effects of regolith megaregolith insulation on the cooling histories of differentiated asteroids the cooling histories and in particular the core cooling rates of differentiated asteroids are calculated employing a variety of thermal conductivity structures in order to simulate the potential insulating effects of regolith and megaregolith brecciated impact rubble layers the regolith is assumed to have thermal conductivity 0 005 the unbrecciated mantle conductivity and its thickness in our most typical model is assumed to be 0 003 the parent body radius the megaregolith if present is assumed to have thermal conductivity 0 1 that of unbrecciated mantle we find that a combination of relatively thick megaregolith and regolith can potentially reduce the core cooling rate by more than a factor of 10 below the rate predicted by models with conventional thermal conductivity structure for any given measured cooling rate the radius implied for the parent asteroid can potentially be reduced by a factor of 5 from the radius predicted by models with conventional thermal conductivity structure realistically the regolith and megaregolith thicknesses required to engender these extreme effects were probably seldom generated except perhaps within the largest asteroids where even if generated they would quickly be reduced by compaction and sintering nonetheless our results for models with plausible regolith and megaregolith thicknesses indicate that most of the iron meteorites and the pallasites probably formed in relatively small r less than 50 km parent bodies we have parameterized our results so that effects of intermediate configurations can readily be calculated the parameterization also facilitates evaluation of additional variables e g the initial temperature the concentrations of long lived radioactive heat sources etc albeit these variables are far less crucial than the thermal conductivity structure our results indicate that the insulation of even a thin regolith causes metallalographic cooling rates to be relatively uniform and practically independent of depth within a given asteroid stochastic differences in cratering regolith production histories may have engendered radically different cooling rates from asteroids of similar radius or similar cooling rates from asteroids of different radius

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

region specific assessment adjustment and weighting of ground motion prediction models application to the 2015 swiss seismic hazard maps we present a strategy for the region specific assessment adjustment and weighting of ground motion prediction models with application to the 2015 swiss national seismic hazard maps the models are provided within a logic tree framework adopted for the probabilistic seismic hazard analysis psha through this framework we consider both aleatory and epistemic uncertainties in ground motion prediction in switzerland a region of low to moderate seismicity and consequently data poor in terms of strong motion records we use both empirical models developed using global strong motion data and stochastic simulation models calibrated to local seismicity characteristic wave propagation effects and site conditions the empirical models were adjusted to account for a the selected hazard reference rock velocity model using v s adjustments and b the median instrumental ground motion data at low magnitudes the use of a carefully calibrated simulation model and v s adjusted empirical ground motion prediction equations allowed us to precisely define the reference rock profile upon which subsequent analyses such as microzonation and site specific hazard can be applied without uncertainty related to the reference condition we implemented partially nonergodic aleatory uncertainties in ground motion prediction through the single station sigma approach this strategy complemented with the known reference rock condition leads to significant reductions in the contribution of uncertainty in ground motion characterization to psha in switzerland however the application of the methodological framework outlined herein extends to any region particularly those of low to moderate seismicity online material tables of adjustment factors to convert selected ground motion prediction equations gmpes to the swiss rock reference and figures showing trellis plots of all adjusted gmpes with uncertainty estimates

seismic evidence for a chemical heterogeneity in the midmantle a strong and slightly dipping seismic reflector beneath the mariana subduction zone 1 a clear later phase 80 s after the direct p wave is observed in most of individual seismograms recorded by a short period seismometer network in japan j array from a cluster of deep earthquakes that occurred at the northern mariana subduction zone this phase 1 shows a p wave particle motion 2 arrives later from earthquakes with shallower focal depths 3 has a steeper incident angle than that of p wave and 4 shows a deviation of a few degrees in the arrival azimuth from that of p wave we interpret it as an s to p converted wave which takes off downward from the source and is reflected at a velocity discontinuity reflector below the earthquakes travel time inversion shows that the seismic reflector dips southwest by 20 at 24 25 n 144 75 e and at a depth of 1115 km with a lateral extension at least 100 100 km the location corresponds to the lower edge of a high velocity anomaly in global tomographic models amplitude and waveform analyses suggest a decrease of s wave velocity by 2 6 and an increase of density by 2 9 within the reflector there is almost no difference in p wave velocity 1 between the reflector and the surrounding mantle the estimated thickness of the reflector is 12 km these observations indicate that the observed seismic structure is more likely to be a chemical reservoir rather than a purely thermal anomaly the seismic reflector might be a piece of subducted oceanic crust as suggested by a previous study it also could be related to the break down of the d phase of dense hydrous magnesium silicates at midmantle pressure condition reported by recent mineral physics studies both scenarios imply that mechanical chemical segregation might occur within the subducted slab at midmantle condition

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

phase transitions in pyrolite and morb at lowermost mantle conditions implications for a morb rich pile above the core mantle boundary abstract subduction of mid oceanic ridge basalt morb gives rise to strong chemical heterogeneities in the earth s mantle possibly extending down to the core mantle boundary phase relations in both pyrolite and morb compositions are precisely determined at high pressures and temperatures corresponding to lowermost mantle conditions the results demonstrate that the post perovskite phase transition occurs in pyrolite between 116 and 121 gpa at 2500 k while post perovskite and sio2 phase transitions occur in morb at 4 gpa lower pressure at the same temperature theory predicts that these phase changes in pyrolite and morb cause shear wave velocity increase and decrease respectively near the northern margin of the large low shear velocity province in the lowermost mantle beneath the pacific reflections from a negative shear velocity jump near 2520 km depth are followed by reflections from a positive velocity jump 135 to 155 km deeper these negative and positive velocity changes are consistent with the expected phase transitions in a dense pile containing a mixture of morb and pyrolitic material this may be a direct demonstration of the presence of accumulations of subducted morb crust in the deep mantle

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

phase transformations in subducted oceanic crust and buoyancy relationships at depths of 600 800 km in the mantle abstract phase transformations in a representative oceanic crust composition morb have been studied at pressures up to 28 gpa at 1200 c and 1500 c using a multi anvil apparatus the assemblage of majorite casio 3 rich perovskite stishovite which is displayed by the morb composition at pressures above 20 gpa was found to transform further into an assemblage containing a new aluminous phase at pressures above 25 gpa this al phase has a complex composition and is also relatively sodium rich its x ray diffraction pattern is similar to that observed for mgal 2 o 4 calcium ferrite type and is tentatively indexed on the basis of an orthorhombic cell yielding a zero pressure density of 3 87 2 g cm 3 majorite garnet was found to remain as the most abundant phase at the highest pressure studied 28 gpa and does not appear likely to transform to perovskite until pressures exceed 29 30 gpa these results imply that the basaltic crust component of subducted oceanic lithosphere would be 0 1 0 2 g cm 3 less dense than surrounding mantle pyrolite between the depths of 660 800 km thereby confirming an earlier hypothesis of anderson moreover the underlying layer of harzburgite would be 0 05 g cm 3 less dense than pyrolite throughout most of this depth interval these buoyancy relationships contribute to a barrier which impedes and may sometimes prevent the entry of slabs into the lower mantle

rock and stiff soil site amplification dependency on vs30 and kappa κ0 abstract a ground motion prediction equation gmpe specific to rock and stiff soil sites is derived using seismic motion recorded on high v s 30 sites in japan this gmpe applies to events with 4 5 m w 6 9 and v s 30 ranging from 500 to 1500 m s stiff soil to rock sites the empirical site coefficients obtained and the comparison with the simulated site functions show that seismic motion on rock and stiff soil sites does not depend only on v s 30 but also on the high frequency attenuation site properties 0 the effects of the site specific 0 on site amplification are analyzed using stochastic simulations with the need to take into account both of these parameters for rock site adjustments adding the site specific 0 into the gmpes thus appears to be essential in future work the rock site stochastic ground motion simulations show that the site specific 0 controls the frequency corresponding to the maximum response spectral acceleration f amp 1 this observation is used to link the peak of the response spectral shape to 0 in this specific japanese dataset and then to add the effects of high frequency attenuation into the previous gmpe from the peak ground acceleration and up to periods of 0 2 s the inclusion of 0 allows the observed bias to be corrected for the intraevent residuals and thus reduces sigma however this 0 determination is limited to a minimum number of rock site records with m w 4 5 and to distances of less than 50 km

fe mg fe mn relations of meteorites and primary heterogeneity of primitive achondrite parent bodies abstract we examine fe mg mn relations of meteorites as represented on plots of molar fe mg ratio vs molar fe mn ratio and use them to consider whether it is meaningful to classify achondrites as primitive or evolved first we demonstrate that fe mg fe mn plots can be used to identify some of the major processes that have affected meteorite parent bodies during both the nebular condensation and accretion and the planetary igneous stages of their evolution examination of compositions of chondrites on this diagram reveals distinct patterns that result from three nebular processes 1 volatility controlled mn mg fractionation 2 metal silicate fractionation under highly reducing conditions and 3 subsequent oxidation leading to variations in feo mgo ratio ordinary chondrites ocs show a characteristic pattern that records all three of these processes and suggests that the latter two are coupled examination of the compositions of achondrites on this diagram shows that all of those that have been classified as primitive lodranites acapulcoites winonaites iab silicate inclusions brachinites and ureilites are easily distinguished from those that have been classified as evolved sncs heds and lunar basalts the mn mg ratios of the former are chondritic while those of the latter are superchondritic hence they plot in two graphically distinct regions of the fe mg fe mn diagram a simple melting calculation reveals that this distinction results principally because the former are residues and the latter are melts or cumulate products of melts rather than because the latter are more evolved additionally however some of the groups classified as primitive achondrites show fe mg fe mn patterns similar to that of ocs constant but distinct mno mgo ratios over large ranges of feo mgo ratio we argue that these trends reflect primary heterogeneity resulting from the same nebular processes as those that affected ocs and therefore preserve evidence that more of the materials that accreted to form planetesimals experienced these processes than is apparent from known chondrites this evidence is preserved principally because these meteorites are residues in contrast groups commonly classified as evolved achondrites show fe mg fe mn patterns that reflect only igneous processing and any evidence for primary heterogeneity of their parent bodies has been obliterated again this is principally because these meteorites represent melts rather than beause they are more evolved usage of the terms primitive and evolved to describe achondrites should be clearly defined

