ground motion relations for eastern north america predictive relations are developed for ground motions from eastern north american earthquakes of 4 0 m 7 25 at distances of 10 r 500 km the predicted parameters are response spectra at frequencies of 0 5 to 20 hz and peak ground acceleration and velocity the predictions are derived from an empirically based stochastic ground motion model the relations differ from previous work in the improved empirical definition of input parameters and em pirical validation of results the relations are in demonstrable agreement with ground motions from earthquakes of m 4 to 5 there are insufficient data to adequately judge the relations at larger magnitudes although they are consistent with data from the saguenay m 5 8 and nahanni m 6 8 earthquakes the underlying model parameters are constrained by empirical data for events as large as m 6 8

the acquisition of source path and site effects from microearthquake recordings using q tomography application to the united kingdom source site and propagation parameters are inverted from a u k database of weak motion events 2 0 m l 4 7 this results in the complete spectral parameterization of over 3200 velocimetric records of 273 events from the year 1992 to 2006 the s wave is extracted from the vertical records and is processed using a multitaper fourier transform we initially use a nonlinear least squares log space optimization to obtain estimates of the attenuation parameter for each spectrum the estimates of t are then used to geometrically constrain a depth dependent q model using a technique adapted from velocity tomography we then invert for the remaining frequency dependent parameters and a collective amplitude parameter from the velocity spectra while fixing the newly computed attenuation parameters based on raytracing through our q model the resultant amplitude parameters are then split into source moments apparent geometrical spreading and site correction factors we find a frequency independent depth dependent q structure a linear relationship proportional to 0 7 m l between moment magnitude m w and local magnitude m l is found in the range of 2 4 7 m l the majority of stress drops are found to range on the order of 0 1 10 mpa a multiple segment apparent geometrical spreading model is found to best describe the amplitude decay with distance accounting for factors such as geometrical spreading and scattering along with multiple phase interference in the analysis window site response functions are found to broadly correlate with regional geology mean amplification occurring in the cenozoic sedimentary rock sites to the southeast of england relative to the harder palaeozoic rock sites of wales and scotland we use a bootstrap analysis technique to analyze the dependence of our results on the data in order to estimate the variance of the results and check the robustness of different inversions synthetic spectra are also computed in order to obtain minimum variance and bias of model parameters associated with the method in applying a geometrical q constraint through the use of q tomography we find that the robustness of the results is significantly increased a thorough analysis of the trade offs involved in the inversion is performed using synthetic datasets we find strong trade offs between the parameters but we are able to show that this covariance is reduced when adopting the q tomography approach

what is the actual structure of samarskite y a tem investigation of metamict samarskite from the garnet codera dike pegmatite central italian alps we investigated by scanning and transmission electron microscopy sem tem wavelength and energy dispersive spectroscopy wds eds and electron diffraction tomography edt several y ree u th nb ta ti oxides from the garnet codera dike pegmatite central italian alps these oxides have compositions in the samarskite y field and yield an amorphous response from the single crystal x ray diffractometer backscattered electron images reveal that the samples are zoned with major substitutions involving u th with respect to y ree at the tem scale the samples show a continuous range of variability both in terms of composition and in radiation damage and the amount of radiation damage is directly correlated with the u content areas with high u content and highly damaged show crystalline randomly oriented nanoparticles that are interpreted as decomposition products of the metamictization process on the other hand areas with lower u content and radiation dose contained within 0 7 10 16 event mg although severely damaged still preserve single crystal appearance such areas noticeably consisting of relicts of the original samarskite structure were deeply investigated by electron diffraction techniques surprisingly the retrieved crystal structure of untreated samarskite is consistent with aeschynite and not with ixiolite or columbite as believed so far after x ray diffraction experiments on annealed samples in particular the resolved structure is a niobioaeschynite y with pnma space group cell parameters a 10 804 1 b 7 680 1 c 5 103 1 a and composition y 0 53 fe 0 22 ca 0 10 u 0 09 mn 0 07 1 nb 1 07 ti 0 47 fe 0 34 ta 0 07 w 0 06 2 o 6 if this finding can be confirmed and extended to the other members of the group namely samarskite yb calciosamarskite and ishikawaite then the samarskite mineral group should be considered no longer as an independent mineral group but as part of the aeschynite group of minerals it is finally suggested that the rare crystalline sub micrometric ixiolite domains occasionally spotted in the sample by tem or the nanoparticles detected in highly metamict areas interpreted as decomposition product of the metamictization process which may have in fact the ixiolite structure act as seeds during annealing leading to the detection of ixiolite peaks in the x ray powder diffractograms

source parameters of earthquakes in eastern and western north america based on finite fault modeling the ground motion from large earthquakes is often predicted based on finite fault modeling in which the fault plane is discretized into small independently rupturing subfaults the radiation from all subfaults is summed at the observation point despite the success of the method in matching observed ground motion char acteristics the physical interpretation of the subfaults has remained largely unclear and a rationale for the choice of the subfault attributes has been lacking two key parameters the subfault size and the maximum slip velocity on the fault govern the amplitude of the source spectrum at intermediate and high frequencies respec tively we determined these key source parameters on an event by event basis for all well recorded moderate to large earthquakes in western north america wna by fitting simulated to observed response spectra we compare the values of these source parameters with those obtained previously for eastern north america ena and the michoacan mexico earthquakes a total of 26 modeled events we find that the characteristic subevent size increases linearly with moment mag nitude in an apparently deterministic manner the subevent size relationship obtained for wna is not statistically different from that obtained for ena in both regions the subevent size follows the trend of log dl 2 0 4 m 4 m 8 where dl is the subfault size in km this trend agrees well with independent studies by somerville et al 1999 and aki 1992 in which the characteristic size of the patches asperities or barriers on earthquake faults was determined these results indi cate that large earthquakes should be viewed as a sequence of smaller events that comprise the large rupture interestingly the characteristic size of these constituent small events appears to be directly related to the size of the overall rupture the slip velocities determined for all 26 earthquakes vary in a narrow range from about 0 25 to 0 60 m sec with a mean of 0 40 m sec and standard deviation of 0 09 m sec the slip velocities for the ena events are distributed randomly over this range while those for the wna region appear to exhibit a decreasing trend with increasing magnitude our results indicate that a generic region independent earthquake source model for engineering prediction of strong ground motions can be developed

