftershocks empirical green s function analysis of geos and terrascope data source parameters of the m 6 1 23 april 1992 joshua tree mainshock and 86 m 1 8 to 4 9 aftershocks are determined using an empirical green s function methodology for the aftershocks deconvolved p and s wave spectra are calculated for 126 pairs of closely spaced events recorded on portable geos stations s wave spectra from the two horizontal components are averaged the deconvolved spectra are fit by a ratio of omega square source models yielding an optimal least squares corner frequency for both the large and the small event in each pair we find no resolved difference between the inferred p and s wave corner frequencies using the standard brune model for stress drop we also find no resolved nonconstant scaling of stress drop with moment although we also conclude that detailed scaling systematics would be difficult to resolve in particular a weak increase of stress drop with moment over a limited moment magnitude cannot be ruled out for magnitudes smaller than m 3 to 3 5 the inferred stress drop values will be limited by the maximum observable corner frequency value of 60 hz for the mainshock source time functions are obtained from mainshock recordings at three terrascope stations pfo pas and gsc using an m 4 3 foreshock as an empirical green s function the results indicate a fairly simple single pulse source time function with clear south to north directivity and an inferred rupture radius of 5 to 6 km the deconvolved source time functions are inverted to obtain a finite rupture model that gives a robust estimate of rupture dimension early aftershocks are found to lie along the perimeters of regions with high mainshock slip the inferred mainshock stress drop value 56 bars is within the range determined for the aftershocks our derived mainshock source spectra do not show resolvable deviation from the omega square model

seismic source parameters from the guerrero subduction zone abstract a method to systematically determine seismic moment and corner frequency from shear wave spectra has been applied to strong motion data recorded in guerrero mexico the method determines a model spectrum that minimizes the misfit from the observed spectrum after a correction for frequency dependent site response has been applied the calculated moments for larger events in guerrero are consistent with moments determined from teleseismic body waves adjusted for differences in focal depth and consequent assumed differences in the velocity and density structure in the source region the average stress drop for the 82 earthquakes with magnitudes from 3 to 7 is 150 bars the spatial distribution of the stress drops shows a distinctive pattern at the northwest end of the guerrero gap adjacent to the aftershock zones of large earthquakes in 1979 and 1985 there is a mix of low and high stress drop events at the southeast end of the guerrero gap where the most recent large earthquake occurred in 1957 there are predominantly high stress drop events this pattern might be caused by the different relative positions of these two active regions in the earthquake cycle although several other explanations cannot be ruled out

north atlantic thermohaline circulation during the past 20 000 years linked to high latitude surface temperature during a surface cooling event 10 000 to 12 000 years ago higher cd ca and lower 13c 12c ratios are observed in benthic foraminifera shells from rapidly accumulating western north atlantic sediments data from sediment cores show that marked nutrient depletion of intermediate waters occurs in association with reduced glacial north atlantic deep water flux it is proposed that cold high latitude sea surface temperatures enhance intermediate water formation at the expense of deep water formation

consideration of the errors inherent in mapping historical glacier positions in austria from the ground and space 1893 2001 the historical record of in situ measurements of the terminus positions of the pasterze and kleines fleiskees glaciers in the eastern alps of austria is used to assess uncertainties in the measurement of decadal scale changes using satellite data topographic maps beginning in 1893 and satellite data from 1976 to 2001 were studied in concert with ground measurements to measure glacier changes ground measurements show that the tongue of the pasterze glacier receded f1150 m from 1893 to 2001 while satellite derived measurements using august 2001 landsat enhanced thematic mapper plus etm data registered to an 1893 topographic map show a recession of 1300 1800 m with an unknown error the measurement accuracy depends on the registration technique and the pixel resolution of the sensor when two satellite images are used when using topographic maps an additional source of error is the accuracy of the glacier position shown on the map between 1976 and 2001 landsat derived measurements show a recession of the terminus of the pasterze glacier of 479f136 m at an average rate of 19 1 m a 1 while measurements from the ground showed a recession of 428 m at an average rate of 17 1 ma 1 four meter resolution ikonos satellite images from 2000 and 2001 reveal a shrinkage of 22 096f46 m 2 in the pasterze tongue the nearby kleines fleiskees glacier lost 30 of its area between 1984 and 2001 and the area of exposed ice increased by 0 44f0 0023 km 2 according to landsat satellite measurements as more recent satellite images are utilized especially data that are geocoded the uncertainty associated with measuring glacier changes has decreased it is not possible to assess the uncertainty when an old topographic map and a satellite image are coregistered

