liquefaction resistance of soils from shear wave velocity a simplified procedure using shear wave velocity measurements for evaluating the liquefaction resistance of soils is presented the procedure was developed in cooperation with industry researchers and practitioners and evolved from workshops in 1996 and 1998 it follows the general format of the seed idriss simplified procedure based on standard penetration test blow count and was developed using case history data from 26 earthquakes and 70 measurement sites in soils ranging from fine sand to sandy gravel with cobbles to profiles including silty clay layers liquefaction resistance curves were established by applying a modified relationship between the shear wave velocity and cyclic stress ratio for the constant average cyclic shear strain suggested by r dobry these curves correctly predicted moderate to high liquefaction potential for 95 of the liquefaction case histories and are shown to be consistent with the standard penetration test based curves in sandy soils a case study is provided to illustrate application of the procedure additional data are needed particularly from denser soil deposits shaken by stronger ground motions to further validate the simplified procedure

constraints on the structure of the himalaya from an analysis of gravity anomalies and a flexural model of the lithosphere the intracontinental subduction of india beneath the himalaya presents several similarities to that occurring at island arcs we study one of those similarities by analyzing gravity anomalies across the himalaya assuming that the topography is supported by the indian elastic plate flexed under the weight of both the overthrust mountains and the sediments in the ganga basin we first examine in detail the effects of each of the following parameters on the configuration of the elastic plate and on the gravity anomalies the flexural rigidity the position of the northern end of the elastic plate the amount of underthrusting of such a plate beneath the range and the density contrasts between the crust and mantle and between the sediments and the crust a plate with a constant flexural rigidity of about 0 7 1025 n m between 0 2 and 2 0 1025 n m allows a good fit to the data from the lesser himalaya and the ganga basin such a plate however cannot underthrust the entire himalaya instead the gravity anomalies show that the moho steepens from only about 3 beneath the lesser himalaya to about 15 beneath the greater himalaya this implies a smaller flexural rigidity beneath the greater himalaya 0 1 to 1 0 1023 n m than beneath the ganga basin and the lesser himalaya even with a thin weak plate beneath the greater himalaya the weight of the mountains depresses the plate too much unless an additional force or moment is applied to the plate the application of a bending moment unit length to the end of the plate of about 0 6 1018 n m is adequate to elevate the indian plate and to bring the calculated gravity anomalies in agreement with those observed both the smaller flexural rigidity and the bending moment can be understood if we assume that part or all of the indian crust has been detached from the lower lithosphere that underthrusts the greater himalaya we study the tectonic implications of these results by means of a series of idealized balanced cross sections from the collision to the present that reproduce several important features of the geology of the himalaya and predict an amount of eroded material comparable to that in the ganga basin and the bay of bengal these cross sections include high grade metamorphic rocks near the main central thrust and a steeper dip of it there than in the lesser himalaya they predict rapid uplift only in the greater himalaya and at the foot of the lesser himalaya

laboratory investigation on assessing liquefaction resistance of sandy soils by shear wave velocity shear wave velocity vs offers engineers a promising alternative tool to evaluate liquefaction resistance of sandy soils and the lack of sufficient in situ databases makes controlled laboratory study very important in this study semitheoretical considerations were first given based on review of previous liquefaction studies which predicted a possible relationship between laboratory cyclic resistance ratio crrtx and vs normalized with respect to the minimum void ratio confining stress and exponent n of hardin equation undrained cyclic triaxial tests were then performed on three reconstituted sands with vs measured by bender elements which verified this soil type dependent relationship further investigation on similar laboratory studies resulted in a database of 291 sets of data from 34 types of sandy soils based on which the correlation between liquefaction resistance and vs was established statistically and further converted to equivalent field conditions with well defined parameters reve

