eolian deposition in the northeast pacific ocean cenozoic history of atmospheric circulation the mass accumulation rate and grain size distribution of the total eolian component of north pacific pelagic clays have been used to evaluate changes in eolian sedimentation and in the intensity of atmospheric circulation that have occurred during the past 70 m y eolian deposition was relatively low approximately 12 mg cm2 1 000 yr in the late cretaceous and paleocene reflecting an increasingly humid environment a peak in accumulation rates across the paleocene eocene boundary may be the result of episodic volcanism in mexico a sharp decrease in grain size across the paleocene eocene boundary is not readily interpreted fine eolian grain size and the low accumulation rates averaging 8 mg cm2 1 000 yr in the eocene and early oligocene are in agreement with low early tertiary thermal gradients and less vigorous atmospheric circulation large increases in grain size between 37 and 30 m y ago 20 and 10 m y ago and 5 m y ago to the present suggest that atmospheric circulation intensified by a factor of 1 5 1 8 and 1 4 respectively at these times eolian accumulation rates increased from 8 mg cm2 1 000 yr at the eocene oligocene boundary to approximately 25 mg cm2 1 000 yr at the end of the miocene with significant changes at 25 and 13 m y ago increased rates about 25 m y ago probably reflect movement of the core site into the influence of the westerlies and the increase 13 m y ago appears to be a response to steepening thermal gradients and intensifying atmospheric circulation resulting from major expansion of antarctic ice in the mid miocene along with a general increase in global aridity in the late cenozoic an order of magnitude increase in eolian accumulation rates 25 to 226 mg cm2 1 000 yr in pliocene pleistocene time coincides with the onset of northern hemisphere glaciation and consequent climatic deterioration the large increase in accumulation rates in pliocene pleistocene time coincides with a relatively smal increase in the intensity of atmospheric circulation compared to that in oligocene and miocene time suggesting that the increased deposition rates were the result of an increase in global aridity in glacial times rather than a further increase in the vigor of the global wind systems

a comparison between the tectonic stress measured in situ and stress parameters from induced seismicity at monticello reservoir south carolina during may and early june 1979 five three component digital seismographs were deployed near the monticello reservoir south carolina to determine the stress drops of reservoir induced earthquakes and compare them with earlier hydrofracture stress measurements of zoback and hickman this issue records for 327 events were obtained 10 of these events each recorded on four or more stations were analyzed to determine stress drops depths for the 10 events ranged from 0 5 to 1 4 km fault plane orientations were calculated from an inversion of the body wave displacements individual radiation pattern corrections were applied in calculating the moments at each station final estimates of seismic moment were obtained by averaging logarithmically the estimates from each component for each event an arithmetic moment was obtained from the individual estimates of the source radius and stress drop was then calculated once from the final estimates of seismic moment and source radius for each event moments of the 10 digitally recorded earthquakes ranged from 2 5 1017 to 2 7 1018 dyne cm for the p wave data and from 4 6 1017 to 4 6 1018 dyne cm for the s wave data the stress drops s wave data only generally ranged from about 0 2 to 4 bars four earthquakes were recorded by a strong motion instrument at the dam site magnitudes m for these events ranged from 2 8 to 3 0 moments taken as averages of the values from each component ranged from 1 7 to 3 4 1020 dyne cm and the stress drops from 13 to 92 bars large differences between the corner frequencies of the two components factors of 2 5 and 4 for two of the events correspond to a large relative uncertainty for these stress drop values nevertheless tens of bars of stress are apparently released for the largest events in the monticello sequence but only a few bars are released for the smaller magnitude events in comparison the in situ stress data measured in two holes give an estimate of shear stress of about 45 bars at 0 2 km depth and 30 to 70 bars at 1 km depth in the northern hole and from 15 20 bars near the surface to almost 70 bars at depth in the southern hole the variation in shear stress inferred from in situ measurements at the deeper levels indicates an inconsistency between the thrust faulting mechanisms of the earthquakes and the state of stress which is more consistent with thrust faulting at 0 2 km depth and strike slip or normal faulting below thus the estimates of shear stress from in situ measurements are of the same order as the stress drops of the m 2 8 3 0 events but about 1 order of magnitude larger than the stress drops obtained for the smaller events

earthquake ground motion estimation using strong motion records a review of equations for the estimation of peak ground acceleration and response spectral ordinates abstract engineering seismology is the link between earth sciences and engineering the main input of engineering seismology in engineering design are loading conditions which must satisfy certain conditions regarding their level and frequency of occurrence during the lifetime of a structure one method for estimating these loading conditions is through equations based on strong ground motion recorded during previous earthquakes these equations have a handful of independent parameters such as magnitude and source to site distance and a dependent parameter such as peak ground acceleration pga or spectral acceleration and the coefficients in the equation are usually found by regression analysis this review examines such equations in terms of data selection accelerogram processing techniques of the strong motion records used to construct the equations the characterisation of earthquake source travel path and local site used and regression techniques employed to find the final equations it is found that little agreement has been reached in the past 30 years of ground motion estimation relation studies workers have chosen their techniques based on the available data which varies greatly with geographical region also it is noted that there is a need to include more independent parameters into ground motion estimation equations if the large uncertainties associated with such equations are to be significantly reduced the data required to do this is unfortunately scarce

sedimentation at manop site h eastern equatorial pacific over the past 400 000 years climatically induced redox variations and their effects on transition metal cycling gravity cores recovered from manganese nodule project site h 6 33 n 92 49 w show marked downcore variations in the abundance of calcium carbonate organic carbon opal manganese and other components deposited over the past 400 000 years variations in the downcore abundance of organic carbon which ranges from 0 2 to 1 0 can be used to hindcast redox conditions in the surface sediments over this time the results indicate that the depth to the manganese redox boundary varied from about 5 to 25 cm below the seafloor during four major cycles downcore variations in solid phase mn ni and cu can be produced by such changes in redox conditions a model which predicts that solid phase mn can be trapped and buried when the mn redox boundary migrates rapidly upward is consistent with the observed organic carbon and mn records and supports the reconstructed redox variations the history of redox variations at site h can be explained by changes with time in surface water productivity major productivity variations at the site occur over 100 kyr cycles with relatively higher productivity occurring during glacial stages thus quaternary climate changes influence surface water productivity redox conditions in sediments and the cycling of transition metals

redox zonation of elements at an oxic post oxic boundary in deep sea sediments abstract deep sea sediments generally provide limited evidence of redox control on the post depositional redistributions of elements this is because only a fraction of any element is reactive and observed elemental distributions are the result of a number of competing processes which are simultaneously active so that redox effects are not dominant a detailed investigation is reported of a core which is unusual in showing unequivocal evidence of direct redox control operating in a homogeneous environment that is relatively free from competing processes a progressive oxidation front has migrated slowly downwards into a uniform turbidite over a long period ca 250 ky the reactive fractions of several redox sensitive elements now show a remarkable degree of organisation around the redox boundary of this front with the different elements exhibiting individual responses solid phase enrichments are not coincident but are arranged in a clear succession of concentration peaks along the redox gradient from oxic to postoxic conditions the succession is mn i fe se and pt cu and pb v zn and sb and u the movement directions of most elements can be inferred from the peak shapes against the homogeneous turbidite background composition the system seems to have been essentially isolated within the sediment for most elements so that no loss or gain can be ascribed to redox processes exceptions are u and v which have been augmented by uptake from ocean bottom waters into the sediments by an efficient redox trap mechanism

quartz albite and diopside solubilities in h 2 o nacl and h 2 o co 2 fluids at 0 5 0 9 gpa the solubility of quartz and incongruent dissolution apparent solubility of albite and diopside in h2o nacl and h2o co2 fluids have been determined at pressures up to 0 9 gpa 9 kbar and temperatures of 500 900 c solubilities of quartz and albite decrease with increasing salt concentration x nacl salt out effect whereas the solubility of diopside increases with increasing x nacl salt in effect quartz solubilities in the systems h2o nacl and h2o co2 are very similar and are proportional to x h2o 2 quartz solubility in nacl rich brines does not change with pressure under the p t conditions of our experiments at 0 9 gpa and 800 c albite solubility in pure water is higher 100 g kg h2o than that of quartz 74 g kg h2o but at nacl concentrations 6 mol these solubilities are very similar albite dissolution is slightly incongruent formation and composition of secondary and quench phases paragonite na margarite amorphous quench spheres indicate that the solution is enriched in sio2 and na2sio3 as fluid composition changes from h2o towards more co2 rich fluids or nacl rich brines the solubilities of albite and quartz decrease by about one order of magnitude but are still measurable at x h2o 0 5 a thermodynamic analysis of new quartz solubility data for h2o co2 fluids at 0 9 gpa indicates that complexing is dominated by sio2 4h2o for water rich fluids but for x h2o 0 7 the mean solvation number decreases to 3 this speciation is similar to that reported previously for lower pressures and is in agreement with recent high p t spectroscopic data for the system h2o sio2 for dissolution of quartz in both h2o co2 and h2o nacl fluids the molecular proportions of silica to water are almost the same at any x h2o assuming similar non ideal water salt interactions irrespective of whether the water is in the fluid or is complexed with silica then the speciation of silica appears to be similar in both h2o co2 and h2o nacl fluids under the experimental conditions we conclude that the speciation of silica in both h2o co2 and h2o nacl fluids at 0 9 gpa and 800 c is comparable is dominated by si oh 4 2h2o and or hydrated species with lower hydration numbers and is also comparable to that proposed for lower p t conditions

the effect of crustal structure on strong ground motion attenuation relations in eastern north america strong ground motion attenuation relations are usually described by smoothly decreasing functions of distance however consideration of wave propagation in the crust suggests that attenuation relations should be more complex such complexity may be present in strong ground motion data for eastern north american earthquakes which show amplitudes in the distance range of 60 to 150 km that lie above the trends at smaller and greater distances using a wavenumber integration method to compute green s functions and close in recordings of several earthquakes as empirical source functions we have generated synthetic seismograms that are in good agreement with regional and strong motion recordings of eastern north american earthquakes from these synthetic seismograms we have shown that the observed interval of relatively high amplitudes may be attributable to postcritically reflected s waves from the moho the presence and location of the interval of relatively high amplitudes is highly dependent on the crustal velocity structure and may therefore be expected to show regional variation however for any realistic structure model there will be a transition in the attenuation relation from an interval at shorter distances less than about 100 km that is dominated by direct waves to an interval at greater distances that is dominated by postcritically reflected waves the synthetic seismograms have response spectral velocities that match those of the recorded data and their m blg values are in good agreement with observed values

an improved alpha scintillation counting method for determination of th u ra 226 th 230 excess and pa 231 excess in marine sediments in a previous paper it was shown that thick source counting is a simple means for determining th u th 230 excess and pa 231 excess concentrations and hence sedimentation rates for deep sea sediments here it is shown that radon escape can lead to inaccurate results if powdered samples are used and that this problem can be overcome by preparing samples as a borate glass before measurement glassed samples also permit a novel measurement of the ra 226 content by measurement of the post fusion buildup of rn 222 a determination shown to be necessary for near surface sediments that have a deficit of ra 226 it is also shown that po 210 is lost during the fusion and that this loss can be allowed for in the calculations the above observations are found on comparisons of measured and calculated count rates for several th and u standards and on comparisons with spectrometry results from four sets of deep sea core samples

geochemistry and morphology of metalliferous sediments and oxyhydroxides from the endeavour segment juan de fuca ridge abstract we present first data on the geochemistry mineralogy and morphology of near vent sediments 35 and 200 m from active vent and ridge flank sediments approximately 3 km from the vent field as well as oxyhydroxide deposits from the endeavour segment juan de fuca ridge the purpose of the study was to understand better the origin and characteristic features of metalliferous sediments associated with base and precious metal massive sulfides in volcanic terrains hydrothermal components in sediments are fe si s rich and mn fe si rich phases sulfides and barite which were exclusively derived from plume fallout sulfides are only a minor constituent of near vent sediments 2 4 wt and were not detected in ridge flank sediments the study suggests that the distribution of hydrothermal phases and associated elements in near vent and ridge flank sediments is affected mainly by processes of agglomeration dissolution absorption and settling that take place within a plume and to a lesser extent post depositional processes rapid deposition of sulfides in the vicinity of the vents is reflected in a sharp drop of the cu concentrations in sediments with increasing distance from the vents besides sulfides important carriers of pb cu zn and co in near vent sediments are fe mn oxyhydroxides that occur together with silica as aggregates of gel like material and flaky particles and as coatings on filaments away from the vents trace metals are mostly in fe mn oxyhydroxides and authigenic fe rich montmorillonite oxyhydroxides at the main endeavour field are interpreted to have originated from oxidation of mound sulfides accompanied by precipitation of primary fe oxyhydroxide silica from low temperature fluids at the mothra field seafloor deposits and chimney crusts composed of fe oxyhydroxide mn silica are considered to be direct precipitates from hydrothermal fluids that have been less diluted with seawater oxyhydroxide deposits exhibit unique microtextures that resemble mineralized microorganisms and may indicate existence of diverse microbial communities