source parameters of microearthquakes in southeastern sicily italy we computed the source parameters of 135 local earthquakes that occurred in southeastern sicily italy between 1994 and 2001 magnitudes ranged from 0 6 to 2 5 the source parameters were determined from the spectral analysis of p waves after corrections for attenuation and site effects p wave quality qp and site s factors are known in the two frequency ranges 3 9 hz and 16 27 hz giampiccolo et al 2003 because the correction for qp and s over the whole spectrum could not be performed a new approach to estimate spectral parameters was applied we defined the new notion of holed spectrum to specify a spectrum lacking corrected spectral amplitude values within a certain frequency range whereas we referred to a whole spectrum to specify when the entire analyzed frequency band was used a detailed statistical analysis showed that dealing with the holed spectrum did not lead to significant differences in the estimate of spectral parameters displacement holed spectra corrected by the attenuation and site response were then used to estimate source parameters seismic moments ranged from 1017 to 1020 dyne cm and source dimensions from 150 to 500 m in general the stress drop values obtained analyzing p wave spectra were very low because they mainly span the range of 0 05 5 bars

monsoon variability and major climatic events between 25 and 0 05 ka bp using sedimentary parameters in the gangotri glacier region garhwal himalaya india abstract gangotri glacier has attracted international attention for its rapid rate of retreat it is one of the best studied himalayan glaciers however there are no unanimous views about the history of climate change for the gangotri glacier we prepared the lithologs textural logs by making two trenches in the kame terraces and analysed it in detail for sediment grain parameters and 14c ams dates to infer the depositional sedimentary environments monsoon variability and major climatic events in the gangotri glacier region the sedimentary parameters and geomorphic analysis revealed that the sediments of the kame terraces are consolidated to semi consolidated stratified very coarse to fine grained layers of sand silt and clay with few gravels and sedimentary structures the sediment size indicating energy of the depositional environment varies from medium to fine sand 1 02 2 26 the standard deviation is poorly sorted 0 89 1 46 which describes that the energy of the depositional environment is continuously fluctuating the positive skewness 0 32 0 98 indicates the excess of finer sediments and dominance of low energy whereas very leptokurtic kurtosis 2 28 4 47 describes the fluctuating energy conditions the present study explains the glacial stages and weak indian summer monsoon ism around 19 5 14 5 13 1 10 1 8 6 7 5 2 2 0 54 0 08 ka bp and warm and intense ism during 23 9 22 7 19 4 1 15 0 05 ka bp the higher percentage of clay in both the trenches around 0 65 0 2 ka bp 1300 1750 ad and higher percentage of silt and low clay content around 1 15 0 55 ka bp 800 1400 ad validates the little ice age lia and medieval warm period mwp respectively

spatial mapping of the b value at mount etna italy using earthquake data recorded from 1999 to 2005 1 the spatial pattern of the b value of the frequency magnitude relation has been analyzed using gridding techniques beneath mount etna italy a regional data set of 2900 events with md duration magnitude 1 5 up to 15 km depth occurring between august 1999 and december 2005 has been used two regions with an abnormally high b value have been found one centered beneath the southern part of the valle del bove above the 6 km below sea level bsl deep basement and the other beneath the summit region 2 km bsl east of the central craters we can infer that these high b value anomalies are regions of increased crack density and or high pore pressure related to the presence of nearby magma storage this interpretation is supported by all the available geophysical evidence such as tomographic studies and geodetic deformation measurements the data set has also been subdivided into five periods corresponding to different phases of volcanic activity 2001 preeruption 2001 eruptive 2002 2003 preeruption 2002 2003 eruptive and 2002 2003 posteruption the minimum magnitude of completeness mc and the b value were computed for each period a volume of anomalously high b values can be observed in each of these periods except for the 2002 2003 preeruption interval this approach has allowed the detection of the transient presence of magmatic intrusions during the various periods evaluated

some aspects of source characteristics of the 19 september 1985 michoacan earthquake and ground motion amplification in and near mexico city from strong motion data abstract the fourier amplitude ratio of the 19 september m s 8 1 to the 21 september 1985 m s 7 6 michoacan earthquakes obtained from data in and near mexico city increases from about 3 5 at 0 5 hz to about 10 at 0 2 hz this increase is neither seen in the coastal data nor in the teleseismic broadband gdsn p wave spectra it is also not predicted by 2 or gusev9s scaling laws we tentatively attribute the increase at frequencies of less than 0 5 hz to a special path and or a depth of energy release effect for the 19 september earthquake the damage to mexico city is mostly related to 0 5 hz energy since at f 0 5 hz the fourier amplitude ratios in and near mexico city along the coast and at teleseismic distances are nearly equal we attribute this energy to the source characteristics of the 19 september earthquake the evidence suggests that the 19 september was about twice more energetic at f 0 5 hz than expected from scaling laws and from spectral regression of coastal earthquakes recorded in mexico city the analysis of strong motion data recorded in mexico city shows that the ground motions in the lake bed zone are amplified by 8 to 50 times with respect to a hill zone site in ciudad universitaria the frequency at which the maximum relative amplification occurs varies from site to site and lies between 0 2 and 0 7 hz the data suggest that f o 4 h where f o frequency at which maximum relative amplitude occurs and and h are the shear wave velocity and the thickness of the clay layer respectively relatively small if any nonlinear behavior of the clay is found at strains of about 0 2 per cent during the great 19 september earthquake for a given lake bed site maximum relative amplitude and f o are roughly constant independent of magnitude depth and azimuth of sources located more than about 200 km ground motion at lake bed sites in mexico city with f o 0 5 hz appear to be amplified 75 times with respect to hard rock coastal sites at equal distances from the source this is also confirmed by m l calculation of the 19 and 21 september earthquakes for the 19 and 21 september earthquakes the average values of m l at hard rock coastal sites 100 distance 250 km are 7 4 and 6 7 whereas they are 8 7 and 8 4 in the lake bed zone distance 300 km respectively

