topography of the 410 and 660 km discontinuities beneath the korean peninsula and southwestern japan using teleseismic receiver functions topography of the 410 and 660 km seismic upper mantle discontinuities beneath the korean peninsula and southwestern japan were determined using teleseismic receiver functions p receiver functions were migrated from delayed times to corresponding piercing conversion points of p to s converted phases using one dimensional 1 d and three dimensional 3 d models receiver functions were then stacked using common conversion point ccp techniques to enhance signal to noise ratios and thereby reduce uncertainty noise the 410 and 660 km discontinuities were clearly imaged as positively valued amplitude peaks of ccp stacked receiver functions in the study area topographic variations were roughly consistent with the low temperature of the subducting pacific plate however the complex structure of the subducting pacific plate produced distinct changes of upper mantle discontinuities which cannot be explained by temperature variations alone depression of the 410 km discontinuity observed in a wide region extending from the korean peninsula to kyushu island may be related to trench rollback history furthermore the topography of the 660 km discontinuity varies significantly with latitude at latitudes higher than 38 n its depth remains unchanged despite the presence of the stagnant slab while significant depression has been observed at latitudes below 36 n this may have been caused by differences in the angles of subduction of the japan slab and the izu bonin slab however heterogeneity of the water content of slabs may also have contributed to this topographical difference

investigation of upper mantle discontinuity structure beneath the central pacific using ss precursors 1 using a high quality broadband seismic data set of precursors to the phase ss we investigate the structure of upper mantle discontinuities beneath the central pacific including the hawaiian hot spot we image structure by stacking over 4000 records into geographic bins retaining periods down to 5 s we consider the effects of correcting for four separate tomographic models of mantle heterogeneity excluding data at distances containing phases that potentially interfere with precursors we find evidence for peak to peak topography of 15 20 km on the 670 km discontinuity and 7 28 km of topography on the 400 km discontinuity weak reflections are detected from discontinuities near 220 and 520 km depth the average transition zone thickness beneath our region is approximately 242 3 km very similar to previous estimates of the global average lateral transition zone thinning and thickening weakly correlate with reduced and increased transition zone shear velocity respectively consistent with a thermal origin to topographical variations on the discontinuities within our study region the transition zone beneath hawaii and to the east of the line island chain is thinned by up to 20 km in a province spanning nearly 1000 km suggesting an excess mantle temperature of 200 k in the oldest crustal regions of our study area 100 ma the 400 km discontinuity is relatively shallow and the transition zone is relatively thick 250 255 km a possible explanation for this pattern includes small scale convection in the upper mantle bringing colder material into the transition zone

global upper mantle structure from finite frequency surface wave tomography 1 we report global shear wave velocity structure and radial anisotropy in the upper mantle obtained using finite frequency surface wave tomography based upon complete three dimensional born sensitivity kernels because wavefront healing effects are properly taken into account finite frequency surface wave tomography improves the resolution of small scale mantle heterogeneities especially for deep anomalies that are constrained by the longest period surface waves in our finite frequency model ffsw1 the globally averaged radial anisotropy shows a transition from positive sh sv to negative anisotropy sv sh at about 220 km consistent with a change in the dominant mantle circulation pattern from predominantly horizontal flow at shallow depths to vertical flow at greater depths the radial anisotropy beneath cratons and the old pacific plate agrees well with previous studies however our model exhibits a strong negative radial anisotropy at depths greater than 120 km beneath mid ocean ridges a feature that is not present in previous upper mantle models more interestingly the depth extent of the ridge anomalies is distinctly different beneath fast and slow spreading centers anomalies beneath fast spreading centers are stronger but the strength decreases rapidly below 250 km in contrast beneath slow spreading centers such as the northern mid atlantic ridge and the red sea anomalies extend down at least to the top of the transition zone the different depth extent of the ridge anomalies suggests that the primary driving force of slow spreading seafloor may be different from that of fast spreading seafloor and that active upwelling beneath slow spreading ridges may play a major role in the opening of the seafloor

in situ gasification of coal a natural example history petrology and mechanics of combustion a 6 m thick coal seam of the upper jurassic and lower cretaceous mist mountain formation in the southeastern canadian cordillera has been burning since 1936 the upper 3 m of coal is being consumed to an estimated depth of 20 m temperatures in excess of 1100 c are locally reached resulting in the melting of overlying sandstones and shales the melted and vitrified rocks contain a new suite of minerals including diopside anorthite cristobalite and tridymite underlying the burnt coal ash is a zone of coke averaging about 10 cm thick which is in turn underlain by unaltered coal within the area of combustion three zones can be distinguished an advance zone where open cracks are developed at the ground surface a zone of active combustion where volatiles driven off the coal bum en route to the surface and at the mouth of vents and an abandoned zone marked by vents some of which act as air intakes approximately 1000 tlyear of coal is consumed giving an energy release of about 1 mw the heat generated is carried both forward and upward by convecting gas thereby coking the coal and baking the roof rock little heat is carried downward as evident from a sharp decrease in vitrinite reflectance below the zone of combustion the baked roof rocks are brittle and extensively fractured providing little roof support the completely fused and scoriaceous rock and welded associated breccias on the other hand have greater coherence this welding hinders roof collapse and thereby assists the passage of gases

the fluid dynamics of a basaltic magma chamber replenished by influx of hot dense ultrabasic magma this paper describes a fluid dynamical investigation of the influx of hot dense ultrabasic magma into a reservoir containing lighter fractionated basaltic magma this situation is compared with that which develops when hot salty water is introduced under cold fresh water theoretical and empirical models for salt water systems are adapted to develop a model for magmatic systems a feature of the model is that the ultrabasic melt does not immediately mix with the basalt but spreads out over the floor of the chamber forming an independent layer a non turbulent interface forms between this layer and the overlying magma layer across which heat and mass are transferred by the process of molecular diffusion both layers convect vigorously as heat is transferred to the upper layer at a rate which greatly exceeds the heat lost to the surrounding country rock the convection continues until the two layers have almost the same temperature the compositions of the layers remain distinct due to the low diffusivity of mass compared to heat the temperatures of the layers as functions of time and their cooling rate depend on their viscosities their thermal properties the density difference between the layers and their thicknesses for a layer of ultrabasic melt 18 mgo a few tens of metres thick at the base of a basaltic 10 mgo magma chamber a few kilometres thick the temperature of the layers will become nearly identical over a period of between a few months and a few years during this time the turbulent convective velocities in the ultrabasic layer are far larger than the settling velocity of olivines which crystallise within the layer during cooling olivines only settle after the two layers have nearly reached thermal equilibrium at this stage residual basaltic melt segregates as the olivines sediment in the lower layer depending on its density the released basalt can either mix convectively with the overlying basalt layer or can continue as a separate layer the model provides an explanation for large scale cyclic layering in basic and ultrabasic intrusions the model also suggests reasons for the restriction of erupted basaltic liquids to compositions with mgo 10 and the formation of some quench textures in layered igneous rocks

anomalous mantle transition zone beneath the yellowstone hotspot track the origin of the yellowstone and snake river plain volcanism has been strongly debated the mantle plume model successfully explains the age progressive volcanic track but a deep plume structure has been absent in seismic imaging here i apply diffractional tomography to receiver functions recorded at usarray stations to map high resolution topography of mantle transition zone discontinuities the images reveal a trail of anomalies that closely follow the surface hotspot track and correlate well with a seismic wave speed gap in the subducting farallon slab this observation contradicts the plume model which requires anomalies in the mid mantle to be confined in a narrow region directly beneath the present day yellowstone caldera i propose an alternative interpretation of the yellowstone volcanism about 16 million years ago a section of young slab that had broken off from a subducted spreading centre in the mantle first penetrated the 660 km discontinuity beneath oregon and idaho and pulled down older stagnant slab slab tearing occurred along pre existing fracture zones and propagated northeastward this reversed polarity subduction generated passive upwellings from the lower mantle which ascended through a water rich mantle transition zone to produce melting and age progressive volcanism the mantle transition zone in the western united states is perturbed along a path that mirrors the line of the yellowstone hotspot track at the surface according to analysis of tomographic data