in situ raman spectroscopic investigation of the structure of subduction zone fluids 1 in situ raman spectra of synthetic subduction zone fluids kalsi3o8 h2o system were measured to 900 c and 2 3 gpa using a hydrothermal diamond anvil cell the structures of aqueous fluid and hydrous melt become closer when conditions approach the second critical endpoint almost no three dimensional network was observed in the supercritical fluid above 2 gpa although a large amount of silicate component is dissolved suggesting that the physical and chemical properties of these phases change drastically at around the second critical endpoint our experimental results indicate that the fluids released from a subducting slab change from aqueous fluid to supercritical fluid with increasing depth under the volcanic arcs

depth of seismicity in the imperial valley region 1977 1983 and its relationship to heat flow crustal structure and the october 15 1979 earthquake focal depths from over 1000 earthquakes occuring between 1977 and 1983 in the imperial valley southern peninsular ranges are used to study relationships between the depth of seismicity heat flow and crustal structure this study used relocated a and b quality events from the california institute of technology catalog that were carefully selected to insure focal depth precision of 2 km regional variations in focal depth appear to be related to regional heat flow variation whereas local variations in focal depth especially in the central imperial valley may be related to crustal structure these variations are studied by rheologic modeling a comparison of focal depths of earthquakes occurring before and after the october 15 1979 m 6 6 earthquake indicates that aftershocks during the first 2 months of the sequence were 2 3 km deeper than earthquakes occurring in other time periods the deepest earthquakes in imperial valley are spatially associated with a subbasement dome near the northern end of the imperial fault this dome coincides with the region where the imperial fault undergoes a transition from stick slip behavior to aseismic fault creep models of slip during the 1979 mainshock are also compared with premainshock and postmainshock seismicity a relocation of the 1940 m 7 1 mainshock suggests that this sequence began by rupturing the same portion of the fault that experienced maximum slip during the 1979 mainshock

piston core record of late paleogene 31 ma to recent seafloor hydrothermal activity in the southwest pacific basin a large diameter piston core containing 8 35 m of metalliferous sediment has been recovered from a small abyssal valley in the remote southwest pacific basin 31 42 194 s 143 30 331 w 5082 m water depth providing unique insight into hydrothermal activity and eolian sedimentation there since the early oligocene a combination of fish teeth sr isotope stratigraphy and inaa geochemical data reveals an exponentially decreasing hydrothermal flux 31 ma to the present although hydrothermal sedimentation related to seafloor spreading explains this trend a complex history of late eocene early oligocene ridge jumps propagating rifts and plate tectonic reorganization of south pacific seafloor could have also played a role a possible hiatus in deposition as recorded by changes in core composition just below 2 m depth is beyond the resolution of the fish teeth sr isotope dating method employed here however the timing of this interval may be coincident with extinction of the pacific farallon ridge at 20 ma a low flux eolian component accumulating at this site shows an increase relative to the hydrothermal component above 2 m depth consistent with dust generating continental sources far to the west australia new zealand this is the first long term paleoceanographic record obtained from within the south pacific bare zone rea et al 2006 an anomalous region where pacific seafloor has largely escaped sediment accumulation since the late cretaceous

average seismic source parameter relations for plate margin earthquakes abstract empirical mb ms and mo data are used to develop an average spectral scaling relation for plate margin earthquakes using equations based upon a rectangular bilateral dislocation model with uniform rupture velocity the spectra give values of fault rupture length and width static stress drop and average fault displacement as a function of mb ms and mo compared to mid plate earthquakes of the same seismic moment the large average plate margin earthquake has a bigger rupture length rupture area and average fault displacement and a smaller rupture width and static stress drop

sediment load and floodplain deposition rates comparison of the fly and strickland rivers papua new guinea 1 rates of aggradation and infilling of accommodation space along lowland channels in response to postglacial sea level rise should depend on sediment supply the strickland and fly rivers join at just 6 m above sea level and have experienced the same holocene sea level rise historically the strickland has carried about 7 times the sediment load and 1 4 times the water discharge as the fly therefore we hypothesize that the lowland strickland floodplain should be more developed and consequently should presently be capturing proportionately less sediment than the floodplain of the lowland fly river we use mine derived elevated pb and ag concentrations in 111 shallow 1 m floodplain cores collected in 2003 to determine deposition rates across the lower strickland floodplain sediment deposition rates decrease across the floodplain with distance from the channel bank and the average rate of deposition is 1 4 cm a over the first 1 km overbank deposition along the lowland sandbedded strickland results in 13 loss of the total load 0 05 km of channel length of the main stem deposition rates over the first 1 km from the channel bank on the strickland are about 10 times those on the fly for estimated natural sediment loads however the proportional loss per channel length on the strickland is less than that on the fly 0 09 km of main stem channel length because of an extensive network of tributary and tie channels that convey sediment to the floodplain on the fly furthermore the lateral migration of the strickland channel is 5 times that on the fly such that most overbank deposits on the strickland are returned to the channel causing the net loss of sediment to the floodplain to be small we conclude that the strickland river which has a much higher overbank deposition rate than the fly river as a function of distance from channel bank nonetheless has significantly less net accumulation than the fly because 1 a large proportion of the sediment load is conveyed up tributaries and tie channels on the fly and 2 lateral migration which presumably results from the higher load on the strickland sweeps sediment back into the channel hence our field observations support our initial hypothesis though the primary reason for this is because of active lateral migration rather than low overbank deposition rates

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

geology of the area of induced seismic activity at monticello reservoir south carolina this study provides geological background information necessary for an evaluation of the earthquake hazard in an area of induced seismic activity at monticello reservoir south carolina this region contains a thick stratified sequence of proterozoic z and cambrian metasedimentary and metavolcanic rocks in the early to middle paleozoic this sequence was recrystallized and deformed under metamorphic conditions that ranged from greenschist to amphibolite facies and experienced at least two episodes of folding the region has been intruded by late kinematic to postkinematic granitoid plutons of silurian and carboniferous ages and by numerous northwest trending diabase dikes of late triassic and early jurassic age the region south of monticello reservoir in the carolina slate belt experienced two episodes of faulting in the late paleozoic and or early to middle mesozoic the older group of faults trends approximately east has only small displacements and is characterized by extensive silicification of the fault zones the younger group of faults trends approximately north has experienced dip slip displacements up to 1700 m and is characterized by carbonate mineralization in the fault zones both sets of faults are cut by an undeformed diabase dike of late triassic or early jurassic age the induced seismic activity around monticello reservoir is occurring in a heterogeneous quartz monzonite pluton of carboniferous age although laterally extensive faults have not been found in the vicinity of the reservoir the pluton contains large enclaves of country rock and is cut by numerous diversely oriented small faults and joints these local inhomogeneities in the pluton together with an irregular stress field are interpreted to control the diffuse seismic activity around the reservoir in view of the apparent absence of lengthy faults it is unlikely that a large magnitude earthquake will occur in response to the stress and pore pressure changes related to the impoundment of monticello reservoir

the geochemistry of redox sensitive trace metals in sediments abstract we analyzed the redox sensitive elements v mo u re and cd in surface sediments from the northwest african margin the u s northwest margin and the arabian sea to determine their response under a range of redox conditions where oxygen penetrates 1 cm or less into the sediments mo and v diffuse to the overlying water as mn is reduced and remobilized authigenic enrichments of u re and cd are evident under these redox conditions with the onset of sulfate reduction all of the metals accumulate authigenically with re being by far the most enriched general trends in authigenic metal accumulation are described by calculating authigenic fluxes for the 3 main redox regimes oxic reducing where oxygen penetrates 1 cm and anoxic conditions using a simple diagenesis model and global estimates of organic carbon rain rate and bottom water oxygen concentrations we calculate the area of sediments below 1000 m water depth in which oxygen penetration is 1 cm to be 4 of the ocean floor we conclude that sediments where oxygen penetrates 1 cm release mn v and mo to seawater at rates of 140 260 60 150 and 5 10 of their respective riverine fluxes using the authigenic metal concentrations and accumulation rates from this work and other literature these sediments are sinks for re cd and u with burial fluxes of 70 140 30 80 and 20 40 respectively of their dissolved riverine inputs we modeled the sensitivity of the response of seawater re cd and v concentrations to changes in the area of reducing sediments where oxygen penetrates 1 cm our analysis suggests a negligible change in seawater re concentration whereas seawater concentrations of cd and v could have decreased and increased respectively by 5 10 over 20 kyr if the area of reducing sediments increased by a factor of 2 and by 10 20 if the area increased by a factor of 3 the concentration variations for a factor of 2 increase in the area of reducing sediments are at about the level of uncertainty of cd ca and v ca ratios observed in foraminifera shells over the last 40 kyr this implies that the area of reducing sediments in the ocean deeper than 1000 m 4 has not been greater than twice the present value in the recent past

kinetics and duration of metamorphic mineral growth in a subduction complex zircon and phengite in the nagasaki metamorphic complex western kyushu japan we applied interface controlled kinetics including interface controlled ostwald ripening and non hydrostatic dissolution precipitation to metamorphic zircon and phengite growth in a high pressure high p metamorphic complex this kinetic modeling yields the growth duration of metamorphic zircon based on the assumption that dissolution and precipitation of zircon is much slower than that of phengite the model was applied to zircon and phengite growth in the nishisonogi unit of the high p nagasaki metamorphic complex western kyushu japan given that detrital zircons that are tens of microns in size remain after metamorphism our model assumption is justified our results show that the duration of metamorphic zircon growth in an individual rock ranges from 10 to 20 myr in general the duration of metamorphic zircon growth in the whole nishisonogi unit is ca 30 myr this prolonged duration implies that high p metamorphism is sustained by continuous subduction of hydrated oceanic crust and overlying trench fill sediments the continuous subduction and accretion of these materials may supply the metamorphic fluid into the high p metamorphic domain in the deeper part of the accretionary prism thereby contributing to interface controlled kinetics in the metamorphic complex

accretion rate of extraterrestrial matter iridium deposited 33 to 67 million years ago iridium measured in 149 samples of a continuous 9 meter section of pacific abyssal clay covering the time span 33 to 67 million years ago shows a well defined peak only at the cretaceous tertiary boundary in the rest of the section iridium ranges from a minimum concentration near 0 35 nanograms per gram in the paleocene to a maximum near 1 7 in the eocene between 63 and 33 million years ago the mean iridium accumulation rate is approximately 13 nanograms per square centimeter per million years correction for terrestrial iridium leads to an extraterrestrial flux of9 3 nanograms of iridium per square centimeter per million years and an estimated annual global influx of 78 billion grams of chondritic matter consistent with recent estimates of the influx of dust meteorites and crater producing bodies with masses ranging from 10 13 to 1018 grams combining the recent flux of objects ranging in mass from 106 to 107 grams with the flux of 1014 to 1015 gram objects indicates that the number of objects is equal to 0 54 divided by the radius in kilometers to the 2 1 power periodic comet showers should increase the cometary iridium flux by a factor of 200 to 600 on a time scale of 1 to 3 million years the predicted iridium maxima more than 30 times background are not present in the intervals associated with the cretaceous tertiary boundary or the tektiteproducing late eocene events

regionalization of crustal coda q in the continental united states a contour map of crustal q sub 0 values for the entire united states is presented based on a scattering model to explain the coda waves of local and near regional earthquakes these coda q sub 0 values are in good agreement with q of lg waves data are obtained from over 250 local earthquakes with most magnitudes between 3 0 and 5 0 recorded by 25 wwssn and 27 lrsm stations throughout the continental united states these two sets of data provide a range of frequencies from 0 5 to 3 5 hz a frequency dependence of q is observed in the range of frequencies considered a power law dependence of the form q q sub 0 f f sub 0 sup eta is assumed the value of frequency dependence eta is found to be maximum in the tectonically active western united states and least in the stable regions of the central and south central united states the lowest q sub 0 values are obtained in the western united states with values ranging from 140 to 200 in the coastal plains average crustal q sub 0 values for the basin and range province vary from 200 to 300 increasing gradually to 400 in the colorado plateau region q sub 0 valuesmore in the columbia plateau vary from 200 to 400 q sub 0 values increase very rapidly along the central and southern rocky mountains from 400 to 800 east of the rocky mountains q sub 0 values increase gradually in the interior plains to a maximum value of around 1300 in the mississippi embayment region farther east q sub 0 values decrease gradually to an almost constant value of 1000 along the appalachian mountains coastal regions of eastern and northeastern united states have a crustal q sub 0 value between 900 to 700 regions of north central and gulf coastal plains show low q sub 0 values ranging from 600 to 400 and less the source factor b f sub p a measure of the intensity of scattering was obtained for several different regions of the continental united states regions of high q sub 0 values exhibit low intensity of scattering less