an experimental investigation into the metastable formation of phosphoran olivine and pyroxene abstract the formation of phosphoran olivine by crystallization from a melt was investigated experimentally using a one atmosphere furnace using san carlos olivine mg fe 2 sio 4 mixed with either iron phosphide fep or magnesium pyrophosphate mg 2 p 2 o 7 both dynamic crystallization and isothermal experiments produced phosphoran olivine as zoned single crystals and as overgrowths surrounding normal phosphorus free olivine grains the crystallization pathways that form phosphoran olivine were traced and confirm that it is a metastable phase that can crystallize from a phosphorus rich melt over timescales of hours to days removal of the p and equilibration of the olivine however requires weeks to months in the presence of silicate melt phosphoran olivine with up to 27 wt p 2 o 5 was generated and up to 69 of the si tetrahedral sites were replaced by p the substitution of si by p into olivine was confirmed as 4 vi m 2 2 iv si 4 3 vi m 2 2 iv p 5 vi phosphoran olivine compositions that vary from mg fe 2 sio 4 to mg fe 1 65 0 35 si 0 3 p 0 7 o 4 have been produced in these experiments phosphoran pyroxene was also generated in a few experiments and forms when phosphoran olivine reacts with either tridymite or melt it has compositions compatible with protopyroxene orthopyroxene pigeonite and sub calcic augite and can contain up to 31 5 wt p 2 o 5 like phosphoran olivine it is also a metastable phase phosphorus replaces si in pyroxene by the following substitution methods 8 iv si 4 3 iv si 4 4 iv p 5 iv with al entering the structure by the exchange 2 iv si 4 iv al 3 iv p 5 phosphoran pyroxene compositions vary from mg fe 8 si 8 o 24 to mg fe 8 si 3 p 4 o 24

the pyroxene pallasites vermillion and yamato 8451 not quite a couple two pallasites vermillion and yamato y 8451 have been studied to obtain petrologic trace element and o isotopic data both meteorites contain low ca and high ca pyroxenes 2 by volume and have been dubbed pyroxene pallasites pyroxene occurs as large individual grains as inclusions in olivine and in other pyroxene and as grains along the edges of olivine symplectic overgrowths sometimes found in main group and eagle station pallasites are not seen in the pyroxene pallasites olivine compositions are fa10 12 similar to those of main group pallasites siderophile trace element data show that metal in the two meteorites have significantly differing compositions that are for many elements outside the range of the main group and eagle station pallasites these compositions also differ from those of iab and iiiab iron meteorites rare earth element ree patterns in merrillite are similar to those seen in other pallasites indicating formation by subsolidus reaction between metal and silicate with the merrillite inheriting its pattern from the surrounding silicates the o isotopic compositions of vermillion and y 8451 are similar but differ from main group or eagle station pallasites as well as other achondrite and primitive achondrite groups although vermillion and y 8451 have similar mineralogy pyroxene compositions ree patterns and o isotopic compositions there is sufficient evidence to resist formally grouping these two meteorites this evidence includes the texture of vermillion siderophile trace element data and the presence of cohenite in vermillion

spin transition of ferric iron in the nal phase implications for the seismic heterogeneities of subducted slabs in the lower mantle abstract al rich phases nal new hexagonal aluminous phase and cf calcium ferrite phase are believed to constitute 10 30 wt of subducted mid ocean ridge basalt morb in the earth s lower mantle in order to understand the effects of iron on compressibility and elastic properties of the nal phase we have studied two single crystal samples fe free na1 14mg1 83al4 74si1 23o12 and fe bearing na 0 71 mg 2 05 al 4 62 si 1 16 fe 2 0 09 fe 3 0 17 o 12 using synchrotron nuclear forward scattering nfs and x ray diffraction xrd combined with diamond anvil cells up to 86 gpa at room temperature a pressure induced high spin hs to low spin ls transition of the octahedral fe3 in the fe bearing nal is observed at approximately 30 gpa by nfs compared to the fe free nal the fe bearing nal undergoes a volume reduction of 1 0 1 2 a3 at 33 47 gpa as supported by xrd which is associated with the spin transition of the octahedral fe3 the fits of birch murnaghan equation of state b m eos to p v data yield unit cell volume at zero pressure v 0 183 1 1 a 3 and isothermal bulk modulus k t 0 233 6 gpa with a pressure derivative k t 0 3 7 2 for the fe free nal v 0 hs 184 76 6 a 3 and k t 0 hs 238 1 gpa with k t 0 hs 4 fixed for the fe bearing nal the bulk sound velocities v of the fe free and fe bearing nal phase are approximately 6 larger than those of al fe bearing bridgmanite and calcium silicate perovskite in the lower mantle except for the spin transition region where a notable softening of v with a maximum reduction of 9 4 occurs in the fe bearing nal at 41 gpa considering the high volume proportion of the nal phase in subducted morb the distinct elastic properties of the fe bearing nal phase across the spin transition reported here may provide an alternative plausible explanation for the observed seismic heterogeneities of subducted slabs in the lower mantle at depths below 1200 km

a petrological and chemical reexamination of main group pallasite formation abstract the large number of pallasite parent bodies suggests that their formation was a common event in asteroid evolution new microprobe data has been generated for pallasite olivines and chromites that indicate subsolidus redox processes while literature data has been collated and correlated to form new results and interpretations the new data include information on metal compositions the metal cooling rates the formation of round and fragmental olivine the close packing of olivine the crystallization of the phosphates phosphoran olivine and orthopyroxene and the bulk pallasite p and s contents a model for main group pallasites has been developed using fractional melting of a chondritic precursor to make a multi layered parent body one portion of this contains a gradational metal olivine pallasite texture concentric downward crystallization of the molten metal is indicated based on cooling rates and metal compositions fractional crystallization of the residual silicate and metallic melts produces the minor phases on cooling comparisons to and a brief review of past models particularly those utilizing mixing have been made

lower mantle seismic scatterers below the subducting tonga slab evidence for slab entrainment of transition zone materials abstract we show evidence that materials with significantly different elastic properties are juxtaposed in the lower mantle immediately below the subducting tonga slab depths 1000 km like the anomalies preferentially located beneath the lower mantle slabs at other pacific subduction zones kaneshima 2009 array analyses of wave form data of short period seismic networks at western united states and japan for deep earthquakes at the tonga slab reveal s to p scatterers with a size less than the wavelengths 10 km the scatterers are located mostly outside of the slab by several tens of kilometers assuming a locally planar interface for the geometry of the scatterers the amplitudes and polarities of the s to p waves are modeled to constrain the properties of the scatterers we find that the scatterers are steeply dipping the vs increases oceanward across the interface and the vs contrasts are at least comparable to that associated with the post spinel transformation 6 it is unclear at this stage what these subslab scatterers represent so we discuss about three mechanisms which seem plausible from mantle dynamics viewpoints 1 they may represent basaltic rocks which were emplaced by partial melting immediately beneath the former oceanic lithosphere asthenosphere boundary lab before the slab started subducting 2 alternatively the elastic anomalies of the scatterers may be caused by localized presence of dehydrated water or 3 the scatterers may correspond to a sharp boundary between fine grained isotropic rocks in the immediate vicinity of the slab and coarse grained anisotropic rocks more distant from the slab the presence of pronounced and localized elastic anomalies preferentially beneath the slabs in the shallow lower mantle whatever its mechanism is implies that a geophysically observable amount of transition zone material is entrained by the subducting slabs into the lower mantle

wetting of mantle olivine by sulfide melt implications for re os ratios in mantle peridotite and late stage core formation this study investigates the effects of variations in the relative fugacities of oxygen and sulfur on the wetting of mantle olivine by molten sulfide experiments were performed on mixtures of san carlos olivine and synthetic fes at 1 bar and 1350 c crucibles were fabricated from san carlos olivine and the fugacities of oxygen and sulfur were controlled by mixing co2 co and so2 gases experimental conditions ranged from logfo2 7 9 to 10 3 and from logfs2 1 5 to 2 5 our experimental results demonstrate that at a given temperature and pressure the olivine sulfide melt dihedral angle is controlled by the concentration of o dissolved in an anion rich melt trace amounts of o dissolve in sulfide melt at fo2 conditions near the iron wustite oxygen buffer and the dihedral angle is 90 at fo2 conditions near the fayalite magnetite quartz oxygen buffer the concentration of dissolved o is near 9 wt and the dihedral angle is 52 allowing small amounts of sulfide melt to form an interconnected network in olivine rich rocks and to migrate via porous flow these results indicate that sulfide melt is likely to be mobile at current upper mantle fo2 and fs2 conditions in mantle peridotite the addition or removal of sulfide melt by porous flow will variably fractionate re os u pb and th pb ratios because os and pb are more chalcophile than re u and th the re os ratio of the peridotite is especially sensitive to this process the mobility of sulfide melt at oxidizing conditions implies that the addition of oxidized chondritic material during the later stages of the accretion of the earth may have facilitated the segregation of core forming material by porous flow if temperatures were in excess of the sulfide solidus

textural equilibria of iron sulfide liquids in partly molten silicate aggregates and their relevance to core formation scenarios the influence of the coexistence of silicate and iron sulfide melts on the wetting of mantle olivine by iron sulfide melt is investigated the dihedral angle between iron alloy and olivine is unaffected by the presence of silicate melt at 1 5 gpa and 1370 1410 c and is much greater than the maximum allowable dihedral angle for melt connectivity at low melt fractions in experimental charges where silicate and sulfide melt occupy the same melt pocket the sulfide melt adheres to olivine grain faces rather than forming discrete droplets the relative interfacial energy between iron sulfide and basaltic silicate melt is lower than that of iron sulfide with olivine but the contrast is not sufficient for basaltic silicate melt to wet fes olivine grain boundaries this result implies that very large silicate melt fractions are necessary to mobilize iron sulfide melts in partially molten silicate phase assemblages therefore segregation of fe rich metallic melts by porous flow at low melt fraction is not a likely process for metal separation the experiments also investigated the influence of the presence of a thermal gradient on sulfide melt migration although the sulfide melt can not migrate through the olivine network by porous flow evidence in the experiments indicates mobility of sulfide through the interconnected silicate melt network the sulfide melt pools in contact with silicate melt at the hot top part of the experimental charges grow over time at the expense of the silicate melt pools in the cooler part of the charge this points to a diffusive transport mechanism for local sulfide redistribution we review literature data on metal olivine wetting angles and find that the metal composition has a dominant influence on the wetting behavior of a metallic liquid on an olivine matrix iron rich metallic liquid compositions are characterized by large dihedral angles 90 the metal olivine dihedral angle decreases with increasing amounts of dissolved light element s c o for light element contents in excess of 59 at the dihedral angle approaches 60 and the wetting behavior of a metallic liquid is similar to that of a silicate liquid