sharp mantle transition from cratons to cordillera in southwestern canada the western canada sedimentary basin marks the transition from the old north american continental lithosphere to young accreted terranes earlier studies in this region have suggested a large number of intricate basement domains as well as major seismic velocity gradients in the mantle to investigate the effect of the accretion and subduction on the mantle structure beneath the western margin of the north american craton we analyze p to s converted waves from upper mantle discontinuities from the canadian rockies and alberta network a regional broadband seismic array based in alberta canada the depths of the 410 and 660 km seismic discontinuities are correlated and on average are 9 km and 7 km greater than their respective global estimates the largest depression is observed beneath the rocky mountain foreland belt in southern alberta which highlights a steep southward westward structural gradient from the cratons to cordillera at lithospheric mantle depths the severity of the depressions especially in the southernmost alberta may be triggered by diffuse partial melt or increased water content above the 410 km discontinuity this result is corroborated by locally increased impedance contrast across the 410 km discontinuity and a strongly depressed 660 km discontinuity a relic mesozoic slab fragment may be partially responsible for the deep olivine phase boundary at the base of the upper mantle

global shear speed structure of the upper mantle and transition zone s u m m a r y the rapid expansion of broad band seismic networks over the last decade has paved the way for a new generation of global tomographic models significantly improved resolution of global upper mantle and crustal structure can now be achieved provided that structural information is extracted effectively from both surface and body waves and that the effects of errors in the data are controlled and minimized here we present a new global vertically polarized shear speed model that yields considerable improvements in resolution compared to previous ones for a variety of features in the upper mantle and crust the model sl2013sv is constrained by an unprecedentedly large set of waveform fits 3 4 of a million broad band seismograms computed in seismogram dependent frequency bands up to a maximum period range of 11 450 s automated multimode inversion of surface and s wave forms was used to extract a set of linear equations with uncorrelated uncertainties from each seismogram the equations described perturbations in elastic structure within approximate sensitivity volumes between sources and receivers going beyond ray theory we calculated the phase of every mode at every frequency and its derivative with respect to sand p velocity perturbations by integration over a sensitivity area in a 3 d reference model the normally small perturbations of the 3 d model required to fit the waveforms were then linearized using these accurate derivatives the equations yielded by the waveform inversion of all the seismograms were simultaneously inverted for a 3 d model of shear and compressional speeds and azimuthal anisotropy within the crust and upper mantle elaborate outlier analysis was used to control the propagation of errors in the data source parameters timing at the stations etc the selection of only the most mutually consistent equations exploited the data redundancy provided by our data set and strongly reduced the effect of the errors increasing the resolution of the imaging our new shear speed model is parametrized on a triangular grid with a 280 km spacing in well sampled continental domains lateral resolution approaches or exceeds that of regionalscale studies the close match of known surface expressions of deep structure with the distribution of anomalies in the model provides a useful benchmark in oceanic regions spreading ridges are very well resolved with narrow anomalies in the shallow mantle closely confined near the ridge axis and those deeper down to 100 120 km showing variability in their width and location with respect to the ridge major subduction zones worldwide are well captured extending from shallow depths down to the transition zone the large size of our waveform fit data set also provides a strong statistical foundation to re examine the validity field of the jwkb approximation and surface wave ray theory our analysis shows that the approximations are likely to be valid within certain time frequency portions of most seismograms with high signal to noise ratios and these portions can be identified using a set of consistent criteria that we apply in the course of waveform fitting

gaseous emissions and sublimates from the truman shepherd coal fire floyd county kentucky a re investigation following attempted mitigation of the fire abstract the truman shepherd coal mine fire floyd and knott counties kentucky has been the subject of several field investigations over the last four years during july and november 2011 and january 2012 field investigations we measured gas emissions collected minerals and characterized the nature of the fire new vents opened over the course of the study and have continued to open since january 2012 coincident with the eastward advance of the fire this is the first study of kentucky coal fires where the original vents were able to be studied in addition to new vents on each subsequent trip neoformed minerals associated with the vents are primarily ammonium sulfates and ammonium chlorides with minor zeolites btex emissions especially benzene vary considerably ranging from relatively low to comparable to those from very large fires such as the ankney coal fire in wyoming vent emission data collected displays a general trend of decreasing carbon dioxide and carbon monoxide emissions from july through january the projected annual greenhouse gas and mercury emissions from the fire are 65 69 t of co 2 4 51 t of co 5 73 t of ch 4 and 1 667 kg hg the november 2011 co co 2 ratios are indicative of more complete combustion than at any other time during the study possibly indicative of decreased moisture in the system

isotopic and geochemical investigation of unit 10 from the eastern layered series of the rhum intrusion northwest scotland sr and nd isotopic compositions together with whole rock sr and nd abundances and olivine compositions are presented for cumulates from unit 10 of the eastern layered series of the rhum intrusion northwest scotland the results show an nd sr isotopic correlation consistent with contamination by high 87 sr 86 sr low 143 nd 144 nd crust there is a strong correlation between the degree of contamination sr and nd whole rock abundance and fe enrichment in cumulus olivine the allivalites are the most contaminated while the basal peridotites are uncontaminated this suggests that the cumulates crystallized from a primitive uncontaminated magma and the allivalites from an evolved contaminated magma subsequently movement of contaminated feldspathic intercumulus liquid has perturbed the isotopic trace element and olivine composition of the upper peridotites

anisotropic shear wave velocity structure of the earth s mantle a global model 1 we combine a new large data set of surface wave phase anomalies long period waveforms and body wave travel times to construct a three dimensional model of the anisotropic shear wave velocity in the earth s mantle our modeling approach is improved and more comprehensive compared to our earlier studies and involves the development and implementation of a new spherically symmetric reference model simultaneous inversion for velocity and anisotropy as well as discontinuity topographies and implementation of nonlinear crustal corrections for waveforms a comparison of our new three dimensional model s362ani with two other models derived from comparable data sets but using different techniques reveals persistent features 1 strong 200 km thick high velocity anomalies beneath cratons likely representing the continental lithosphere underlain by weaker fast anomalies extending below 250 km which may represent continental roots 2 weak velocity heterogeneity between 250 and 400 km depths 3 fast anomalies extending horizontally up to 2000 3000 km in the mantle transition zone beneath subduction zones 4 lack of strong long wavelength heterogeneity below 650 km suggesting inhibiting character of the upper mantle lower mantle boundary and 5 slow velocity superplumes beneath the pacific and africa the shear wave radial anisotropy is strongest at 120 km depth in particular beneath the central pacific lateral anisotropic variations appreciably improve the fit to data that are predominantly sensitive to the uppermost and lowermost mantle but not to the waveforms that control the transition zone and midmantle depths tradeoffs between lateral variations in velocity and anisotropy are negligible in the uppermost mantle but noticeable at the bottom of the mantle

convective exchange between pore fluid and an overlying reservoir of denser fluid a post cumulus process in layered intrusions abstract we describe experiments on buoyancy driven exchange between fluid in a porous bed of glass balls and an overlying reservoir of denser fluid fingers of the dense fluid penetrated downwards into the porous medium when the two fluids had equal viscosities the rate of convective exchange was proportional to permeability and the density difference between the fluids and was inversely proportional to viscosity when the fluids had different viscosities the rate further depended on the viscosity ratio raised to the power 0 4 if a layer of dense new melt is emplaced above a porous cumulus pile forming the floor of a magma chamber an analogous process may occur as the new melt can percolate down into the pore space and expel the less dense intercumulus liquid convective exchange may proceed at rates of metres per year to tens of metres per year in basic to ultrabasic magmatic systems this conclusion strongly depends on the porosity of the cumulus pile and is less sensitive to the magmatic viscosities chemical and textural effects will result from this process such as re equilibration and resorption of cumulus crystals when intercumulus melt exchange is incomplete lateral geochemical gradients may be preserved in cumulate rocks