orbital scale stratigraphy and high resolution analysis of biogenic components and deep water oxygenation conditions in the japan sea during the last 640 kyr abstract paleoceanographic conditions in the japan sea changed drastically during the late quaternary in association with orbital and suborbital cycles and glacio eustatic sea level changes however few studies have examined long term sediment records older than 160 ka because of the lack of long and continuous cores and the difficulty in constructing high resolution age models in this study we first constructed an orbital scale stratigraphy of the sediments covering the last 640 kyr by comparing the specmap 18o curve and the 18o curve of planktonic foraminifera 18opf in the japan sea together with the combination zones of dominant planktonic foraminifera species then we reconstructed temporal variations in biogenic silica biosil and biogenic carbonate biocarb contents calculated from high resolution major element analysis data determined by an xrf microscanner in order to evaluate the deep water oxygenation conditions we also defined excess s as the difference between the content of s in the sediments and that for normal marine sediments calculated from the organic carbon content corg estimated from lightness l by assuming a total sulfur content stotal corg ratio of 0 36 and examined its variability biosil shows orbital scale variation and is generally low except during interglacial maxima when global sea level was high enough to allow a strong influx of the tsushima warm current biocarb shows orbital and suborbital scale variations and tends to be higher in dark layers deposited during glacial stages whereas the relationship is reversed during interglacial stages the low biocarb in dark layers deposited during interglacial stages is probably due to dissolution of biogenic carbonate caused by the increase in surface productivity as a result of the strong influx of nutrient rich east china sea coastal water and consequent increase in surface productivity and decomposition rate of organic matter in the intermediate water excess s tends to be higher in thicker dark layers deposited during glacial maxima when the sea level dropped below 90 m compared to adjacent light layers suggesting development of euxinic deep water conditions during these periods the results demonstrated the presence of orbital and suborbital scale variations in biosil and biocarb and their association with dark and light layers in the japan sea that reflect variations in the nature and strength of inflow through the tsushima strait controlled by both climatic and sea level changes whereas higher excess s reflects the development of euxinic deep water condition during glacial maxima in association with glacio eustatic sea level drops below 90 m during the last 640 kyr

site amplifications for generic rock sites seismic shear wave velocity as a function of depth for generic rock sites has been estimated from borehole data and studies of crustal velocities and these velocities have been used to compute frequency dependent amplifications for zero attenuation for use in simulations of strong ground motion we define a genetic rock site as one whose velocity at shallow depths equals the average of those from the rock sites sampled by the borehole data most of the boreholes are in populated areas for that reason the rock sites sampled are of particular engineering significance we consider two genetic rock sites rock corresponding to the bulk of the borehole data and very hard rock such as is found in glaciated regions in large areas of eastern north america or in portions of western north america the amplifications on rock sites can be in excess of 3 5 at high frequencies in contrast to the amplifications of less than 1 2 on very hard rock sites the consideration of unattenuated amplification alone is computationally convenient but what matters for ground motion estimation is the combined effect of amplification and attenuation for reasonable values of the attenuation parameter k 0 the combined effect of attenuation and amplification for rock sites peaks between about 2 and 5 hz with a maximum level of less than 1 8 the combined effect is about a factor of 1 5 at 1 hz and is less than unity for frequencies in the range of 10 to 20 hz depending on t using these amplifications we find provisional values of about ao 70 bars and k 0 0 035 sec for rock sites in western north america by fitting our empirically determined response spectra for an m 6 5 event to simulated values the borehole data yield shear velocities 033o of 618 and 306 rrdsec for rock and soil sites respectively when averaged over the upper 30 m from this we recommend that v30 equals 620 and 310 m sec for applications requiring the average velocity for rock and soil sites in western north america by combining the amplifications for rock sites and the site factors obtained from our analysis of strong motion data we derive amplifications for sites with 17 3o 520 m sec nehrp class c corresponding to a mix of rock and soil sites and v3o 310 and 255 m sec average soil and nehrp class d sites respectively for the average soil site the combined effect of amplification and attenuation exceeds a factor of 2 0 for frequencies between 0 4 and about 4 hz with a peak site effect of 2 4 the peak of the nehrp class d site effect is 2 7

complexity of the mw 6 3 2009 l aquila central italy earthquake 2 broadband strong motion modeling 1 near fault strong ground motions 0 1 10 hz recorded during the mw 6 3 2009 l aquila earthquake exhibit great spatial variability modeling the observed seismograms allows linking distinct features of the observed wavefield to particular source and propagation effects and provides insights on strong motion complexity from this moderate magnitude event we utilize a hybrid integral composite approach based on a k square kinematic rupture model combining low frequency coherent and high frequency incoherent source radiation and providing omega squared source spectral decay several source model features proven to be stable by means of an uncertainty analysis in the preceding low frequency 2 hz

paleoenvironmental changes in the japan sea during the last 85 000 years five distinct changes in the paleoenvironment of the japan sea within the last 85 000 years are revealed from the sedimentary record of a piston core recovered from the oki ridge changes in both surface and deepwater conditions are registered by changes in lithology calcium carbonate content organic carbon content oxygen and carbon isotope ratios and microfossil assemblages including calcareous nannoplankton diatoms radiolaria and foraminifera between 85 and 27 ka the warm tsushima current did not flow into the japan sea and cold surface water conditions prevailed environments at the seafloor fluctuated between dysaerobic to weakly oxic conditions between 27 and 20 ka freshwater input to the japan sea probably from the huang ho river in china stratified the water column and the severe anoxic conditions eliminated most benthic fauna between 20 and 10 ka the cold oyashio current flowed into the japan sea through the tsugaru strait reestablishing deepwater ventilation shallow water benthic assemblages of the north pacific ocean subsequently colonized the japan sea and occupied the vacant niches of the deep basins between 10 and 8 ka the foraminifer compensation level fcl gradually rose to a depth shallower than 1000 m and bottom conditions changed from dysaerobic to oxic at 10 ka the warm tsushima current started to flow into the japan sea through the tsushima strait to establish the modern oceanographic regime which has existed since 8 ka the eustatic sea level during the last glacial maximum was above the sill depths 130 m of the tsushima and tsugaru straits assuming that tectonic movements at these straits were negligible for the last 20 ka