mass dependent cadmium isotopic variations in nature with emphasis on the marine environment abstract we report a survey of natural mass dependent cadmium isotope fractionation measured by thermal ionization mass spectrometry using a double spike technique ds tims over sixty samples of natural terrestrial cd from diverse environments including morb oib continental loess hydrogenic and hydrothermal ferromanganese deposits and sphalerites both oceanic and from major continental ore deposits were analysed our results are expressed in terms of e 112 110 cd which are deviations in 112 cd 110 cd from our in house jmc cd standard in parts per 10 4 the total e 112 110 cd variation is relatively small with a range of only 5 e units and is one to two orders of magnitude smaller than that previously found in meteorites the morb oib and loess e 112 110 cd values are similar and provide a good estimate for the bulk silicate earth bse value which is 0 95 0 12 relative to our cd standard e 112 110 cd 0 16 relative to munster jmc cd taken together these data suggest little cd isotope fractionation takes place during crust mantle segregation cd isotopic compositions of continental sphalerite zns deposits worldwide and high temperature oceanic hydrothermal sulphides show remarkably similar e 112 110 cd values consistent with our estimate for the bse in contrast mid temperature oceanic sulphides from a single extinct hydrothermal chimney display over 4 e units variation along with the most negative values these variations are most probably caused by precipitation redissolution of sulphide phases en route within the hydrothermal system the e 112 110 cd variability found in worldwide marine fe mn deposits reflects the seawater cd isotope signal upon precipitation from ambient seawater a decrease in e 112 110 cd is observed in passing from shallow water fe mn deposits to those from deeper waters 2000 m depth this shift is explained by biological fractionation related to the uptake of dissolved seawater cd by phytoplankton in the upper water column the relatively uniform e 112 110 cd values close to zero at great depths are consistent with regeneration and remineralization of cd at depth our data suggest that cd isotopes much like the cd ca ratio in foraminifera could potentially serve as a proxy for past changes in biological productivity the temporal cd isotope record in a fe mn crust archive at 2000 m depth from the ne atlantic suggests no gross long term changes in cd cycling took place over the past 8 ma

planktonic foraminiferal cd ca paleonutrients or paleotemperature records of cd ca in planktonic foraminiferal calcite of globigerinoides bulloides in cores from the subantarctic region of the southern ocean show large glacial interglacial variations with lower cd ca by 0 06 0 10 mol mol 1 at glacial times interpretation of these records in terms of lower dissolved phosphate and inferred higher glacial nutrient utilization has significant implications for glacial atmospheric carbon dioxide pco2 draw down however box core top data for g bulloides in the north atlantic suggest that the incorporation of cd into planktonic foraminifera relative to seawater dcd is temperature sensitive dcd 0 637 exp 0 15t when the subantarctic planktonic cd ca records are corrected for this temperature dependence they show little or no glacial interglacial diferences if as seems likely this observation can be interpreted to indicate a minimal change 0 5 mol kg 1 in surface water phosphate concentrations then the explanation for lowered glacial pco2 must be looked for elsewhere

pattern of retreat and related morphological zones of gangotri glacier garhwal himalaya india abstract gangotri one of the longest valley glaciers of the garhwal himalaya has attracted global attention due to rapid rate of retreat it is characterized by supraglacial moraines supraglacial lakes intensive crevasses active and inactive tributary glaciers which were mainly responsible for the enhanced recession rate of the glacier however contrary to the generally accepted notion of global warming the gangotri glacier has been experiencing diminishing rates of retreat during last five decades high retreat rate of 38 m y observed in 1970s has been reduced in 1980s and maintaining the similar trend in the recent decades with reduced rate of retreat around 10 m y in 2015 the measurement of equilibrium line altitude ela and ablation area over the last few decades also explained that the response of gangotri glacier is not in pace with the global warming trend glacial gl and glacio fluvial gf features have been identified as the marker morphological zones which provides information about pattern of retreat and ela the sediment size decreases whereas sorting roundness and percentage of matrix increases from gl gf zone the glacial zone contains the primary sediments and provides information about the pattern of retreat and ela the glacio fluvial outwash plain exhibits modification of glacial signatures and often contains secondary sediments further different rate of fluctuation observed in different glaciers indicate that the glaciers are not uniformly responding with change in climatic conditions especially with respect to global warming such observations and present study suggest that fluctuation of a glacier is not only controlled by global warming induced temperature but also governed by characteristics of the glacier and local morphological factors hence the analysis of the pattern of retreat ela and retreat related morphological zones provide real information and precise glacial history of the area