mantle layering from scs reverberations 2 the transition zone this is the second paper in a four part sequence that examines the nature of mantle layering using the scsn phases and internal reflections observed within the reverberative interval of sh polarized seismograms mantle reflectivity profiles for 18 seismic corridors sampling portions of indonesia australia and the western and central pacific are constructed from low frequency 25 mhz scs reverberations i e scsn type phases reflected once from internal mantle discontinuities modeling the reflectivity profiles using synthetic seismograms yields precise path specific estimates of the travel times to the 410 km and 660 km discontinuities and their reflection coefficients the data are consistent with an olivine dominated model of the transition zone marked by two major phase transitions having average apparent depths of 414 2 km and 660 2 km and impedance contrasts of 0 046 0 010 and 0 072 0 010 respectively the interpath variations observed in the reverberation travel times imply that the topography on the two discontinuities is of the order of 20 km peak to peak and is negatively correlated consistent with an endothermic transition at 660 km whose clapeyron slope magnitude is comparable to that of the 410 km exothermic transition in the case of the 660 km discontinuity we have been able to supplement these long wavelength 1500 5000 km observations with an estimate of intrapath topography inferred from the frequency dependence of the 660 km reflection coefficient which gives peak to peak variations less than 40 km on scale lengths of 500 1500 km for the 660 km discontinuity the observed topography is significantly less than the dynamic topography expected for a simple compositional interface in regions of subduction however we do observed an intriguing negative correlation between the apparent depth and the reflection coefficient of the 660 km discontinuity which may involve small compositional variations plausible explanations for this correlation include heating of an initially cool chemical boundary layer gravitationally trapped above an endothermic phase transition loss of reflected energy due to local curvature or roughness of the reflector and or extreme topography occurring on a small compositional component to the discontinuity 40 of the total impedance contrast by stripping the 410 km and 660 km peaks from the composite path reflectivity profile we identify three minor reflectors at mean depths of 520 710 and 900 km the shallowest may mark the phase spinel phase transition the 710 km discontinuity can be attributed to the ilmenite gamet perovskite phase transition although changes in perovskite symmetry can potentially provide explanations for both the 710 km and 900 km features

terminology for layered intrusions the terminology of igneous cumulates was originally formulated on the concept that the rocks were concentrations of minerals accumulated by crystal settling it is now well established for several major intrusions that plagioclase that had been typed as cumulus should in fact have floated in its parental magmatic liquid nevertheless the terminology has been valuable in the classification of the rocks of these and other intrusions and it has been useful in certain aspects of their genetic interpretation the name cumulate is therefore redefined so that crystal settling is a possible but not essential process in the origins of the rocks to which it is applied the overall nomenclature of layered intrusions is then reviewed and definitions of names are refined and systematized to clarify their applications careful distinction is made between descriptive and genetic names a cumulate is defined as an igneous rock characterized by a framework of touching mineral crystals and grains that evidently were concentrated through fractional crystallization of their parental magmatic liquids a layer is a sheetlike unit of cumulate that is a distinctive entity in its compositional and or textural features a lamina is a thin 2 5 cm sharply defined layer igneous lamination is a general name for planar structure that is pervasive through cumulates on the scale of their grain size layering is the overall structure and fabric manifest through combinations of layers laminae and lamination the difference between layers and layering is essentially the difference between individuals and a population and the terms that describe one are not necessarily appropriate to the description of the other but the fundamental variants of all of layering lamination grading in layers and layer contacts can essentially be described by one or more of the four modifiers grain size modal textural and cryptic where the last refers to cumulus miner al compositions a system for subdividing layered intrusions is proposed in which distinction is made between general divisions ranked as series zones and subzones and prominent units that are called groups members rhythmic units and cyclic units applications to the skaergaard bushveld muskox stillwater and other intrusions are briefly described

simultaneous inversion for mantle shear velocity and topography of transition zone discontinuities summary until now modelling of three dimensional 3 d velocity variations in the mantle and topography of the transition zone discontinuities have been considered separately velocity models were obtained assuming that the radii of the discontinuities are constant then the travel time data sensitive to the topography such as the ss precursors were corrected for the effect of 3 d seismic structure and inverted for depth variations of a discontinuity such a procedure is unsatisfactory as it may introduce artefacts that could significantly affect the topographic results the opposite trade off is less likely to introduce conceptually important changes in the velocity distribution but should also be considered in this study we bring together the same set of s velocity sensitive data as used by gu et al and combine it with a large set of differential travel times of ss s400s s s670s and direct measurements of s400s s670s we formulate the inverse problem in terms of the volumetric 3 d and topographic 2 d perturbations for both the 400 and 670 km discontinuities the best fitting model of the joint inversion significantly improves the variance reduction of ss s400s and ss s670s residuals the velocity distribution in the resulting model topos362d1 is very similar to that in model s362d1 with correlation coefficients 0 9 throughout the mantle which indicates that lateral variations of discontinuity depths have only minor influence on global modelling of velocity important changes however have been made to the topography of the 400 and 670 km discontinuities with respect to those obtained earlier assuming an existing velocity model the overall undulation of the 400 km discontinuity is considerably less than that reported by earlier global studies in topos362d1 its maximum variation does not exceed 12 km the strong degree 1 component before the joint inversion has decreased such that the correlation between the velocities above the discontinuity and the shape of the discontinuity itself has substantially diminished spatially this result means a significant diminution in the strength of the earlier reported depression of the 400 km discontinuity under the pacific the power spectrum of the topography of the 670 km discontinuity has been enriched in long wavelength component especially in degree 2 the range of depth variations is 18 km and its shape correlates well with the radially averaged velocity perturbations in the transition zone at wavelengths greater than 1000 km there is little correlation between the depth perturbations of the 400 and 670 km discontinuities the topography of the 400 km discontinuity does not appear to be strongly influenced by thermal structures potentially associated with subduction processes and plumes this implies that thermal influence on the olivine to phase transformation may not fully account for the observed depth variations dynamical effects and potential variations in composition may be important near the top of the transition zone

a three dimensional radially anisotropic model of shear velocity in the whole mantle summary we present a 3 d radially anisotropic s velocity model of the whole mantle saw642an obtained using a large three component surface and body waveform data set and an iterative inversion for structure and source parameters based on non linear asymptotic coupling theory nact the model is parametrized in level 4 spherical splines which have a spacing of 8 the model shows a link between mantle flow and anisotropy in a variety of depth ranges in the uppermost mantle we confirm observations of regions with vsh vsv starting at 80 km under oceanic regions and 200 km under stable continental lithosphere suggesting horizontal flow beneath the lithosphere we also observe a vsv vsh signature at 150 300 km depth beneath major ridge systems with amplitude correlated with spreading rate for fast spreading segments in the transition zone 400 700 km depth regions of subducted slab material are associated with vsv vsh while the ridge signal decreases whilethemid mantlehasloweramplitudeanisotropy vsv in the lowermost 300 km which appears to be a robust conclusion despite an error in our previous paper which has been corrected here the 3 d deviations from this signature are associated with the large scale low velocity superplumes underthecentralpacificandafrica suggestingthatvsh vsv isgeneratedinthepredominant horizontal flow of a mechanical boundary layer with a change in signature related to transition to upwelling at the superplumes

determination and analysis of long wavelength transition zone structure using ss precursors summary global mapping of 410 and 660 km discontinuity topography and transition zone thickness has proven to be a powerful tool for constraining mantle chemistry dynamics and mineralogy numerous seismic and mineral physics studies suggest that the 410 km discontinuity results from the phase change of olivine to wadsleyite and the 660 km discontinuity results from the phase change of ringwoodite to perovskite and magnesiowustite underside reflections of the 410 and 660 km discontinuities arrive as precursors to ss with the recent development of a semi automated method of determining ss arrivals we have more than tripled the flanagan and shearer 1998a data set of handpicked ss waveforms we are able to increase resolution by stacking waveforms in 5 rather than 10 radius bins as well as increasing data coverage significantly in the southern hemisphere the resulting ss s410s and ss s660s times are heavily influenced by upper mantle velocity structure we perform a joint inversion for discontinuity topography and velocity heterogeneity as well as performing a simple velocity correction to the precursor differential times and find little difference between the two methods the 660 km discontinuity topography and transition zone thickness are correlated with velocities in the transition zone whereas the 410 km discontinuity topography is not in addition the 410 km discontinuity topography is not correlated with the 660 km discontinuity topography rather anticorrelated as expected due to the opposite signs of the clapeyron slopes of their respective phase changes these results suggest that whereas the topography of 660 km discontinuity could be dominated by thermal effects the topography of the 410 km discontinuity is likely dominated by compositional effects in addition unlike previous studies which find less topography on the 410 km discontinuity than on the 660 km discontinuity our 410 and 660 km topography have similar amplitudes

