surface wave tomography of the western united states from ambient seismic noise rayleigh and love wave phase velocity maps summary we present the results of rayleigh wave and love wave phase velocity tomography in the western united states using ambient seismic noise observed at over 250 broad band stations from the earthscope usarray transportable array and regional networks all available threecomponent time series for the 12 month span between 2005 november 1 and 2006 october 31 have been cross correlated to yield estimated empirical rayleigh and love wave green s functions the love wave signals were observed with higher average signal to noise ratio snr than rayleigh wave signals and hence cannot be fully explained by the scattering of rayleigh waves phase velocity dispersion curves for both rayleigh and love waves between 5 and 40 speriod were measured for each interstation path by applying frequency time analysis the average uncertainty and systematic bias of the measurements are estimated using a method based on analysing thousands of nearly linearly aligned station triplets we find that empirical green s functions can be estimated accurately from the negative time derivative of the symmetric component ambient noise cross correlation without explicit knowledge of the source distribution the average traveltime uncertainty is less than 1 s at periods shorter than 24 s we present rayleigh and love wave phase speed maps at periods of 8 12 16 and 20 s the maps show clear correlations with major geological structures and qualitative agreement with previous results based on rayleigh wave group speeds

using surface waves recorded by a large mesh of three element arrays to detect and locate disparate seismic sources author posting the authors 2018 this article is posted here by permission of the royal astronomical society for personal use not for redistribution the definitive version was published in geophysical journal international 215 2018 942 958 doi 10 1093 gji ggy316

stepwise onset of monsoon weather observed in the nepal himalaya mountain weather changes in the nepal himalaya were intensively examined during the 2003 monsoon onset using in situ datasets observed by multiple automatic weather stations aws distributed across the coordinated enhanced observing period ceop himalaya reference site at locations with significant differences in altitude onset of monsoon rainfall characterized as nighttime precipitation was initiated simultaneously at all stations with the occurrence and migration of a monsoon depression in the north of the bay of bengal satellite infrared images detected evident suppression of diurnal cloud development after the onset about two weeks prior to the onset the mountain weather abruptly changed such that the daytime valley wind at lower elevations weakened associated with morning clouds and the nighttime southerly wind began at upper elevations the timing corresponded with the weakening of the westerly wind over the himalaya due to the northward shift of the upper subtropical jet stream the time lag between the precipitation onset and the change in the mountain weather was confirmed by 9 yr of in situ aws data the mechanism of nighttime southerly winds at high elevations is also discussed in relation to large scale monsoon flow and local circulation

structure of lower carboniferous basins of nw ireland and its implications for structural inheritance and cenozoic faulting abstract the geometry of lower carboniferous basins across the northern part of ireland is characterised by a gradual change in polarity of structure from a predominantly southward dipping fault system in northern ireland through the lough allen basin and into a mainly northward dipping fault system of connemara in the southwest this polarity change is reflected in the emergence of northward facing uplifted footwall blocks such as at croagh patrick and the ox mountains in the southwest with southward facing blocks in the northeast despite these structural changes there is a great degree of along strike continuity of lower carboniferous structure strain and displacement with the system forming a link between comparable sized and coeval basins in northern england and scotland to the east and the canadian maritime provinces to the west the spatial distribution of carboniferous normal faults suggests that caledonian structure such as the fair head clew bay line plays an important role in the localisation of post caledonian strain although the reactivation of individual caledonian structures may be less common the terrain of the west of ireland is strongly influenced by major carboniferous faults offsetting the base carboniferous unconformity as opposed to previously suggested cenozoic normal faulting of a tertiary peneplain