stochastic finite fault modeling of ground motions from the 1994 northridge california earthquake i validation on rock sites the stochastic method of simulating ground motions from finite faults is validated against strong motion data from the m 6 7 1994 northridge california earthquake the finite fault plane is subdivided into elements each element is as signed a stochastic o92 spectrum and the delayed contributions from all subfaults are summed in the time domain simulated horizontal acceleration time histories and fourier spectra at 28 rock sites are compared with observations we first perform simulations using the slip distribution on the causative fault derived from strong motion teleseismic gps and leveling data wald et al 1996 we then test the performance of the method using quasi random distributions of slip and alternative hypocenter locations this is important because the rupture initiation point and slip distribution are in general not known for future earthquakes the model bias is calculated as the ratio of the simulated to the observed spectrum in the frequency band of 0 1 to 12 5 hz averaged over a suite of rock sites the mean bias is within the 95 confidence limits of unity showing that the model provides an accurate prediction of the spectral content of ground motions on average the maximum excursion of the model bias from the unity value when averaged over all 28 rock stations is a factor of approximately 1 6 at most frequencies it is below a factor of 1 4 interestingly the spectral bias and the standard deviation of the stochastic simu lations do not depend on whether the fault slip distribution and hypocenter location are based on data or are randomly generated this suggests that these parameters do not affect the accuracy of predicting the average characteristics of ground motion or they may have their predominant effect in the frequency range below about 0 1 hz below the range of this study the implication is that deterministic slip models are not necessary to produce reasonably accurate simulations of the spectral content of strong ground motions this is fortunate because such models are not available for forecasting motions from future earthquakes however the directivity effects controlled by the hypocenter location are important in determining peak ground ac celeration at individual sites although the method is unbiased when averaged over all rock sites the simulations at individual sites can have significant errors generally a factor of 2 to 3 which are also frequency dependent factors such as local geology site topography or basin propagation effects can profoundly affect the recordings at individual stations to generate more accurate site specific predictions empirical responses at each site could be established

hydrothermal processes in the fen alkaline carbonatite complex southern norway abstract we present detailed textural and chemical analyses of the hydrothermal sulfide and ree th nb mineralization observed in the fen complex southern norway which is the biggest carbonatite related ree and th deposit in europe the alkaline silicate rocks and carbonatites of the fen complex underwent two hydrothermal alteration events that caused i the formation of sulfides and ii re mobilization of ree fe and al this renders the fen complex an ideal locality to study the genesis of hydrothermal sulfide and ree mineralization in carbonatites our observations record a hydrothermal alteration history of the fen carbonatite complex which is relevant to many carbonatite complexes worldwide the first alteration event pyrite stage caused the crystallization of sulfides mostly pyrite in all lithologies and was induced by a sulfide rich fluid 1 that was probably derived from adjacent mafic alkaline silicate rocks veins formed during this hydrothermal event show a typical succession from magnetite via pyrite i hematite magnetite to pyrite ii a subsequent alteration event is characterized by the interaction of two evolving fluids namely 1 a ree rich fluid 2 that was probably derived from the carbonatites autometasomatic fluid and 2 an oxidizing meteoric fluid 3 that mainly introduced si and was in equilibrium with the basement host rocks the interaction of these two fluids with the carbonatitic rocks resulted in various characteristic types of calcite hematite rocks locally called rodberg during their late stage silicification by fluid 3 p was mobilized from magmatic apatite and reprecipitated in close by rodberg veins as small fluorapatite monazite veins the interaction of the carbonatite derived fluid 2 and meteoric fluid 3 also resulted in the formation of distinct zones of lree phases notably ree f carbonates bastnasite parisite synchysite monazite and allanite and hree phases including samarskite aeschynite and an unnamed nb fe ree th oxide the most pronounced hree enrichment occurs in domains of strongest hydrothermal alteration which was probably caused by preferential precipitation of hree rich complexes coupled with later partial leaching of lree by f rich fluids during silicification thorium rich minerals were precipitated in close association with hree rich minerals implying similar hydrothermal behaviour of th and hree

pyroclastic mechanisms for carbonatite intrusion evidence from intrusives in the fen central complex se norway study of field relations and mesostructures of a heterogeneous intrusive body of ankeritic ferrocarbonatite and mafic silicate rocks damtjernite and their hydrothermally altered equivalent roberg i e hematite calcite dolomite carbonatite in the fen complex se norway reveals crosscutting contacts with wallrock gneiss which demonstrates the intrusive nature of the ferrocarbonatite gradual transitions between the two units demonstrate their simultaneous emplacement the ferrocarbonatite contains frequent xenoliths of country rock gneisses and intrusive rocks in a fragmental matric minor late intrusive bodies also contain fragments of rodberg some of the matrix carbonate fragments show signs of accretionary growth with development of subparallel laminations of alternating carbonate and chlorite rich material ferrocarbonatite and damtjernite were emplaced as several pulses of fluidized material and fluidization took place at a shallow level in the crust the intrusion mechanism was pyroclas

carbon sulfur plots to show diagenetic and epigenetic sulfidation in sediments abstract organic carbon vs sulfide sulfur plots are now being used regularly by many geochemists to help understand recent and ancient depositional environments and diagenetic processes usually these plots are useful to recognize nonmarine vs marine environments or oxic vs anoxic vs euxinic depositional environments however c vs s plots can also indicate diagenetic and epigenetic events that produce excess sulfide four new examples are presented and discussed