variability in ground motions root mean square acceleration and peak acceleration for the 1971 san fernando california earthquake data from the 1971 san fernando california earthquake provided the opportunity to study the variation of ground motions on a local scale the uncertainty in ground motion was analyzed by studying the residuals about a regression with distance and by utilizing the network of strong motion instruments in three local geographic regions in the los angeles area our objectives were to compare the uncertainty in the peak ground acceleration pga and root mean square acceleration rmsa about regressions on distance and to isolate components of the variance we find that the rmsa has only a slightly lower logarithmic standard deviation than the pga and conclude that the rmsa does not provide a more stable measure of ground motion than does the pga as is commonly assumed by conducting an analysis of the residuals we have estimated contributions to the scatter in high frequency ground motion due to phenomena local to the recording station building effects defined by the depth of instrument embedment and propagation path effects we observe a systematic decrease in both pga and rmsa with increasing embedment depth after removing this effect we still find a significant variation a standard deviation equivalent to a factor of up to 1 3 in the ground motions within small regions circles of 0 5 km radius we conclude that detailed studies which account for local site effects including building effects could reduce the uncertainty in ground motion predictions as much as a factor of 1 3 attributable to these components however an irreducible component of the scatter in attenuation remains due to the randomness of stress release along faults during earthquakes in a recent paper joyner and boore 1981 estimate that the standard deviation associated with intra earthquake variability corresponds to a factor of 1 35

attenuation relationships of peak ground acceleration and velocity for crustal earthquakes in taiwan strong seismic ground motion data obtained by the taiwan strong motion instrumentation program tsmip and central mountain strong motion array cmsma are used to derive new attenuation relationships for the vertical and horizontal peak ground acceleration pga and peak ground velocity pgv for crustal earthquakes in taiwan more than 7900 three component accelerograms recorded from 51 crustal earthquakes in taiwan with m w magnitudes ranging from 4 0 to 7 1 have been analyzed to study the dependence of peak ground motion parameters on magnitude distance regional and local site effects through attenuation relationships we first found that for both pga and pgv the attenuation relationships decay faster with distance for the vertical component than for the horizontal component also the attenuation relationships decay faster with distance for the vertical pga than for the vertical pgv we further compared the attenuation relationships for three subregions chy iwa and nto and the whole taiwan region twn it is found that the chy area has higher ground motion either in pga or pgv than the other areas especially at near source distances this is because the chy area is located on a thick recent alluvial plain comparison of our new attenuation relationships with strong motion data from the 1999 chi chi earthquake m w 7 7 and the 2003 cheng kung earthquake m w 6 8 shows that the attenuation relationships developed for m w 7 can be extrapolated to make reasonable estimates of strong motion from larger m w 7 earthquakes finally we analyzed the residuals to investigate variations of pga and pgv with respect to site conditions the results show that 1 the residual contour maps especially for the pgv have high consistency with the regional geology and topography of taiwan 2 the pgv residual contours reveal that taipei basin changhua plain chianan plain pingtung valley ilan plain and taitung longitudinal valley have high residual values note that most major metropolitan areas all fall in high residual areas 3 the site classification based on geologic criteria by lee et al 2001 can be simplified into three classes that is class e for soft soils a combination of classes c and d for dense and stiff soils and class b for rocks these three site classes are mostly distributed respectively in the alluvial plains at an elevation less than 50 m in terraces and hills at an elevation less than 1000 m and in high mountainous areas

empirical ground motion attenuation relations for the eastern alps in the magnitude range 2 5 6 3 in this paper we use a large data set of seismometric and accelerometric recordings 3168 vertical and 1402 for each of the horizontal components collected by various networks in the eastern alps to estimate empirical ground motion attenuation relations valid in the magnitude range 2 5 6 3 for distances of up to 130 km relations are developed for horizontal and vertical peak ground acceleration and velocity arias intensity response spectral acceleration and fourier amplitude for 46 periods between 0 1 and 2 sec we adopt a simple magnitude dependent attenuation model predicting closer attenuation curves and decreasing distance attenuation for increasing magnitude we use truncated regression analysis to deal with the problem of non triggering stations with respect to other approaches our solution does not require any discarding of data or the knowledge of which stations did not trigger our relations agree with others suitable for the study region for magnitudes greater than 5 8 while they have a faster attenuation for lower magnitudes in an attempt to reduce the standard deviation we have introduced soil classification into the relation as well as a characterization of sites by means of h v ratios these ratios were estimated either by earthquakes receiver function or by the background seismic noise nakamura s ratios similar to findings in other studies the improvement obtained with soil classification is negligible while h v ratios reduce the standard deviation by up to 22 finally we have investigated the implications of these new relations for seismic hazard assessment considering two sites of interest located in northeastern italy udine and gemona in both cases the difference in the hazard estimates for return periods shorter than 100 years is notable with respect to all other available relations

seismic moments local magnitudes and coda duration magnitudes for earthquakes in central california onscale seismograms recorded at stations in the u s geological survey s usgs central california seismic network calnet have been used to estimate the seismic moment m and local magnitude ml for earthquakes of 1 ml 4 located on the san juan bautista and parkfield sections of the san andreas fault the coyote lake section of the calaveras fault the sargent fault and near livermore these data together with m and ml estimates for 4 ml 6 earthquakes in these areas cannot be fit with a single linear log m versus ml relation rather the data are consistent with log m 1 5 ml 16 for 3 ml 6 with log m 1 2 ml 17 for 1 1 2 ml 3 1 2 and with a slope of to 1 fro 1 2 ml 1 1 2 whereas usgs coda duration magnitude md is consistent with ml for 1 1 2 ml 3 md is larger than ml at ml 1 1 2 and smaller than ml at ml 3 log m can be estimated to a precision of 0 2 for 1 md 3 1 2 earthquakes in central california by applying log m 1 2 md 17 to the md that have been routinely published by the usgs

near source attenuation of peak horizontal acceleration strong motion data recorded within 50 km of the rupture zone were used to study near source attenuation characteristics of horizontal peak ground acceleration for worldwide earthquakes of magnitudes 5 0 to 7 7 the data base consisted of 229 horizontal components of peak acceleration recorded from 27 earthquakes including the 15 october 1979 imperial valley earthquake these data were found to be adequately represented by the functional relationship pga a exp b m r c m d where pga represents the mean of the peak values scaled from the two horizontal components of each recording m is richter magnitude and r is distance from the fault rupture zone peak acceleration was found to be lognormally distributed with a standard error representing a 45 per cent increase in the median estimate the regression analysis statistically confirmed the results of earthquake simulation studies that have predicted peak acceleration to become independent of magnitude and distance in the near field an extensive sensitivity study showed that predictions based on our attenuation relationships are stable with respect to reasonable model and parameter variations an analysis of residuals was used to investigate the behavior of peak acceleration with respect to various earthquake site and recording parameters the more significant findings being 1 a similarity in the level of acceleration recorded on soil or rock 2 larger than average accelerations recorded at sites located on shallow soils or in areas of steep topography 3 larger than average accelerations associated with earthquakes having reverse fault mechanisms and 4 lower than average accelerations recorded in large embedded structures

the 1982 enola arkansas swarm and scaling of ground motion in the eastern united states abstract the north central arkansas swarm which began in january of 1982 and was still active as of december 1983 has produced over 30 000 events three of these events had duration magnitudes greater than 4 0 fifty three locatable events in the magnitude range 3 8 and below were recorded during the 2 1 2 weeks our 10 digital seismographs were in place the hypocentral locations are confined to a tight cluster with a radius of approximately 1 km depths range between 4 and 7 km focal mechanisms determined for 10 of the events show a combination of strike slip and normal faulting source parameters seismic moment source radius and stress drop were calculated for 48 of the events the seismic moments range from 10 18 to 10 21 dyne cm while the stress drops range from 0 2 to 60 bars acceleration spectra are band limited at the high end at 30 hz the stress drops increase with seismic moment up to 10 20 dyne cm but appear to be constant at greater moment values the arkansas source parameters are similar to other body wave source parameters determined from near source investigations of earthquakes in eastern and central north america e g new brunswick and south carolina and in california e g mammoth lakes oroville and anza but differ substantially from lg wave source parameters estimated for earthquakes in the eastern and central united states

removal of230th and231pa from the open ocean concentrations of230th and231pa were measured in particulate matter collected by sediment traps deployed in the sargasso sea site s2 the north equatorial atlantic site e and the north equatorial pacific site p as well as in particles collected by in situ filtration at site e concentrations of dissolved th and pa were determined by extraction onto manganese dioxide adsorbers at site p and at a second site in the sargasso sea site d dissolved230th 231pa activity ratios were 3 6 at sites p and d in contrast for all sediment trap samples from greater than 2000 m unsupported230th 231pa ratios were 22 35 average 29 7 ratios were lower in particulate matter sampled at shallower depths particles filtered at 3600 m and 5000 m at site e had ratios of 50 and 40 results show that suspended particulate matter in the open ocean preferentially scavenges th relative to pa most of the230th produced by decay of234u in the open ocean is removed by adsorption to settling particulate matter in contrast less than 50 of the231pa produced by decay of235u is removed from the water column by this mechanism mixing processes transport the remainder to other sinks

electrical conductivity of the plagioclase nacl water system and its implication for the high conductivity anomalies in the mid lower crust of tibet plateau in order to investigate the origin of the high conductivity anomalies geophysically observed in the mid lower crust of tibet plateau the electrical conductivity of plagioclase nacl water system was measured at 1 2 gpa and 400 900 k the relationship between electrical conductivity and temperature follows the arrhenius law the bulk conductivity increases with the fluid fraction and salinity but is almost independent of temperature activation enthalpy less than 0 1 ev the conductivity of plagioclase nacl water system is much lower than that of albite nacl water system with similar fluid fraction and salinity indicating a strong effect of the major mineral phase on the bulk conductivity of the brine bearing system the high conductivity anomalies of 10 1 and 100 s m observed in the mid lower crust of tibet plateau can be explained by the aqueous fluid with a volume fraction of 1 and 9 respectively if the fluid salinity is 25 the anomaly value of 10 1 s m can be explained by the aqueous fluid with a volume fraction of 6 if the salinity is 10 in case of southern tibet where the heat flow is high the model of a thin layer of brine bearing aqueous fluid with a high salinity overlying a thick layer of partial melt is most likely to prevail

some recent lg phase displacement spectral densities and their implications with respect to the prediction of ground motions in eastern north america abstract lg phase displacement spectral density corner periods of recent earthquakes in central new brunswick and central arkansas are used to point out a potential source of dispersion in the relative scaling of eastern north american strong motion data the corner periods of one of the central new brunswick and several of the larger central arkansas earthquakes are atypical of other events of similar magnitude and seismic moment in the region the maximum far field ground motion of an earthquake is a function of its corner period therefore strong motion data of earthquakes that exhibit atypical characteristics such as a displaced corner period are a source of dispersion in the scaling of that strong motion data if plotted as a function of magnitude or seismic moment

constraints on the mobilization of zr in magmatic hydrothermal processes in subduction zones from in situ fluid melt partitioning experiments the partitioning of zr between high p t aqueous fluids and melts has been investigated in situ in the haplogranite h2o and haplogranite f h2o systems to assess the mobilization of high field strength elements hfse in magmatic hydrothermal processes in subduction zones the partition coefficients d f mzr were determined from zr concentrations measured in situ by synchrotron x ray fluorescence sxrf in both aqueous fluids and f free or f bearing hydrous haplogranite melts equilibrated in diamond anvil cells at 575 to 800 c and 0 3 to 2 4 gpa this experimental approach eliminates the need for internal or external calibrations of the sxrf signal and or post mortem analysis of the melt phase hence decreasing the total uncertainties on d f mzr below 16 above 0 6 gpa zr partitions favorably into the hydrous silicate melt in both f free and f bearing systems with d f mzr that range between 0 19 0 02 and 0 38 0 03 however the relatively high d f mzr values indicate that alkali silica rich aqueous fluids generated by metamorphic devolatilization may contribute significantly to the recycling of hfse in subduction zones the efficient uptake of zr and likely other hfse by subduction zone fluids regardless of their nature aqueous fluid hydrous melt or supercritical fluid supports the idea that the typical hfse depletion recorded in arc magmas does not result from their incompatibility in water rich slab derived fluids but most probably originates from complex fluid melt rock interactions occurring at the slab interface and within the mantle wedge at shallow crustal pressure conditions 800 c and 0 3 gpa zr partitions reversely into the aqueous fluid in the presence of fluorine d f mzr 1 40 0 10 as observed for nb at similar conditions by webster et al 1989 the enrichment of the aqueous phase in hfse zr nb at shallow crustal conditions is likely related to the enhanced peralkalinity of low pressure f bearing aqueous fluid with temperature that provides the favorable conditions for their mobilization via the formation of hfse o si na clusters this mechanism may control the enrichment in hfse and plausibly other rare metals such as ree in early magmatic fluids exsolved from granitic melts leading to the formation of hfse enriched aggregates in shallow magmatic hydrothermal environments e g strange lake and thor lake nechalacho deposit canada galineiro complex spain