detrital muscovite 40ar 39ar ages from carboniferous sandstones of the british isles provenance and implications for the uplift history of orogenic belts major progradations of clastic sediments are recorded in the sedimentary record of the famennian and the visean namurian of the united kingdom and surrounding waters we have determined 40ar 39ar ages of 162 detrital muscovites from 11 coarse sandstones which were deposited between 370 and 465 ma spanning both progradations detrital mica ages are dominated by a peak at 415 ma with minor peaks at 440 ma and 390 ma the 415 ma muscovites are derived from the unroofing of the scandian nappes during the compressional phase of the caledonian orogeny in scandinavia the 440 ma muscovites record pre scandian orogenic activity which is rarely preserved in the orogenic record thermochronological evidence suggests that episodic postorogenic uplift and exhumation events kept the scandian orogen a major topographic feature and likely a sediment source for over 100 million years after nappe emplacement and implicates tectonic rather than climatic control on the clastic sediment progradations the near total absence of detrital muscovites with ages 415 ma suggests that the scandian nappes had not been entirely eroded despite repeated uplift during the postorogenic extension the river s which supplied the sediments probably ran parallel to the strike of the major scandian thrusts along the length of the caledonian orogen in a manner analogous to the major river systems of contemporary orogenic highlands

valley winds and the diurnal circulation over plateaus abstract the role of valley winds in the diurnal circulation of large scale mountain massifs like the tibetan plateau is investigated we consider a circular plateau with radial valleys leading to the surrounding lowlands a low resolution grid point model is used to compute the diurnal circulation above the plateau and in the valleys the circulation is driven by the diurnal variation of the surface temperature the model produces valley winds and a diurnal circulation above the plateau in qualitative agreement with observations the inflow towards the plateau in the valleys is strongest in the afternoon there is nocturnal outflow during the day a low pressure system with a corresponding cyclonic circulation around the massif resides at the plateau and we find high pressure well above it at night it is the reverse it is demonstrated that the valley winds contribute significantly to the fluxes of mass and moisture in the plateau s diurnal circulation linear calculations for a neutrally stratified at

crustal imaging across the north anatolian fault zone from the autocorrelation of ambient seismic noise seismic images of active fault zones can be used to examine the structure of faults throughout the crust and upper mantle and give clues as to whether the associated deformation occurs within a narrow shear zone or is broadly distributed through the lower crust limitations on seismic resolution within the crust and difficulties imaging shallow structures such as the crust mantle boundary moho place constraints on the interpretation of seismic images in this study we retrieve body wave reflections from autocorrelations of ambient seismic noise the instantaneous phase coherence autocorrelations allow unprecedented ambient noise images of the north anatolian fault zone nafz our reflection profiles show a moho reflected p wave and additional structure within the crust and upper mantle we image a distinct vertical offset of the moho associated with the northern branch of the nafz indicating that deformation related to the fault remains narrow in the upper mantle

subsidence in late paleozoic basins in the northern appalachians during the interval between continental collision in the devonian and continental breakup in the triassic the northern appalachians became the site of a wide plate boundary zone of dominantly right lateral strike slip as is typical of intracontinental transforms tectonism was both diachronous and rapidly variable along strike through regimes of pure strike slip transpressional deformation and rapid subsidence of extensional basins up to 9 km of mainly nonmarine clastic sediments accumulated in these local depocenters which subsided episodically in two stages 1 an initial phase of stretching and thinning of the lithosphere when subsidence was rapid fault controlled and often accompanied by volcanism and 2 a subsequent phase of gradual thermal subsidence during which the depositional basins expanded to bury the earlier border faults and progressively younger sedimentary units onlapped basement the largest depocenter the magdalen basin opened as a pull apart between strike slip faults in newfoundland and new brunswick from late devonian to early carboniferous subsequent thermal subsidence affected a large area during medial and late carboniferous a phenomenon that is well recorded to the north and west where no later tectonism occurred in areas to the south and east of the basin strike slip on other faults continued into the time of thermal subsidence introducing complications such as localized transpressional deformation and rapid subsidence in smaller pull aparts