focused synthetic aperture radar processing of ice sounder data collected over the greenland ice sheet the authors developed a synthetic aperture radar sar processing algorithm for airborne spaceborne ice sounding radar systems and applied it to data collected in greenland by using focused sar phase corrected coherent averaging they improved along track resolution by a factor of four and provided a 6 db processing gain over unfocused sar coherent averaging without phase correction based on a point target analysis for a greenland ice sounding data set also they demonstrated that the focused sar processing reduced clutter and enabled them to identify bedrock interface returns buried in clutter using focused sar technique they processed data collected over a key 360 km long portion of the 2000 m contour line of southwest greenland to the best of their knowledge these are the first high quality radar ice thickness measurements over this key location moreover these ice thickness measurements have been used for improving mass balance estimates of the greenland ice sheet

dem analysis of soil fabric effects on behaviour of sand the effects of initial soil fabric on the shear behaviour of granular materials are investigated by employing distinct element method dem numerical analysis soil specimens are represented by an assembly of non uniform sized spherical particles dem specimens that have different initial contact normal distributions were prepared at two different densities loose and dense and then isotropically consolidated triaxial tests were simulated with the following conditions a different drainage conditions undrained drained b different modes of shearing compression extension and c different directions of shearing vertical horizontal the numerical analysis results are compared qualitatively with the observed experimental data and the effects of initial soil fabric on resulting soil behaviours are discussed the discussions include the effects of specimen reconstitution methods effects of large preshearing and anisotropic characteristics in drained and undrained conditions the effects of initia

deformation warming and softening of greenland s ice by refreezing meltwater when basal meltwater refreezes the resulting warm ice can influence the flow dynamics of the ice sheet above an analysis of airborne gravity and radar data identifies extensive basal ice units across the northern greenland ice sheet that coincide with areas of deformed ice and fast ice flow

a comparison of radio echo sounding data and electrical conductivity of the grip ice core the depth of reflecting layers in arctic ice sheets has been determined by electromagnetic echo sounding using a varying distance between transmitter and receiver to determine the radar wave velocity the depth of the radar reflecting layers is compared with a profile of electrical conductivity measurements ecms from the greenland ice core project grip ice core in order to determine the velocity of the radar waves in the ice cap by using several reflecting layers it is possible to isolate the firn correction of the wave velocity and to estimate the accuracy of the calculated electromagnetic wave velocity the measured firn correction is compared with the correction calculated from the density profile and a comparison between the depth profiles of ecm and radar based on the corrected electromagnetic wave velocity is presented this profile shows that acid layers which originate from major volcanic eruptions show up as reflecting radar horizons

heat focussing granite genesis and inverted metamorphic gradients in continental collision zones abstract the thermal conductivity of sedimentary rocks is usually much lower than that of crystalline rocks gneisses and granites continental collision zones are characterized by large scale thrusts which superpose crystalline basement and sedimentary layers this leads to heat refraction effects of significant magnitude sedimentary layers act as a barrier to the transport of heat we show that the peculiar geometry of a gently sloping sedimentary layer thrust into more conductive rocks is very efficient in diverting the vertical flux of heat temperatures can vary by more than 50 along the horizontal and reach a marked maximum at the top of crystalline layers these results are in general agreement with the main features of orogenic belts as exemplified by the himalayas they explain why the young leucogranites of the main central thrust mct are confined to a narrow belt at the top of the basement slab they also account for the inverted metamorphic gradient observed there in a crustal accretionary wedge folding and thrusting modify the structure of the upper crust by thickening the sedimentary cover and by introducing sedimentary rocks at depth this leads to high temperatures at shallow depths in specific places les zones de collision continentale se caracterisent par de grands chevauchementsafaible pendage qui empilent les unes sur les autres des couches de socle cristallin et des couches sedimentaires cette structure particuliere engendre d importants effets de refraction thermique en effet leur conductibilitethermiqueetant normalement bien plus faible que celle des roches cristallines les formations sedimentaires font office de barrieres pour le transfert thermique le flux de chaleur se trouve fortement devie dans un plan horizontal la temperature peut varier de plus de 50 les maximaetant situesal interface superieur des dalles cristallines en ces endroits precis les isothermes profonds remontent tres significativement ces resultats rendent bien compte de plusieurs faits essentiels observes dans l himalaya zoneographie inverse du metamorphisme localisation des leucogranites le long d une bandeetroite situee au sommet de la dalle du tibet