attenuation of strong ground motion in canada from a random vibrations approach abstract theoretical relations are developed for the attenuation of horizontal peak ground acceleration pga and velocity pgv in canada with emphasis on eastern canada the theoretical basis is a composite of several approaches at intermediate epicentral distances results from random vibration theory hanks and mcguire 1981 boore 1983 which can be used to describe pga and pgv in terms of shear radiation implied by brune9s 1970 source model are applied to canadian earthquakes motions are extended into the near source region using arguments concerning magnitude scaling joyner and boore 1981 at distances greater than two crustal thicknesses ground motions are attributed largely to the lg phase and are attenuated accordingly nuttli 1982 the resulting attenuation relations for pga and pgv in eastern canada are in excellent agreement with strong motion data from moderate eastern canadian and central united states earthquakes compared to empirical attenuation relationships based on modified mercalli intensity the theoretical model predicts a stronger dependence of peak ground motions on magnitude in other respects amplitude levels and distance decay empirical and theoretical predictions are similar the model predicts that eastern events will have higher peak accelerations but similar peak velocities in comparison to their western counterparts of the same moment magnitude this arises from the relative enrichment of eastern earthquakes in higher frequencies

scaling of ground motion parameters state of stress and focal depth the ground motion parametersrv and ra where r is hypocentral distance v is peak velocity is density and a is peak acceleration are found observationally to be strong functions of stress state and linearly related to focal depth z if the stress state and focal depth are properly taken into account then the ground motion parameters depend on the seismic moment m0 as expected from basic scaling principles that is rv m01 3 and ra is independent of earthquake size regression lines fitted to observations covering broad ranges in seismic moment and focal depth indicate that for extensional and compressional tectonic regimes corresponding to normal and thrust or reverse faulting earthquakes respectively peak acceleration is given by ra 1 08 mpa 3 06 mpa km z normal and ra 5 65 mpa 8 76 mpa km z thrust and for peak velocity rv m01 3 10 4 m2 s n m 1 3 3 00 0 69 km 1 z normal and rv m01 3 10 4 m2 s n m 1 3 4 63 1 82 km 1 z thrust for strike slip earthquakes the data currently are insufficient to define regression fits but such lines would definitely lie between those for the normal and thrust stress regimes these equations are appropriate for ground motion at small hypocentral distance as recorded in a whole space it follows that for comparable hypocentral depth peak acceleration in a compressional tectonic regime for example much of the eastern united states is a factor of about 3 greater than in an extensional regime such as nevada and for peak velocity a similar comparison yields a factor of 2 difference the similarity in behavior of the peak acceleration parameter to crustal strength estimated from byerlee s law of friction with respect to depth and stress state indicates that crustal strength is probably the factor governing the seismic source processes that give rise to the high frequency peak ground motion analysis of the peak acceleration data in the context of crustal strength suggests bounds on this ground motion parameter as recorded at a typical surface site that depend on stress state specifically a normal 0 5 g and a thrust 1 9 g thus the state of stress as well as the focal depth clearly is an important factor to be taken into account in the prediction of seismic ground motion

attenuation relations for strong seismic ground motion in the himalayan region strong motion data from various regions of india have been used to study attenuation characteristics of horizontal peak acceleration and velocity the strong ground motion data base considered in the present work consists of various earthquakes recorded in the northern part of india since 1986 with magnitudes 5 7 to 7 2 using these data relations for horizontal peak acceleration and velocity which are begin gathered log 10 a 1 14 0 31m 0 65log 10 r hfill log 10 v 0 571 0 41m 0 768log 10 r hfill end gathered have been proposed wherea is the peak horizontal acceleration in cm sec2 v is the peak horizontal velocity in mm sec m is body wave magnitude andr is the hypocentral distance in km the proposed relations are in reasonable agreement with the small amount of strong ground motion data available for the northern part of india the present results will be useful in estimating strong ground motion parameters and in the earthquake resistant design in the himalayan region

observations on cretaceous abyssal hills in the northeast pacific abstract an abyssal hills area of 50 60 km in the northeast pacific was studied using bottom transponder navigation closely spaced survey lines and long traverse oblique photography the block faulted north south hills are bounded by scarps commonly with 40 slopes on these steep scarps sedimentation is inhibited and pillow basalts often crop out an ash layer of high acoustic reflectivity at about 7 m subbottom depth blankets the area this ash occurs in multiple beds altered to phillipsite and is highly consolidated a 24 m y age for the ash is based on ichthyolith dates from samples in the overlying sediments acoustically transparent neogene sediments above the ash are thickest in trough bottoms and are absent or thin on steep slopes these neogene sediments are composed of pale brown pelagic clays of illite quartz smectite chlorite and kaolinite dark brown pelagic clays rich in smectite and amorphous iron oxides underlie the neogene surficial sediments manganese nodules cover the bottom in varying percentages the nodules are most abundant near basement outcrops and where the subbottom ash layer is absent

average seismic source parameter relations for mid plate earthquakes mid plate earthquakes which are defined as having their epicenters at least 500 km from plate margins represent a small portion of the total global seismicity however because those occurring within continental interiors are characterized by anomalously large damage areas they are of particular interest empirical mb ms and m o data are used to develop scaling relations for mid plate earthquakes from them it is found that the corner period t o2 of their far field displacement spectra varies as the one fourth power of the seismic moment which indicates that average stress drop increases as seismic moment increases by use of savage s 1972 rectangular bilateral dislocation model the derived spectra of mid plate earthquakes yield estimates of fault rupture length and width average fault displacement and source rise time as a function of seismic moment these relations show that large mid plate earthquakes such as the 1886 south carolina and 1811 and 1812 new madrid events do not require large fault rupture length

scaling differences between large interplate and intraplate earthquakes a study of large intraplate earthquakes with well determined source parameters shows that these earthquakes obey a scaling law similar to large interplate earthquakes in which m 0 l 2 or u l where l is rupture length and u is slip in contrast to interplate earthquakes for which 1 10 5 for for the intraplate events 6 10 5 which implies that these earthquakes have stress drops about 6 times higher than interplate events this result is independent of focal mechanism type this implies that intraplate faults have a higher frictional strength than do plate boundaries and hence that faults are velocity or slip weakening in their behavior this factor may be important in producing the concentrated deformation that creates and maintains plate boundaries

enhanced sedimentation along the equator in the western pacific measurements on cores from the ontong java plateau demonstrate that on equator sediment accumulates more 230th than is produced in the overlying water column in contrast cores from 3 8 n accumulate an amount of excess 230th more nearly equal to that produced in the overlying water column taken together with the observation that both the caco3 and non caco3 components of the sediment accumulate at approximately twice the rate in on equator than in off equator cores broecker et al 1999 this requires either that the rain of the larger amount of organic matter generated above the equatorial upwelling plume entrains excess clay and 230th during its fall to the sea floor or that physical transport processes either in the upper ocean or near the sea bed redistribute sediments in such a way that they preferentially accumulate in a narrow 1 latitude equatorial centered belt

the dependence of peak horizontal acceleration on magnitude distance and site effects for small magnitude earthquakes in california and eastern north america abstract one hundred and ninety free field accelerograms recorded on deep soil 10 m deep were used to study the near source scaling characteristics of peak horizontal acceleration for 91 earthquakes 2 5 m l 5 0 located primarily in california of the six attenuation relationships developed in this study the one considered most reliable is given by the expression ln p h a 2 5 0 1 0 6 2 3 m l 1 0 ln r 7 2 8 where pha is the mean of the two horizontal components of peak acceleration in g m l is local magnitude r is epicentral distance in kilometers and is a random error term with mean of zero and standard deviation of 0 506 an analysis of residuals based on an additional 171 near source accelerograms from 75 earthquakes indicated that accelerograms recorded in building basements sited on deep soil have 30 per cent lower accelerations and that free field accelerograms recorded on shallow soil 10 m deep have 82 per cent higher accelerations than free field accelerograms recorded on deep soil accelerations recorded on rock were found to be similar in amplitude to those recorded on deep soil a separate analysis of site effects for the imperial valley and oroville regions of california indicated that peak accelerations from individual sites can depart significantly from predictions based on broad site classifications an analysis of residuals based on 27 selected strong motion recordings from 19 earthquakes in eastern north america indicated that near source accelerations associated with frequencies less than about 25 hz are consistent with predictions based on attenuation relationships derived for california once site effects and differences in regional magnitude scales are taken into account

the paleoclimatic record provided by eolian deposition in the deep sea the geologic history of wind the mineral component of pelagic sediment is brought to the deep sea by transport in the wind extraction and analysis of this dust allows estimation of the past aridity of the eolian source region via flux determinations and of the intensity of the transporting winds from grain size data these two parameters the grain size and mass flux of dust vary independently there are three significant sources of modern dust eastern and central asia northwest africa and arabia all in the northern hemisphere as the rainfall associated with the intertropical convergence zone is an effective barrier to southerly transport of dust the northern hemisphere is an order of magnitude more dusty than is the southern an asymmetry that has characterized most of the cenozoic eolian flux data show that most of the northern hemisphere was more arid during glacial maxima with 3 to 5 times as much dust transported during glacial stages than during interglacials only northwestern south america varied in the opposite sense the periodicity of quaternary variation in both eolian flux and eolian grain size data is strongly influenced by the milankovitch cycles of orbital variability wind intensities vary on a shorter time scale than the general 100 kyr cycles of glaciation and general aridity eolian grain sizes display forcing at precessional 19 and 23 kyr tilt 41 kyr and at approximately 30 kyr periodicities as a result the generalization that winds are uniformly stronger during glacial times is not valid whole cenozoic records show that the largest change in dust flux an order of magnitude increase occurred in the northern hemisphere and reflects continental drying associated with the late pliocene onset of northern hemisphere glaciation southern hemisphere eolian records show no sign of paleoclimatic changes in the late pliocene the most important change in cenozoic atmospheric circulation was a severalfold reduction in wind intensity that occurred at the time of the paleocene eocene boundary before then latest cretaceous and paleocene winds were essentially as strong as those of the late cenozoic this shift appears to be one of several climatic responses to a change in the nature and amount of global heat transport at about 55 ma

growth rate variations of manganese nodules and crusts induced by paleoceanographic events time markers at about 3 ma 6 5 ma and 14 ma are common to 16 manganese nodules and crusts from different localities in the world oceans these time markers correspond to variations in the growth rates in the inner structure and in the chemistry of the samples the observed time markers could be related to 1 changes of the bottom water velocity and 2 variations in the manganese and iron contents in the deep ocean the time markers were determined by high resolution 10be dating applying the accelerator mass spectrometry facility at the eidgenossische technische hochschule zurich

rutile solubility in albite h2o and na2si3o7 h2o at high temperatures and pressures by in situ synchrotron radiation micro xrf abstract rutile is an important mineral host for high field strength elements so its solubility in geologic fluids at high pressure and temperature plays an important role in the crustal and mantle processes that control the terrestrial cycling of these elements however experimental measurements of rutile solubility are in conflict by a factor of more than 100 at most studied conditions we performed new measurements of rutile solubility in h 2 o albite and h 2 o na 2 si 3 o 7 ns3 fluids by in situ synchrotron radiation x ray fluorescence spectroscopy using modified bassett type hydrothermal diamond anvil cells minimum detection limits were 1 9 and 2 3 ppm ti by weight for the two cells three albite h 2 o experiments at starting bulk compositions of 2 7 6 7 and 10 3 wt albite involved spectral acquisition at rutile saturation in the presence of albite crystals melt or a single homogeneous fluid phase after accounting for the additional phases corrected fluid compositions were 0 6 to 7 5 wt dissolved silicate over the run conditions at 2 7 wt albite rutile dissolution rate was slow and steady state was not achieved at 600 800 c however at higher dissolved albite contents constant solubility with time was observed rutile solubilities in the presence of a single fluid phase at 700 c 0 79 gpa 5 4 wt albite and at 800 c 1 10 gpa 6 7 wt albite were 37 2 and 156 6 ppm respectively these data agree with results acquired using hydrothermal piston cylinder methods with long run times and suppression of new crystal growth but not with data derived from visual observation in hydrothermal diamond anvil cells this discrepancy is likely due to lack of equilibrium in the latter approach two experiments in 10 and 30 wt ns3 at 660 800 c 0 5 0 1 gpa show extreme concentration dependent enhancement of rutile solubility to 4500 ppm the data indicate a strong positive correlation between rutile solubility and na al because na k al is likely to be greater than unity in aqueous fluids at high pressure and temperature due to incongruent dissolution of albite and micas the increase in rutile solubility along the albite ns3 join points to the possibility of significant ti transport by silicate bearing aqueous fluids in the lower crust and upper mantle