a model for the evolution of hematite carbonatite based on whole rock major and trace element data from the fen complex southeast norway abstract ree rich hematite carbonatites are found in numerous carbonatite complexes worldwide commonly associated with ankerite bearing carbonatites the mineralogy of the hematite carbonatites contradicts a primary magmatic origin hematite calcite dolomite carbonatite in the fen complex southeast norway was formed by postmagmatic oxidation and partial dissolution of ankeritic ferrocarbonatite in this process major components such as cao mgo and co 2 and trace elements such as the light rare earths were removed from the rock while more insoluble components fe 2 o 3 th y and the middle rare earths were retained in the solid residue it is possible to model the alteration of the rocks in terms of a two stage recrystallization and leaching process corresponding to two distinct stages of the reequilibration of the carbonatite mineralogy the first step took place at oxygen fugacities below the hematite magnetite buffer ferrous iron in part leached from the system the second at more oxidizing conditions fe immobile the most strongly altered carbonatite has lost more than 70 of its original volume during reequilibration ferrous iron and ree leached from the ferrocarbonatite during early reequilibration precipitated as hydrothermal magnetite pyrite ores with accessory ree minerals reequilibration leaching and redeposition processes like those recognized at fen may be important factors controlling the mineralogy and geochemistry of ree enriched carbonatites in general

analysis of the thm behaviour in a clay based engineered barrier system ebs modelling of the he e experiment mont terri url to understand the complex thermo hydro mechanical thm processes and their evolution in a clay based engineered barrier systems ebs during the closure phase of a geological repository for radioactive waste a 1 2 scale in situ heating experiment he e experiment has been ongoing since 2011 in the mont terri rock laboratory based on the experimental data a fully coupled thm 3d simulation using the finite element program opengeosys was carried out the main objectives of the simulation were to interpret the experimental observations to understand the thermally induced thm interactions and to analyse the different material properties five experimental phases were numerically interpreted in order to take into account the changes in the temporary material properties during experimental operations these included the tunnel excavation the ventilation the emplacement of the bentonite ebs the heating phase and the phase after shutdown of the heater a non isothermal richards flow model was used to take into account the evaporation and vapour diffusion during the heating the material behaviours of ebs in association with the saturation dependent thermal conductivity and the water retention behaviour under high temperatures were analysed in detail the strong thermal hydraulic and mechanical anisotropic properties of the opalinus clay were described by a transversely isotropic model

simulating strong motions of large earthquakes using recordings of small earthquakes the loma prieta mainshock as a test case abstract a simple method is developed for predicting ground motions for future large earthquakes for specific sites by summing and filtering recordings of adjacent small earthquakes this method is tested by simulating strong motion records for the loma prieta earthquake m 7 0 using aftershocks m 3 7 to 4 0 recorded at the same sites i use an asperity rupture model where the rms stress drop averaged over the fault plane is constant with moment the observed spectra indicate that stress drop remains constant from the m 3 aftershocks up to the m 7 mainshock about six orders of magnitude in seismic moment each simulation sums the seismogram of one aftershock with time delays appropriate for propagating rupture and incorporates directivity and site response the simulation scales the spectrum in accordance with a constant stress drop 2 source model in this procedure the high frequency energy of the aftershock sum above the corner frequency of the aftershock is not reduced when it is convolved with the mainshock slip velocity function unlike most previous methods of summation for most cases the spectra 0 6 to 20 hz peak accelerations and durations of the simulated mainshock records are in good agreement with the observed strong motion records even though only one aftershock waveform was used in each simulation this agreement indicates that the response of these soil sites is essentially linear for accelerations up to about 0 3 g the summed aftershock records display the same site dependent values of f max as the mainshock records implying that f max is a site effect rather than a property of the mainshock rupture process

earthquake ground motion prediction equations for eastern north america new earthquake ground motion relations for hard rock and soil sites in eastern north america ena including estimates of their aleatory uncertainty vari ability have been developed based on a stochastic finite fault model the model incorporates new information obtained from ena seismographic data gathered over the past 10 years including three component broadband data that provide new in formation on ena source and path effects our new prediction equations are similar to the previous ground motion prediction equations of atkinson and boore 1995 which were based on a stochastic point source model the main difference is that high frequency amplitudes f 5 hz are less than previously predicted by about a factor of 1 6 within 100 km because of a slightly lower average stress parameter 140 bars versus 180 bars and a steeper near source attenuation at frequencies less than 5 hz the predicted ground motions from the new equations are generally within 25 of those predicted by atkinson and boore 1995 the prediction equations agree well with available ena ground motion data as evidenced by near zero average residuals within a factor of 1 2 for all frequencies and the lack of any significant residual trends with distance however there is a tendency to positive residuals for moderate events at high frequencies in the distance range from 30 to 100 km by as much as a factor of 2 this indicates epistemic uncertainty in the prediction model the positive residuals for moderate events at 100 km could be eliminated by an increased stress parameter at the cost of producing negative residuals in other magnitude distance ranges adjustment factors to the equations are provided that may be used to model this effect

sediment fabrics oxygenation history and circulation modes of japan sea during the late quaternary abstract the quaternary hemipelagic sediments of the japan sea are characterized by centimeter to decimeter scale alternations of heavily bioturbated organic poor light layers and finely laminated organic rich dark layers these dark and light layers which can be correlated throughout the deeper part of the basin are considered to reflect changes in bottom water oxygenation however depositional mechanisms responsible for individual dark layers and causes of oxygen depletion are not fully understood two possible settings for deposition of organic rich dark layers are recognized one is a stratified ocean like the black sea where limited vertical advection results in euxinic conditions in the deeper parts of the basin the other is an upwelling region like the arabian sea where the oxygen minimum zone is intensified by enhanced nutrient upwelling and surface productivity in this study fabrics of hemipelagic sediments deposited in the japan sea during the last 160 ka were studied in three cores collected from different latitudes and water depths fabrics were classified into 4 classes based on corresponding bottom water oxygenation level five dark layer types were defined based on the distribution patterns of sediment fabric classes within each dark layer comparison of dark layer types at shallower and deeper sites in a chronologic framework provided evidence for five different modes of deep water circulation these circulation modes which reflect relative intensities of upwelling and density stratification appear to be related to global sea level changes as well as climate impact on the nature of water influx through the tsushima strait