short period surface wave phase velocities across the conterminous united states abstract surface wave phase velocity maps for the full footprint of the usarray transportable array ta across the conterminous united states are developed and tested three component long period continuous seismograms recorded on more than 1800 seismometers most of which were deployed for 18 months or longer are processed using a noise cross correlation technique to derive inter station love and rayleigh dispersion curves at periods between 5 and 40 s the phase velocity measurements are quality controlled using an automated algorithm and then used in inversions for love and rayleigh phase velocity models at discrete periods on a 0 25 by 0 25 pixel grid the robustness of the results is examined using comparisons of maps derived from subsets of the data a winter summer division of the cross correlation data results in small model differences indicating relatively minor sensitivity of the results to seasonal variations in the distribution of noise sources division of the dispersion data based on inter station azimuth does not result in geographically coherent model differences suggesting that azimuthal anisotropy at the regional scale is weak compared with variations in isotropic velocities and does not substantially influence the results for isotropic velocities the phase velocity maps and dispersion measurements are documented and made available as data products of the 10 year long usarray ta deployment

amplification and attenuation across usarray using ambient noise wavefront tracking as seismic traveltime tomography continues to be refined using data from the vast usarray data set it is advantageous to also exploit the amplitude information carried by seismic waves we use ambient noise cross correlation to make observations of surface wave amplification and attenuation at shorter periods 8 32 s than can be observed with only traditional teleseismic earthquake sources we show that the wavefront tracking approach can be successfully applied to ambient noise correlations yielding results quite similar to those from earthquake observations at periods of overlap this consistency indicates that the wavefront tracking approach is viable for use with ambient noise correlations despite concerns of the inhomogeneous and unknown distribution of noise sources the resulting amplification and attenuation maps correlate well with known tectonic and crustal structure at the shortest periods our amplification and attenuation maps correlate well with surface geology and known sedimentary basins while our longest period amplitudes are controlled by crustal thickness and begin to probe upper mantle materials these amplification and attenuation observations are sensitive to crustal materials in different ways than traveltime observations and may be used to better constrain temperature or density variations we also value them as an independent means of describing the lateral variability of observed rayleigh wave amplitudes without the need for 3 d tomographic inversions

evolution of the lithosphere in the indian ocean from combined earthquake and ambient noise tomography rayleigh wave dispersion extracted from ambient seismic noise has been widely used to image crustal and uppermost mantle structure applications of this approach in continental settings are abundant but there have been relatively few studies within ocean basins by cross correlating ambient noise recorded at broadband seismic stations around the indian ocean we demonstrate the feasibility of extracting high quality long period 10 30 mhz rayleigh waves that traverse the entire ocean basin high quality rayleigh wave cross correlation functions can be obtained from stacking waveforms over less than two years at land stations and less than four years at island stations we show that adding the dispersion information extracted from ambient noise to a global earthquake data set can improve the resolution of phase velocity maps by about 20 in the northern indian ocean where the station distribution is the best we find that a plate cooling model with a potential temperature of 1450 c and plate thickness of 125 km can fit both the seismic observations and seafloor topography the seychelles mascarene plateau is characterized by anomalously slow velocity at 30 mhz the inclusion of ambient noise data in the tomographic inversion shifts the slow velocity anomaly into better agreement with the topographic relief allowing us to estimate its crustal thickness and confirm that the plateau s elevation is supported by thick crust the 10 and 20 mhz phase velocity maps show a strong asymmetry across the central indian ridge that is best explained by eastward asthenospheric flow emanating from nearby hotspots