an empirical estimate of near source ground motion for a major mb 6 8 earthquake in the eastern united states abstract three empirical techniques are used to estimate ground motion amplitudes in the near source region of a major earthquake hypothesized to occur along the east coast of the united states these techniques include the estimation of strong motion parameters from the statistical analysis of selected strong motion records from empirical and theoretical attenuation relations and from modified mercalli intensity source parameters for the hypothesized earthquake were selected to be similar to those inferred for the 1886 charleston south carolina earthquake the epicentral region is characterized by a modified mercalli intensity of x from which magnitudes of m b 6 8 m s 7 2 and m 7 2 were estimated inferred fault mechanisms for the hypothesized event vary from strike slip on a vertical fault to reverse or reverse oblique slip on a fault dipping as shallow as 45 the median estimate of peak horizontal acceleration for a point located 15 km from the surface projection of fault rupture is 0 30 g independent of site geology corresponding estimates of peak horizontal velocity are 35 cm sec for soil and soft sedimentary rock sites and 18 cm sec for crystalline basement rock sites strong motion parameters for a point located 15 km from the epicenter corresponding to a point located directly above the rupture zone of the hypothesized earthquake are estimated to be approximately 80 per cent higher than these estimates or about 0 55 g for peak acceleration and about 63 and 33 cm sec for peak velocity on soil soft rock and crystalline rock respectively corresponding velocity acceleration ratios are 115 cm sec g for soil soft rock sites and 60 cm sec g for crystalline rock sites standard deviations associated with the natural logarithm of peak horizontal acceleration and velocity are estimated to be 0 5 and 0 7 respectively representing an 84th percentile estimate or equivalently an upper 68 per cent confidence limit that is approximately 65 per cent higher than the median for acceleration and 100 per cent higher than the median for velocity while these strong motion values are generally higher than those currently used in the seismic design of most structures in the eastern united states their impact on the seismic safety of specific sites in the region will depend on an assessment of the probability of occurrence of an earthquake of this size within the near source region of these sites

late cenozoic sedimentation and metal deposition in the north pacific similar major chemical variations in cores from three sites across a wide area of the north pacific are modeled by coupling the vertical and horizontal motions of the pacific plate with a constant authigenic flux of elements into the sediments superimposed over this flux is an input of detrital material of relatively constant chemical composition the major features of sediment chemistry of cores from the north pacific apparently vary in a fairly uniform and systematic manner and these variations are consistent with cenozoic plate movement elements with a significant authigenic component e g mn co cu ni display high concentrations at depth in cores that correspond to the period when the seafloor while under the low productivity subtropical gyre of the n pacific accumulated sediment at an extremely slow rate 1 mm kyr these concentrations were diluted when the sites experienced an increase in the eolian mass accumulation rate first brought about by migration into the influence of the westerlies and then dominantly by the huge input of wind blown detritus which corresponded to the onset of northern hemisphere glaciation a comparison of 10be profiles to the profiles of metal concentrations is used to reveal the occurrence of haituses in the sediment column over the past 8 m y

the solubility of corundum in h2o at high pressure and temperature and its implications for al mobility in the deep crust and upper mantle abstract the solubility of corundum in h 2 o was measured at 700 1100 c and 0 5 2 0 gpa using a piston cylinder apparatus and weight loss methods at 700 c 0 5 gpa al concentration is 0 41 0 15 millimolal 1 analytical error corundum solubility increases strongly with pressure p and temperature t reaching 2 57 0 15 millimolal at 700 c 2 0 gpa and 27 3 1 5 millimolal at 1100 c 2 0 gpa the results were fitted with the equation log m al 1 131 3827 t 2 277 7336 t log h 2 o where m al is molality of al h 2 o is the density of h 2 o in g cm 3 and t is in kelvin the data indicate that al can have significant solubility in h 2 o during metamorphic and metasomatic processes in the deep crustal and upper mantle

influence of shimada seamount on sediment composition in the eastern tropical north pacific abstract shimada seamount is a large young volcanic edifice in the east central pacific that is not associated with any active spreading center or known hot spot the sediments on the abyssal plain surrounding shimada seamount consist of pelagic clay with ferromanganese micronodules and zeolites the pelagic clay is mostly barren of microfossils except for a few occurrences of highly corroded specimens of radiolaria and diatoms eolian terrigenous material is the dominant component of the pelagic clay to a depth of at least 8 m below sea floor with minor contributions from volcanic debris and hydrothermal and hydrogenous sources the average amount of basaltic debris is only 0 25 but concentrations are as high as 10 in some samples the average hydrothermal component metalliferous sediment is 8 8 with a maximum of about 13 at 7 5 m below sea floor in one core the hydrogenous component mostly as ferromanganese micronodules averages 4 1 with a maximum of 5 6 there is no calcareous biogenic debris and essentially no siliceous biogenic debris in the past a decrease in hydrothermal components through time may have been the result of a decrease in relative importance of hydrothermal influences or an increase in the flux of terrigenous debris transported by the northeast trade winds because volcanic activity is still active on shimada seamount or has been in the recent past the observed increase in relative abundance of terrigenous components probably was the result of increased wind transport and not decreased hydrothermal activity shimada seamount may be an important local source of metalliferous sediment in the eastern equatorial north pacific and may have been an even more important source in the past

source spectral scaling inversion for two earthquake sequences offshore western norway abstract short period and high frequency noress observations from two after shock sequences offshore western norway with epicentral distances of 424 and 405 km respectively have been used in testing a new hedgehog inversion procedure for determination of source spectral scaling characteristics based on a previously developed spectral ratio method this inversion procedure provides insight into resolution properties uncertainties and trade off considerations between source parameters the two main events analyzed have m l magnitudes of about 5 while the smallest aftershocks are about 1 5 with seismic moments in the range 10 17 to 10 12 nm the observed spectral ratios support 2 source models for both of the earthquake sequences but only if certain constraints are imposed on the scaling parameter that determines the stress drop sensitivity with respect to seismic moment in that case stress drop is found to be almost independent of seismic moment of 3 24 for one of the sequences and increasing with moment of 3 80 for the other without such constraints which may not be justifiable in the case of earthquake sequences equally good solutions are found for 3 models in which case attains values around 5 to 6 indicating strongly increasing stress drop external constraints on the source spectral slope and or corner frequency will similarly help in resolving the method which also simultaneously determines corner frequencies or stress drop if adopting some model relating this to corner frequency for all of the events albeit with a poorer resolution can either use independently determined seismic moments or it can determine these as part of the inversion quite similar results are obtained in those two cases reflecting essentially the quality of the initial moment determinations the observed variations in stress drop sensitivity between two earthquake sequences only 84 km apart and occurring in similar tectonic environments are consistent with the considerable variations that have been observed on a larger scale caution is therefore needed if the scaling relations derived in this study are applied to other events larger ones and or series of main events or to different seismic regions

new brunswick strong ground motion records abstract although large earthquakes including several of magnitude 7 are known to have occurred in eastern canada since the arrival of european settlers in the 16th century no significant strong ground motion records were available until 1982 and earthquake engineering design relies on extrapolation of results from mostly california data modified to take into account the well known lower attenuation of felt intensities in the east in january 1982 a m b 5 7 earthquake occurred in the sparsely populated central region of new brunswick and was felt at ground level to distances of 400 km quickly installed strong motion recorders registered peak acceleration over 50 of gravity at high frequencies close to a m b 5 0 aftershock this is an order of magnitude higher than expected from the reported intensities and from the absence of significant damage however peak ground velocities as well as the low frequency fourier components of acceleration are consistent with accepted ground motion intensity relations this highlights again the need to go beyond the single parameter scaling of ground motion for purposes of the building code for ordinary buildings and for special engineering structures the large dynamic range of the digital records from the eastern canadian telemetered seismic network allows limited extrapolation of the strong motion records to the larger earthquakes and by inference to perhaps other eastern earthquakes in granitic environments such as charlevoix temiskaming and cornwall where large magnitudes appear to be generated in small source volumes resulting in explosion like high frequency but short duration near source ground motions

an experimental study of trace element fluxes from subducted oceanic crust we have determined experimentally the hydrous phase relations and trace element partitioning behaviour of ocean floor basalt protoliths at pressures and temperatures 3 gpa 750 1000 c relevant to melting in subduction zones to avoid potential complexities associated with trace element doping of starting materials we have used natural pristine mid ocean ridge basalt morb from kolbeinsey ridge and altered oceanic crust aoc from deep sea drilling project leg 46 20 n atlantic approximately 15 wt water was added to starting materials to simulate fluid fluxing from dehydrating serpentinite underlying the oceanic crust the vapour saturated solidus is sensitive to basalt k2o content decreasing from 825 6 25 c in morb 0 04 wt k2o to 750 ci n aoc 0 25 wt k2o textural evidence indicates that near solidus fluids are sub critical in nature the residual solid assemblage in both morb and aoc experiments is dominated by garnet and clinopyroxene with accessory kyanite epidote fe ti oxide and rutile plus quartz coesite phengite and apatite below the solidus trace element analyses of quenched silica rich melts show a strong temperature dependence of key trace elements in contrast to the trace elementdoped starting materials of previous studies we do not observe residual allanite instead abundant residual epidote provides the host for thorium and light rare earth elements lree preventing lree from being released rlree 1500 and la smpum where pum indicates primitive upper mantle 1 most closely matching the geochemical signal of arc lavas worldwide were generated from aoc at 800 850 c

accumulation rates of th 230 pa 231 and some transition metals on the bermuda rise abstract measurements of 238u 234u 230th 232th 231pa mn fe co ni cu and zn were made on 23 samples from core gpc 5 a 29 m giant piston core from a water depth of 4583 m on the northeastern bermuda rise 33 41 2 n 57 36 9 w this area is characterized by rapid deposition of sediment transported by abyssal currents unsupported 230th and 231pa are present throughout the core but because of large variations in the sedimentation rate show marked departures from exponential decay with depth the trend with depth of the 231 pa ex 230 th ex ratio is consistent with the average accumulation rate of 36 cm 1000 y reported earlier on the basis of radiocarbon dating and caco3 stratigraphy when expressed on a carbonate free basis concentrations of mn co ni cu zn 230thex and 231paex all show cyclic variations positively correlated with those of caco3 the correlations can be explained by a model in which all of these constituents including caco3 are supplied to the sediments from the water column at a constant rate concentration variations are controlled mainly by varying inputs of terrigenous detritus with low inputs occurring during interglacials and high inputs during glacials relationships between the metal and 230thex concentrations permit estimates of the rates at which the metals are removed to the sediment by scavenging from the water column the results in g cm2 1000 y are 4300 1100 for mn 46 16 for ni and 76 26 for cu these rates are somewhat larger than ocean wide averages estimated by other methods and the absolute rate of 230th accumulation in gpc 5 averages about nine times higher than production in the overlying water column this part of the bermuda rise and similar bottom current deposits may act as important accumulators of elements scavenged from seawater

stochastic prediction of ground motion and spectral response parameters at hard rock sites in eastern north america empirical predictions of ground motions from large eastern north american earthquakes are hampered by a lack of data for such events for this reason most prediction techniques have been based at least in part on data from the seismically active and well instrumented western north america concentrating on the prediction of response spectra on hard rock sites we have used a relatively new theoretical technique that does not require western data to make ground motion predictions for eastern north america this method often referred to as the stochastic model has its origins in the work of hanks and mcguire who treat high frequency motions as filtered random gaussian noise for which the filter parameters are determined by a seismological model of both the source and the wave propagation the model has been successfully applied to the predictions of ground motions in the western united states and to short period magnitudes from large to great earthquakes worldwide for our application the essential parameters of the model are estimated by using existing data from small to moderate eastern north american earthquakes a crucial part of the model is the relation between seismic moment and corner frequency the relation proposed in 1983 by nuttli for mid plate earthquakes leads to predictions of ground motions that are lower than available data by a factor of about 4 on the other hand a constant stress parameter of 100 bars gives model predictions in good accord with the data to aid in applications the ground motion predictions are given in the form of regression equations for earthquakes of magnitude 4 5 to 7 5 at distances within 100 km of the source the explanatory variables are hypocentral distance and moment magnitude m because predictions are often required in terms of m g rather than m we have used the theoretical model to establish a relation between the two magnitudes the predicted relation agrees with the sparse data available although the large uncertainties in the observed magnitudes for the larger events as well as the sensitivity of the theoretical magnitude to the attenuation model make it difficult to discriminate between various source scaling models