strong ground motion simulation of the 6 april 2009 l aquila italy earthquake on 6 april 2009 an earthquake of mw 6 13 herrmann et al 2011 occurred in central italy close to the town of l aquila although the earthquake is considered to be a moderate size event it caused extensive damage to the surround ing area the earthquake is identified with significant directivity effects high amplitude short duration motions are observed at the stations that are oriented along the rupture direction whereas low amplitude long duration motions are observed at the stations oriented in the direction opposite to the rupture the complex nature of the earthquake combined with its damage potential brings the need for studies that assess the seismological characteristics of the 2009 l aquila mainshock in this study we present the strong ground motion simulation of this particular earthquake using a stochastic finite fault model with a dynamic corner frequency ap proach for modeling the resulting ground motions we choose two finite fault source models that take into account the source complexity of the l aquila mainshock in order to test the sensitivity of ground motion parameters to the seismic wave attenua tion parameters we use two different attenuation models obtained in the study region using weak motion and strong motion databases comparisons are made between the attenuation of synthetics and ground motion prediction equations gmpes synthetic ground motions are further compared with the observed ones in terms of fourier amplitude and response spectra at 21 strong ground motion stations that recorded the mainshock within an epicentral distance of 100 km the spatial distribution of shaking intensity obtained from the did you feel it project and site survey results are compared with the spatial distributions of simulated peak ground motion intensity parameters our results show that despite the limitations of the method in simulating the directivity effects the stochastic finite fault model seems an effective and fast tool to simulate the high frequency portion of ground motions

anoxia vs productivity what controls the formation of organic carbon rich sediments and sedimentary rocks discussion the prevailing explanation for the origin of organic rich sediments and rocks invokes deposition under conditions of anoxia however recent research suggests that high primary production and not water column anoxia provides the first order control on the accumulation of organic rich facies in the modern oceans oxygen minima do not appear to have any direct effect on carbon accumulation in continental margin or marginal sea environments sediments accumulating in the modern black sea the type euxinic basin are not particularly enriched in organic matter despite the presence of an anoxic water column although a sapropel containing extremely high carbon concentrations was deposited during the holocene at a time when the basin was oxic results of a recently published co pled ocean atmosphere model indicate that during the cretaceous thermohaline and surface circulation in the oceans was similar to or more intense than modern conditions despite the overall equable climate such conditions confound the idea that circulation in the cretaceous atlantic for example was punctuated by oceanic anoxic events brought about by more sluggish circulation sporadic temporal and spatial increases in primary production reflecting changes in the behavior and or state of the ocean atmosphere system constitute a more tenable explanation for the occurrence of modern and quaternary carbon rich sediments and cretaceous black shales consequently the fundamental control on the accumulation of carbon rich facies in the oceans and marginal seas is not the presence or absence of anoxia

an empirical study of earthquake source spectra for california earthquakes we generalize source path and site effects for california earthquakes as functions of magnitude and distance based on regression analysis of 1000 fourier acceleration spectra from 43 california earthquakes in the moment magnitude range from 4 4 to 7 4 recorded at rupture distances from 1 to 200 km empirically derived source spectra for california earthquakes are generally inconsistent with the spectral shape implied by a brune omega squared point source model this is manifested by magnitude and frequency dependence of the brune model parameters for ex ample the brune stress parameter that best matches the data at high frequencies decreases from a value of about 120 bars at m5 5 to a value near 50 bars at m7 5 at frequencies below 1 hz though source spectra have much lower spectral ampli tudes than predicted by the brune point source model for these values of stress this discrepancy grows with increasing magnitude finite fault simulations indicate that this is a consequence of the breakdown of the validity of the point source approxi mation for large ruptures a stochastic finite fault model in which the fault is dis cretized as a number of subfaults each of which is represented by a brune omega squared point source correctly matches the observed spectral shapes and amplitudes the spectral decay parameter kappa representing average near surface attenuation of high frequency motion at rock sites increases with increasing magnitude from values near 0 035 sec at m5 5 to 0 050 sec at m7 5 magnitude dependence of kappa may be interpreted as evidence of nonlinearity for typical california sites subjected to strong ground motion comparisons of our empirical source spectra for california to corresponding spec tra for eastern north america suggest that the spectral amplitudes are similar in the two regions for low frequency motions f 2 hz for m5 5 f 0 5 hz for m7 5 for equivalent crustal conditions the eastern events appear to have enhanced high frequency near source amplitudes relative to the california events this is particularly pronounced for large magnitude earthquakes

experimental determination of stability relations between monazite fluorapatite allanite and ree epidote as a function of pressure temperature and fluid composition the experimental alteration of monazite to allanite ree epidote fluorapatite and or fluorapatite britholite was investigated at 450 to 610 mpa and 450 to 500 c experiments involved monazite albite k feldspar muscovite biotite sio 2 caf 2 and variety of fluids including h 2 o kcl h 2 o nacl h 2 o cacl 2 h 2 o na 2 si 2 o 5 h 2 o 1 m hcl 2 m naoh 2 m koh 1 m ca oh 2 2 m ca oh 2 and caco 3 h 2 o the reaction products or lack thereof clearly show that the stability relations between monazite fluorapatite and allanite or ree epidote are more dependent on the fluid composition and the ratio of silicate minerals than on the p t conditions a high ca content in the fluid promotes monazite dissolution and the formation of fluorapatite and allanite or ree epidote lowering the ca content and raising the na content in the fluid decreases the solubility of monazite but promotes the formation of allanite replacing na with k in the same fluid causes fluorapatite with a britholite component to form from the monazite however allanite and ree epidote are not formed monazite is stable in the presence of nacl brines in kcl brine monazite shows a very limited reaction to fluorapatite when the fluid is na 2 si 2 o 5 h 2 o strong dissolution of monazite occurs resulting in the mobilization of rees and actinides to form fluorapatite britholite and turkestanite these experimental results are consistent with natural observations of the partial to total replacement of monazite by fluorapatite ree epidote and allanite in fluid aided reactions involving the anorthite component in plagioclase at mid to high grade metamorphic conditions in contrast an alkali bearing environment with excess na prevents the growth of allanite and eventually promotes the precipitation of secondary monazite the results from this study provide implications for geochronology and for deducing fluid compositions in metamorphic rocks