source parameters from locally recorded aftershocks of the 9 january 1982 miramichi new brunswick earthquake abstract source parameters are derived from 111 locally recorded three component seismograms of 40 aftershocks magnitude 1 0 to 3 5 of the 9 january 1982 miramichi new brunswick earthquake this data set greatly expands the set of three component data recorded at small source to receiver distances in eastern north america preliminary analysis showed that some aftershock spectra were modified by strong site effects the need to understand and account for site effects when analyzing the aftershock data in terms of simple source models led to a two part data analysis first site effects were modeled as a seismic wave resonance in a thin layer 0 to 10 m of low seismic impedance glacial till over a high seismic impedance bedrock half space second we calculated source parameters from sh wave seismograms and amplitude spectra incorporating what had been learned about site resonances correcting for obvious site effects partially succeeded in reducing scatter in the source parameter determinations but some site dependent discrepancies remain seismic moments range from 1 10 18 to 5 10 20 dyne cm and corner frequencies from 5 to 45 hz brune model stress drops primarily range between 5 and 300 bars stress drop apparently increases with increasing seismic moment trends in apparent stress calculated from radiated energy and seismic moment parallel trends in stress drop corner frequencies from these locally recorded data are greater than those derived from regionally recorded l g waves for earthquakes of comparable moment this result contradicts a recently proposed m 0 4 constant source scaling law based primarily on l g data

planktic foraminiferal sedimentation and the marine calcite budget 1 the vertical flux and sedimentation rate of planktic foraminiferal tests are quantified and a global planktic foraminiferal cac0 3 budget is presented test and calcite flux rates are calculated according to the distribution of species obtained from multinet and sediment trap samples modern planktic foraminiferal population dynamics are discussed as a prerequisite for the quantification of the calcite budget highlighting the importance of ecological autecological e g reproduction and biogeochemical conditions that determine the presence or absence of species to complete the open marine particulate caco 3 inventory the contribution of coccolithophores pteropods and calcareous dinophytes is discussed based on the studied regions the global planktic foraminiferal calcite flux rate at 100 m depth amounts to 1 3 3 2 gt yr 1 equivalent to 23 56 of the total open marine caco 3 flux the preservation of tests varies on a regional and temporal scale and is affected by local hydrography and dissolution during most of the year off peak periods many tests dissolve above 700 m water depth while settling through the water column with on average only 1 3 of the initially exported caco 3 reaching the deep seafloor pulsed flux events mass dumps of fast settling particles yield a major contribution of tests to the formation of deep sea sediments on average 25 of the initially produced planktic foraminiferal test cac0 3 settles on the seafloor the total planktic foraminiferal contribution of caco 3 to global surface sediments amounts to 0 36 0 88 gt yr 1 32 80 of the total deep marine calcite budget

attenuation and source properties at the coso geothermal area california we use a multiple empirical green s function method to determine source properties of small m 0 4 to 1 3 earthquakes and p and s wave attenuation at the coso geothermal field california source properties of a previously identified set of clustered events from the coso geothermal region are first analyzed using an empirical green s function egf method stress drop values of at least 0 5 1 mpa are inferred for all of the events in many cases the corner frequency is outside the usable bandwidth and the stress drop can only be constrained as being higher than 3 mpa p and s wave stress drop estimates are identical to the resolution limits of the data these results are indistinguishable from numerous egf studies of m 2 5 earthquakes suggesting a similarity in rupture processes that extends to events that are both tiny and induced providing further support for byerlee s law whole path q estimates for p and s waves are determined using the multiple empirical green s function megf method of hough 1997 whereby spectra from clusters of colocated events at a given station are inverted for a single attenuation parameter with source parameters constrained from egf analysis the estimates which we infer to be resolved to within 0 01 sec or better exhibit almost as much scatter as a function of hypocentral distance as do values from previous single spectrum studies for which much higher uncertainties in individual estimates are expected the variability in estimates determined here therefore suggests real lateral variability in q structure although the ray path coverage is too sparse to yield a complete three dimensional attenuation tomographic image we invert the inferred value for three dimensional structure using a damped least squares method and the results do reveal significant lateral variability in q structure the inferred attenuation variability corresponds to the heat flow variations within the geothermal region a central low q region corresponds well with the central high heat flow region additional detailed structure is also suggested