crustal structure and variability of the himalayan border of tibet reversed critical wide angle reflection profiles of the crust mantle boundary south of the yarlung zangbo suture in tibet reveal a deep 70 km moho extending north from the high himalayas whilst to the south the moho is 15 km higher even further south reflections from 35 km depth may correspond to the moho of peninsular india

lunar and terrestrial crusts a constrast in origin and evolution abstract planetary crusts differing in composition from that of the bulk planet and containing large concentrations of incompatible elements such as k u and th may arise in two distinctly different ways the first exemplified by the moon involves flotation of a feldspathic crust during an initial melting episode in which much of the planetary body was molten the second probably more common type of crust is formed as a consequence of partial melting in response to radioactive heating in the planetary interior and the eruption of basaltic lavas examples include the lunar maria and the oceanic crust of the earth subsequent partial melting episodes involving recycling into the mantle or lower crustal melting episodes produce more acidic crusts of which the terrestrial continental crust forms the type example the upper crust requires at least three successive partial melting events

deep seismic reflection waves and structure of the crust from dangxung to yadong on the xizang plateau tibet abstract in this paper we study the travel times velocities and spectral distributions of reflected waves generated by underwater explosions in lakes on the xizang plateau the crustal structure on both sides of the yarlung zangbo river has been estimated by the inverse solution known as damped least squares the depth of the moho is 70 73 km in the region north of the yarlung zangbo river the depth of the moho in the southern region is 68 45 km there is a low velocity 5 47 km s 1 layer in the crust and the crustal thickness decreases from north to south in the xizang plateau

influence of nonplastic fines on shear wave velocity based assessment of liquefaction many false positives no liquefaction detected when the normalized shear wave velocity cyclic stress ratio vs1 csr combination indicated that it should have been are observed in the database used in the simplified liquefaction assessment procedure based on shear wave velocity two possible reasons for false positives are the presence of a thick surface layer of nonliquefiable soil and the effects of fines on cyclic shear resistance crr and vs1 about 67 of the false positives that could not have been caused by an overlying thick surface layer are associated with silty sands with less than 35 fines the effects of fines on the liquefaction resistance of silty sands and on the shear wave velocity are analyzed theoretical crrfield versus vs1 curves for silty sands containing 0 to 15 nonplastic fines are established they show that the theoretical crr vs1 correlations for silty sands with 5 to 15 nonplastic fines are all located to the far left of the semi empirical curves that separate liquefac

controls on source and depth of emplacement of granitic magma large granitic batholiths emplaced in high grade metamorphic rocks at mid crustal levels were relatively hydrous compared with major batholiths emplaced at very shallow levels those emplaced at mid crustal levels were probably generated by partial melting of crustal rocks at only slightly deeper levels those emplaced at shallow levels are associated with penecontemporaneous volcanic ejecta and were probably generated at deep crustal or possibly mantle depths

ice stream related patterns of ice flow in the interior of northeast greenland ice flow in the interior of the ne quadrant of the greenland ice sheet is focused on the large ice stream draining the north side of the summit dome the rapid ice flow in the stream is apparent in the surface features in the stream and at the margins in the broad scale topography that drives ice flow and in satellite derived ice motion information the patterns of ice flow in the upper half of the stream are remarkable for their level of organization simple geometry and effects on local surface topography the stream begins less than 100 km from the ice divide as a current 15 km wide and then broadens symmetrically downstream by the addition of ice from the sides to a width of more than 60 km elevation data and visible band imagery show that the stream has marginal troughs tens of meters deep in its upper reach which are coincident with regions of high shear strain rate the topography of the margins and undulating surface of the stream is generated by the ice flow the surface undulations in the stream are fixed in location and shape over the 5 year period from 1994 to 1999 the enhanced flow presents a challenge for researchers trying to understand the history of ice discharge from a significant area in the interior of the ice sheet