hydrothermal transport deposition and fractionation of the ree experimental data and thermodynamic calculations abstract for many years our understanding of the behavior of the ree in hydrothermal systems was based on semi empirical estimates involving extrapolation of thermodynamic data obtained at 25 c haas et al 1995 wood 1990a since then a substantial body of experimental data has accumulated on the stability of aqueous complexes of the ree these data have shown that some of the predictions of haas et al 1995 are accurate but others may be in error by several orders of magnitude however application of the data in modeling hydrothermal transport and deposition of the ree has been severely hampered by the lack of data on the thermodynamic properties of even the most common ree minerals the discrepancies between the predictions of haas et al 1995 and experimental determinations of the thermodynamic properties of aqueous ree species together with the paucity of data on the stability of ree minerals raise serious questions about the reliability of some models that have been proposed for the hydrothermal mobility of these critical metals in this contribution we review a body of high temperature experimental data collected over the past 15 years on the stability of ree aqueous species and minerals using this new thermodynamic dataset we re evaluate the mechanisms responsible for hydrothermal transport and deposition of the ree we also discuss the mechanisms that can result in ree fractionation during their hydrothermal transport and deposition our calculations suggest that in hydrothermal solutions the main ree transporting ligands are chloride and sulfate whereas fluoride carbonate and phosphate likely play an important role as depositional ligands in addition to crystallographic fractionation which is based on the differing affinity of mineral structures for the ree our models suggest that the ree can be fractionated hydrothermally due to the differences in the stability of the lree and hree as aqueous chloride complexes

nd pb and sr isotope systematics of fluorite at the amba dongar carbonatite complex india evidence for hydrothermal and crustal fluid mixing the cretaceous amba dongar complex contains one of the largest fluorite deposits 11 6 million tons at 30 wt caf 2 associated with any carbonatite fluorite mineralization postdates carbonatite emplacement and takes the form of replacement hydrothermal veins concentrated at the carbonatite country rock contact sr isotope ratios from the amba dongar fluorites reveal large isotopic variations that can only be attributed to reaction between a carbonatite derived f rich fluid and continental crust or crustal derived fluid the extremely variable initial 87 sr 86 sr ratios 0 70910 0 71729 are intermediate between those of the carbonatites 0 70549 0 70628 and the host bagh sandstones 0 75359 0 78274 they correlate negatively with sr abundances dances sr isotope ratios from intrasample fluorites show large isotopic variations 0 70910 0 71425 that cover almost the entire range of values found for all of the fluorites measured from amba dongar the pb isotope ratios from the fluorites are also variable and differ from those of the country rocks compared to the carbonatites most contain similar 207 pb 204 pb and 208 pb 204 pb ratios but more radiogenic 206 pb 204 pb values galena and pyrite coeval with fluorite mineralization have pb isotope ratios which overlap those from most of the fluorites but which are isotopically distinct from one another in contrast initial 143 nd 144 nd isotope ratios from most of the fluorites are relatively uniform 0 51240 051247 quite different to those from the surrounding bagh sandstones 0 51122 0 51149 but similar to those from the carbonatites 0 51248 0 51253 the new isotopic results are partly consistent with a model for fluorite deposition involving interaction between ground waters within the surrounding country rocks and an f rich carbonatite derived fluid deans and powell 1968 the variation in the sr isotope composition for the fluorites suggests that certain physio chemical parameters of the mineralizing fluids were changing with time of deposition

fluid mediated partial alteration in monazite the role of coupled dissolution reprecipitation in element redistribution and mass transfer monazite ce lree th u ca p si o4 with complex zoning in th and other elements is commonly observed in metamorphic and igneous rocks the hypothesis that this alteration is a product of fluid mediated element mass transfer has been tested in the piston cylinder press caf2 assembly cylindrical graphite oven at 1 000 mpa and 900 c and in cold seal autoclaves on a hydrothermal line at 500 mpa and 600 c experiments included a relatively homogeneous monazite ce 7 8 wt tho2 from a heavy mineral sand plus a series of alkali bearing fluids including 2n naoh 2n koh and na2si2o5 h2o experiments were conducted using bse imaging emp analysis and both tem and hrtem a subset of monazite grains from each experiment show evidence of partial alteration in the form of areas enriched in th si with sharp curvilinear compositional boundaries extending from the grain rim into the monazite interior these thsio4 enriched textures are similar to those commonly seen in natural examples of metasomatised monazite in both magmatic and metamorphic rocks in the na2si2o5 h2o experiments scarce inclusions of britholite formed in the altered monazite the altered monazite is also characterised by strong depletion in pb ca and y thorium and si mobility coupled with the formation of britholite inclusions during partial alteration in the monazite grain is considered to be the product of fluid aided coupled dissolution reprecipitation as opposed to solid state diffusion since other fluids including nacl and kcl brines do not result in the formation of these textures the experimental replication of thsio4 enriched areas in the monazite strongly suggests that similar textures in monazite observed in nature are fluid induced specifically by alkali bearing fluids if true complex metasomatically induced textures in monazite could yield information concerning the nature of the fluid responsible for their formation as well as allow for the dating of the metasomatic event presuming that all the original radiogenic pb has been removed

simulation of acceleration field of the lushan earthquake ms7 0 april 20 2013 china abstract the acceleration field of the lushan earthquake ms7 0 april 20 2013 china is simulated using a new modified version of the stochastic finite fault method exsim based on a dynamic corner frequency approach to incorporate the effect of heterogeneous slip distribution on the variation of source spectrum we adopt an empirical source spectral model and derive the corresponding dynamic parameters which vary with the cumulative seismic moment of the ruptured area the new modified method is validated by 1 comparison of the simulation results with those obtained from the exsim method using near fault ground motion data of the 1994 northridge earthquake 2 comparison of simulated pga contour map inferred from synthetic time histories at 315 grid locations with the observed pga shakemap for the 2013 lushan earthquake 3 comparison of simulated pga with those predicted by ground motion prediction equations gmpes and 4 comparison of simulated time histories with observed acceleration records at six strong motion stations during the mainshock of the lushan earthquake in which local site response is considered in the simulation these comparisons confirm the validity of the new simulation procedure for purposes of regional strong ground motion estimation limitations of the procedure in modeling the phasing of different arrivals in the seismic signal and near surface response of geologic deposits are discussed