study of the lithospheric and upper mantle discontinuities beneath eastern asia by ss precursors summary we analyse broad bandss waveform data recorded by several networks in europe with sources mainly in the west pacific to study the underside reflections of teleseismic ss waves in the lithosphere and the upper mantle beneath eastern asia and the nw pacific ocean ss bounce points sample a corridor from the aleutian kamchatka and japan subduction zones through the north china craton and central asian orogenic belt to the tibetan plateau the corridor passes through different tectonic units such as subduction zones an old continental shield a fold belt and a high plateau we investigate the seismic structure of the lithosphere and the mantle transition zone beneath the different geotectonic units along the profile and infer the correlation of geodynamic processes at different depths we explore the short period frequency content in the ss waveform data and use moveout correction and common midpoint stack to acquire profiles with high lateral and depth resolution from the crust to the mantle transition zone clear ss precursors of the 410 and 660 km discontinuities show the effects of the interaction between the subducted oceanic lithosphere and the mantle transition zone beneath the nw pacific subduction zones a low velocity layer has also been detected beneath the 410 km discontinuity and can be traced along the entire profile due to the improved resolution acquired by the method presented here we have been able to study the shallower structures such as the moho and the lithosphere asthenosphere boundary by ss precursors the continental moho can be clearly seen along this corridor the depth variation agrees well with earlier receiver function results we also see negative reflectors along the profile at varying depths which can be interpreted as the lithosphere asthenosphere boundary

modeling the three dimensional structure of macroscopic magma transport systems application to kilauea volcano hawaii we report the results of modeling the three dimensional internal structure of kilauea s magmatic passageways the approach uses a clear plexiglass model containing equally spaced levels upon which well located seismic hypocenters are plotted application of constraining geologic and geophysical criteria to this distributed volume of earthquakes permits the interpretation of seismic structures produced by fracturing in response to locally high fluid pressures four magma transport and storage structures have been identified within and beneath kilauea 1 primary conduit the conduit transporting magma into kilauea s summit storage reservoir rises from the model base 14 6 km to the 6 5 km depth level it is a zone of intense fracturing and inferred intrusion whose horizontal sections are elliptical in planform over its height the average major axis of the component horizontal sections is 3 3 km with an average minor axis of 1 7 km this yields an aspect ratio of 0 52 at the 14 6 km level the strike of the major axis is n67 e during passage from the upper mantle through the oceanic crust this axis rotates in a right handed sense until the strike is n41 w at the 6 5 km level 2 magma chamber complex floor the interval from 6 5 to 5 7 km immediately over the primary conduit is aseismic this suggests differentially high fluid to rock ratios and relatively weak pathways for further vertical transport into higher levels of the storage complex as well as lateral leakage eastward into the mauna ulu staging area for later vertical ascent beneath the upper east rift zone seismicity within the immediately subjacent rocks that form the top of the primary conduit at 6 5 km suggests that this inferred magma rich horizon forms the effective floor of the summit storage complex 3 magma chamber crown intense seismicity over the 1 1 1 9 km depth interval defines an elliptical region in plan view the top of this region has a broad apex with an average major axis of 1 5 km and an average minor axis of 1 1 km producing an aspect ratio of 0 73 this region coincides with the epicentral position of summit vertical displacement maxima during inflationary deformation and is interpreted as a region of intense diking crowning the summit storage complex 4 upper east rift zone pipe from a depth of 5 7 km a cylindrical region of seismicity rises beneath the upper east rift zone to the 1 9 km level where it merges with the subhorizontal upper east rift zone duct this pipe like zone has a mean diameter of 1 4 km and a vertical axis that pierces the surface of the volcano at the intersection of the koae fracture system and the upper east rift zone we suggest this pipe forms a principal connection between the base of the summit storage reservoir and near surface storage compartments and ducts in the upper east rift zone in this role the pipe is suggested to have contributed heavily to mauna ulu s magma supply during 1969 1974 the model of magma transport and storage thus constructed provides a context in which other types of data e g ground deformation and electrical conductivity may be interpreted as well as a means of refining petrological inferences based on lava chemistry

mantle transition zone beneath the central tien shan lithospheric delamination and mantle plumes abstract we investigate structure of the mantle transition zone mtz under the central tien shan in central asia by using recordings of seismograph stations in kyrgyzstan kazakhstan and adjacent northern china we apply p wave receiver functions techniques and evaluate the differential time between the arrivals of seismic phases that are formed by p to sv mode conversion at the 410 km and 660 km seismic boundaries the differential time is sensitive to the thickness of the mtz and insensitive to volumetric velocity anomalies above the 410 km boundary under part of the southern central tien shan with the lowest s wave velocity in the uppermost mantle and the largest thickness of the crust the thickness of the mtz increases by 15 20 km relative to the ambient mantle and the reference model iasp91 the increased thickness is a likely effect of low about 150 k temperature this anomaly is indicative of delamination and sinking of the mantle lithosphere the low temperature in the mtz might also be a relic of subduction of the oceanic lithosphere in the paleozoic but this scenario requires strong coupling and coherence between structures in the mtz and in the lithosphere during plate motions in the last 300 myr our data reveal a reduction of thickness of the mtz of 10 15 km under the fergana basin in the neighborhood of the region of small scale basaltic volcanism at the time near the cretaceous paleogene boundary the reduced thickness of the mtz is the effect of a depressed 410 km discontinuity similar to that found in many hotspots this depression suggests a positive temperature anomaly of about 100 150 k consistent with the presence of a thermal mantle plume a similar depression on the 410 km discontinuity is found underneath the tarim basin

the further adventures of tin man vertical temperature gradients at the lotts creek coal mine fire perry county kentucky abstract the lotts creek coal mine fire developed in an abandoned underground and surface mine in the hindman hazard no 9 coalbed in the hazard north 7 minute quadrangle in a study conducted in april and may 2012 an array of five thermocouples with 1 m vertical separation between individual thermocouples was suspended in an active vent of the fire data were collected from each thermocouple for 21 days at 1 min intervals for many days small thermal gradients were noted on 3 may 2012 the 10th day of the investigation a relatively extreme thermal event occurred with a nearly 95 c difference in the 2 m between the 2nd and 4th thermocouples other extreme heating events were noted but none as intense as the latter event such events were overprinted on the diurnal and shorter breathing cycles of the fire and the complications induced by changing atmospheric conditions and the shifting of the fire front as the coal burned the 3 may thermal event may have been a result of a sudden opening of a vent with the consequent influx of air increasing the intensity of the fire since the experiment was run remotely without visits to the site between the time of placement and pick up of the data logger assembly no one witnessed the incident