high pressure phase relation of kreep basalts a clue for finding the lost hadean crust abstract the phase relations mineral chemistry and density of kreep basalt were investigated at pressures of 12 125 gpa and temperatures up to 2810 k by a combination of large volume multi anvil press experiments and in situ synchrotron x ray diffraction measurements in a laser heated diamond anvil cell our results showed that grossular rich majorite garnet liebermannite and al bearing stishovite are dominant in the upper to middle part of the upper mantle while in the lowermost transition zone a dense ti rich casio3 perovskite exsoluted from the garnet which becomes more pyropic with increasing pressure at lower mantle conditions these minerals transform into an assemblage of bridgmanite ca perovskite al stishovite the new aluminium rich nal phase and the calcium ferrite type cf phase at pressures higher than 50 gpa nal phase completely dissolved into the cf phase which becomes the main deposit of alkali metals in the lower mantle the density of kreep estimated from phase compositions obtained by energy dispersive x ray spectroscopy eds in scanning sem and transmission tem electron microscopes was found substantially denser than pyrolite suggesting that the earth primordial crust likely subducted deep into the earth s mantle after or slightly before the final solidification of magma ocean at 4 53 ga radiogenic elements u th and 40k which were abundant in the final residue of magma ocean were brought down along the subduction of the primordial crust and generate heat by decay after the settlement of the primordial crust on top of the cmb suggesting the non homogeneous distribution of radiogenic elements in the hadean mantle with implications for the thermal history of the earth

regional stochastic gmpes in low seismicity areas scaling and aleatory variability analysis application to the french alpsregional stochastic gmpes in low seismicity areas scaling and aleatory variability analysis

magnitude scaling rate in ground motion prediction equations for response spectra from large shallow crustal earthquakes abstract we have evaluated the magnitude scaling rates msrs the rate of increase in the predicted spectrum with increasing moment magnitude of five modern ground motion prediction equations gmpes for response spectra including four next generation attenuation nga models and a model developed for data from japan we have found that msrs for crustal earthquakes with a moment magnitude over 7 vary significantly among the five models by a factor of 2 3 for some cases the variation of msrs among the four nga models is alarmingly large considering that they were derived from largely the same dataset and used the same site parameters we have selected 641 strong motion records from shallow crustal earthquakes with a moment magnitude over 7 from the nga dataset and 69 from the 2008 wenchuan china earthquake with a moment magnitude of 7 9 all within a short distance of 200 km from the fault rupture plane to illustrate the extreme extent of magnitude scaling we have fitted an attenuation model without a magnitude term to this dataset based on an observation that an increase in one moment magnitude unit is related to an increase in fault length by a factor of 5 10 a significant increase in shaking duration which cannot be fully accounted for by response spectra and limited or no increase in ground motion amplitude the statistical analyses of the results indeed suggest that a zero magnitude scaling at spectral periods over 0 6 s may be reasonable for our dataset while the required apparent magnitude scaling at short periods may be due to other factors such as stress drop a parameter that is not used in any of the models considered we will provide some plausible explanations for the possible zero magnitude scaling that can be considered as the lower limit of the uncertain magnitude scaling rate

crystal chemistry of lunar merrillite and comparison to other meteoritic and planetary suites of whitlockite and merrillite merrillite also known as whitlockite is one of the main phosphate minerals along with apatite that occur in lunar rocks martian meteorites and in many other groups of meteorites signi cant structural differences between terrestrial whitlockite and lunar and meteoritic varieties warrant the use of merrillite for the h free extraterrestrial material and the systematic enrichment of ree in lunar merrillite warrants the use of re merrillite laser raman spectroscopy of extraterrestrial merrillite and terrestrial whitlockite con rms the absence of h in the former and presence of h in the latter lunar merrillite ideally mg fe 2 mn 2 2 ca18 x y ree x na2 x p si 14o56 contains high concentrations of y ree reaching just over 3 atoms per 56 o atoms or up to 18 wt as y re 2o3 in the absence of extensive si p substitution the availability of the na site limits y ree substitution to 2 atoms per 56 o atoms higher concentrations of y ree with coupled substitution of si for p to balance charge are possible but rare in lunar material intrinsically low na concentrations in lunar rocks combined with the typical formation of merrillite in late stage basaltic mesostasis or residual intercumulus melt pockets produce these high ree concentrations lunar merrillite typically contains 0 1 0 4 na atoms per 56 o atoms for comparison martian merrillite contains signi cantly higher na concentrations up to 1 7 na atoms per 56 o atoms and much lower ree concentrations meteoritic merrillite has relatively low ree contents but exists in both ca rich and na rich varieties concentrations of fe and mg in all varieties sum to near 2 atoms per 56 o atoms merrillite in lunar crustal lithologies typically has mg fe however fe rich mare basalts contain up to 1 8 fe 2

an experimental study of ostwald ripening of olivine and plagioclase in silicate melts implications for the growth and size of crystals in magmas we carried out an experimental study to characterize the kinetics of ostwald ripening in the forsterite basalt system and in the plagioclase an65 andesite system eight experiments were done in each system to monitor the evolution of mean grain size and crystal size distribution csd with time t the experiments were performed in a 1 atmosphere quench furnace at 1 250 c for plagioclase and 1 300 c for olivine very contrasted coarsening kinetics were observed in the two series in the plagioclase series the mean grain size increased as log t from 3 m to only 8 7 m in 336 h the kinetic law in log t means that ostwald ripening was rate limited by surface nucleation at plagioclase liquid interfaces in the olivine series the mean grain size increased as t1 3 from 3 m to 23 2 m in 496 h a kinetic law in t1 3 is expected when ostwald ripening is rate limited either by diffusion in the liquid or by grain growth dissolution controlled by a screw dislocation mechanism the shape of olivine csds in particular their positive skewness indicates that grain coarsening in the olivine experiments was controlled by a screw dislocation mechanism not by diffusion as the degrees of undercooling t or supersaturation involved in ostwald ripening are essentially 1 c the mechanisms of crystal growth identified in our experiments are expected to be those prevailing during the slow crystallisation of large magma chambers we extrapolated our experimental data to geological time scales to estimate the effect of ostwald ripening on the size of crystals in magmas in the case of plagioclase ostwald ripening is only efficient for mean grain sizes of a few microns to 20 m even for a time scale of 105 years it can however result in a significant decrease of the number of small crystals per unit volume and contribute to the development of convex upwards csds for olivine the mean grain size increases from 2 3 m to 70 m in 1 year and 700 m in 103 years a mean grain size of 3 mm is reached in 105 years accordingly the rate of grain size dependent processes such as compaction of olivine rich cumulates or melt extraction from partially molten peridotites may significantly be enhanced by textural coarsening

stony iron meteorites history of the metal phase according to tungsten isotopes abstract the global composition of the early solar system is thought to be roughly chondritic in terms of refractory components and this means that metal and silicate should be present together in early planetesimals to fully understand the metal silicate differentiation process within the eucrite parent body epb it is important to try and identify the metal reservoir that is complementary to the silicate part the isotope 182 of tungsten w a siderophile element is partly formed from the decay of 182 hf and w isotopes are useful for examining metal silicate segregation the w isotopic composition expected for the metal that is complementary to eucrites falls in the range of iron meteorites however mesosiderites seem to be genetically linked to eucrites based on petrologic and oxygen isotopic similarities therefore we undertook the analysis of the metal phase of these stony irons here we present tungsten isotopic data for mesosiderite and pallasite metal to characterize their parent body bodies and to assess possible relationships with eucrites all stony iron metals are depleted in radiogenic tungsten by 1 3 to 4 2 e units relative to the terrestrial standard while chondrites for comparison are depleted by 1 9 e units in addition to w isotopic heterogeneity from one stony iron to another there is also w isotopic heterogeneity within individual meteorites a formation model is tentatively proposed where we show that mesosiderites pallasites and eucrites could possibly come from the same parent body several hypotheses are discussed to explain the isotopic heterogeneity the production of cosmogenic tungsten the in situ decay of hafnium present in inclusions and tungsten diffusion processes after metal silicate mixing during the cooling of the meteorites the two latter hypotheses provide the best explanation of our data

regional correlations of vs30 and velocities averaged over depths less than and greater than 30 meters using velocity profiles from sites in japan california turkey and europe we find that the time averaged shear wave velocity to 30 m vs30 used as a proxy for site amplification in recent ground motion prediction equations gmpes and building codes is strongly correlated with average velocities to depths less than 30 m vsz with z being the averaging depth the correlations for sites in japan corresponding to the kik net network show that vs30 is systematically larger for ag ivenvsz than for profiles from the other regions the difference largely results from the placement of the kik net station locations on rock and rocklike sites whereas stations in the other regions are generally placed in urban areas underlain by sediments using the kik net velocity profiles we provide equations relating vs30 to vsz for z ranging from 5 to 29 m in 1 m increments these equations and those for california velocity profiles given in boore 2004b can be used to estimate vs30 from vsz for sites in which velocity profiles do not extend to 30 m the scatter of the residuals decreases with depth but even for an averaging depth of 5 m a variation in logvs30 of 1 standard deviation maps into less than a 20 uncertainty in ground motions given by recent gmpes at short periods the sensitivity of the ground motions to vs30 uncertainty is considerably larger at long periods but is less than a factor of 1 2 for averaging depths greater than about 20 m we also find that vs30 is correlated with vsz for z as great as 400 m for sites of the kik net network providing some justification for using vs30 as a site response variable for predicting ground motions at periods for which the wavelengths far exceed 30 m online material estimates of vs30 at k net stations