tectono magmatic controls of post subduction gold mineralisation during late caledonian soft continental collision in the southern uplands down longford terrane britain and ireland a review abstract the southern uplands down longford terrane sudlt within the british caledonides hosts several economically significant gold occurrences including a 45 km long gold trend in central ireland that includes the proven deposit at clontibret however the region is relatively underexplored for gold and the well constrained geology and tectonic history of the terrane provide a firm geological framework for investigating the roles of tectonic magmatic and metamorphic processes in gold mineralisation during the transition from subduction of oceanic lithosphere to soft thin skinned continental collision the sudlt is an ordovician silurian fore arc accretionary complex that evolved into a foreland basin fold and thrust belt during continental collision in earliest devonian times comparable terranes in phanerozoic orogenic belts globally host significant orogenic gold deposits however the sudlt exhibits a very low metamorphic grade and mineralisation exhibits similarities with orogenic intrusion related and post subduction porphyry gold systems gold in the sudlt predominantly occurs as a lattice constituent of arsenopyrite and pyrite within quartz carbonate veins and disseminated within phyllic and propylitic potassic alteration haloes around quartz carbonate veins and some minor intrusions fluid inclusion data indicate that the gold was deposited from a low salinity mesothermal 330 c carbonic fluid of mixed magmatic metamorphic origin consistent with caledonian orogenic conditions gold mineralisation occurred at shallow crustal depths of less than 10 km and exhibits a broad spatial association with major ne sw trending caledonoid shear zones d1 economically significant gold mineralisation in the sudlt is most commonly hosted by transverse nw se and n s trending fractures d3 constrained to between 418 and 410 ma that cut anchizone epizone facies volcaniclastic turbiditic metasedimentary host rocks the mineralised d3 structures cut and are cut by broadly coeval polyphase diorite and granodiorite intrusions gold mineralisation is associated with the early dioritic i type metaluminous oxidised phase of trans suture suite magmatism that straddles the iapetus suture but predates the later emplacement of s type granitic magma the host structures were subsequently reactivated during late palaeozoic mesozoic and cenozoic times and host younger base metal deposits pb zn cu sn sb mineralisation occurred in early devonian times 418 and 410 ma following arrival of the avalonian continental margin at the subduction trench at 420 ma coeval with the onset of regional transtension post subduction lithospheric mantle delamination and k lamprophyric and mafic to intermediate calc alkaline magmatism gold in the sudlt therefore provides a case study for relationships between post subduction porphyry and orogenic gold mineralisation in soft continental collision zones the transient geodynamic setting between subduction and transtension common during soft continental collision provided the critical elements of the mineralising system a metasomatically fertilised mantle source transient geodynamics favourable lithospheric architecture for the rapid transfer of mass and energy from subcrustal to upper crustal levels thin skinned deformation and relatively low exhumation favours the preservation of mineral deposits in the upper crust

surface wave array tomography in se tibet from ambient seismic noise and two station analysis i phase velocity maps summary empirical green s functions egfs between pairs of seismographs can be estimated from the time derivative of the long time cross correlation of ambient seismic noise these egfs reveal velocity dispersion at relatively short periods which can be used to resolve structures in the crust and uppermost mantle better than with traditional surface wave tomography we combine rayleigh wave dispersion estimates from egfs and from traditional two station ts analysis into a new approach to surface wave array tomography with data from dense receiver arrays we illustrate the methodology with continuous broad band recordings from a temporary seismographic network on the southeastern part of the tibetan plateau in sichuan and yunnan provinces sw china the egfs are robust under temporal changes in regional seismicity and the use of either ambient noise approximated by records without signal from events with magnitude mb 5 or 4 or surface wave coda produces similar results the egfs do not strongly depend on the presence of large earthquakes but they are not reciprocal for stations aligned in the n s direction this directionality reflects the paucity of seismicity to the north of the array using a far field representation of the surface wave green s function and an image transformation technique we infer from the egfs the rayleigh wave phase velocity dispersion in the period band from 10 30 s a classical ts approach is used to determine rayleigh wave phase velocity dispersion between 20 120 s together they constrain phase velocity variations for t 10 120 s which can be used to study the structure from the crust to the upper mantle beneath se tibet short and intermediate period 10 80 s phase velocities are prominently low suggesting that the crust and upper mantle beneath se tibet is characterized by slow shear wave propagation