simultaneous determination of site responses and source parameters of small earthquakes along the atotsugawa fault zone central japan velocity seismograms recorded at nine local stations from 102 small earthquakes on the atotsugawa fault zone central japan with seismic moment from 3 10 17 to 3 10 21 dyne cm are analyzed to obtain the s wave spectra a genetic algorithm is applied to determine the earthquake source parameters and site responses simultaneously the stability of both site responses and source parameters are experimentally tested as well as the effects of different q models the resulting source parameters show that the stress drops appear to vary systematically with the location of earthquakes events located on the mozumi fault or the junction of the mozumi and the atotsugawa faults have higher stress drops than those on the creeping section and southernmost part of the atotsugawa fault the relationship between seismic moment and corner frequency constructed by combining our results and those of iio 1986 for other regions in japan shows that a single scaling relation does not apply in a moment range of 10 10 to 10 25 dyne cm a steplike change in scaling relationship occurs between 5 10 18 and 5 10 20 dyne cm corresponding to corner frequencies between 15 and 25 hz this observation suggests that earthquakes are most likely a multihierarchical system divided by characteristic sizes according to aki9s 1980 model a characteristic source dimension 100 200 meters may represent a critical size of the barriers distributed in the fault zone at which the barrier effects are balanced by the dynamic effect of the source process

spatially variable response of himalayan glaciers to climate change affected by debris cover the present state and future evolution of himalayan glaciers has been controversial an analysis of remotely sensed frontal changes and surface velocities from glaciers in the greater himalaya between 2000 and 2008 shows large regional variability in the responses of himalayan glaciers to climate change

evolution of a debris covered glacier in the western himalaya during the last four decades 1971 2016 a multiparametric assessment using remote sensing and field observations abstract this study assesses the response of the panchi nala glacier bhaga basin western himalaya to climate change by monitoring multiple glacier parameters namely length area debris cover snowline altitude sla surface ice velocity siv and surface elevation change h these parameters were analysed using high resolution satellite images corona kh 4b and sentinel 2 msi and medium resolution ones landsat tm etm oli and terra aster acquired between 1971 and 2016 along with extensive field observations considering only dimensional changes the glacier appears to have low rates of recession 4 54 2 56 m y 1 and deglaciation 0 11 0 04 y 1 over the study period 1971 2016 however siv and h values reveal a significant slowdown 33 87 1992 93 2015 16 and an extensive lowering 1 62 0 06 m y 1 2000 2013 on the glacier the debris cover area and sla also increased by 23 50 1 74 and 287 63 m respectively during 1971 2016 increase in the mean winter minimum temperature and decrease in the winter snowfall are probably the main drivers of glacier depletion we conclude that the significant slowdown extensive surface lowering development of a proglacial lake and appearance of the supraglacial lakes collectively indicate a severe glacier degeneration this forewarns that the glacier may experience an accelerated pace of wastage in the future

temporal fluctuations and frontal area change of bangni and dunagiri glaciers from 1962 to 2013 dhauliganga basin central himalaya india abstract glaciers have been receding for the last 100 years in many glaciated regions of the world and the rate of recession has accelerated during the last 60 years recent assessments of changes in glaciers in the himalaya have usually recognized their variable rate of recession the present study deals with snout retreat frontal area vacation and estimation of the equilibrium line altitude ela of bangni and dunagiri glaciers in the dhauliganga basin central himalaya india using multi image satellite data landsat mss 1976 landsat tm 1990 landsat etm 2005 and survey of india topographic maps 1962 1 50 000 along with field surveys 2012 to 2014 for the period of 1962 2013 the meteorological data of the india meteorological department imd and trmm suggested that the central himalaya received less precipitation between 1960 and 1990 because of the less precipitation glaciers receded rapidly during this period the present study shows that bangni and dunagiri glaciers retreated 2080 162 m and 484 38 m with average rates of 41 3 2 m a 1 and 9 0 6 m a 1 between 1962 and 2013 respectively during this period bangni and dunagiri glaciers lost about 17 and 11 of their length respectively the result also suggested that bangni glacier vacated 598 948 12 257 m2 frontal area while dunagiri glacier vacated 170 428 7833 m2 frontal area between 1962 and 2013 moreover the estimated ela change for bangni glacier was 64 30 m upward during the study period the geological survey of india gsi 1998a b suggested that the ela of dunagiri glacier rose 28 m between 1984 and 1992 and that the glacier lost 16 106 m3 w e ice with an average rate of loss of 1 04 m w e a 1 the geomorphology of the dunagiri valley reflected that bangni and dunagiri glaciers were joined together in the past nevertheless these two glaciers retreat at different rates indicating that climate change is not the only factor in glacier retreat but that geometry size shape slope and orientation of the glacier and basin topography also plays a major role