a petrologic chemical and isotopic study of monument draw and comparison with other acapulcoites evidence for formation by incipient partial melting abstract we have conducted petrologic chemical and isotopic studies of acapulcoites acapulco monument draw yamato 74063 alh a77081 alh a81261 alh a81315 alh 78230 alh a81187 and alh 84190 in an attempt to constrain their genesis acapulcoites have distinctly different oxygen isotopic compositions than silicate inclusions in iab and iiicd irons winonaites and ureilites and thus formed on a different parent body oxygen isotopic compositions which are slightly heterogeneous within the group overlap with lodranites indicating a likely origin on a common parent body these groups can be distinguished on the basis of mafic silicate grain size all acapulcoites have mafic silicate compositions intermediate between e and h chondrites roughly chondritic mineralogies achondritic equigranular textures micrometer to centimeter sized veins of fe ni fes which cross cut silicate phases rapid metallographic cooling rates at 600 400 c 103 105 c myr and trapped noble gas abundances comparable to type 3 4 ordinary chondrites they exhibit variable mafic silicate zoning abundance of fe ni fes veins ree abundances and patterns and possibly cosmic ray exposure ages 5 7 ma momument draw and yamato 74063 retain rare relict chondrules phosphates are associated with fe ni fes veins or form separate veins in monument draw and acapulco heating and cooling of acapulcoites occurred very early in the history of the solar system as evidenced by the 39ar 40ar ages of 4 51 ga these ages appear distinctly younger than the likely formation time for acapulco of 4 557 ga but are older than analogous 39ar 40ar ages for most chondrites acapulcoites formed from a precursor chondrite which differs from known chondrites in mineral and oxygen isotopic compositions heating to 950 1000 c resulted in melting at the fe ni fes cotectic but silicates did not melt silicate textures resulted from extensive solid state recrystallization heating was by noncollisional sources e g 26al electromagnetic induction despite uncertainties owing to a lack of data acapulcoites may have experienced a three stage thermal history of slow cooling at high temperature rapid cooling at intermediate temperatures and slow cooling at low temperatures possibly resulting from breakup and gravitational reassembly of the parent body the complex thermal history is also reflected in disequilibrium ree abundances one or at most two impact events 7 ma and possibly 5 ma ago are consistent with the cosmic ray exposure ages of all four acapulcoites for which cosmogenic noble gas data exist

massive chromite in the brenham pallasite and the fractionation of cr during the crystallization of asteroidal cores abstract large 2 mm chromite grains are present in iiiab iron meteorites and in the main group pallasites pmg closely related to high au iiiab irons pallasites seem to have formed by the intrusion of a highly evolved metallic magma from a iiiab like core into fragmented olivine of the overlying dunite mantle high cr contents are commonly encountered during the analyses of metallic samples of high au iiiab irons and main group pallasites an indication that cr contents were high in the intruding liquid and that cr behaved as an incompatible element during the crystallization of the iiiab magma contrary to expectations based on the negative iiiab cr ni and cr au trends among low au iiiab irons in a region about 10 cm across in the brenham main group pallasite massive chromite fills the interstices between olivine grains the site normally occupied by metal in brenham and other pallasites the massive chromite may have formed as a late cumulus phase because fe ni was also crystallizing its absence in the chromite rich region suggests a separation associated with differences in liquid buoyancy the coexisting chromite and olivine are zoned in the olivine feo is highest in pallasitic olivine metal regions lowest in rims adjacent to chromite and intermediate in the cores of these olivines chromite shows the opposite zoning with the highest feo contents at grain edges adjacent to olivine the observed gradients are those expected to form by fe mg exchange between olivine and chromite during slow cooling at subsolidus temperatures compared to normal brenham contents of phosphoran olivine and phosphates are higher in the chromitic pallasitic region we also report data for large to massive chromites present in pmg molong and in high au iiiab bear creek that like brenham formed from a highly evolved magma the bear creek chromite has a much lower mg content than that in the pallasites implying that in the pmg the mg was extracted from the olivine during high temperature reaction with the precipitating chromite there are other circumstantial arguments indicating that cr was incompatible in the metal during the crystallization of the iiiab magma with the concentration in the residual magma rising from an initial value of about 300 g g to a value around 700 g g when bear creek and brenham were formed we consider possible explanations for these negative cr au and cr ni trends and find the most probable one to be that they reflect sampling artefacts resulting from analysts avoiding visible chromite and the commonly associated phase fes when choosing metal samples

scale limits of free silica seismic scatterers in the lower mantle abstract lower mantle seismic scatterers are often interpreted in terms of subducted basaltic crust which should contain free silica phases that are seismically fast however free silica phases are unstable in a peridotite lower mantle as they react with ferropericlase magnesiowustite to form silicate perovskite nonetheless conservative estimates and recent measurements of diffusion coefficients in silicate perovskite suggest that free silica phases may persist as polycrystalline armored relics in lower mantle peridotite at length scales equivalent to those observed for seismic scatterers simple numerical simulations also suggest that polycrystalline silica may persist within subducted metabasalts

assessment of site effects in alpine regions through systematic site characterization of seismic stations abstract in the framework of the renewal project of the swiss strong motion network ssmnet a procedure for site characterization has been established the aim of the procedure was to systematically derive realistic 1d velocity profiles at each station it is mainly based on the analysis of surface waves particularly from passive experiments and includes cross checks of the derived amplification functions with those obtained through spectral modeling of recorded earthquakes the systematic use of three component surface wave analysis allowing the derivation of both rayleigh and love dispersion curves also contributes to the improvement of the quality of the retrieved profiles the procedure is applied to the 30 ssmnet stations installed on various site types within the project covering different aspects of seismic risk the characterization of these 30 sites gives an overview of the variety of possible effects of surface geology on ground motion in the alpine area such effects ranged from deamplification at hard rock sites to amplification up to a factor of 15 in lacustrine sediments with respect to the swiss reference rock velocity model the derived velocity profiles are shown to reproduce observed amplification functions from empirical spectral modeling although many sites are found to exhibit 1d behavior the procedure allows the detection and qualification of 2d and 3d effects the sites are therefore classified with respect to the occurrence of 2d 3d resonance and edge generated surface waves in addition to the large and deeply incised alpine valleys of the rhone the rhine and the aar smaller structures such as local alpine valleys and alluvial fans are shown to exhibit 2d 3d behavior

re os and pd ag systematics in group iiiab irons and in pallasites using improved analytical techniques which reduce the re blanks by factors of 8 to 10 we report new re os data on low re and low pge pallasites pal anom and iiiab irons the new pallasite samples nearly double the observed range in re os for pallasites and allow the determination of an isochron of slope 0 0775 0 0008 t 4 50 0 04 ga using the adjusted 187 re 1 66 10 11 a 1 and initial 187 os 188 os 0 0 09599 0 00046 if the data on different groups of pallasites including the anomalous pallasites are considered to define a whole rock isochron their formation would appear to be distinctly younger than for the iron meteorites by 60 ma five iiiab irons acuna bella roca chupaderos grant and bear creek with re contents ranging from 0 9 to 2 8 ppb show limited re os fractionation and plot within errors on the iiab iron meteorite isochron of slope 0 07848 0 00018 t 4 56 0 01 ga and initial 187 os 188 os 0 0 09563 0 00011 many of the meteorites were analyzed also for pd ag and show 107 ag enrichments correlated with pd ag requiring early formation and fractionation of the feni metal in a narrow time interval after injection of live 107 pd t 1 2 6 5 ma into the solar nebula based on pd ag the typical range in relative ages of these meteorites is 10 ma the pd ag results suggest early formation and preservation of the 107 pd 107 ag systematics both for iiiab irons and for pallasites while the younger re os apparent age for pallasites suggests that the re os system in pallasites was subject to re equilibration the low re and low pge pallasites show significant re os fractionation higher re os as the re and pge contents decrease by contrast the iiiab irons show a restricted range in re os even for samples with extremely low re and pge contents there is a good correlation of re and ir contents the correlation of re and os contents for iiiab irons shows a similar complex pattern as observed for iiab irons morgan et al 1995 and neither can be ascribed to a continuous fractional crystallization process with uniform solid metal liquid metal distribution coefficients

seismic scatterers in the mid lower mantle abstract recent seismological studies have revealed that rocks with significantly different elastic properties are juxtaposed in the mid lower mantle and often scatter seismic waves efficiently enough to be detected by seismic array analyses seismic networks all over the world with various aperture and geometry have been utilized for detecting scattered waves a large number of objects that act as scatterers in the mid lower mantle have been mapped out by analyzing several different types of scattered waves mostly of short period s to p scattering p to p scattering prior to pp waves p to p scattering prior to p p p to p scattering in p coda waves and p to p scattering prior to pkp the scatterers have a lesser size that is smaller than the wavelengths 10 km and probably extend several tens of kilometers at least the mid mantle scatterers are most likely to represent basaltic rocks that subducted into the lower mantle revealing the elastic properties relative to the surrounding rocks and the geometry of the individual scatterers as well as the global distribution of the scatterers should shed new light on the style of mantle convection relevant observations of mid lower mantle scatterers are reviewed and the directions of future progress are suggested

high pressure transitions in the system mgal2o4 caal2o4 a new hexagonal aluminous phase with implication for the lower mantle abstract phase transitions in mgal 2 o 4 and caal 2 o 4 and in the binary system mgal 2 o 4 caal 2 o 4 were established at high pressures and high temperatures mgal 2 o 4 spinel dissociates to periclase and corundum at 15 16 gpa and 1200 c 1600 c with an equilibrium boundary of p gpa 12 3 0 0023 t c the mixture recombines into a phase with calcium ferrite structure at about 26 5 gpa at 1600 c at 780 c 1400 c caal 2 o 4 crystallizes with the calcium ferrite structure at pressure above 8 9 gpa at lower pressures phases iii and iv are stable on the join mgal 2 o 4 caal 2 o 4 solubility of mgal 2 o 4 component into caal 2 o 4 rich calcium ferrite is limited to about 10 mol at 20 21 gpa and 1200 c and a new phase with composition of mg x ca 1 x al 2 o 4 x 0 66 0 8 was found to be stable at pressure above 15 gpa powder x ray diffraction data show that the new phase possesses hexagonal symmetry moreover it is interpreted that an al rich phase observed in high pressure assemblage of mid ocean ridge basalt morb above 25 gpa by irifune and ringwood irifune t ringwood a e 1993 phase transformations in subducted oceanic crust and buoyancy relationships at depths of 600 800 km in the mantle earth planet sci lett 117 101 110 has the same structure as the hexagonal phase found in this study rather than calcium ferrite structure and another al rich phase synthesized at 24 27 gpa in high pressure experiments from natural pyrope rich garnet starting material is also similar to the hexagonal phase these results suggest that aluminous phase of the hexagonal structure would be one of major constituent minerals of subducted oceanic crust in the upper part of the lower mantle

oxygen isotope variation in stony iron meteorites asteroidal material delivered to earth as meteorites preserves a record of the earliest stages of planetary formation high precision oxygen isotope analyses for the two major groups of stony iron meteorites main group pallasites and mesosiderites demonstrate that each group is from a distinct asteroidal source mesosiderites are isotopically identical to the howardite eucrite diogenite clan and like them are probably derived from the asteroid 4 vesta main group pallasites represent intermixed core mantle material from a single disrupted asteroid and have no known equivalents among the basaltic meteorites the stony iron meteorites demonstrate that intense asteroidal deformation accompanied planetary accretion in the early solar system