global scale analysis of the mantle pds phases a global scale analysis of travel times of the mantle pds phases converted from p to s from the discontinuity at a depth d beneath the receiver is presented most of the data are related to p 410 s and p 660 s recorded by the broadband stations of geoscope incorporated research institutions for seismology iris and other networks in order to provide a good global scale coverage published measurements at 37 stations are complemented by our measurements at 45 stations lateral resolution of our data is many times higher than that of ss and its precursors previously used for similar purposes but we have fewer data in the oceans lateral variations of travel times of the major pds phases are strongly correlated with the lateral p and s velocity variations in the uppermost mantle as revealed by tomographic studies the scaling coefficient between the teleseismic s and p residuals as found from the variations of travel times of the major pds phases is around 3 7 for north america and around 3 3 for the rest of the world almost all the differential travel times t p 660 s t p 410 s are in the range of 1 s relative to the average value of 24 0 s if the lateral variations of the velocities within the mantle transition zone mtz can be neglected the corresponding variations of thickness of the mtz are in the range of 10 km relative to the standard depth of 250 km and do not show significant correlation with either velocities in the upper mantle above the mtz or with the variations of thickness of the mtz as found in some recent studies of precursors to ss there is a weak but marginally significant positive correlation between the variations of thickness of the mtz inferred from our data and the s velocity variations in the mtz as given by su et al 1994 this correlation suggests that both variables contain temperature dependent components lateral variability of the mtz is also manifested by extreme weakness of p 410 s at several locations this may indicate either anomalous topography on 410 km discontinuity or strong broadening of the otherwise sharp discontinuity at some stations there are arrivals that can be interpreted as p 520 s this interpretation implies that the strengh and or sharpness of 520 km discontinuity as well as its depth are laterally variable in a broad range

subducted lithosphere beneath the kuriles from migration of pp precursors abstract we seismically image both thermal and chemical heterogeneity of the mantle beneath the kurile subduction zone using p wave energy reflected from the underside of discontinuities arriving as precursors to the seismic phase pp we take advantage of new broadband seismic data provided by the high lava plains seismic experiment and earthscope s usarray collecting a dataset of 31 high quality sumatran earthquakes sampling beneath the kuriles we employ high resolution array analysis techniques including migration and vespagrams to identify precursory arrivals and study lateral variations in discontinuity depth sharpness and impedance of the mantle transition zone we find the 410 km boundary is at 395 km near the subducting kurile slab though the boundary is 410 425 km deep elsewhere in regions away from subduction we do not detect a laterally continuous underside reflection of p waves from the 660 km discontinuity however in the vicinity of the subducting kurile slab we detect robust p660p reflections from interfaces near 620 670 km depth signifying an increase in the impedance contrast at 660 km depth we also detect deeper reflectors down to 720 km depth beneath the kurile slab in a localized area cold aluminum depleted harzburgitic lithosphere residing at the base of the transition zone best explains the local enhancement of the 660 km discontinuity p wave impedance contrast our new discontinuity measurements support the hypothesis of cold depleted lithosphere stagnating at the 660 km discontinuity beneath the kuriles subduction zone and imply the 660 km boundary can locally impede mantle flow and produce chemical heterogeneity within the transition zone

roughness of the mantle transition zone discontinuities revealed by high resolution wavefield imaging we processed two independent data sets 2 458 973 three component seismograms from all earthscope transportable array usarray stations and 141 080 pairs of high quality receiver functions from the earthscope automated receiver survey using the generalized iterative deconvolution method and shaped the output with a 0 1 hz ricker wavelet we used these data as input to our 3 d plane wave migration method to produce an image volume of p to s scattering surfaces under all of the lower 48 states model simulations show that compared to the widely used common conversion point stacking method our method is capable of resolving not only dipping discontinuities but also subtler details of amplitude and topography variations at scales near the diffraction limit maps of attributes derived from these discontinuities reveal several previously unobserved features of the 410 and 660 discontinuities d410 and d660 topography with many tens of kilometers is resolved at a range of scales additionally we observed large variations of amplitude on the radial component and in the radial to transverse amplitude ratio that correlate with inferred variations in discontinuity topography we argue that this combination of observations can be explained by roughness at a range of scales the structural fabric we imaged is preferentially aligned orthogonal to the farallon north american relative motion two regions we infer to have exceptional roughness show spatial correlation with locations where tomography models indicate that the subducted slab is passing through the transition zone we suggest that these rough regions are indicators of vertical mantle flows through the transition zone

constraints on upper mantle discontinuities from observations of long period reflected and converted phases stacked images combining over 5 years of long period global digital seismograph network data reveal many phases associated with reflections and conversions from upper mantle discontinuities these images show travel time and amplitude relative to a reference phase which is aligned and normalized on all seismograms prior to stacking results obtained for p s ss and pp reference arrivals resolve numerous phases from discontinuities near 410 and 660 km while some of the stacks also show evidence for a weaker discontinuity near 520 km phases of particular interest include p and sh multiples resulting from topside reflections precursors to ss from underside reflections and p to sv converted phases these phases can be clearly seen both in the waveform stacks and in cross correlation analysis of individual seismograms travel times for these arrivals are converted to discontinuity depths relative to velocities in the preliminary reference earth model and empirical corrections are applied for the effects of lateral velocity variations in the upper mantle average apparent depths to the discontinuities for the different phases agree to within 3 km for the 410 km discontinuity to within 4 km for the 520 km discontinuity and to within 8 km for the 660 km discontinuity the best global averages are obtained from the ss precursor data which indicate discontinuities at 415 519 and 659 km discontinuity depths obtained from the p to sv converted phases at over 35 individual seismic stations exhibit variations of less than 20 km apparent depths to the 660 km discontinuity consistently show greater variability than depths to the 410 km discontinuity supporting recent laboratory results which indicate that the clapeyron slope for the 660 km discontinuity is significantly larger in magnitude than the slope for the 410 km discontinuity precursors to ss seen between 110 and 180 are particularly useful for mapping possible lateral variations in discontinuity depths since each arrival can be associated with a single underside reflection point apparent discontinuity depths computed from ss precursors for different tectonic regions agree to within about 5 km the ss precursors have especially good coverage near the subducting slabs in the northwest pacific analysis of apparent discontinuity depths in this area suggests the presence of a broad 1000 to 1500 km wide region near the slab in which the 660 km discontinuity is depressed by about 20 km measuring absolute amplitudes for these phases is difficult due to the large corrections required to compensate for the effects of incoherent stacking relative amplitude analysis suggests that the p and s wave impedance changes at 410 km are about 0 8 1 1 times the size of the changes at 660 km and that the contrasts at 520 km are between 0 3 and 0 6 of the changes at 410 km

global de correlation of the topography of transition zone discontinuities analysis of long period shear wave underside reflections from upper mantle discontinuities shows the shape of the 410 km discontinuity to be neither globally nor locally correlated with that of the 660 km discontinuity the long wavelength pattern of 410 topography is dominated by degree 1 spherical harmonics and has a reasonable correlation with the seismic velocity perturbations in the mantle above it the global topography of 660 dominated by degree 2 spherical harmonics is strongly correlated with shear wave velocity variations in the transition zone the poor correlation between the observed topography of the 410 and 660 km discontinuities is inconsistent with a simple model of large scale whole mantle flow thus implying a more complex pattern which includes at least temporary accumulation of subducted material in the transition zone ringwood and irifune nature 331 1988 131 136 tackley et al nature 361 1993 699 704 the modest seismic discontinuity at 520 km is well observed when the reflections are under mid age oceans but is not observed when they are under continental shields interpretation of this observation in terms of olivine depletion in the deep continental mantle indicates the possible existence of continent ocean chemical heterogeneity at depths exceeding 500 km