evolution of debris flow and moraine failure in the gangotri glacier region garhwal himalaya hydro geomorphological aspects abstract a debris flow occurred in the foreland of gangotri glacier by its former tributary meru bamak glacier between 16 and 19 july 2017 we investigated the debris flow using pre and post event field observations hydro meteorological data along with remote sensing assessments to understand the mechanism and evolution of the debris flow a large volume of sediments 7 9 106 m3 0 1 106 m3 moved from the meru bamak and adjoining neela taal 4380 m a s l during the debris flow depositing 6 5 106 m3 0 1 106 m3 of sediments in the frontal region 4050 m a s l of the gangotri glacier this event transported sediments up to 1 5 km downstream as a debris flow fan type feature during the event 18 of the sediments were transferred by the meltwater stream the stream of the meru bamak completely dissected and exposed the ice cored left lateral moraine of the gangotri glacier this event comprehensively reworked the morainic material and entirely changed the morphology of the pro glacial area a small pro glacial lake area 5075 m2 is also observed at the snout of gangotri glacier because of the blockage by morainic material and sediments a sharp increase in the concentration of suspended sediments ssc reaching 11 370 and 10 605 mg l on july 18 and 19 respectively was recorded at bhojwasa 3 km downstream multiple factors such as recession of gangotri glacier degraded ice cored moraine loose sediments at the front of the meru bamak and continuous rainfall created favourable conditions for the debris flow therefore geomorphic hazards associated with glacial retreat need to be investigated intensively in the himalaya especially in areas where significant glacial retreat is observed lateral moraines are exposed and the unstable slopes are occupied by the tributary glaciers

cadmium zinc copper and barium in foraminifera tests the concentrations of cadmium zinc copper and barium have been determined on 2 mg samples of single species foraminifera populations cleaning techniques were tested using north atlantic core tops and followed by a detailed downcore study for the last 30 000 years in south atlantic core v22 174 raw foram tests cleaned by crushing followed by ultrasonic removal of fine grained material and dissolved in a ph 5 5 acetate buffer contain appreciable amounts of trace elements associated with ferromanganese and alumino silicate contaminants a reductive complexing cleaning treatment reduces ferromanganese contamination by 1 2 orders of magnitude acetate buffers at ph 5 5 complex iron and raise the solubility of ferromanganese oxides these buffers are unsuitable for separating carbonate lattice bound trace elements from the fraction associated with ferromanganese phases improved mechanical and ultrasonic reductive cleaning combined with a mild dissolution in distilled water under 1 atm pco2 reduces contaminant levels another order of magnitude the cd and zn concentrations order 10 8 mole cd mole ca and 10 5 mole zn mole ca of species with low surface area show an increase with decreasing isotopic temperatures this increase is consistent with the increasing concentrations of these metals from low values in surface waters to higher values at depth the variance of cd and zn over the last 30 000 years in the central south atlantic is consistent with the probable variability of the dissolved trace elements at the calcification levels of the species analyzed cu and ba are irreproducible and probably sensitive to residual contaminant phases the trace element content of the tests differs from levels observed in a recent coprecipitation study foraminifera may be a significant vector in zinc cycling in the ocean

attenuation of short period p waves at mount st helens an increase of seismicity occurred at mount st helens between may and july 1998 with more than 900 events md 2 2 recorded by the pacific north west seismograph network this article describes an attempt to estimate the temporal and spatial variation in seismic attenuation using 200 microearthquakes that occurred before january 1995 april 1998 during and after august december 1998 the period of higher seismicity and recorded on three different one component seismic stations epicentral distances of the studied events ranged between 0 5 and 15 km we performed the analysis distinguishing the deep depth 5 5 km from shallow depth 5 5 km events we used the frequency decay method to estimate the quality factor q and station site correction s for p waves in the frequency bands 2 7 and 18 30 hz the results show that the attenuation varies from site to site systematically and decreases with depth lower qp values are obtained for focal depths less than 5 5 km moreover the spatial variations of qp show minimum values 30 in the crater area that are interpreted as due to a low density mass distribution under the crater we find that qp was 30 higher before the period of high seismicity than after this change may be attributed to an increase of pressure in the magma chamber producing new cracks and or reopening of pre existing cracks which are the most viable mechanisms for increasing attenuation

cd ca ratios of in situ collected planktonic foraminiferal tests 1 the cd ca ratios of planktonic foraminiferal tests have been used to reconstruct surface water nutrient utilization and paleoproductivity the reliability of this proxy has hitherto not been comprehensively studied however to fill this gap we present novel cd ca data for in situ sampled and sedimentary planktonic foraminifers of the species globigerinoides ruber g sacculifer globigerina bulloides orbulina universa and globorotalia truncatulinoides from the arabian sea and the north atlantic the cd ca ratios obtained for g ruber sampled from the live habitat generally display a correlation with seawater phosphate content but no such trend is observed for g sacculifer this distinct behavior may reflect different ecological niches or species specific incorporation of cd into the calcite shells of the organisms the cd ca ratios of g ruber g sacculifer and g bulloides from surface sediments are consistently higher than those obtained for live collected specimens of the same species postdepositional alteration of the tests is unlikely to be responsible for these systematic differences rather they appear to reflect a combination of factors including the formation of calcite crusts with high cd contents the different timescales that are represented by in situ and sedimentary foraminiferal tests and the dominance of tests from periods of high productivity in sediments our results also reveal higher cd ca ratios for live g ruber than for settling tests of the same species this suggests that planktonic foraminiferal shells are partially dissolved while they individually settle through the water column sedimentary tests however will be less affected by dissolution processes because these shells are primarily deposited in mass sinking events which feature much higher settling velocities than those experienced by single settling shells