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

spin transition of ferric iron in the calcium ferrite type aluminous phase we investigated fe free and fe bearing cf phases using nuclear forward scattering and x ray diffraction coupled with diamond anvil cells up to 80 gpa at room temperature octahedral fe3 ions in the fe bearing cf phase undergo a high spin to low spin transition at 25 35 gpa accompanied by a volume reduction of 2 0 and a softening of bulk sound velocity up to 17 6 based on the results of this study and our previous studies both the nal and cf phases which account for 10 30 vol of subducted morb in the lower mantle are predicted to undergo a spin transition of octahedral fe3 at lower mantle pressures spin transitions in these two aluminous phases result in an increase of density of 0 24 and a pronounced softening of bulk sound velocity up to 2 3 for subducted morb at 25 60 gpa and 300 k the anomalous elasticity region expands and moves to 30 75 gpa at 1200 k and the maximum of the v reduction decreases to 1 8 this anomalous elastic behavior of fe bearing aluminous phases across spin transition zones may be relevant in understanding the observed seismic signatures in the lower mantle

experimental investigations of trace element fractionation in iron meteorites ii the influence of sulfur abstract we have investigated the partitioning of ir ge ga w cr au p and ni between solid metal and metallic liquid as a function of temperature and s concentration of the metallic liquid partition coefficients for siderophile elements such as ir w ga and ge increase by factors of 10 100 as the sconcentration of the metallic liquid increases from 0 30 wt partition coefficients for other siderophile elements such as ni au and p increase by only factors of 2 3 in contrast partition coefficients for the more chalcophile element cr decrease these experimentally determined partition coefficients have been used in conjunction with a fractional crystallization model to reproduce the geochemical behavior of ni p au and ir during the magmatic evolution of groups iiab iiiab iva and ivb iron meteorites the mean s concentration for each group increases in the order ivb iva iiiab iiab in accord with cosmochemical prediction however we are unable to reproduce the geochemical behavior of ge ga w and cr in an internally consistent way we conclude that the magmatic histories of these iron meteorite groups are more complex than has been generally assumed

phase transition and density of subducted morb crust in the lower mantle abstract phase relations mineral chemistry and density of a natural mid oceanic ridge basalt morb composition were investigated up to 134 gpa and 2300 k by a combination of in situ x ray diffraction measurements and chemical analyses using transmission electron microscope tem results demonstrate that the morb composition consists of mgsio 3 rich perovskite stishovite casio 3 perovskite and cafe 2 o 4 type al phase in the upper part of the lower mantle the most abundant mineral of mgsio 3 rich perovskite undergoes phase transition to a cairo 3 type post perovskite phase above 110 gpa and 2500 k post perovskite phase is similar in composition to perovskite except considerably high na 2 o content stishovite transforms to cacl 2 type sio 2 phase above 62 gpa and 2000 k and further to pbo 2 type phase above 110 gpa pbo 2 type sio 2 phase includes large amount of al 2 o 3 which significantly expands its stability relative to cacl 2 type phase phase transition of casio 3 perovskite from tetragonal to cubic was also observed with increasing temperature cafe 2 o 4 type al phase is stable to the bottom of the mantle the density of morb crust was calculated using volume data combining with measured chemical compositions and calculated mineral proportions the former morb crust is denser than the average lower mantle at all depths greater than 720 km contrary to earlier predictions the subducted basaltic crust may have accumulated at the base of the mantle

new moment magnitude scale evidence of stress drop magnitude scaling and stochastic ground motion model for the french west indies in this study we analyse records from the les saintes seismic sequence following the mw 6 3 earthquake of 2004 november 11 which occurred close to guadeloupe french west indies 485 earthquakes with magnitudes from 2 to 6 recorded at distances between 5 and 150 km are used s waves fourier spectra are analysed to simultaneously determine source path and site terms the results show that the duration magnitude routinely estimated for the events that occurred in the region underestimate moment magnitude by 0 5 magnitude units over the whole magnitude range from the inverted seismic moments and corner frequencies we compute brune s stress drops we show that stress drops increase with increasing magnitude the same pattern is observed on apparent stresses i e the seismic energy to moment ratio however the rate of increase diminishes at high magnitudes which is consistent with a constant stress drop model for large events using the results of the inversions we perform ground motion simulations for the entire data set using the smsim stochastic simulation tool the results show that a good fit 0 25 with observed data is achieved when the source is properly described by its moment magnitude and stress drop and when site effects are taken into account although the magnitude dependent stress drop model is giving better results than the constant stress drop model the interevent variability remains high which could suggest that stress drop depends on other parameters such as the depth of the hypocentre in any case the overall variability is of the same order of magnitude as usually observed in empirical ground motion prediction equations

seismic evidence for a 920 km discontinuity in the mantle analysis of hundreds of seismograms from a seismic array in the japanese islands reveals a seismic discontinuity at a depth of about 920 km in the mantle beneath the tonga subduction zone this discontinuity is also evident beneath subduction zones in the japan and flores seas the discontinuity probably represents either a change in mantle chemical composition or the signature of the subducted slab s garnet layer

morphological analysis of olivine grains annealed in an iron nickel matrix experimental constraints on the origin of pallasites and on the thermal history of their parent bodies two types of pallasites can be distinguished on the basis of the grain shape of olivine rounded or angular it has been suggested that these two types of textures resulted from different degrees of annealing at high temperature in the parent body in order to characterize the kinetics of rounding of olivine grains in an fe ni matrix we carried out a series of annealing experiments using a mixture of olivine and fe ni powder we were able to reproduce at a miniature scale the range of textures in pallasites the rate of rounding was rapid enough to be observed and measured at the scale of a few micrometers to 20 m even though the experiments were performed below the solidus of the fe ni metal for instance grains 14 m in diameter became nearly spherical within 7 days at 1400 oc for the morphological analysis of olivine grains we used two independent techniques the critical diameter method and the gaussian diffusion resample method a new technique specially developed for our study both techniques indicate that the rounding time scale is proportional to the cube of the grain size and that morphological adjustments in our experiments occurred by volume diffusion in the olivine lattice not by surface diffusion along the olivine metal boundaries we used our experimental data to estimate the time scales required for the development of olivine metal textures in natural pallasites we determined that small scale rounding of olivine grains in a solid metal matrix can be produced within relatively short time intervals 100 years to produce rounded olivine grains 0 1 mm in radius at 1300 1400oc

a predictive equation for the vertical to horizontal ratio of ground motion at rock sites based on shear wave velocity profiles from japan and switzerland abstract ratios of vertical to horizontal v h ground motion are important for the computation of scenario compatible vertical design spectra they are therefore a crucial aspect of seismic hazard analysis we characterize the v h ratio at rock sites in terms of the recording site s average quarter wavelength velocity a predictive equation is presented which can be used for reconstructing the expected v h ratio of the 5 damped response and fourier spectra for rock sites given a known shear wave velocity profile the equation is based on the regression analysis of two datasets one from switzerland and one from japan the two datasets allow us to analyze well characterized hard rock sites in switzerland using small earthquakes m w 2 while the magnitude range is increased up to events of m w 7 3 using strong motion recordings from japan s kik net seismic network it is shown that a correlation exists between the quarter wavelength velocity at a given frequency and the v h ground motion ratio small differences possibly due to velocity measurement bias or topographical and basin effects existed when analyzing the individual regional datasets apart from near source distances r v h no clear magnitude or distance dependence of the v h ratios is present in either of the datasets of earthquake recordings we show that the same correlation exists for response spectra and fourier spectra of recorded ground motion a similar correlation was derived for ambient vibrations recorded at swiss station sites resulting in larger values of v h at a given frequency and thereby indicating that v h is sensitive to the composition of the wave field finally uncertainties in the v h models are presented we separate the sources of uncertainty into source and site specific components and present the single site sigma uncertainty measure for site specific hazard analyses

regional stochastic gmpes in low seismicity areas scaling and aleatory variability analysis application to the french alps we generate stochastic ground motion prediction equations gmpes for a wide magnitude range m w 3 8 that are adapted to the french alps based on inversions of source path and site terms from weak motion accelerometric data drouet et al 2010 we build seismological stochastic models to use in conjunction with the simulation program stochastic method simulation smsim to stochastically simulate ground motion response spectral amplitudes all the input parameters are considered random variables and the uncertainty is propagated through simulations by random sampling of the corresponding distributions constant and magnitude dependent stress parameter models are compared with variable large magnitude stress levels stochastic simulations are performed for periods between 0 01 and 3 s m w from 3 to 8 epicentral distances from 1 to 250 km and two site conditions rock v s 30 800 m s and hard rock v s 30 2000 m s these synthetic data are then regressed to produce stochastic gmpes using an up to date regression form the parameterization of which can be defined in terms of different distance metrics i e epicentral hypocentral joyner boore or rupture distance the impact of the uncertainty on each input parameter on the gmpe standard deviation is determined through sensitivity analysis the major contributors to the uncertainty are the site model both v s 30 and the high frequency parameter which affect the within event standard deviation and the uncertainty on the stress parameter which affects the between event term the gmpes are compared to real data using statistical analysis of residuals two sets of strong motion data are considered the reference database for seismic ground motion in europe resorce and the worldwide next generation attenuation databases as well as weak motion data recorded in france the results show that the magnitude dependent stress parameter models for magnitudes below 4 6 fit the french data better and a large magnitude constant stress parameter of 10 mpa gives a better fit to strong motion data online material tables of ground motion prediction equation coefficients