diagnosing non meteorically induced variations in the chemistry of saline springs of the vrancea seismic area romania a monitoring operation conducted over more than seven years has been addressing chemical fluctuations displayed by several cool low discharge springs located close to the highly seismic vrancea area romania those outflows compositions proved to be strongly controlled by binary essentially isochemical mixing between a deep origin brine and meteoric freshwater by taking advantage of this particular setting there have been constructed diagrams aimed at investigating how the groundwater discharges na k mg geothermometric parameters fluctuated as a function of the chloride content taken to be an estimator of the freshwater induced dilution we made use of the reciprocal algebraic relationships existing between the equations describing the na k mg geothermometric parameters na k temperature and k mg temperature on the one hand and the so called maturity index mi on the other in an accordingly derived plot of mi against the logarithm of the chloride concentration a series of data points being quite uniformly off set from the mi dilution curve constructed for an apparently regular period suggested that episodically all concerned springwaters were simultaneously subject to some similar changes in the controlling geochemical processes one such modification intervened 3 4 months before the occurrence of the strongest earthquake m text w 5 8 of the hydrochemical monitoring period the consequently derived interpretation was that then the numerical values of certain geothermometric coefficients were likely altered such a process could be consistent with changes in the alkali feldspars solubility relationships possibly in response to episodic al si complexing which might develop within a hypothesised still active exhumation channel

complete miscibility between silicate melts and hydrous fluids in the upper mantle experimental evidence and geochemical implications the phase relationships between silicate melts and hydrous fluids were studied by direct visual observation in an externally heated diamond anvil cell complete miscibility of silicate melt and water was observed for a wide range of melt compositions including nepheline jadeite dacite haplogranite and ca bearing granite some evidence for complete miscibility was also observed in the system basalt h2o the critical temperatures in all systems decrease rapidly with pressure at 15 kbar the critical temperature for nepheline is around 550 c for jadeite around 800 c and for granitic compositions it is close to 900 c in general the critical temperatures appear to increase with silica content in the system our results suggest that there is complete miscibility between silicate melts and water in most of the upper mantle except at very shallow depths this means that a water saturated solidus cannot be defined any more in the deeper parts of the upper mantle very silica rich melt inclusions found in spinel lherzolites associated with fluid inclusion are probably the result of the unmixing of a supercritical fluid containing comparable amounts of water and silicate components the decomposition of amphibole in a subducted slab occurs at conditions where the miscibility gap between fluid and silicate melt is not yet closed while the decomposition of phengite and lawsonite occurs far beyond the critical curve accordingly the fluids released by the breakdown of these minerals should have very different properties highly mobile hydrous fluids containing little dissolved silicate should be produced by amphibole breakdown while the decomposition of lawsonite and phengite will lead to much more silicate rich and less mobile fluid phases

a multitracer approach to the study of erosion in the northeast equatorial pacific abstract erosion of sediment at two sites within the siliceous clay province of the northeast equatorial pacific is investigated by examining radionuclide radiolarian and percent smectite profiles of three cores a numerical model of the sediment is presented that examines the effect of various particle rain rates erosion rates and biological mixing parameters on these profiles 230 th because of its longer half life is a more sensitive tracer of erosion than 231 pa because the input of these radionuclides into the sediment is not well defined however conservative tracers such as the percent smectite of the clay fraction and fossil radiolarians are used to constrain the rate of sediment recycling dissolution of radiolarians though can greatly affect the interpretation of the observed biostratigraphy

regional relationships among earthquake magnitude scales various magnitude scales commonly used and the interrelationships among them are reviewed it is shown that problems exist with all of the magnitude scales being used in the united states when using regional catalogs for example it is often necessary to determine how the reported magnitudes were determined often such information is not available although the potential errors are quite large both the ms and the mb scales were designed to be universal scales however both ms and mb magnitudes are often determined beyond the applicable range of the equations used to define the two scales furthermore the ms magnitudes are not generally available for moderate to small earthquakes in most earthquake catalogs the mb magnitudes are more generally available than ms values however there is also much greater variation in the way mb is determined in particular a significant change in the mb scale occurred in the early 1960 s when the world wide standard seismograph network wwssn was established this change in instrumentation used to determine mb values had a significant effect on estimated magnitudes post 1960 values are lower and the saturation level of the mb scale the older longer period instruments recorded larger mb magnitudes than can be recorded with the wwssn instruments in addition great care must be taken when selecting the mb magnitudes of western u s earthquakes because the values are often in considerable error owing to the fact that they were determined at distances less than 25 and were not properly corrected for attenuation in the upper mantle or asthenosphere the seismic body wave magnitude mb of an earthquake is strongly affected by regional variations in the q structure composition and physical state within the earth therefore because of differences in attenuation of p waves between the western and eastern united states a problem arises when comparing mb values for the two regions a regional mb magnitude bias exists which depending on where the earthquake occurs and where the p waves are recorded can lead to magnitude errors as large as unit there is also a significant difference between mb and ml values for earthquakes in the western united states an empirical link between the mb of an eastern u s earthquake and the ml of an equivalent western earthquake is given by ml 0 57 0 92 mb east this result is important when comparing ground motion between the two regions and for choosing a set of real western u s earthquake records to represent eastern earthquakes

evaluation of empirical ground motion relations in southern california regression analysis to develop empirical ground motion relations that predict ground motion characteristics as a function of magnitude and distance are an essential part of seismic design and probabilistic seismic hazard assessment several different ground motion relations have been presented based on different data and assumptions this study evaluates five that were judged likely to be appropriate for southern california we test them against the strong motion data recorded in this region between 1933 and 1994 for magnitudes between 5 0 and 7 5 and for distances up to 150 km the ground motion parameters examined are peak acceleration and response spectral acceleration sa at 0 3 1 0 and 3 0 sec periods some of the ground motion relations are more consistent than others with the limited set of southern california data but none of them stand out as either best or unacceptable residuals from all of these models indicate that as the magnitude increases the standard deviation decreases at high frequencies but increases for sa 3 0 sec among those found to be most consistent significant differences remain with respect to predicting ground motion under conditions not yet sampled by the existing observational data set e g near source shaking for large earthquakes theoretical simulations are used elsewhere in this report ni et al 2000 anderson 2000 to help resolve these ambiguities the implications with respect to probabilistic seismic hazard assessment are explored in field and petersen 2000

magnitude the relation of ml to mblg abstract the m blg magnitude developed by nuttli 1973 for the central united states is adapted to other regions of the world by incorporating a specific term for the spatial coefficient of anelastic attenuation using region specific values m blg values are determined for earthquakes occurring near the wwssn stations bks gsc and dug a comparison of the m blg values with published m l magnitudes shows that these two magnitude scales are essentially equivalent between magnitudes 3 to 5 because of this observation we now have a direct way of comparing eastern and western united states earthquake sizes for the purpose of adapting western strong motion data bases to the east and also for understanding teleseismic magnitude biases

empirical magnitude and spectral scaling relations for mid plate and plate margin earthquakes abstract published values of body wave magnitude m b surface wave magnitude m s and seismic moment m o for mid plate and plate margin earthquakes are analyzed to determine their inter relationship and to develop scaling laws for earthquake spectra all of the plate margin earthquakes used in the study occurred near the border of the pacific ocean the mid plate earthquakes occurred in both continental plate interiors and oceanic plate interiors for mid plate earthquakes the m b m s relation can be represented by two straight lines of slope one and two the intersection of the two lines corresponds to the body wave magnitude for which the corner period of the spectrum is at 1 sec the m b m s relation for plate margin earthquakes is more complicated because the derived spectra exhibit two corner periods a principal feature of the m b m o and m s m o relations is the fact that the large plate margin earthquakes have a higher m o value than the mid plate earthquakes for the same m b or m s because m b is a measure of the spectral amplitude for frequencies at which damaging ground motion occurs and m 0 is a measure of the spectrum at very long periods it follows that mb is a good estimator of strong ground motion whereas a moment derived magnitude is not the latter however is a good measure of fault rupture area the derived spectra of the mid plate earthquakes are flat at the long periods and have a slope of two at the short periods their seismic moment varies as the fourth power of the corner period implying that the stress drop increases as the moment increases for the large plate margin earthquakes the derived spectra are flat at the long periods have a slope of one at intermediate periods and a slope of two at short periods the stress drops are almost independent of moment for the larger plate margin earthquakes the moment magnitude relations for mid plate earthquakes indicate that an m s 8 7 event requires a fault rupture length of only 60 km for a fault width of 20 km a plate margin earthquake of m s 8 7 and fault width of 20 km would require a fault length of 6000 km obviously impossible assuming a fault width of 20 km an m s 8 2 earthquake has a rupture length of about 850 km which is as large as can be expected for strike slip faults such as the san andreas of california subduction zone earthquakes on the other hand if they have fault widths as great as 200 km can give rise to m s 8 7 earthquakes

an investigation into earthquake ground motion characteristics in eastern north america abstract a random vibration model of the hanks mcguire type is used to predict peak ground motions at rock sites in eastern north america the assumed geometric decay and distance dependent duration approximate the propagation of direct body waves at short distances and lg waves at regional distances the model predicts peak acceleration and velocities as well as response spectra and magnitude for a given seismic moment and corner frequency to predict ground motions for a given lg magnitude m lg the model is first used to calculate the seismic moment corresponding to that magnitude assuming a source scaling law then knowing the moment and corner frequency the model is used to calculate peak ground motions available data from strong motion recordings and from the ectn and lrsm networks modified to estimate horizontal ground motions on rock where appropriate are used to verify the model9s assumption and predictions modified mercalli intensity data are also used ground motions predicted by the model with a stress drop of 50 to 200 bars agree with the ground motion data but the m lg values computed by the model for given seismic moments do not agree with nuttli9s 1983 moment versus m lg data for large earthquakes resolution of the latter disagreement awaits the collection of instrumental data from large events in eastern north america

aftershock sequences of the 1982 miramichi new brunswick earthquakes the mb 5 7 miramichi new brunswick earthquake of 9 january 1982 was located by comparison to the aftershock distribution in central new brunswick canada at 47 00 n 66 60 w with a focal depth of 7 km and an uncertainty of 3 km on each of the spatial coordinates the main shock was followed by a long and complex aftershock sequence with four events m 4 5 and more than 800 events m 1 0 until 30 june 1982 the aftershocks were studied by three temporary field networks set up in the epicentral areas from 10 to 20 january 2 to 7 april and 17 to 23 june 1982 and by the permanent canadian seismograph networks the aftershock activity was concentrated in a volume approximately 6 km ns 6 km ew 8 km deep and arranged in a north trending conjugate v pattern the miramichi earthquakes were predominatly thrust earthquakes occurring on north trending mid to high angle faults in the upper 8 km of the crust in the presence of an east west compressive horizontal regional stress field detailed field surveys have not yet been able to associate the earthquakes with any known preexisting faults the main shock had a moment of 2 2 0 7 1024 dyne cm and a stress drop of 35 to 70 bars the rupture started at 7 km depth on a plane striking 195 dipping 50 down to the west and propagated up to the east with a rake angle of 120 aftershocks deeper than 3 5 km had composite mechanisms very similar to the main shock s but shallower events took place on more steeply dipping planes up to 78 dip the rupture planes of the main shock and its principal aftershocks may have been similarly curved the magnitude frequency relationship b 0 8 of the aftershocks was comparable to the regional one the aftershock activity decayed as t 0 8 and had the highest rate of activity following the principal aftershock on 11 january that aftershock mb 5 4 appears to have ruptured the east dipping plane conjugate to the main shock s plane two other principal aftershocks mb 5 1 on 9 january and mb 5 0 on 31 march were associated with the main shock rupture plane while the fourth large event mb 4 7 on 16 june occurred 30 km west of the other activity and was seemingly unrelated however all the earthquakes were apparently associated with the same granitic terrain the miramichi earthquakes did not produce any significant surface faulting one small 25 mm surface displacement was found but it was identified as a secondary stress induced movement along a preexisting joint