magmatic fluids in the fen carbonatite complex s e norway three different types of carbonatite magma may be recognized in the cambrian fen complex s e norway 1 peralkaline calcite carbonatite magma derived from ijolitic magma 2 alkaline magnesian calcite carbonatite magma which yielded biotite amphibole sovite and dolomite carbonatite and 3 ferrocarbonatite liquids related to 2 and or to alkaline lamprophyre magma damjernite apatite formed during the pre emplacement evolution of 2 contains inclusions of calcite and dolomite devitrified mafic silicate glass and aqueous fluid all of these inclusions have a magmatic origin and were trapped during a mid crustal fractionation event p 4 kbars t 625 c where apatite and carbonates precipitated from a carbonatite magma which coexisted with a mafic silicate melt the fluid inclusions contain water dissolved ionic species mainly nacl with minor polyvalent metal salts and in some cases co2 two main groups of fluid inclusions are recognized type a co2 bearing inclusions of approximate molar composition h2o 88 90 co 27 5 nacl 5 d 0 85 0 87 g cm3 type b co2 free aqueous inclusions with salinities from 1 to 24 wt nacleq and densities betwen 0 7 and 1 0 g cm3 more strongly saline type b inclusions salinity ca 35wt d 1 0 to 1 1 g cm3 contain solid halite at room temperature and occur in overgrowths on apatite type a inclusions probably contain the most primitive fluid from which type b fluids have evolved during fractionation of the magmatic system type b inclusions define a continuous trend from low towards higher salinities and densities and formed as a result of cooling and partitioning of alkali chloride components in the carbonatite system into the fluid phase available petrological data on the carbonatites show that the fluid evolution in the fen complex leads from a regime dominated by juvenile co2 h2o fluids during the magmatic stage to groundwater derived aqueous fluids during post magmatic reequilibration

the slip history of the 1994 northridge california earthquake determined from strong motion teleseismic gps and leveling data we present a rupture model of the northridge earthquake determined from the joint inversion of near source strong ground motion recordings p and sh teleseismic body waves global positioning system gps displacement vectors and permanent uplift measured along leveling lines the fault is defined to strike 122 and dip 40 to the south southwest the average rake vector is determined to be 101 and average slip is 1 3 m the peak slip reaches about 3 m our estimate of the seismic moment is 1 3 0 2 10 26 dyne cm potency of 0 4 km3 the rupture area is small relative to the overall aftershock dimensions and is approximately 15 km along strike nearly 20 km in the dip direction and there is no indication of slip shallower than about 5 to 6 km the up dip strong motion velocity waveforms are dominated by large s wave pulses attributed to source directivity and are comprised of at least 2 to 3 distinct arrivals a few seconds apart stations at southern azimuths indicate two main s wave arrivals separated longer in time about 4 to 5 sec these observations are best modeled with a complex distribution of subevents the initial s wave arrival comes from an asperity that begins at the hypocenter and extends up dip and to the north where a second larger subevent is centered about 12 km away the secondary s arrivals at southern azimuths are best fit with additional energy radiation from another high slip region at a depth of 19 km 8 km west of the hypocenter the resolving power of the individual data sets is examined by predicting the geodetic gps and leveling displacements with the dislocation model determined from the waveform data and vice versa and also by analyzing how well the teleseismic solution predicts the recorded strong motions the general features of the geodetic displacements are not well predicted from the model determined independently from the strong motion data likewise the slip model determined from geodetic data does not adequately reproduce the strong motion characteristics whereas a particularly smooth slip pattern is sufficient to satisfy the geodetic data the strong motion and teleseismic data require a more heterogeneous slip distribution in order to reproduce the velocity amplitudes and frequency content although the teleseismic model can adequately reproduce the overall amplitude and frequency content of the strong motion velocity recordings it does a poor job of predicting the geodetic data consequently a robust representation of the slip history and heterogeneity requires a combined analysis of these data sets

a 36 kyr geochemical record from the sea of japan of organic matter flux variations and changes in intermediate water oxygen concentrations intervals of organic c and carbonate rich laminated sediments occur in the sea of japan with roughly the same frequency as temperature changes observed in greenland ice cores providing clear evidence of rapid oceanographic change during the past 36 kyr planktonic foraminiferal 18o data suggest that only the laminated sediments deposited during the last glacial maximum lgm and perhaps one other interval formed during a period of increased water column stratification sedimentary re and mo data are consistent with bottom waters that were sulfidic during the lgm and suboxic during other laminated intervals results of a numerical model of corg and re burial are consistent with a mechanism whereby an increased corg flux to the seafloor drove oxygen concentrations toward depletion during times of deposition of the suboxic laminated intervals such a process could have resulted from increased upwelling driven either by increased deep water formation due to colder and or more saline surface waters or by stronger northeasterly monsoonal winds

the effect of quaternary alluvium on strong ground motion in the coyote lake california earthquake of 1979 abstract the effect of alluvium on strong ground motion can be seen by comparing two strong motion records of the coyote lake california earthquake of 6 august 1979 m l 5 9 one record at a site on franciscan bedrock had a peak horizontal acceleration of 0 13 g and a peak horizontal velocity of 10 cm sec the other at a site 2 km distant on 180 meters of quaternary alluvium overlying franciscan had values of 0 26 g and 32 cm sec amplifications by factors of 2 and 3 horizontal motions computed at the alluvial site for a linear plane layered model based on measured p and s velocities show reasonably good agreement in shape with the observed motions but the observed peak amplitudes are greater by a factor of about 1 25 in acceleration and 1 8 in velocity about 15 per cent of the discrepancy in acceleration and 20 per cent in velocity can be attributed to the difference in source distance the remainder may represent focusing by refraction at a bedrock surface concave upward there is no clear evidence of nonlinear soil response fourier spectral ratios between motions observed on bedrock and alluvium show good agreement with ratios predicted from the linear model in particular the observed frequency of the fundamental peak in the amplification spectrum agrees with the computed value indicating that no significant nonlinearity occurs in the secant shear modulus computations show that nonlinear models are compatible with the data if values of the coefficient of dynamic shear strength in terms of vertical effective stress are in the range of 0 5 to 1 0 or greater the data illustrate that site amplification may be less a matter of resonance involving reinforcing multiple reflections and more the simple effect of the low near surface velocity application of traditional seismological theory leads to the conclusion that the site amplification for peak horizontal velocity is approximately proportional to the reciprocal of the square root of the product of density and shear wave velocity