equations of state of na k al host phases and implications for morb density in the lower mantle abstract we report equations of state eos of two important silicate phases known to store na k and al at pressures and temperatures prevailing in the earth s lower mantle using laser heated diamond anvil cell we produced the ca ferrite type cf and the new aluminum rich nal phases using different synthetic and natural starting materials at pressures ranging from 23 to 65 gpa unit cell volumes were investigated by means of angle dispersive x ray diffraction at the id30 beamline of the esrf synchrotron ring grenoble france cf phases were synthesized in naalsio4 mgal2o4 and naalsio4 mg fe 2sio4 systems and for a natural mid ocean ridge basalt morb the insertion of mgal2o4 in the naalsio4 based lattice has reduced effects on the cf phase eos whereas that of mg fe 2sio4 is mainly to increase the room pressure volume cf phases most relevant to the earth s mantle show compression behavior comparable to the pure naalsio4 cf phase with bulk moduli values close to k0 190 gpa and k0 4 we also synthesized nal phases in naalsio4 mgal2o4 system and using cana and k rich silicate glasses as starting materials all nal compounds investigated show similar compression behavior except for one anomalously naalsio4 rich composition for nal phase with the most natural conditions relevant composition we refine bulk moduli of k0 182 gpa and k0 6 we then model the density profiles expected for the cf and nal phases using our newly determined eos and the most accurate chemical compositions reported in the literature these two phases appear significantly less dense than a pyrolitic type material at all lower mantle pressures and 300 k however the density profiles calculated for mineral assemblages corresponding to typical morb compositions point out to denser morbs compared to the pyrolite this is due to the high fe content in morb yielding a densest fe rich perovskite that counterbalances the lower densities of the cf and nal phases the density gap is calculated between 0 4 and 4 0 depending on the starting morb composition and pressure

main group pallasites thermal history relationship to iiiab irons and origin we have determined metallographic cooling rates below 975 k for eight main group mg pallasites from ni profiles across taenite lamellae of known crystallographic orientation in metallic regions with widmanstatten patterns comparison with profiles generated by modeling kamacite growth gave cooling rates ranging from 2 5 to 18 k myr relative cooling rates were also inferred from the sizes of cloudy zone particles in 28 mg pallasites 86 170 nm and tetrataenite bandwidths in 20 mg pallasites 1050 2170 nm as these parameters are positively correlated with each other and negatively correlated with the metallographic cooling rates these three different techniques show that mg pallasites cooled below 975 k at significantly diverse rates since samples from the core mantle boundary should have indistinguishable cooling rates mg pallasites could not have cooled at this location group iiiab irons which were previously thought to be core samples from the mg pallasite body have faster cooling rates 50 350 k myr and smaller cloudy zone particle sizes and tetrataenite bandwidths this shows that iiiab irons cooled faster than mg pallasites and could not plausibly be from the same body the absence of related iron meteorites and achondrites and our thermal constraints suggest that mg pallasites cooled at diverse depths in a pallasitic body consisting of well mixed olivine and metallic fe ni such a body may have formed during an impact on a differentiated asteroid or protoplanet that mixed olivine mantle fragments with residual ir poor molten metal from the out ermost part of a core that chemically resembled the iiiab core and was 80 fractionally crystallized separation of the solid core and most of the associated mantle may have resulted from a grazing hit and run impact with a larger protoplanet or asteroid thermal calculations suggest that the radius of the pallasitic body was 400 km but the likely presence of a regolith would reduce this estimate considerably 2010 elsevier ltd all rights reserved

observations of the mid mantle discontinuity beneath indonesia from s to p converted waveforms 1 s to p conversions were employed to derive a coherent discontinuity structure beneath indonesia analysis of data recorded by three regional arrays from nine deep earthquakes not only confirmed the results of previous studies on the existence of the mid mantle discontinuity beneath the java arc but also revealed its presence north to kalimantan island s to p waves converted at the discontinuity were observed on the stacked diagrams with a negative slowness relative to the p wave and a conversion depth ranging from 1080 km in the west to 930 km in the east

effect of spin transition of iron on the thermal conductivity of fe al bearing bridgmanite abstract thermal conductivity of bridgmanite bdg is the important physical property controlling the heat transfer inside the earth here we report room temperature lattice thermal conductivity of fe al bearing bdg with chemical compositions of mg0 848fe0 090al0 206si0 856o3 and mg0 718fe0 123al0 281si0 878o3 measured up to 125 gpa and 74 gpa respectively using the pulsed light heating thermoreflectance technique in a diamond anvil cell we found that the lattice thermal conductivity of these bdg samples show abnormal reduction in the pressure range of 20 40 gpa at 300 k which is probably due to the spin transition of fe3 in octahedral si site b site we propose that the lattice thermal conductivity of bdg is reduced by 46 16 when fe is in the mixed spin state which may form a thermal insulating layer in the earth s mid lower mantle in addition we provide a thermal conductivity model of bdg taking into account the effect of compositional difference and the spin transition of fe our conductivity model indicates that the thermal conductivity of bdg in the pyrolitic lower mantle is more than twice as high as that in the descending morb which is likely to create heterogeneity of lateral heat flux through the earth s core mantle boundary

stagnant slab a review a stagnant slab is a subducted slab of oceanic lithosphere subhorizontally deflected above across or below the 660 km discontinuity this phenomenon has now been widely recognized beneath subduction zones around the circum pacific and in the mediterranean collaboration of seismic and electromagnetic observations mineral physics measurements and geodynamic modeling has begun to provide a consistent picture of stagnant slab

attenuation relations of strong ground motion in japan using site classification based on predominant period a spectral acceleration attenuation model for japan is presented in the present study the data set includes a very large number of strong ground motion records up to the 2003 off tokach main and aftershocks site class terms instead of individual site correction terms are used the site classes of recording stations are from a recent study on site classification for strong motion recording stations in japan according to a classification scheme that has been used in japanese engineering design the use of site class terms enables tectonic source type effects to be identified and accounted for in the present model the effects of a faulting mechanism for crustal earthquakes also are accounted for for crustal and interface earthquakes a simple form of an attenuation model with respect to distance is able to capture the main strong motion characteristics and achieves unbiased estimates for subduction slab events a simple distance modification factor is employed to achieve plausible and unbiased predictions the effects of source depth tectonic source type and faulting mechanism of crustal earthquakes are significant the need for magnitude squared terms is evaluated and the use of magnitude squared terms reduces the interevent error further

density magnetic susceptibility and the characterization of ordinary chondrite falls and showers bulk and grain densities of 132 ordinary chondrites from the vatican observatory collection were measured and compared with their magnetic susceptibility for the most part using previously measured values ten new susceptibility measures were taken for this study grain density and magnetic susceptibility combined provide a reliable method of classifying un weathered ordinary chondrites unlike traditional chemical tests this method is fast nondestructive and characterizes the whole rock making it especially appropriate for surveying large collections the system is less viable for finds extensive weathering of metallic iron in an h chondrite can cause it to plot among l chondrites while heavily weathered l chondrites plot among the ll group this system has revealed outlier stones that may be misclassified meteorites or mislabeled samples in every case where the magnetic susceptibility of a meteorite does not fit its putative classification the grain density is also found to be in disagreement in a manner consistent with either severe weathering or misidentification an analysis of stones from five showers shows that excluding outliers these samples tend to cluster tightly within their appropriate groups in a plot of grain versus magnetic susceptibility

testing the global applicability of ground motion prediction equations for active shallow crustal regions abstract large research initiatives such as the global earthquake model gem or the seismic hazard harmonization in europe share projects concentrate a great collaborative effort on defining a global standard for seismic hazard estimations in this context there is an increasing need for identifying ground motion prediction equations gmpes that can be applied at both global and regional scale with increasing amounts of strong motion records that are now available worldwide observational data can provide a valuable resource to tackle this question using the global dataset of allen and wald 2009 we evaluate the ability of 11 gmpes to predict ground motion in different active shallow crustal regions worldwide adopting the approach of scherbaum et al 2009 we rank these gmpes according to their likelihood of having generated the data in particular we estimate how strongly data support or reject the models with respect to the state of noninformativeness defined by a uniform weighting such rankings derived from this particular global dataset enable us to explore the potential of gmpes to predict ground motions in their host region and also in other regions depending on the magnitude and distance considered in the ranking process we particularly focus on the influence of the distribution of the testing dataset compared with the gmpe s native dataset one of the results of this study is that some nonindigenous models present a high degree of consistency with the data from a target region two models in particular demonstrated a strong power of geographically wide applicability in different geographic regions with respect to the testing dataset the models of akkar and bommer 2010 and chiou et al 2010

derivation of a reference shear wave velocity model from empirical site amplification abstract the definition of a reference bedrock condition representative of a region of interest is of great significance in seismic hazard assessment it is highly beneficial when ground motion prediction equations are referenced to a specific site condition particularly in the case of site specific seismic hazard analyses when known the effect of any given site with respect to the reference can then be applied to the predicted ground motion however the choice of a reference velocity profile is not straightforward mainly due to the high variability of the velocity structure in the shallower layers a new method to define the regional reference rock profile is proposed the method relates quarter wavelength average velocity at a site to frequency dependent amplification a reference bedrock velocity profile can then be directly defined in relation to expected amplification characteristics over a number of sites we compare 27 quarter wavelength velocity profiles from seismic station locations in switzerland with empirical amplification functions derived from spectral modeling from this comparison a set of frequency dependent calibration relationships is established assuming that the reference profile is defined by a lack of any relative amplification the quarter wavelength velocity profile that corresponds to unitary spectral amplification can be extracted the reference velocity profile can then be obtained through an inversion procedure and defines the reference for the ground motion prediction equation gmpe the proposed reference velocity profile is compared with previous reference velocity profiles a good agreement is found between the different methods additionally an estimation of the transfer function for the swiss reference rock condition is provided this can be used to correct recorded or estimated spectral amplitudes for the local response of the reference site finally it is shown that the coefficients from the aforementioned correlations can be used to estimate a generic amplification function at any site with a known quarter wavelength velocity profile

chemical zoning of olivine in several pallasites chemical zoning profiles of olivines in the esquel imilac and yamato 8451 pallasites were measured by using an electron probe microanalyzer in order to study their cooling histories pallasite olivines are considered to be compositionally uniform but show faint zoning for fe mg cao al2o3 cr2o3 and mno within a few hundred micrometers from the rim the cao al2o3 and cr2o3 contents of olivines in pallasites decrease gradually toward the rim the fe mg zoning and the mno enrichment in olivine rims of pallasite olivines may reflect a redox process on the basis of diffusion calculations to estimate the cooling rate by using chemical zoning of pallasite olivine the formation process of chemical zoning was discussed similar cooling rates obtained for the fe mg cao and mno profiles of an olivine imply that these zoning patterns formed during the same event