fluid infiltration and transport of major minor and trace elements during regional metamorphism of carbonate rocks wepawaug schist connecticut usa geochemical alteration of metacarbonate layers due to fluid infiltration during greenschist and amphibolite facies metamorphism was investigated based on 149 whole rock analyses of the wepawaug schist usa ankerite albite ank ab rare ankerite oligoclase ank ol biotite bt amphibole amp and diopside di index mineral zones developed during progressive metamorphism acadian orogeny and devolatilization co2 h2o s loss ank ab ank ol and bt zone rocks were altered along some lithologic contacts and in reaction selvages around veins mass changes included gains of na y and in many cases p and fe k rb and ba were typically lost and sr was lost except where calcite precipitated in and around calcite bearing veins na gain and k loss reflect muscovite destruction and albite growth in response to infiltration of fluids from surrounding metapelitic and metapsammitic metaclastic rocks at higher metamorphic grades k rb and ba were lost when biotite broke down to form amphibole or diopside these elements were transported out of metacarbonate layers down chemical potential gradients at lithologic contacts and in selvages na was lost as plagioclase reacted to form clinozoisite zoisite czo zo calc silicates cm to dm scale thickness rich in amphibole and czo zo amp zones or diopside and zo di zones formed at layer margins and in selvages via extreme metasomatism including major 1 addition of al si and in many rocks fe 2 destruction of calcite and 3 loss of ca and volatiles volatile losses near 90 percent relative to low grade precursors demonstrate that calc silicate formation resulting from al si metasomatism is an important source of co2 to be considered when assessing regional devolatilization al mass gains for calc silicates indicate that large quartz veins and some lithologic contacts were loci for massive time integrated fluid fluxes of 105 m3 m 2 heavy rare earth elements hree were gained in the ank ab through the amp zones and a di zone example gained light and mid ree including sm and nd the ree gains coincide with gains of y and in most cases p suggesting that p and y complexes transport ree volume was lost progressively from the unveined interiors of metacarbonate beds attaining 20 to 30 percent loss in the di ii zone mass addition due to veining reduced volume losses and in some cases produced volume gains reaction transport modeling indicates that fluid flow was mostly layer parallel was focused along lithologic contacts fractures and permeable horizons and was accompanied by diffusion and or mechanical dispersion at high angles to the flow directions the metasomatic fluids infiltrated from surrounding metaclastic and or syn metamorphic igneous rocks thus interaction of fluids derived from different rock types must be considered when assessing mass transfer in lithologically diverse mountain belts

electrical conductivity of clinopyroxene nacl h2o system at high temperatures and pressures implications for high conductivity anomalies in the deep crust and subduction zone

source parameters for aftershocks of the oroville california earthquake abstract a suite of 111 strong motion accelerograms for 14 aftershocks of the oroville california earthquake m l 5 7 1 august 1975 that range in local magnitude m l from 2 8 to 5 2 has been analyzed to obtain estimates of seismic moment m o source radius r o and stress drop in addition to the focal parameters of location depth and fault plane solution this data set which is unusually complete for near source 20 km on scale readings allows for greater precision in the calculation of various measures of stress difference as represented by the brune stress drop the apparent stress the a rms stress drop and the dynamic stress drop in addition the seismicity following each aftershock and state of stress seem to correlate with particular estimates of stress drop seismic moments were calculated from the asymptotic long period spectral levels which were corrected for the radiation pattern of a double couple point source they range from 1 4 10 21 dyne cm for a m l 2 8 shock to 3 3 10 23 dyne cm for a m l 5 1 event a least squares fit between m l and the logarithm m o yields log m 0 1 36 0 22 m l 16 8 1 1 for m l 4 3 and log m 0 1 1 0 14 m l 18 0 51 for m l 4 1 these relationships are qualitatively in agreement with the response of the wood anderson instrument to a brune pulse stress drops from the brune formulation range about 14 to 170 bars stress drop is correlated with depth in that the deepest events have the largest stress drops and no large stress drops occur at the shallow depths apparent stresses are smaller than the brune stress drops and show a weaker depth dependence over the depth interval for which they are available the stress drop calculated from the rms of acceleration a rms was approximately constant at about 90 bars for 5 of the 7 larger events analyzed the two high values of 160 and 190 bars were obtained only for the two events which had marked aftershock sequences of their own these results may be interpreted in terms of the state of stress simple fracture criteria and mechanisms for the generation of aftershocks the increase with depth of the envelope of the brune stress drops may be caused by an increase in shear stress from overburden pressure smaller stress drop events can occur at any depth interval the causal mechanism of aftershocks is not known but probably includes a change in the frictional properties of the fault suggesting that the a rms stress drop is a measure of the frictional or dynamic stress release

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

fluid inclusion examination of the transition from magmatic to hydrothermal conditions in pegmatites from san diego county california thermometric properties and compositions of fluid inclusions in quartz are used to constrain the roles that fluid soluble elements principally li b cl and f have in controlling the transition from magmatic to hydrothermal mineral paragenesis in pegmatites and to ultimately understand why some pegmatites in the san diego county pegmatite district contain abundant gem quality li bearing minerals in pockets whereas others do not in this district lithium cesium tantalum type pegmatites occur in the mesozoic peninsular ranges batholith emplacement of the dikes occurred at low pressures 200 300 mpa that resulted in the formation of large miarolitic cavities pockets some of which contain gem quality li bearing minerals two pegmatite suites were studied the gem bearing himalaya and the more barren la posta the inclusions measured in this study further underscore highly undercooled crystallization of pegmatites pressure corrected homogenization temperatures t h of 400 to 515 and 70 to 425 c were obtained for primary inclusions in the intermediate zone and the core respectively of a la posta dike primary inclusions in the intermediate zone and the massive quartz core of the himalaya pegmatite have t h ranges of 350 to 420 and 150 to 300 c respectively the high portion of the latter temperature range is interpreted to represent the conditions that existed during the initial crystallization of minerals that line pegmatite pockets the most important cations in fluid inclusions in both pegmatites are na b3 and li lithium concentrations are much higher in inclusions in the himalaya pegmatite up to 51 at of all cations within the massive quartz in the core zone in the la posta pegmatite few primary inclusions contain appreciable li the b content of inclusions in both pegmatites is high up to 65 at of cations the dominant anions in the inclusions are cl f and formula 1 the data suggest that hydrothermal fluids that collected in pockets were acidic and promoted the growth of tourmaline and other minerals that are stable in acidic solutions in both pegmatites na and b dominate secondary inclusions these inclusions reveal fluids stripped of li and k by crystallization of lepidolite within fractures of primary minerals throughout the pegmatites and sometimes as an alteration product in pockets the lowering of alkali h ratios in the fluid stabilized clays including kaolinite that line the walls of pockets coeval crystallization of terminated quartz crystals with clays is consistent with its precipitation from the fluids 1 embed mml math 1 gif

the ml scale in southern california measurements 9 941 of peak amplitudes on wood anderson instruments or simulated wood anderson instruments in the southern california seismographic network for 972 earthquakes primarily located in southern california were studied with the aim of determining a new distance correction curve for use in determining the local magnitude m l events in the mammoth lakes area were found to give an unusual attenuation pattern and were excluded from the analysis as were readings from any one earthquake at distances beyond the first occurrence of amplitudes less than 0 3 mm the remaining 7 355 amplitudes from 814 earthquakes yielded the following equation for m l distance correction log a 0 log a 0 1 110log r 100 0 00189 r 100 3 0 where r is hypocentral distance in kilometers a new set of station corrections was also determined from the analysis the standard deviation of the m l residuals obtained by using this curve and the station corrections was 0 21 the data used to derive the equation came from earthquakes with hypocentral distances ranging from about 10 to 700 km and focal depths down to 20 km with most depths less than 10 km the log a 0 values from this equation are similar to the standard values listed in richter 1958 for 50 200 km the effect at close distances is consistent with that found in several other studies and is simply due to a difference in the observed 1 r geometrical spreading for body waves and the 1 r 2 spreading assumed by gutenberg and richter in the construction of the log a 0 table m l s computed from our curve and those reported in the caltech catalog show a systematic dependence on magnitude small earthquakes have larger magnitudes than in the catalog and large earthquakes have smaller magnitudes by as much as 0 6 units to a large extent these systematic differences are due to the nonuniform distribution of data in magnitude distance space small earthquakes are preferentially recorded at close distances relative to large earthquakes for large earthquakes however the difference in the two magnitudes is not solely due to the new correction for attenuation magnitudes computed using richter s log a 0 curve are also low relative to the catalog values the differences in that case may be due to subjective judgment on the part of those determining the catalog magnitudes the use of data other than the caltech wood anderson seismographs the use of different station corrections or the use of teleseismic magnitude determinations whatever their cause the departures at large magnitude may explain a 1 0 0 7 proportionality found by luco 1982 between m l s determined from real wood anderson records and those from records synthesized from strong motion instruments if it were not for the biases in reported magnitudes luco s finding would imply a magnitude dependent shape in the attenuation curves we studied residuals in three magnitude classes 2 0 m l 3 5 3 5 m l 5 5 and 5 5 m l 7 0 and found no support for such a magnitude dependence based on our results we propose that local magnitude scales be defined such that m l 3 correspond to 10 mm of motion on a wood anderson instrument at 17 km hypocentral distance rather than 1 mm of motion at 100 km this is consistent with the original definition of magnitude in southern california and will allow more meaningful comparison of earthquakes in regions having very different attenuation of waves within the first 100 km

premelting polymerization of crustal and mantle fluids as indicated by the solubility of albite paragonite quartz in h2o at 1 gpa and 350 620 c abstract the composition and structure of dissolved silicates in model crustal and upper mantle fluids was assessed by measuring the solubility of the assemblage albite paragonite quartz in h 2 o from 350 to 620 c at 1 gpa natural low albite and quartz were equilibrated with h 2 o paragonite grew in all experiments due to incongruent dissolution of albite quartz melting occurred at 635 5 c solute concentrations at subsolidus conditions were determined by analysis of quenched fluids or mineral weight loss and mass balance bulk solubility of the mineral assemblage increased from 1 to 8 oxide wt with rising temperature si al and na all increase in concert the solutions were slightly peralkaline and possess si na al 1 5 molar at all conditions studied extrapolated thermodynamic data were used to predict solubility at the conditions investigated experimentally calculated solubility agreed with that measured from 350 to 500 c however above 500 c the calculations underpredict solubility to an increasing degree as the hydrothermal melting point is approached the excess measured solubility points to increasing abundance of aqueous si al si and na al si polymers polymerized solutes predominate in all near solidus solutions rising to 80 of total dissolved solids at the melting point the observations support a conceptual model in which as the temperature of the system rises isobarically at 1 gpa the silicate components dissolved in the aqueous phase begin to polymerize significantly within 100 c of the melting point the polymerized solutes may facilitate condensation of more polymerized hydrous silicate liquid at the hydrothermal melting point from the perspective of isobaric cooling the fluid crossing the solidus retains na al si o clusters or fragments that are less polymerized than those which comprised the melt but more polymerized than has previously been inferred for the aqueous phase the high concentrations of na al and si in the form of polymeric clusters will yield substantial mass transfer by near solidus metamorphic and magmatic fluids in the crust and mantle and likely promote dissolution transport and precipitation of nominally insoluble refractory rock components

modeling ground motion attenuation in eastern north america abstract in this study we have utilized our understanding of the physics of elastic wave propagation to simulate ground motions within about 200 km from earthquakes in eastern north america detailed crustal velocity structure models were developed for sources located in the grenville and appalachian provinces the former consists of a single gradient in the crust while the latter contains a mid crustal discontinuity and a deep moho semi empirical synthetic seismograms were computed by convolving the generalized ray response of the structures with an empirical source function obtained from a recording close to the source peak ground motions derived from the synthetic seismograms adequately interpolate the sparse empirical data while providing information on the wave propagation phenomena that define ground motion attenuation they suggest that peak ground motion amplitudes are controlled by in order of increasing range the upgoing direct s wave the diving s wave post critical reflections from the mid crustal or moho discontinuities and finally l g

late cenozoic changes in atmospheric circulation deduced from north pacific eolian sediments abstract isolation and analysis of the eolian component of late cenozoic pelagic sediments from the north pacific provides direct information concerning changes in atmospheric circulation a 50 increase in intensity of both the prevailing westerlies and the tradewinds coincides with increasing pole to equator temperature gradients resulting from the onset of northern hemisphere glaciation at the same time the mass flux of dust from continents to the north pacific increased by a factor of 4 5 apparently reflecting significantly increased continental aridity associated with the late cenozoic glacial ages