probabilistic framework for liquefaction potential by shear wave velocity this paper presents a new empirical equation for assessing liquefaction resistance of soils based on shear wave velocity vs and the results of probabilistic analyses based on this empirical equation a database consisting of in situ shear wave velocity measurements and field observations of liquefaction nonliquefaction in historic earthquakes is analyzed this database is first used to train and test an artificial neural network to predict the occurrence of liquefaction nonliquefaction based on soil and seismic load parameters the successfully trained and tested neural network is then used to establish the empirical equation the concept of clean soil equivalence is introduced and used in the development of the empirical equation the established empirical equation represents a deterministic method for assessing liquefaction resistance of a soil based on this newly developed deterministic method probabilistic analyses of the cases in the database are conducted using the logistic regression approach and

correlation between cyclic resistance and shear wave velocity for providence silts as an alternative to a field based liquefaction resistance approach cyclic triaxial tests with bender elements were used to develop a new correlation between cyclic resistance ratio crr and overburden stress corrected shear wave velocity vs1 for two nonplastic silts obtained from providence rhode island samples of natural nonplastic silt were recovered by block sampling and from geotechnical borings split spoon sampling the data show that the correlation is independent of the soils stress history as well as the method used to prepare the silt for cyclic testing the laboratory results indicate that using the existing field based crr vs1 correlations will significantly overestimate the cyclic resistance of the providence silts the strong dependency of the crr vs1 curves on soil type also suggests the necessity of developing silt specific liquefaction resistance curves from laboratory cyclic tests performed on reconstituted samples

deformation of leucogranites of the crystalline main central sheet in southern tibet china abstract towards the top of the main central sheet in southern tibet china leucogranites intrude metamorphic rocks related to rocks of the main central thrust in the himalayas our study shows that the leucogranites suffered a northward shear deformation the significance of this event is discussed in terms of gravity driven decollement of the 10 000 m thick tethyan sedimentary pile over its crystalline basement

radiostratigraphy and age structure of the greenland ice sheet 2015 the authors several decades of ice penetrating radar surveys of the greenland and antarctic ice sheets have observed numerous widespread internal reflections analysis of this radiostratigraphy has produced valuable insights into ice sheet dynamics and motivates additional mapping of these reflections here we present a comprehensive deep radiostratigraphy of the greenland ice sheet from airborne deep ice penetrating radar data collected over greenland by the university of kansas between 1993 and 2013 to map this radiostratigraphy efficiently we developed new techniques for predicting reflection slope from the phase recorded by coherent radars when integrated along track these slope fields predict the radiostratigraphy and simplify semiautomatic reflection tracing core intersecting reflections were dated using synchronized depth age relationships for six deep ice cores additional reflections were dated by matching reflections between transects and by extending reflection inferred depth age relationships using the local effective vertical strain rate the oldest reflections dating to the eemian period are found mostly in the northern part of the ice sheet within the onset regions of several fast flowing outlet glaciers and ice streams reflections typically do not conform to the bed topography disrupted radiostratigraphy is also observed in a region north of the northeast greenland ice stream that is not presently flowing rapidly dated reflections are used to generate a gridded age volume for most of the ice sheet and also to determine the depths of key climate transitions that were not observed directly this radiostratigraphy provides a new constraint on the dynamics and history of the greenland ice sheet