phase stability and elastic properties of the nal and cf phases in the namg2al5sio12 system from first principles new hexagonal aluminous nal phase and orthorhombic calcium ferrite cf type phase are considered to be major mantle components of the mid ocean ridge basalt morb at pressure and temperature conditions in the lower mantle which can potentially host alkali elements with large ionic radii the high pressure stability and elastic properties of both nal and cf phases are therefore of fundamental importance for understanding the fate of subducted morb here we report those properties of the namg2al5sio12 system studied by means of the first principles computation method nal was found to transform to the cf phase at 39 6 gpa accompanied by discontinuities in density 1 8 as well as compressional wave 0 2 shear wave 0 9 and bulk sound 1 0 velocities the property of subducted morb was evaluated using these results and the velocity contrast between pyrolite and morb of 5 was found to be quite comparable to the shear velocity anomaly observed for seismic scatterers at depths from 1100 to 1800 km however since the transformation of the nal to cf phase within morb produces insignificant increases in the seismic velocities it would be seismologically undetectable on the other hand the anisotropy change associated with the phase transition is significant and could be seismically detectable using observations such as shear wave splitting measurements since the cf phase is considerably more anisotropic compared to the nal phase

optical signatures of low spin fe3 in nal at high pressure the iron spin transition directly affects properties of lower mantle minerals and can thus alter geophysical and geochemical characteristics of the deep earth while the spin transition in ferropericlase has been documented at p 60 gpa and 300 k experimental evidence for spin transitions in other rock forming minerals such as bridgmanite and post perovskite remains controversial multiple valence spin and coordination states of iron in bridgmanite and post perovskite are difficult to resolve with conventional spin probing techniques optical spectroscopy on the other hand can discriminate between high and low spin and between ferrous and ferric iron at different sites here we establish the optical signature of low spin fe3 o6 a plausible low spin unit in bridgmanite and post perovskite by optical absorption experiments in diamond anvil cells we show that the optical absorption of fe3 o6 in new aluminous phase nal is very sensitive to the iron spin state and may represent a model behavior of bridgmanite and post perovskite across the spin transition specifically an absorption band centered at 19 000 cm 1 is characteristic of the 2t2g 2t1g 2a2g transition in low spin fe3 in nal at 40 gpa constraining the crystal field splitting energy of low spin fe3 to 22 200 cm 1 which we independently confirm by first principles calculations together with available information on the electronic structure of fe3 o6 compounds we show that the spin pairing energy of fe3 in an octahedral field is 20 000 23 000 cm 1 this implies that octahedrally coordinated fe3 in bridgmanite is low spin at p 40 gpa

search for seismic discontinuities in the lower mantle summary indications of lower mantle discontinuities have been debated for decades but still little is known about their properties and their origins are enigmatic in our study broad band recordings of deep events are examined for the presence of signals from the lower mantle discontinuities with a novel technique we deconvolve vertical component of the p wave coda in the period range around 10 s by the s waveform and stack many deconvolved traces with moveout time corrections in synthetic seismograms for an earth model without lower mantle discontinuities the strongest signal thus detected in the time window of interest is often s 410 p phase generated as s and reflected as p from the 410 km discontinuity above the source in actual seismograms there are other phases that can be interpreted as converted from s to p at discontinuities in the lower mantle beneath the seismic source we summarize the results of processing the seismograms 1 of deep events in sunda arc at seismograph stations in east asia 2 deep kermadec fiji tonga events at the j array and freesia networks in japan and stations in east asia and 3 deep events in the northwest pacific region mariana izu bonin and the japan arc recorded at stations in north america in our data there are indications of discontinuities near 860 880 1010 1120 1170 1250 and 1670 1800 km depths the clearest signals are obtained from the discontinuity at a depth of 1200 km we argue that the 900 1200 and 1700 km discontinuities are global but laterally variable in both depth and strength seismic stratification of the lower mantle may have bearings on the patterns of subduction as revealed by tomographic models

minor element zoning and trace element geochemistry of pallasites i report here on an ion probe study of minor element spatial distributions and trace element concentrations in six pallasites pallasite olivines exhibit ubiquitous minor element zoning that is independent of grain size morphology and adjacent phases ca cr ti v and ni concentrations decrease from center to rim by factors of up to 10 while mn is generally unzoned or increases slightly at the very edge of some olivine grains the maximum concentrations of these elements at the center of olivine vary from grain to grain within the same meteorite and among the pallasites studied these zoning profiles are consistent with thermal diffusion during rapid cooling the inferred cooling rates at high temperature regimes are orders of magnitude faster than the low temperature metallographic cooling rates similar to0 5 to 2degreesc ma this suggests that pallasites like mesosiderites have experienced rather complicated thermal histories i e cooling rapidly at high temperatures and slowly at low temperatures

developing an application specific ground motion model for induced seismicity abstract a key element of quantifying both the hazard and risk due to induced earthquakes is a suite of appropriate ground motion prediction equations gmpes that encompass the possible shaking levels due to such events induced earthquakes are likely to be of smaller magnitude and shallower focal depth than the tectonic earthquakes for which most gmpes are derived furthermore whereas gmpes for moderate to large magnitude earthquakes are usually derived to be transportable to different locations and applications taking advantage of the limited regional dependence observed for such events the characteristics of induced earthquakes warrant the development of application specific models a preliminary ground motion model for induced seismicity in the groningen gas field in the netherlands is presented as an illustration of a possible approach to the development of these equations the gmpe is calibrated to local recordings of small magnitude events and captures the epistemic uncertainty in the extrapolation to larger magnitude considered in the assessment of the resulting hazard and risk

elasticity of single crystal nal phase at high pressure a potential source of the seismic anisotropy in the lower mantle the new hexagonal aluminous phase named the nal phase is expected to be stable at depths of 1200 km in subducted slabs and believed to constitute 10 30 wt of subducted mid ocean ridge basalt together with the cafe2o4 type aluminous phase here elasticity of the single crystal nal phase is investigated using brillouin light scattering coupled with diamond anvil cells up to 20 gpa at room temperature analysis of the results shows that the substitution of iron lowers the shear modulus of the nal phase by 5 6 gpa but does not significantly affect the adiabatic bulk modulus the nal phase exhibits high velocity anisotropies with avp 14 7 and avs 15 12 for the fe bearing phase at ambient conditions the high avs of the nal phase mainly results from the high anisotropy of the faster vs1 13 9 15 8 while the slower vs2 appears almost isotropic 0 1 2 8 at ambient and high pressures the avp and avs of the nal phase decrease with increasing pressure but still have large values with avp 11 4 and avs 14 12 for the fe bearing sample at 20 4 gpa the extrapolated avp and avs of the fe free and fe bearing nal phases at 40 gpa are larger than those of bridgmanite at the same pressure together with its spin transition of iron and structural transition to the cf phase the presence of the nal phase with high velocity anisotropies may contribute to the observed seismic anisotropy around subducted slabs in the uppermost lower mantle

experimental investigation of the partitioning of phosphorus between metal and silicate phases implications for the earth moon and eucrite parent body abstract the solid metal silicate melt partition coefficient for p d p has been determined experimentally at 1190 c and 1300 c the dependence of the partition coefficient on oxygen fugacity has been investigated and is consistent with a valence state of 5 for p in the silicate melt the experimental partition coefficients are given by log d p 1 21 log o 2 15 95 at 1190 c log d p 1 53 log o 2 17 73 at 1300 c the experimentally determined partition coefficients may be used to interpret the low p la ratios of the earth moon and eucrites relative to c1 chondrites the low p la ratios in the eucrites may be explained by partitioning of p into 5 to 25 of a sulfur bearing metallic liquid assuming equilibration and separation of the liquid metal from the silicates at low degrees of partial melting of the silicates the low w la ratios in the eucrites compared to c1 chondrites require the separation of an additional 2 to 10 solid metal the lowering of both p la and w la ratios in the moon may be explained by partitioning of p and w into metal during formation of a small core by separation of liquid metal from silicate at low degrees of partial melting of the silicates the w la ratios in the earth and moon are virtually indistinguishable while p la ratios differ by a factor of two the concentrations of feo also appear to be different these observations are difficult to reconcile with the hypothesis of a terrestrial origin of the moon following formation of the earth s core but are consistent with independent formation of the earth and moon

searching for seismic scattering off mantle interfaces between 800 km and 2000 km depth 1 we systematically examined seismic data from deep earthquakes in the western and northwestern pacific tonga fiji and south america for signs of sharp gradients in seismic properties that could represent either a mineralogical phase change or the boundary between geochemical reservoirs in the earth s lower mantle this involved the stacking of short period vertical component teleseismic waveforms from the dense pacific northwest seismic network and searching for evidence of s to p conversions at sharp mantle structures between 800 and 2000 km depth with these data we estimate we should be able to detect seismic discontinuities with vs 2 transition width 20 km and limited local topography using data from over 45 earthquakes we found no evidence of a horizontal global discontinuity neither near 920 km nor near 1700 km beneath the four convergent margins studied here consistent with previous results we detected a deep structure with topography near 1600 km beneath the marianas region because we observed the signal over a large geographical region beneath the marianas 10 n to 20 n it is likely a coherent local structural and not a point source the absence of such a structure beneath the northwest pacific the tonga fiji region or south america argues against a global feature near 1600 km depth however the lack of convincing and consistent scattering suggests that no composition boundary or thermal boundary layer exists between 800 to 2000 km depth beneath the convergent zones studied that has vs 2 locally limited topography and a transition interval 20 km