ducks low cost thermal monitoring units for near vent deployment abstract during 1999 we designed and tested a thermal monitoring system to provide a cheap robust modular real time system capable of surviving the hostile conditions encountered proximal to active volcanic vents in november 2000 the first system was deployed at pu u o o kilauea hawai i to target persistently active vents aside from some minor problems such as sensor damage due to tampering this system remained operational until january 2004 the success of the prototype system led us to use the blueprint for a second installation at stromboli aeolian islands italy this was deployed dug into a bomb proof bunker during may 2002 and survived the april 2003 paroxysmal eruption despite being located just 250 m from the vent in both cases careful waterproofing of connectors and selection of suitable protection has prevented water damage and corrosion in the harsh atmosphere encountered at the crater rim the pu u o o system cost us 10 000 and comprises four modules sensors transmission and power hub repeater station and reception site the sensor component consists of three thermal infrared thermometers housed in pelican cases fitted with germanium arsenide selenium windows two 1 field of view fov sensors allow specific vents to be targeted and a 60 fov sensor provides a crater floor overview a hard wire connection links to a pelican case housed microprocessor modem and power module from here data are transmitted via a repeater site to a dedicated pc at the hawaiian volcano observatory here data are displayed with a delay of 3 s between acquisition and display the modular design allows for great flexibility at stromboli 1 and 15 fov sensor modules can be switched depending changes in activity style and crater geometry in addition a direct line of site to the stromboli reception center negates the repeater site requirement reducing the cost to us 5500 for a single sensor system we have also constructed self contained units with internal data loggers for us 1500 unit these have been tested at kilauea stromboli etna masaya santiaguito fuego pacaya poas soufriere hills villarrica and erta ale these instruments have proved capable of detecting thermal signals associated with 1 gas emission 2 gas jetting events 3 crater floor collapse 4 lava effusion 5 lava flow in tubes 6 lava lake activity 7 lava dome activity and 8 crater lake skin temperature

upper mantle discontinuity topography from thermal and chemical heterogeneity using high resolution stacks of precursors to the seismic phase ss we investigated seismic discontinuities associated with mineralogical phase changes approximately 410 and 660 kilometers km deep within earth beneath south america and the surrounding oceans detailed maps of phase boundary topography revealed deep 410 and 660 km discontinuities in the down dip direction of subduction inconsistent with purely isochemical olivine phase transformation in response to lowered temperatures mechanisms invoking chemical heterogeneity within the mantle transition zone were explored to explain this feature in some regions multiple reflections from the discontinuities were detected consistent with partial melt near 410 km depth and or additional phase changes near 660 km depth thus the origin of upper mantle heterogeneity has both chemical and thermal contributions and is associated with deeply rooted tectonic processes

imaging upper mantle discontinuity topography using underside reflection data this paper presents a method to invert underside reflection p d p or s d s arrivals data for lateral depth variations of upper mantle discontinuities combining traveltime and amplitude data the method greatly improves the resolution of small scale undulations obtained by existing imaging methods and does not suffer from the long wavelength biases that are likely to be present in currently available models existing inversion methods account for the large size of the fresnel zone of underside reflections but not for its complexity arising from the mini max traveltime nature of pp and ss related waves this neglect results in long wavelength artefacts from small scale undulations of the discontinuities obscurring true long wavelength depth variations the inversion method presented in this paper uses a complex valued sensitivity kernel derived from the representation of underside reflections through a kirchhoff integral formulation the sensitivity kernel accounts for the varying sensitivity of the waveforms to discontinuity structure over the fresnel zone the method is applied to a large synthetic data set the data set consists of p d p amplitudes and traveltimes the results show that the new inversion method resolves depth variations on a lateral scale that is smaller than the size of the fresnel zone of individual underside reflections but larger than the dominant wavelength retaining the resolution of large scale variations the results presented here suggest that the discontinuity depth variations induced by slab penetration of the 670 discontinuity could be resolved by current broad band p670p data sets

lateral variations in the unit 7 8 boundary zone of the rum eastern layered intrusion nw scotland implications for the origin and timing of cr spinel seam formation the rum layered suite nw scotland hosts cr spinel seams at the bases of peridotite troctolite macro rhythmic units in the eastern portion of the intrusion here we present detailed field observations together with microstructural and mineral chemical analyses for the unit 7 8 cr spinel seam and associated cumulates in the eastern layered intrusion detailed mapping and sampling reveal significant lateral variations in the structural characteristics and mineral compositions of the unit 7 8 boundary zone rocks although the cr spinel seam is laterally continuous over 3 km it is absent towards the centre and the margins of the intrusion the compositional characteristics of cr spinel and plagioclase vary systematically along strike exhibiting a chemical evolution towards more differentiated compositions with increasing distance from the main feeder conduit of the rum intrusion the long loch fault on the basis of our combined datasets we propose that the upper part of the troctolite the anorthosite layer underlying the cr spinel seam and the seam itself formed during a multi stage magma replenishment event the stages can be summarised as follows 1 peridotite schlieren and anorthosite autoliths formed following melt infiltration and cumulate assimilation in the crystal mush of the unit 7 troctolite 2 the anorthosite layer then formed from the unit 7 troctolite crystal mush by thermal erosion and dissolution due to infiltrating magma 3 subsequent dissolution of the anorthosite layer by new replenishing magma led to peritectic in situ crystallisation of the unit 7 8 cr spinel seam with 4 continued magma input eventually producing the overlying unit 8 peridotite in the central part of the rum layered suite the aforementioned assimilation of the troctolitic footwall formed the anorthosite layer however the absence of anorthosite in close proximity to the long loch fault can be explained by enhanced thermochemical erosion close to the feeder zone and its absence close to the margins of the intrusion at maximum distance from the long loch fault may be due to cooling of the magma and loss of erosion potential in line with other recent studies on pge bearing chromitites in layered intrusions we highlight the importance of multi stage intrusive magma replenishment to the formation of spatially coupled anorthosite and cr spinel seams as well as the lateral mineral chemical variations observed in the unit 7 8 boundary zone cumulates

nanominerals and ultrafine particles in sublimates from the ruth mullins coal fire perry county eastern kentucky usa abstract mineral sublimates from the ruth mullins fire in abandoned underground and surface mines in the high volatile a bituminous middle pennsylvanian hazard no 7 coalbed perry county kentucky were examined by optical mineralogy x ray diffraction xrd and high resolution transmission electron microscopy hr tem optical examination revealed the presence of salammoniac and a fine unidentified fibrous mineral xrd also showed the presence of salammoniac along with trace amounts of quartz kaolinite and possibly phengite both cubic and dendritic salammoniac forms were observed with hr tem gypsum jarosite with cubic pseudomorphs after pyrite and fe minerals including cr bearing hematite in association with jarosite were observed with hr tem dehydration of jarosite can lead to the formation of less hydrous fe sulfates and hematite

mantle discontinuity structure beneath the southern east pacific rise from p to s converted phases receiver functions derived from teleseismic body waves recorded by ocean bottom seismometers on the southern east pacific rise reveal shear waves converted from compressional waves at the mantle discontinuities near 410 and 660 kilometer depth the thickness of the mantle transition zone between the two discontinuities is normal relative to the global average and indicates that upwelling beneath the southern east pacific rise is not associated with an excess temperature in the mantle transition zone

imaging mantle transition zone thickness with sds ss finite frequency sensitivity kernels summary we invert differential sds ss traveltime residuals measured from stacked waveforms and finitefrequency sensitivity kernels for topography on the 410 and 660 km discontinuities this approach yields higher resolution images of transition zone thickness than previous stacking methods which simply average smooth over topographic features apparent structure measured using simple stacking is highly dependent upon the bin size of each stack by inverting for discontinuity topography with a variety of bin sizes we can more accurately calculate the true structure the inverted transition zone model is similar to simple stack models with an average thickness of 242 km but the lateral variations in thickness are larger in amplitude and smaller in scale fast seismic velocities in 3 d mantle models such as sb4l18 correlate with areas of thicker transition zone the elongated curvilinear regions of thickened transition zone that occur near subduction zones are narrow and high amplitude which suggests relatively little lateral spreading and warming of subducted lithosphere within the transition zone the anomalously thin transition zone regions are laterally narrow and not broadly continuous if these variations in transition zone thickness are interpreted as thermal in nature then this model suggests significant temperature variations on small lateral scales

the intrusion of fluid mechanics into geology during the last few years a number of fluid dynamicists often in collaboration with geologists have been investigating problems suggested by geology and creating the new field of geological fluid mechanics the research has uncovered many new fluid mechanical phenomena and the studies have ranged widely over theoretical contributions laboratory experiments and confirmatory field observations this paper presents an overview of part of the field with a strong emphasis on the novel fluid mechanical concepts the presentation includes discussion of some of the effects of cooling and crystallization and the resulting convective motions the flow of gravity currents at both high and low reynolds number and the erosion of solid retaining walls by hot turbulent flows