upb geochronology of gangdese transhimalaya plutonism in the lhasa xigaze region tibet abstract a series of different plutons from the lhasa xigaze segment of the gangdese transhimalaya belt has been studied by high resolution u pb analyses of zircon using zircon fractions of 5 100 grains each selected upon specific grain characteristics for two diorites located east of xigaze dazhuka the zircons yield concordant ages of 93 4 1 0 and 94 2 1 0 m y respectively also concordant ages of 41 1 0 4 and 41 7 0 4 m y have been obtained for two granodiorites collected southwest of lhasa qushui the precision on the ages of two granites from the xigaze and lhasa area is limited by two factors the presence of inherited radiogenic lead and the occurrence of subsequent lead loss however some concordant zircons detected in both granites define approximate ages of about 67 and 53 m y respectively the inherited lead components show that melting of precambrian material was involved in magma genesis the u pb ages substantiate a magmatic activity lasting from mid cretceous cenomanian to eocene lutetian time such a period of plutonism at the southern margin of eurasia as well as the occurrence of magma generation from continental crust suggest that the gangdese range results from the subduction of tethys oceanic lithosphere indian plate underneath eurasia eurasian plate if this model is true the collision of india with eurasia along the lhasa xigaze sector postdates the emplacement of the 41 m y old gangdese granodiorites i e the collision occurred after lutetian time

constraints on the structure of the tibet plateau from pure path phase velocities of love and rayleigh waves pure path phase velocities of love and rayleigh waves across the tibet plateau are determined for the period range 30 90 s and for two opposite directions of propagation along the length of the plateau the method used is a two event method similar in principle to the classical two station method where the roles of stations and events are interchanged the success of this method is due to a favorable geometry whereby events located at each end of the plateau align to within 1 of a great circle path with one wwssn station at teleseismic distance to the east and one to the west body wave modeling is used to constrain depth and source mechanism of the events in order to calculate the corresponding source phases for surface waves phase velocities are determined to within 0 02 km s or better for rayleigh waves and 0 007 km s for love waves the constraints added by these data to the crust and upper mantle structure beneath tibet are discussed in the light of previous studies the best fitting model has a 65 km thick crust with low average crustal velocities and an sn velocity of 4 65 km s the low velocity zone is limited to the depth range 100 150 km the interesting result of this study is that both love and rayleigh wave data can be matched to within 1 in phase velocity by a unique isotropic model this points to a similarity with a stable region upper mantle structure such as that of the canadian shield finally additional rayleigh wave phase velocity data are used to compare propagation on different paths in the vicinity of tibet the tarim basin to the north of tibet stands out as having a distinct crustal structure more similar to an average tectonic region structure moreover evidence is presented for the existence of a very low velocity region at the western end of tibet which correlates well with a pronounced gravity low observed in that area

geochemical investigations of the origin of the manaslu leucogranite himalaya nepal the himalayan orogeny is characterized by an intraplate subduction zone the thrusting of the tibetan slab over the foreland is probably responsible for the origin of the manaslu type leucogranites this geochemical study tries to examine the crustal origin of the granite to verify whether the paragneisses of the tibetan slab are the most probable parent material and to determine the subsequent petrogenetic processes the rb sr systematics suggest that 1 1 the scatter of data points in the 87sr86srvs 87rb86sr diagram may be due to the heterogeneity of the initial 87sr86sr ratios 2 2 the initial isotopic ratios are very high 0 730 0 760 and are in agreement with those of the gneisses of the tibetan slab at the time of the melting pb isotopic ratios are homogeneous they are also consistent with a crustal prehistory the ree and th contents are unexpectedly low in comparison with the much higher contents of the parent material monazite left in the residue of melting or more probably extracted in an early stage of the magmatic history may explain the observed ree and th abundances alternatively field observations show that the emplacement of the granite has been accompanied by a very strong hydrothermal activity in consequence the low ree and th contents of the granite could also be due to the loss by solution during prolonged fluid circulation throughout the granitic melt and the sr and pb isotope distribution to the effect of late to post magmatic fluids the isotopic character of which was determined by the underlying tibetan slab