lower mantle scattering profiles and fabric below pacific subduction zones abstract the earth s mantle is compositionally evolving principally through the process of mid ocean ridge basalt production 95 by lithospheric area but also by way of arc magmatism 5 and continental growth reymer a schubert g 1984 phanerozoic addition rate to the continental crust and crustal growth tectonics 3 63 77 rowley d b 2002 rate of plate creation and destruction 180 ma to present geol soc am bull 114 927 933 convection eventually must mix these products back into the mantle but the details of the mixing process are unknown we report here new observational data documenting the location of differentiated material in the present day lower mantle and scattering power profiles with depth small scale 10 km objects which efficiently scatter short period s waves are present in the mantle lying below the pacific ocean rim at depths between 1100 and 1800 km we also observe a reduction in scattering power with depth indicating that the objects represent bodies richer in differentiated basalt than the surrounding mantle the scattering objects appear to be deformed to various degrees and usually form clusters separated from each other by a distance of 100 to 200 km the clusters probably represent folds of the order of 100 km probably corresponding to early stage of mixing process because the scattering power does not increase with depth neither does a permanent barrier to flow exist in the mid mantle nor does the intrinsic density of basalt prevent re entrainment into mantle flow from the bottom of the mantle

paucity of sulfide in a large slab of esquel new perspectives on pallasite formation the 0 7 ton esquel meteorite found in patagonia before 1951 is a typical main group pallasite in most respects we examined petrographically a slab 1 m long having an area of 3000 cm2 that shows the typical pallasitic texture with fragmental olivine phase abundances in vol are olivine 66 metal 32 schreibersite 0 76 troilite 0 46 and chromite 0 31 esquel can be divided into four lithologies 1 pallasitic matrix consisting of olivine fragments embedded in metal 81 2 large 5 cm olivine nodules having low metal contents 18 3 massive metal 0 3 and 4 zones dominated by fes and fine olivine 0 7 main group pallasites appear to have formed by the intrusion of a highly evolved low ir high ni au and s metallic magma into fragmented olivine this model implies that fes should be abundant in main group pallasites and we had speculated that examination of an exceptionally large slab might reveal a high troilite content we found instead an exceptionally low fes content new compositional data confirm that esquel has a lower au content than other main group pallasites having similar ir contents literature data based however on relatively small sections suggest that high au pallasites have higher s contents than esquel but have lower s contents than expected from a trapped melt model we conclude that a relatively complex model is required to explain the origin of main group pallasites after intrusion the degree of crystallization of the metallic magma varied from location to location but in almost all cases an fes rich liquid either escaped or formed fes rich pallasitic rocks that are underrepresented in the meteorite inventory

reference s wave velocity profile and attenuation models for ground motion prediction equations application to japan defining the reference rock or soil condition related to ground motion prediction is an important aspect of seismic hazard analysis in a previous study by the authors a method was proposed to establish a reference rock profile for switzerland through the comparison of empirical amplification functions with shear wave velocity profiles at 27 selected sites of the swiss national seismic network the retrieved velocity profile served as reference for a regional ground motion prediction equation however a lacking piece of information remained the anelastic attenuation for such a reference profile reference attenuation is essential to correctly model and interpret amplification at high frequencies in the present study we extended our approach to simultaneously model both the reference shear wave velocity profile and the corresponding attenuation for japan we compared site specific attenuation measurements with quarter wavelength average velocities at 36 soil and rock sites from the japanese kik net strong motion network the selected sites are characterized by a lack of observed resonance phenomena in order to avoid trade off between amplification and attenuation effects we establish a parametric model through regression analysis the resulting model gives us the possibility to estimate anelastic attenuation of a rock site with a given velocity profile and provides the base for host to target adjustments of real or modeled ground motion

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

reference rock site condition for central and eastern north america abstract the reference rock site condition has two important applications for ground motion prediction in the stable continental region of central and eastern north america cena 1 it represents the site condition for which ground motions are computed using semiempirical ground motion prediction equations in addition 2 it represents the site condition to which site amplification factors which are used to modify ground motion intensity measures for softer site condition are referenced i e site amplification is unity for reference rock we define reference rock by its shear s and compression p wave velocities as well as a site attenuation parameter 0 which is used in stochastic ground motion simulation methods prior definitions of reference rock conditions in cena were based mostly on indirect large scale crustal velocity inversions and judgment we compile and interpret a unique database of direct velocity measurements to develop criteria for assessing the presence of reference rock site condition based on measured seismic velocities and their gradient with respect to depth we apply the criteria to available profiles and perform rigorous statistical analysis from which we recommend s and p wave velocities of 3000 and 5500 m s respectively for the reference rock condition we recommend that for practical applications use ranges of reference s and p wave velocities of 2700 3300 m s and 5000 6100 m s respectively the ranges are based on a 5 change in amplification using quarter wavelength theory we do not find evidence for regional dependence of the reference velocities which are derived principally from three general geographic regions 1 atlantic coast 2 continental interior and 3 appalachian mountains our data do not provide reference velocities for the gulf coast region the recommended velocity compatible reference rock site kappa is 0 006 s

formation of olivine textures in pallasites and thermal history of pallasites in their parent body an analysis of the textures of pallasites has been made using data concerning the kinetic and rheological properties of silicates and metals pallasites containing rounded olivines e g the springwater and brehnam pallasites have been heated to above the solidus temperature of the metallic iron phases 1270 k the rounded olivines of grain size 0 5 1 0 cm observed in the springwater pallasites were formed between 1270 and 1370 k on the other hand those of grain size 0 5 1 0 mm as found in the brehnam pallasites may have been heated to above 1370 k however the duration of heating at such high temperatures must have been less than 5 103 y pallasites containing angular olivines with microscopically rounded corners e g the eagle station dora pallasites have suffered shock events fracturing the olivine grains which may correspond to collisions during the accretional stage of the parent body and experienced successive annealing during cooling from a temperature between 1150 and 1270 k

a stochastic ground motion model for switzerland abstract we present a stochastic ground motion model for switzerland a model for the far field fourier amplitude spectra of earthquakes is first proposed constrained by ground motions observed from small local and regional earthquakes in addition to macroseismic intensities observed from large damaging events in switzerland we then use this model in a stochastic simulation technique to generate predictions of peak ground acceleration and velocity and 5 damped response pseudo spectral acceleration we facilitate the prediction of ground motions from finite fault sources through the use of the r eff distance metric and show that magnitude and distance scaling behavior of events up to m w 7 5 is broadly consistent with next generation attenuation and japanese models ground motion prediction uncertainty is described in terms of between and within event uncertainties through residual analysis of response spectra finally single station sigma is derived accounting for the prediction uncertainty at a given site without the ergodic assumption consistency of the model is emphasized through its compatibility with other seismic hazard products the model is referenced to a generic rock profile that was developed by utilizing velocity profiles of the sites of seismic stations and is calibrated at higher magnitudes to the swiss regional macroseismic intensity prediction model furthermore the model is based on moment magnitudes from the recently developed earthquake catalogue of switzerland 2009 ecos09 the well defined reference for the model means that it can easily be adapted for a site specific application for instance through the use of proxies such as quarter wavelength velocity and travel time average shear wave velocity in the upper 30 m v s 30

characterizing the vertical to horizontal ratio of ground motion at soft sediment sites a predictive equation to obtain the vertical to horizontal ratio v h of ground motion for rock sites has been established in a previous article the method was based on the comparison between v h of fourier and response spectra of earthquakes with the quarter wavelength average velocity at discrete frequencies we extend this approach to account for resonance phenomena at soft sediment sites in order to do so a new parameter is defined and included in the comparison with the v h spectra the new parameter is directly derived from the quarter wavelength velocity and represents the frequency dependent seismic impedance contrast at the site we show that extending the correlation in this three dimensional space is beneficial to reconstruct v h of the 5 damped response spectra at soft sediment sites v s 30 800 m s for which a shear wave velocity profile is available in this study we analyze 220 sites of the japanese kik net strong motion network these sites were selected from the entire network through comparison of the fundamental frequencies estimated from the recordings and by indirect modeling methods from the analysis two types of predictive equations are then established the first based on frequency dependent and the second on frequency independent correlations these can subsequently be used to reconstruct the v h spectrum at any site with a known shear wave velocity profile for both equations uncertainties of the v h models are provided and a sensitivity study to magnitude distance dependence is presented finally we show an example of the application of the model at four selected soft sediment sites of the swiss seismic network

tubular symplectic inclusions in olivine from the fukang pallasite olivine from the fukang meteorite like that from many other pallasites contains distinctive arrays of parallel straight tubular inclusions they differ in their extension and linearity from those in terrestrial olivines they comprise approximately 1 of the total volume most have lens shaped cross sections but some are rounded the major axis of the lens shaped inclusions is rigorously oriented along olivine 001 and the rounded ones lie along olivine 010 and a few along 100 the linear nature and orientations of the inclusions suggest that they nucleated on screw dislocations perhaps formed through shock triggering high resolution transmission electron microscopy tem and energy dispersive x ray spectroscopy show that the inclusions consist of symplectic intergrowths of chromite diopside and silica that appear to have formed by exsolution from the host olivine the symplectites consist of chromite lamellae with approximately 35 nm spacings that grew outward from a central plane with interstitial diopside and silica contrast modulations having an average spacing of 4 4 nm occur within the chromite lamellae using a reaction front model we estimate that exsolution occurred over a period of 30 to 100 min suggesting rapid cooling at high temperature the crystallographic observations and inferences on growth rate are consistent with the hypothesis that the inclusions nucleated during heating following dislocation formation in a shock event perhaps concurrent with that proposed to have disrupted the pallasite parent body

metallographic cooling rates of the iiiab iron meteorites abstract an improved computer simulation program has been developed and used to re measure the metallographic cooling rates of the iiiab irons the largest iron meteorite chemical group the formation of this chemical group is attributed to fractional crystallization of a single molten metallic core during solidification group iiiab irons cooling rates vary by a factor of 6 from 56 to 338 c my the cooling rate variation for each meteorite is much smaller than in previous studies and the uncertainty in the measured cooling rate for each meteorite is greatly reduced the lack of correction for the orientation of the kamacite taenite interface in the cooling rate measurement of a given meteorite in previous studies not only leads to large cooling rate variations but also to inaccurate and low cooling rates the cooling rate variation with ni content in the iiiab chemical group measured in this study is attributable in part to the variation in nucleation temperature of the widmanstatten pattern with ni content and nucleation mechanism however the factor of 6 variation in cooling rate of the iiiab irons is hard to explain unless the iiiab asteroidal core was exposed or partially exposed in the temperature range in which the widmanstatten pattern formed measurements of the size of the island phase in the cloudy zone of the taenite phase and re os data from the iiiab irons and the pallasites make it hard to reconcile the idea that pallasites are located at the boundary of the iiiab asteroid core