fluid dynamic and geochemical evolution of cyclic unit 10 rhum eastern layered series lithological major element trace element and sr isotope data from cyclic unit 10 of the rhum eastern layered series are presented the lower 65 metres of the unit are peridotite subdivided on textural and geochemical grounds into a lower homogeneous portion approximately 50 metres thick and an upper heterogeneous portion approximately 15 metres thick the uppermost 16 5 metres of the unit are allivalite there are steep geochemical gradients across the peridotite allivalite boundary in ni content of olivine and whole rock sr isotope composition calculations are presented on the geochemical evolution of a rhum picritic liquid undergoing olivine precipitation both when the olivines remain suspended in the residual liquid as they precipitate and when they are continuously fractionated quenched groundmass and olivine compositions from the rhum dykes and the unit 10 peridotite olivines show good agreement with the suspension model but are inconsistent with the fractionation model the rhum chamber is thought to have been replenished with a picritic liquid from which olivine crystallized while held in suspension however replenishment by a highly olivine phyric basalt is also possible the peridotite probably accumulated rapidly as olivines were dumped out of suspension onto the chamber floor the lower part of the peridotite is a poikilitic adcumulate it is suggested that this formed by convective circulation of melt in the pores of the pile of cumulus olivines in the latter stages of adcumulus growth more fe rich and isotopically contaminated magma entered the top of the cumulus pile causing cumulus olivines to re equilibrate and giving the intercumulus plagioclase a higher sr isotope ratio than lower down the olivines in the allivalite show steep stratigraphic gradients in major element composition but not in their ni content they also show substantial variation in major element composition laterally within the allivalite it is suggested that these features are a consequence of postcumulus re equilibration of olivine with migrating intercumulus magma

in situ gasification of coal a natural example additional data on the aldridge creek coal fire southeastern british columbia a burning coal seam at aldridge creek southeastern british columbia has been monitored over a 3 year period to document the geometry of the fire front subsidence history and gas emissions the fire front is advancing at about 13 5 m year at an angle of about 45 70 to the strike of the coal seam based on near surface temperature anomalies the zone of combustion carbonization and gasification appears to extend down the dip of the coal seam about 40 m and to a depth below ground surface of 20 m the geometry of the fire front is mainly the result of the insulation provided by the overburden which facilitates higher temperatures in advance of the fire at depth with advance of the fire front the upper 2 3 m of coal is coked and partly burnt resulting in subsidence of the overlying strata along concentric faults heat is initially conducted and with opening of fractures convected with emission gases to the surface in hotter zones at temperatures approaching the melting point of the rocks radiat

finite frequency effects in global surface wave tomography summary we compare traditional ray theoretical surface wave tomography with finite frequency tomography using 3 d born sensitivity kernels for long period fundamental mode dispersion measurements the 3 d kernels preserve sidelobes beyond the first fresnel zone and fully account for the directional dependence of surface wave scattering and the effects of timedomain tapering and seismic source radiation tomographic inversions of love and rayleigh phase delay measurements and synthetic checkerboard tests show that 1 small scale s wave velocity anomalies are better resolved using finite frequency sensitivity kernels especially in the lowermost upper mantle 2 the resulting upper mantle heterogeneities are generally stronger in amplitude than those recovered using ray theory and 3 finite frequency tomographic models fit long period dispersion data better than ray theoretical models of comparable roughness we also examine the reliability of 2 d phase velocity sensitivity kernels in global surface wave tomography and show that phase velocity kernels based upon a forwardscattering approximation or previously adopted geometrical simplifications do not reliably account for finite frequency wave propagation effects 3 d sensitivity kernels with full consideration of directional dependent seismic scattering are the preferred method of inverting long period dispersion data finally we derive 2 d boundary sensitivity kernels for lateral variations in crustal thickness and show that finite frequency crustal effects are not negligible in long period surface wave dispersion studies especially for paths along continent ocean boundaries unfortunately we also show that in global studies linear perturbation theory is not sufficiently accurate to make reliable crustal corrections due to the large difference in thickness between oceanic and continental crust

topography of the 410 km and 660 km discontinuities beneath the japan sea and adjacent regions by analysis of multiple scs waves the northwest pacific subduction region is an ideal location to study the interaction between the subducting slab and upper mantle discontinuities due to the sparse distribution of seismic stations in the sea previous studies mostly focus on mantle transition zone mtz structures beneath continents or island arcs leaving the vast area of the japan sea and okhotsk sea untouched in this study we analyzed multiple scs reverberation waves and a common reflection point stacking technique was applied to enhance consistent signals beneath reflection points a topographic image of the 410 km and 660 km discontinuities is obtained beneath the japan sea and adjacent regions one dimensional and 3 d velocity models are adapted to obtain the apparent and true depth we observe a systematic pattern of depression 10 20 km and elevation 5 10 km of the 660 with the topography being roughly consistent with the shift of the olivine phase transition boundary caused by the subducting pacific plate the behavior of the 410 is more complex it is generally 5 15 km shallower at the location where the slab penetrates and deepened by 5 10 km oceanward of the slab where a low velocity anomaly is observed in tomography images moreover we observe a wide distribution of depressed 410 beneath the southern okhotsk sea and western japan sea the hydrous wadsleyite boundary caused by the high water content at the top of the mtz could explain the depression the long history trench rollback motion of pacific slab might be responsible for the widely distributed depression of the 410 ranging upward and landward from the slab

gaseous emissions from the lotts creek coal mine fire perry county kentucky abstract the lotts creek coal mine fire is burning in abandoned works of the pennsylvanian hazard no 9 coal perry county kentucky over the few months separating sampling trips the fire showed a definite migration to the south several vents sampled on the first trip were extinct on the second trip the flux of major gases varies from 1100 to 440 000 mg s m 2 co 2 and 2 co with the gas temperature being one of the principal drivers of the emissions variations the higher the temperature the more co 2 produced mercury also showing wide variation from 45 to 740 ng s m 2 could not be measured at all vents due to temperature limitations inherent in the instrument in addition to co 2 co and hg a number of gases among the volatile aliphatic and volatile aromatic compounds are emitted in potentially dangerous amounts

global variability of transition zone thickness 1 we analyze recordings from more than 3000 shallow earthquakes and measure s410s s660s differential travel times on a global scale these differential times are obtained using a novel cross correlation technique that eliminates effects associated with a priori assumptions of crustal thickness and velocity variations above the upper mantle transition zone our measurements show absolute perturbations up to 8 s from the global average 242 km which imply transition zone thickness variations of 20 km on a length scale of 2000 km the transition zone under major subduction zones e g the western pacific and south america is significantly thicker than the global average this could be associated with large scale depressions of the 660 km discontinuity due to the accumulation of cold oceanic lithosphere at the base of the upper mantle a narrow transition zone is observed under the central pacific and northern atlantic oceans we also observe a modest anticorrelation between s410s s660s times and the delay times of shear waves predicted using s12 wm13 su et al 1994 in the transition zone which suggests considerable thermal influence on the large scale topography of the 410 and 660 km discontinuities the lack of a stronger anticorrelation suggests that 1 compositional heterogeneities may be present and 2 a significant fraction of thermal anomalies near the transition zone do not extend through the transition zone and influence both the 410 and the 660 km discontinuities a regional analysis shows that the transition zone is on average 6 8 km thicker under continents than under oceans this implies a temperature difference of 50 70 c however we do not observe a clear correlation between thickness and the age of the crust

receiver functions in northeast china implications for slab penetration into the lower mantle in northwest pacific subduction zone abstract seismic studies of the subducting lithosphere and the upper mantle discontinuities in the northwest pacific subduction zone beneath japan and northeast china have suggested contrary subduction scenarios there was little consensus on the issue whether the subducting slab penetrates the upper mantle discontinuities into the lower mantle or it is deflected atop of the 660 km discontinuity over several hundred kilometers we calculate receiver functions from a recent seismic broadband station network located in northeast china and find topographic variations of the upper mantle discontinuities a deeper than normal 660 km discontinuity is observed over an area of 400 km and it coincides with the stagnant slab imaged by seismic tomography the 660 km discontinuity is locally depressed by more than 35 km and the transition zone is thickened by more than 20 km in the east of the region where it encounters the slab these observations provide evidence of the slab accumulating in the mantle transition zone and locally penetrating into the lower mantle