determination of molybdenum isotope fractionation by double spike multicollector inductively coupled plasma mass spectrometry 1 molybdenum isotopic compositions are precisely determined by mc icp ms measurements using a mo double spike the double spike is added prior to chemical purification so that laboratory and instrumental mass fractionations are separated from natural mass dependent fractionation fractionation is determined on four mo mass ratios providing an internal consistency check the external standard reproducibility is at 0 06 per mil on the 98mo 95mo ratio 2 standard deviation using a normal microconcentric nebuliser with a cyclonic spray chamber the minimum quantity of mo is 1 g for high precision results a hydrothermal molybdenite shows fractionation of 0 3 per mil on the 98mo 95mo ratio relative to our standard johnson matthey 1000 g ml 0 3 icp standard solution lot 602332b fine grained sediments show fractionation of 0 1 and 0 3 per mil on the 98mo 95mo ratio the observed mo isotope fractionation is small but resolvable with the presented high resolution technique

response of the himalayan glacial cycles to multiple equilibrium of climate system a review abstract the astronomical theory of milankovitch supports the waxing and waning of ice sheets and polar glaciers by orbital forcing excluding the fact that small changes in solar radiation flux are difficult to reconcile with the amplitude of glacial cycles the numerical model explaining the 100 kyr problem has now revealed that the phase locking mechanism of orbital forcing has started to modulate the climatic transitions since 1 2 myr back and remained locked till present climatic state rial et al 2013 however the true evidence to confirm it is not present the present study is an attempt to comprehend the concept of synchronization of summer insolation modulation and internal climate forcing responsible for glacial interglacial termination present in and around the himalaya tibet and worldwide we present geographical evidences of glaciations from the himalayan tibet region pointing out that responses i e 18 24 kyr and 60 70 kyr bp glaciation events are similar to the progression in climatic data and glaciations cycles for the last 100 kyr the compelling evidence presents a possible explanation towards synchronized modulation of 100 kyr orbital cycles with 41 kyr obliquity cycles coincidently resulting in unprecedentedly large glaciation around the last glacial cycle 60 70 kyr bp and the last glacial maxima 18 24 kys bp by considering the influence of internal and external factors on glacier mechanism we underline the most probable cause of 41 kyr cycle obliquity as the foremost driver of glaciations in the himalaya and tibet on longer timescales we provide several lines of evidence to establish the possible connection of glaciation events and orbital cycles with the help of geographical and geological records consistent with the fact that resonance might be faded through time but the effect of frequency modulation still persists in the system

glacial geomorphology and recent glacial recession of the harmukh range nw himalaya abstract a comprehensive description of the glaciation and glacial geomorphology of the harmukh range northwest himalaya is reported first time in this study the geomorphic system of the range is dominated by glaciation and provides an excellent opportunity to assess the glacial fluctuations from the late quaternary to the present using a time series of the satellite data from 1992 to 2018 the glacier area snout and equilibrium line altitude ela changes of the existing glaciers in the harmukh range were estimated the glacier cover has receded from 7 47 0 58 km2 in 1992 to 6 24 0 62 km2 in 2018 a deglaciation of 16 46 0 24 the glaciers showed an upward shift in ela from 47 m to 80 m during the last two and a half decade the observations revealed that other than the climatic factors the ela change and glacier recessions are influenced by the glacier size mean altitude and the aspect of the glaciers further the high resolution google earth images supplemented by field observations were used for mapping various glacial geomorphic landforms the nature of glacial grooves overdeepenings the height of the lateral moraine deposits and trimlines indicated appreciable thickness of the former glaciers the pattern of the glaciated valleys revealed that the area has predominantly experienced alpine type of glaciation with most of the glaciers centred on the harmukh peak based on the shape and the number of lateral moraine ridges present it is suggested that the area has witnessed three major glacial advances by tracing the outer limits of the glacial valleys moraine boulders and ice scoured terrain it was estimated that the glaciers in the range covered 629 km2 during the glacial maxima the presence of numerous rock glaciers and debris free cirque glaciers on the north eastern slopes of the range indicated a strong climatic and topographical control on the pattern situation and extent of glaciers however there is a need for detailed field based mapping of the glacial geomorphology and geochronological study in order to better understand the nature and extent of paleo glaciation the observed glacier recession and the past climatic variations in this hitherto understudied glaciated region of the kashmir himalaya