shear wave velocity based probabilistic and deterministic assessment of seismic soil liquefaction potential abstractshear wave velocity vs offers a means to determine the seismic resistance of soil to liquefaction by a fundamental soil property this paper presents the results of an 11 year international project to gather new vs site data and develop probabilistic correlations for seismic soil liquefaction occurrence toward that objective shear wave velocity test sites were identified and measurements made for 301 new liquefaction field case histories in china japan taiwan greece and the united states over a decade the majority of these new case histories reoccupy those previously investigated by penetration testing these new data are combined with previously published case histories to build a global catalog of 422 case histories of vs liquefaction performance bayesian regression and structural reliability methods facilitate a probabilistic treatment of the vs catalog for performance based engineering applications where possible uncertainties of the variables comprising both the seismic demand an

phase relationships of s type granite with h2o to 35 kbar muscovite granite from harney peak south dakota muscovite granite 13 8 muscovite 4 8 normative corundum was reacted with varying percentages of h 2o in cold seal vessels at 2 kbar and in piston cylinder apparatus between 10 and 35 kbar the diagrams illustrating melting crystallization relationships are p t sections with both excess h 2o and with no h 2o added 0 66 h 2o in rock t x h 2o sections at 15 kbar and 25 kbar showing h 2o undersaturated conditions the h 2o undersaturated surface for the crystallization of quartz coesite small amounts of aluminosilicate minerals persist to higher temperatures glass compositions measured by electron microprobe from samples with 5 h 2o at 15 kbar confirm that liquids are syenitic through at least 100 c above the solidus as predicted from the effect of pressure on the residua system results are explained successfully by phase relationships involving muscovite quartz and orthoclase in k 2o al 2o 3 sio 2 h 2o with reactions depicted in a p total p e h 2o t model with special reference to the divariant surfaces in the region p e h 2o p total with reduced p e h 2o or a h 2o produced either by small amounts of h 2o and h 2o undersaturation or by co 2 h 2o mixtures subsolidus dehydration reaction temperatures decrease vapor present solidus temperatures increase and muscovite stability in presence of liquid increases in general muscovite biotite and amphibole can be precipitated from magmas containing only a few tenths per cent h 2o although the h 2o undersaturated liquids coexisting with crystals may contain 3 or more dissolved h 2o this particular granite cannot be a primary magma from mantle or subducted oceanic crust it is a possible product of partial fusion of pelitic rocks between about 20 km and 40 km depth given sufficient h2o and xenocrystal muscovite or sillimanite from the source rocks the phase relationships are consistent with the idea of s type granites but not sufficient to prove the origin of this rock additional tests require phase relationships of other associated granitic rocks and details of geochemistry geophysics and field relationships

correlation between liquefaction resistance and shear wave velocity of granular soils a micromechanical perspective the shear wave velocity method has become an increasingly popular means to evaluate the liquefaction potential of granular soils understanding the fundamental mechanism underlying existing empiric

contrasting18o enrichment and origins of high himalayan and transhimalayan intrusives abstract twelve analysed leucogranites of the high himalaya in bhutan chung la monlakarchung and garhwal badrinath are among the most 18 o enriched granites known 11 5 12 4 18 o smow with two exceptions and separate minerals show good isotopic concordance the data strongly support an origin of the granites by anatexis of continental basement such as the indian crystalline basement sheet or slab undercut by the main central thrust of which five samples were analysed in contrast the pre collision transhimalayan gangdese batholiths to the north of the indus tsangpo suture as exemplified by the ladakh intrusives show an initially oceanic trend of 18 o vs sio 2 that becomes gradually somewhat enriched with respect to hachijo jima while not completely outside the range of enrichment that seems possible by fractional crystallisation this could tie in with the 87 sr inhomogeneities reported by honegger et al 9 which may be due to assimilation of variably radiogenic eurasian continental basement for both the leucogranites and ladakh intrusives the 18 o levels and the concordance between minerals rule out significant cumulative water rock ratios in syn or post magmatic interaction with subsurface waters