late proterozoic and carboniferous ultramafic magmatism of carbonatitic affinity in southern norway ultramafic dikes with carbonatitic affinities damtjernites in southern norway were generated during two magmatic events separated by about 275 ma the older event is late proterozoic and the younger is mid carboniferous more than 50 satellitic damtjernite intrusions occur within a 1500 km2 large region surrounding the fen central complex phlogopite macrocrysts from 10 of these satellites yield a rb sr isochron age of 578 24 ma 2 expanded errors this demonstrates that the late proterozoic carbonatitic magmatism centered at the fen central complex occurred on a regional scale this region is termed the fen province the emplacement of the magmas in the fen province most likely occurred in connection with minor extensional tectonic activity on the baltic platform during the drift phase after the proto atlantic opening sr isotopic data also show that a dike mineralogically and chemically similar to the fen damtjernites was emplaced at 324 4 ma mid carboniferous this dike very likely dates the initiation of magmatism in the oslo rift consequently very similar carbonate bearing ultramafic magmas were generated within the south norwegian mantle during the relatively minor fen event and in the initial extensional period when the magma production in the oslo rift was still low

land ocean linkages over orbital and millennial timescales recorded in late quaternary sediments of the japan sea late quaternary sediments of the japan sea are characterized by centimeter to meter scale alternations of dark and light layers which are synchronous basinwide high resolution analyses of the sediments from ocean drilling program site 797 reveal that deposition of the meter scale alternations reflect variations in paleoceanographic conditions which were closely associated with glacio eustatic sea level changes through the modulation of the volume and character of the influx to the sea through the tsushima strait the centimeter to decimeter scale alternations reflect millennial scale variations which are possibly associated with dansgaard oeschger d o cycles with each dark layer appearing to correspond to an interstadial this variability is attributed to the development of a humid climate in central to eastern asia and the consequent increase in discharge from the huanghe and changjiang rivers during interstadials this caused expansion of the east china sea coastal water ecscw which penetrated more strongly into the japan sea the increased influence of the lower salinity nutrient enriched ecscw reduced deep water ventilation and enhanced the surface productivity leading to the development of anoxic bottom waters and deposition of the dark layers thus the centimeter to decimeter scale alternations of the dark and light layers record wet and dry cycles in central to eastern asia possibly associated with d o cycles

ground motion attenuation from the 1995 kobe earthquake based on simulations using the hybrid green s function method because of the limited number of strong motion stations in the kobe area at the time of the 1995 kobe earthquake information about the characteristics of the near fault ground motion acceleration in bedrock is sparse in this study we estimated the near fault ground motion and derived characteristics of its attenuation on rock using an hybrid broadband technique and a source model that have been validated against data we found that at high frequencies the near fault ground motion produced by the kobe earthquake was of the same level as that predicted by the empirical attenuation relation for japanese crustal earthquakes the areas with the largest peak horizontal acceleration are located at the extremities of the fault and include most of the kobe city

multi stage formation of ree minerals in the palabora carbonatite complex south africa the 2060 ma old palabora carbonatite complex pcc south africa comprises diverse ree mineral assemblages formed during different stages and reflects an outstanding instance to understand the evolution of a carbonatite related ree mineralization from orthomagmatic to late magmatic stages and their secondary post magmatic overprint the 10 rare earth element minerals monazite ree f carbonates bastnasite parisite synchysite ancylite britholite cordylite fergusonite ree ti betafite and anzaite are texturally described and related to the evolutionary stages of the pcc the identification of the latter five ree minerals during this study represents their first described occurrences in the pcc as well as in a carbonatite complex in south africa the variable ree mineral assemblages reflect a multi stage origin 1 fergusonite and ree ti betafite occur as inclusions in primary magnetite bastnasite is enclosed in primary calcite and dolomite these three ree minerals are interpreted as orthomagmatic crystallization products 2 the most common ree minerals are monazite replacing primary apatite and britholite texturally related to the serpentinization of forsterite or the replacement of forsterite by chondrodite textural relationships suggest that these two ree minerals precipitated from internally derived late magmatic to hydrothermal fluids their presence seems to be locally controlled by favorable chemical conditions e g presence of precursor minerals that contributed the necessary anions and or cations for their formation 3 late stage post magmatic ree minerals include ancylite and cordylite replacing primary magmatic ree sr carbonates anzaite associated with the dissolution of ilmenite and secondary ree f carbonates the formation of these post magmatic ree minerals depends on the local availability of a fluid whose composition is at least partly controlled by the dissolution of primary minerals e g ree fluorocarbonates this multi stage ree mineralization reflects the interplay of magmatic differentiation destabilization of early magmatic minerals during subsequent evolutionary stages of the carbonatitic system and late stage fluid induced remobilization and re precipitation of precursor ree minerals based on our findings the palabora carbonatite complex experienced at least two successive stages of intense fluid rock interaction

a statistical model for ground motion produced by earthquakes at local and regional distances to adapt random process theory techniques for statistical estimation of peak ground motion to more realistic earth models we constrain the parameters of duration geometrical spreading and spectral shape by modeling the main ground motion as being the result of major contributions by the direct s wave and supercritically reflected s waves the results of our modeling are constrained to be consistent with values from full wave synthetics for the test models the combination of estimation theory and theoretical amplitude spectrum of the main ground motion within the ergodic window successfully predicts the mean peak vertical ground displacements velocities and accelerations of the 1982 miramichi earthquakes in new brunswick canada in addition upon considering the effects of source depth and crustal structure for the november 25 1988 saguenay earthquake m 5 8 in quebec canada the predicted mean peak horizontal ground accelerations match the observed data very well the effects of source depth and crustal structure on the peak ground motion are complicated for different source sizes and at different epicentral distance ranges