density changes during the fractional crystallization of basaltic magmas fluid dynamic implications the dynamical behaviour of basaltic magma chambers is fundamentally controlled by the changes that occur in the density of magma as it crystallizes in this paper the term fractionation density is introduced and defined as the ratio of the gram formula weight to molar volume of the chemical components in the liquid phase that are being removed by fractional crystallization removal of olivine and pyroxene whose values of fractionation density are larger than the density of the magma causes the density of residual liquid to decrease removal of plagioclase with fractionation density less than the magma density can cause the density of residual liquid to increase during the progressive differentiation of basaltic magma density decreases during fractionation of olivine olivine pyroxene and pyroxene assemblages when plagioclase joins these mafic phases magma density can sometimes increase leading to a density minimum calculations of melt density changes during fractionation show that compositional effects on density are usually greater than associated thermal effects in the closed system evolution of basaltic magma several stages of distinctive fluid dynamical behaviour can be recognised that depend on the density changes which accompany crystallization as well as on the geometry of the chamber in an early stage of the evolution where olivine and or pyroxenes are the fractionating phases compositional stratification can occur due to side wall crystallization and replenishment by new magma with the most differentiated magma tending to accumulate at the roof of the chamber when plagioclase becomes a fractionating phase a zone of well mixed magma with a composition close to the density minimum of the system can form in the chamber the growth of a zone of constant composition destroys the stratification in the chamber a chamber of well mixed magma is maintained while further differentiation occurs unless the walls of the chamber slope inwards in which case dense boundary layer flows can lead to stable stratification of cool differentiated magma at the floor of the chamber in a basaltic magma chamber replenished by primitive magma the new magma ponds at the base and evolves until it reaches the same density and composition as overlying magma successive cycles of replenishment of primitive magma can also form compositional zonation if successive cycles occur before internal thermal equilibrium is reached in a chamber in a chamber containing well mixed plagioclase saturated magma the primitive magma can be either denser or lighter than the resident magma in the first case the new magma ponds at the base and fractionates until it reaches the same density as the evolved magma mixing then occurs between magmas of different temperatures and compositions in the second case a turbulent plume is generated that causes the new magma to mix immediately with the resident magma

gross errors in upper mantle discontinuity topography from underside reflection data summary currnet models of upper mantle discontinuity topography derived from traveltime variations of long period underside reflections pdp or sds waves may contain gross errors due to the use of geometrical optics in relating observed traveltimes to depth variations of the discontinuity near the reflection point the use of geometrical optics is not valid if variations in the depth of the discontinuities exist on a lateral scale smaller than the size of the fresnel zone in the data geometrical optics does not take into account the large size and the complex structure of the traveltime surface of underside reflections and may introduce spurious structure when used in inversions examples of synthetic long period pdp waveforms for reflections near subducting lithosphere show that scattering from expected small scale depth variations of the discontinuities inside slabs causes complex waveform variations for a 15 20s pdp wave these small scale depth variations with a scale length of 4 are smaller than the fresnel zone roughly 20 but larger than the pdp wavelength at 420 km depth about 150 200 km the synthetic waveforms are processed to obtain pdp traveltimes which are in turn converted to apparent discontinuity depth at the reflection point using geometrical optics the apparent discontinuity depth variations are not only of the same order of magnitude as those obtained from real data but also exhibit artefacts that closely resemble features observed in current models it is shown that large scale wavelengths of the order of 1000 km downwarping of the 670 km discontinuity near subduction zones derived from underside reflection data can be explained as the long wavelength manifestation of a single small scale wavelengths of several hundreds of kilometres deflection of the discontinuity inside and near subducting slabs

peridotite sills and metasomatic gabbros in the eastern layered series of the rhum complex mapping of the eastern layered series els of the rhum ultrabasic complex on the northern flank of hallival shows that peridotite and allivalite troctolite or gabbro layers are laterally discontinuous and vary both in thickness and lithology peridotite generally has sharp upper and lower contacts against the allivalites which sometimes cut across the layering in the allivalite reaction dissolution and hybridization effects between peridotite and allivalite are developed locally some troctolite layers terminate as isolated fingered blocks in peridotite there are many small peridotite bodies which are clearly intrusive into allivalite and have previously been identified as distinct peridotite sheets and plugs they are petrographically almost identical to the major stratiform peridotites and in some cases are apophyses from them we propose that many of the peridotite layers in the els formed as thick sills of picritic magma emplaced into a partly solidified layered troctolite complex the stratiform gabbros of the els are heterogeneous layered rocks that commonly contain relicts of troctolite and anorthosite wavy metre scale contacts between gabbro and troctolite cut across pre existing grain size modal and rhythmic layering with little disruption these metasomatic gabbros mimic the textures grain size and rhythmic layering of their troctolitic protoliths we propose that many of the els gabbros formed as a result of interaction between porous troctolites and a low temperature basaltic melt residual basaltic melt segregated from solidifying peridotite may have caused this metasomatism

geophysical evidence for the locations shapes and sizes and internal structures of magma chambers beneath regions of quaternary volcanism this paper is a review of seismic gravity magnetic and electromagnetic techniques to detect and delineate magma chambers of a few cubic kilometres to several thousand cubic kilometres volume a dramatic decrease in density and seismic velocity and an increase in seismic attenuation and electrical conductivity occurs at the onset of partial melting in rocks the geophysical techniques are based on detecting these differences in physical properties between solid and partially molten rock although seismic refraction techniques with sophisticated instrumentation and analytical procedures are routinely used for detailed studies of crustal structure in volcanic regions their application for magma detection has been quite limited in one study in yellowstone national park u s a fan shooting and time term techniques have been used to detect an upper crustal magma chamber attenuation and velocity changes in seismic waves from explosions and earthquakes diffracted around magma chambers are observed near some volcanoes in kamchatka strong attenuation of shear waves from regional earthquakes interpreted as a diffraction effect has been used to model magma chambers in alaska kamchatka iceland and new zealand one of the most powerful techniques in modern seismology the seismic reflection technique with vibrators was used to confirm the existence of a strong reflector in the crust near socorro new mexico in the rio grande rift this reflector discovered earlier from data from local earthquakes is interpreted as a sill like magma body in the kilauea volcano hawaii mapping seismicity patterns in the upper crust has enabled the modelling of the complex magma conduits in the crust and upper mantle on the other hand in the usu volcano japan the magma conduits are delineated by zones of seismic quiescence three dimensional modelling of laterally varying structures using teleseismic residuals is proving to be a very promising technique for detecting and delineating magma chambers with minimum horizontal and vertical dimensions of about 6 km this technique has been used successfully to detect low velocity anomalies interpreted as magma bodies in the volume range 10 3 10 6 km 3 in several volcanic centres in the u s a and in mt etna sicily velocity models developed using teleseismic residuals of the cascades volcanoes of oregon and california and kilauea volcano hawaii do not show appreciable storage of magma in the crust however regional models imply that large volumes of parental magma may be present in the upper mantle of these regions in some volcanic centres teleseismic delays are accompanied by p wave attenuation and linear inversion of spectral data have enabled computation of three dimensional q models for these areas the use of gravity data for magma chamber studies is illustrated by a study in the geysers clear lake volcanic field in california where a strong gravity low has been modelled as a low density body in the upper crust this body is approximately in the same location as the low velocity body delineated with teleseismic delays and is interpreted as a magma body in yellowstone national park magnetic field data have been used to map the depth to the curie isotherm and the results show that high temperatures may be present at shallow depths beneath the yellowstone caldera the main application of electrical techniques in magma related studies has been to understand the deep structure of continental rifts electromagnetic studies in several rift zones of the world provide constraints on the thermal structure and magma storage beneath these regions