very low solubility of rutile in h2o at high pressure and temperature and its implications for ti mobility in subduction zones the solubility of rutile in h2o has been measured at 1000 1100 c 1 2 gpa the data indicate that solubility is very low over the investigated range with a maximum of 4 7 millimol kg h2o at 1100 c 2 gpa the data were fit with the equation log m ti 4 892 10470 t 0 1923 p where m ti is ti molality t is in kelvins and p in gpa when compared to previous results the new data indicate substantially lower solubility opposite pressure dependence and thermodynamic properties of the reaction rutile tio2 aq that are now consistent with other oxide hydrolysis reactions calculations of ti transport during mantle metasomatism by h2o in subduction zone environments predict much lower ti mobility at all conditions these results offer strong support for models of ti retention in eclogites during slab devolatilization and require that examples of significant ti mass transfer be explained by complexing agents in solution most likely aluminosilicate complexes

thermodynamics of sio2 h2o fluid near the upper critical end point from quartz solubility measurements at 10 kbar abstract quartz solubility in sio 2 h 2 o fluid was measured at 10 kbar and 750 1130 c in a piston cylinder apparatus at 1035 c solubility was determined by weight loss of single crystals equilibrated with h 2 o rich fluid at higher temperature t the fluid phase coexisting with quartz quenched to a glass and solubility was determined by phase assemblage bracketing quartz present or absent with glass in quenched charges at 700 to 1000 c quartz solubility increases at an accelerating rate from 1 2 mol to 8 9 mol sio 2 above 1000 c there is a sharp increase to nearly equimolar fluids in equilibrium with quartz at 1080 c at t 1080 c sio 2 concentration increases less strongly the data confirm the existence of a critical end point on the hydrous melting curve of quartz and imply it lies at 1080 c and 9 5 10 kbar two independent approaches to calculating sio 2 activity at 1080 c from a mixing model for aqueous sio 2 extrapolated from lower temperatures and from depression of the melting temperature of quartz by h 2 o indicate nearly constant values over the wide compositional range of 20 60 mol sio 2 the activity of h 2 o a h at the same conditions calculated by integration of the gibbs duhem relation shows a plateau of very high a h 0 93 in the same broad composition range at 60 mol there is an abrupt change in h 2 o dissolution mechanism as sio 2 activity becomes proportional to its mole fraction at high silica concentration the activity concentration relations at 1080 c and 10 kbar were fitted to a subregular solution model giving interchange energies for sio 2 and h 2 o of respectively 25 3 and 14 3 kj mol roughly constant sio 2 activity of the near critical fluid despite a factor of 3 increase in x h2o can be explained by progressively greater amounts of hydrogen bonding of h 2 o molecules to polymerized silica units so that the effective concentration of these units remains nearly constant as h 2 o increases the sudden onset of critical phenomena in the system sio 2 h 2 o as temperature and pressure increase over narrow intervals approaching 1080 c and 10 kbar is thus explained as mainly a convergent or cooperative compositional effect in which polymerization and hydrogen bonding both play important roles

attenuation of peak horizontal acceleration and velocity from italian strong motion records italian strong motion data were used to study attenuation characteristics of horizontal peak ground acceleration and velocity the data base consisted of 190 horizontal components of accelerograms recorded in italy since 1976 from 17 earthquakes of magnitudes 4 6 to 6 8 the resulting equations are log a 1 562 0 306 m log r 2 5 8 2 1 2 0 169 s log v 0 710 0 455 m log r 2 3 6 2 1 2 0 133 s where a is peak horizontal acceleration in g v is peak horizontal velocity in centimeters second m is magnitude r is the closest distance to the surface projection of the fault rupture in kilometers and s is a variable taking the values of 0 and 1 according to the local site geology peak acceleration and velocity were found to be lognormally distributed with a standard error representing respectively a 49 and 64 per cent increase in the median estimate we considered a magnitude dependent shape of the attenuation curves but we found no basis for it in the data attenuation relationships developed using epicentral distance in place of fault distance gave similar results with higher standard errors and higher predicted values for short distances and high magnitudes sensitivity studies performed with the analysis of the residuals showed that predictions based on our relatiaons are stable with respect to reasonable variations of the model and the seismic areas providing the data comparisons with attenuation relationships proposed for western north america showed differences of the same order of magnitude as the statistical prediction uncertainty

sedimentary indicators of atmospheric activity in the northern hemisphere during the cenozoic abstract the concentrations and accumulation rates of eolian phases and the mineralogy of sediments from a north pacific core ll44 gpc3 have been used to evaluate changes in eolian sedimentation and atmospheric activity during the cenozoic the quartz content and clay mineralogy of the sediments reflect changing source areas for eolian material whereas the accumulation rates of eolian phases reflect climatic variation and wind intensity eolian sedimentation decreased from 70 to 50 m y ago at the site as it moved north out of the equatorial pacific where it was supplied with eolian debris from north america and africa low rates of eolian sediment accumulation 50 to 25 m y ago reflect the temperate humid environment of the early tertiary and the lack of vigorous atmospheric circulation at that time from 25 to 7 m y ago eolian accumulation increased as the site moved into the influence of the westerlies from 7 to 3 m y ago there was a more rapid increase in accumulation of eolian material at the site which was not accompanied by changes in mineralogy or quartz content and was therefore related to climatic change and more vigorous atmospheric circulation about 2 5 m y ago a dramatic increase in eolian sedimentation accompanied the onset of dry northern hemisphere glaciation

constancy of oceanic deposition of 10 be as recorded in manganese crusts recent developments in the use of nuclear accelerators as high energy mass spectrometers1 2 has renewed interest in the study of cosmogenic 10be half life 1 5 myr as a geophysical time tracer the accelerator techniques enable us to measure 10be with a sensitivity of 107 atoms or less the potential age dating span with 10be is extended back to at least 15 myr bp providing that the 10be production and deposition rates remain constant or nearly constant over that time period a knowledge of the long term constancy in the 10be deposition rate is thus very important we report here the first detailed measurements of 10be and 9be in two ferromanganese oxide crusts from the sea floor of the equatorial atlantic sample no k 9 21 and the north pacific schw 1d each representing 10 myr of accumulation history we have found in these crusts that the deposition of 10be and 10be 9be during the past 7 9 myr has been constant averaged over time intervals of 1 myr the variation is within 6 before that time both crusts show similar significant deviations the 7 9 myr demarcation may be related to the reported late miocene global abyssal circulation change in the ocean3

electrical conductivity of albite quartz water and albite water nacl systems and its implication to the high conductivity anomalies in the continental crust abstract the electrical conductivities of albite water albite quartz water and albite water nacl systems have been measured in terms of impedance spectroscopy at 1 gpa and 400 1000 k the relationship between electrical conductivity and temperature in the albite quartz water system cannot be expressed by the arrhenian formula whereas that in the brine bearing system follow the arrhenian law showing small temperature dependence the electrical conductivity of the albite quartz water samples decreased with decreasing temperature from 1000 to 800 k then increased rapidly upon further cooling from 800 to around 550 k the bulk conductivities of the albite quartz water system are consistent with variation of the total concentration of the dissolved electric charge carriers of h oh na alo 2 and hsio 3 in aqueous fluid with temperature based on the thermal dynamic calibration there is a small negative dependence of bulk conductivity on aqueous fluid fraction electrical conductivity of the albite water nacl samples is higher than that of the albite quartz water samples which shows the following features 1 small dependence of conductivity on the temperature 2 increase of electrical conductivity with the fluid fraction and the salinity our results suggest that the high conductivity anomalies of 10 1 s m typically observed in the continental crust can be explained by the presence of albite and quartz with fluid fraction as low as 0 014 at temperatures lower than 650 k in the case that the geotherm is higher than 650 k the observed value of 10 1 s m can be explained by the brine bearing albite with a fluid fraction of 1 vol if the salinity is similar to the seawater

zr complexation in high pressure fluids and silicate melts and implications for the mobilization of hfse in subduction zones abstract field observations and solubility experiments show evidence for the efficient mobilization of nominally insoluble hfse i e ti zr nb and hf by high pressure fluids probably via complexation with polymerized alkali silica dissolved species and halogens f and cl here we investigate the complexation of zr in subduction related fluids aqueous fluids and hydrous haplogranite melts up to 800 c and 2 4 gpa using x ray absorption spectroscopy xanes and exafs in a hydrothermal diamond anvil cell and provide evidence for the formation of zr o si na polymeric species in alkali alumino silicate fluids at high pressure zr 4 speciation in dilute fluids 2 5 wt hcl is dominated by 8 fold coordinated zr h 2 o 8 4 hydrated complexes at room conditions and no evidence for extensive zr cl complexation in the fluid was found up to 420 c as confirmed by ab initio xanes calculations of various zro 8 x cl x clusters the addition of na and si dissolved species from 35 to 60 wt dissolved na 2 si 2 o 5 ns2 into the fluid favors the formation of alkali zirconosilicate clusters zr o si na similar to those found in vlasovite na 2 zrsi 4 o 11 with zr 4 in octahedral coordination with oxygen zr o distance 2 09 0 04 a and 6 si na second neighbors zr si na distance 3 66 0 06 a this coordination environment also dominates zr speciation in f free and f bearing ns2 and haplogranite glasses and high pressure hydrous haplogranite melts 15 5 33 wt dissolved h 2 o in the investigated pressure temperature range the xas analyses assisted by ab initio xanes calculations are not conclusive concerning the extent of zr f complexation in hydrous granitic melts alkali zirconosilicate zr o si na clusters such as those identified in this study may explain the enhanced solubility of zircon zrsio 4 and other hfse bearing minerals in alkali aluminosilicate bearing aqueous fluids produced by dehydration and melting of the slab and provide a favorable mechanism for the mobilization of hfse in subduction zones fluid rock interactions and or p t variations as fluids migrate through the mantle wedge could affect the stability of these complexes triggering the precipitation of hfse bearing accessory phases that are eventually recycled into the mantle contributing to the dispersion of hfse these processes provide a possible explanation for the characteristic hfse depletion recorded in arc magmas

comparison of source scaling relations of eastern and western north american earthquakes source scaling relations have been obtained for earthquakes in eastern north america and other continental interiors and compared with a relation obtained for earthquakes in western north america the scaling relation for eastern north american earthquakes was constructed from measurements of seismic moment and source duration obtained by the waveform modeling of seismic body waves the events used include nine events of m blg magnitude 4 7 to 5 8 that occurred after 1960 and four earlier events with magnitudes between 5 5 and 6 6 the scaling relation for events in other continental interiors was used for comparative purposes and to provide constraints for large magnitudes detailed analysis of the uncertainties in the scaling relations has allowed the resolution of two important issues concerning the source scaling of earthquakes in eastern north america first the source characteristics of earthquakes in eastern north america and other continental interiors are consistent with constant stress drop scaling and are inconsistent with nonconstant scaling models such as that of nuttli 1983 second the stress drops of earthquakes in eastern north america and other continental interiors are not significantly different from those of earthquakes in western north america and have median values of approximately 100 bars the source parameters of earthquakes in eastern north america are consistent with a single constant stress drop scaling relation whereas the source parameters of earthquakes in western north america are much more variable and show significant departures from an average scaling relation in which stress drop decreases slightly with seismic moment

sedimentary environments and chemical composition of pacific pelagic sediments abstract the chemical compositions of 140 deep sea sediment samples collected in the pacific ocean were determined by inaa and icp oes methods in order to study the relationship between elemental abundances and the environment of their sedimentation in particular we observed horizontal changes along the longitude of 170 w across the pacific in calcareous ooze there is a positive relationship between ca content and sr content however the mg content is influenced more by basic rock detritus than by biogenic carbonate our observations of red clays suggest 1 the ti al ratio is a good indicator of the contribution of mafic rock detritus 2 the hydrogenous component of pelagic sediments is characterized by high co and mn content but not high v content fe content is influenced primary by basic rock detritus 3 there is a good correlation between p content and cu content high p and cu contents are characteristic of the high primary production zones in pelagic areas for example the equatorial zone the mn content is also considered to be influenced by the primary productivity of overlying surface water

rapid quench hydrothermal experiments at mantle pressures and temperatures new experimental methods for the encapsulation extraction and analysis of large volumes of aqueous fluids enable studies of mineral solubilities and dissolution kinetics with the piston cylinder apparatus quench rates and volumes of experimental fluids with these methods are comparable with those used in modern hydrothermal experiments employing cold seal vessels analyses of fluid compositions are reproducible and consistent with independent results the techniques permit experimental investigations that will better characterize fluid rock interaction in such environments as subducting slabs the mantle wedge barrovian metamorphic belts and middle to lower crustal granulites