overall recession and mass budget of gangotri glacier garhwal himalayas from 1965 to 2015 using remote sensing data thinning rates for the debris covered gangotri glacier and its tributary glaciers during the period 1968 2014 length variation and area vacated at the snout from 1965 to 2015 and seasonal variation of ice surface velocity for the last two decades have been investigated in this study it was found that the mass loss of gangotri and its tributary glaciers was slightly less than those reported for other debris covered glaciers in the himalayan regions the average velocity during 2006 14 decreased by 6 7 as compared with that during 1993 2006 the debris covered area of the main trunk of gangotri glacier increased significantly from 1965 until 2015 with the maximum rate of increase 0 8 0 2 km2 a 1 during 2006 15 the retreat 9 0 3 5 m a 1 was less in recent years 2006 2015 but the down wasting 0 34 0 2 m a 1 in the same period 2006 2014 was higher than that 0 20 0 1 m a 1 during 1968 2006 the study reinforced the established fact that the glacier length change is a delayed response to climate change and in addition is affected by debris cover whereas glacier mass balance is a more direct and immediate response therefore it is recommended to study the glacier mass balance and not only the glacier extent to conclude about a glacier s response to climate change

comparison of satellite derived with ground based measurements of the fluctuations of the margins of vatnajokull iceland 1973 92 vatnajokull iceland is the earth s most studied ice cap and represents a classical glaciological field site on the basis of s palsson s seminal glaciological field research in the late 18th century since the 19th century vatnajokull has been the focus of an array of glaciological studies by scientists from many nations including many remote sensing investigations since 1951 landsat derived positions of the termini of 11 outlet glaciers of vatnajokull were compared with frontal positions of six of these 11 outlet glaciers determined by field observations during the period 1973 92 the largest changes during the 19 year period 1973 92 occurred in the large lobate surge type outlet glaciers along the southwestern western and northern margins of vatnajokull tungnaarjokull receded 1413 112 m 1380 1 m from ground observations and bruarjokull receded 1975 191 m 2096 5 m from extrapolated ground observations between 1973 and 1992 satellite images can be used to delineate glacier margin changes on a time lapse basis if the glacier margin can be spectrally discriminated from terminal moraines and sandur deposits and if the advance recession is larger than maximum image pixel size local knowledge of glaciers is critically important however in the accurate delineation of glacier margins on landsat images

empirical green s function analysis taking the next step an extension of the empirical green s function egf method is presented that involves determination of source parameters using standard egf deconvolution followed by inversion for a common attenuation parameter for a set of colocated events recordings of three or more colocated events can thus be used to constrain a single path attenuation estimate i apply this method to recordings from the 1995 1996 ridgecrest california earthquake sequence i analyze four clusters consisting of 13 total events with magnitudes between 2 6 and 4 9 i first obtain corner frequencies which are used to infer brune stress drop estimates i obtain stress drop values of 0 3 53 mpa with all but one between 0 3 and 11 mpa with no resolved increase of stress drop with moment with the corner frequencies constrained the inferred attenuation parameters are very consistent they imply an average shear wave quality factor of approximately 20 25 for alluvial sediments within the indian wells valley although the resultant spectral fitting using corner frequency and is good the residuals are consistent among the clusters analyzed their spectral shape is similar to the the theoretical one dimensional response of a layered low velocity structure in the valley an absolute site response cannot be determined by this method because of an ambiguity between absolute response and source spectral amplitudes i show that even this subtle site response can significantly bias estimates of corner frequency and if it is ignored in an inversion for only source and path effects the multiple egf method presented in this paper is analogous to a joint inversion for source path and site effects the use of colocated sets of earthquakes appears to offer significant advantages in improving resolution of all three estimates especially if data are from a single site or sites with similar site response

debris flow initiation in proglacial gullies on mount rainier washington article i nfo effects of climate change retreating glaciers and changing storm patterns on debris flow hazards concern managers in the cascade range usa and mountainous areas worldwide during an intense rainstorm in november 2006 seven debris flows initiated from proglacial gullies of separate basins on the flanks of mount rainier gully heads at glacier termini and widespread failure of gully walls imply that overland flow was trans formed into debris flow along gullies we characterized gully change and morphology and assessed spatial distributions of debris flows to infer the processes and conditions for debris flow initiation slopes at gully heads were greater than 0 35 m m 1 19 and exhibited a significant negative relationship with drainage area a break in slope drainage area trends among debris flow gullies also occurs at 0 35 m m 1 representing a possible transition to fluvial sediment transport and erosion an interpreted hybrid model of debris flow initi ation involves bed failure near gully heads followed by sediment recruitment from gully walls along gully lengths estimates of sediment volume loss from gully walls demonstrate the importance of sediment inputs along gullies for increasing debris flow volumes basin comparisons revealed significantly steeper drainage networks and higher elevations in debris flow producing than non debris flow producing proglacial areas the high slopes and elevations of debris flow producing proglacial areas reflect positive slope elevation trends for the mount rainier volcano glacier extent therefore controls the slope distribution in proglacial areas and thus potential for debris flow generation as a result debris flow activity may increase as glacier termini retreat onto slopes inclined at angles above debris flow initiation thresholds