deep characterization of the santiago basin using hvsr and cross correlation of ambient seismic noise abstract continuously recorded seismic ambient noise is used to investigate the intermediate and deep structure of the santiago basin for seismic site response evaluation single station h v spectral ratios hvsr were used as a proxy to identify zones with high stiffness soils and low impedance contrast with the underlying bedrock as a complement of available surface geology information frequency domain cross correlation of the vertical components of ambient noise were calculated and used to estimate phase velocity dispersion curves associated to station pairs over different soil deposits in addition noise correlation functions ncfs calculated from time domain cross correlation of the vertical seismic noise records were used to estimate group velocity dispersion curves and to verify results from the spectral method data processing from both methods resolves a frequency band between 0 1 and 8 0 hz a critical band for civil infrastructure that is difficult to determine with traditional local scale passive surface wave methods station pairs with high signal correlation over stiff soils in the center south and east part of the basin mainly associated to flat hvsr response yielded robust phase velocity dispersion curves that vary approximately from 3 5 km s at 0 1 hz to 1 km s at 4 hz shear wave velocity profiles inverted from the dispersion curves show high average shear wave velocities that also have a pronounced increase rate with depth and a lack of clear soil bedrock interface at depths predicted by available gravimetric data

the geology of the western part of the fintona block northern ireland evolution of carboniferous basins the western part of the fintona block is divided into four fault bounded segments that contain red bed sediments formerly assigned to the lower old red sandstone dating by miospores indicates the presence of deposits of early devonian age in the irvinestown segment late visean early silesian age in the tempo lisbellaw segment and late visean early silesian and late silesian ages in the milltown segment northward migration of the early carboniferous marine transgression in the northern part of ireland coincided with the sequential propagation of back stepping faults and resulted in the development of diachronous facies belts between late courceyan and arundian times tectonic uplift of a possible southwesterly extension of the tyrone igneous complex gave rise to the deposition of asbian to pendleian red beds to the south of a massif an interface between these red beds and contemporaneous marine sediments farther to the south is recognized and dated a new non marine basin containing brigantian and pendleian red beds also developed to the north of the massif a waterlogged floodplain that developed during westphalian a times may be coeval with more widespread coal bearing sequences elsewhere in ireland alluvial fans prograded southwards over this plain during westphalian b times when faults bordering a northern landmass were reactivated

two receiver measurements of phase velocity cross validation of ambient noise and earthquake based observations phase velocities derived from ambient noise cross correlation are compared with phase velocities calculated from cross correlations of waveform recordings of teleseismic earthquakes whose epicentres are approximately on the station station great circle the comparison is conducted both for rayleigh and love waves using over 1000 station pairs in central europe we describe in detail our signal processing method which allows for automated processing of large amounts of data ambient noise data are collected in the 5 80 s period range whereas teleseismic data are available between about 8 and 250 s resulting in a broad common period range between 8 and 80 s at intermediate periods around 30 s and for shorter interstation distances phase velocities measured from ambient noise are on average between 0 5 per cent and 1 5 per cent lower than those observed via the earthquake based method this discrepancy is small compared to typical phase velocity heterogeneities 10 per cent peak to peak or more observed in this period range we nevertheless conduct a suite of synthetic tests to evaluate whether known biases in ambient noise cross correlation measurements could account for this discrepancy we specifically evaluate the effects of heterogeneities in source distribution of azimuthal anisotropy in surface wave velocity and of the presence of near field rather than far field only sources of seismic noise we find that these effects can be quite important comparing individual station pairs the systematic discrepancy is presumably due to a combination of factors related to differences in sensitivity of earthquake versus noise data to lateral heterogeneity the data sets from both methods are used to create some preliminary tomographic maps that are characterized by velocity heterogeneities of similar amplitude and pattern confirming the overall agreement between the two measurement methods

diurnal winds in the himalayan kali gandaki valley part i observations abstract the diurnal wind system of the kali gandaki valley in nepal was explored in september and october 1998 in a field campaign using pilot balloons as the main observational tool this valley connects the plateau of tibet with the indian plains the river crosses the himalayas forming the deepest valley on earth intense upvalley winds blow up this valley during the day observations were made along the river at various spots selected between the exit point from the himalayas and the source close to the plateau of tibet the strongest upvalley winds were found between marpha and chuksang with typical speeds of 15 20 m s 1 the upvalley wind sets in first at the ground but an upvalley wind layer of 1000 2000 m depth forms quickly after the onset this deep inflow layer persists up to lo manthang a town located a few kilometers south of the plateau of tibet deceleration in the late afternoon and evening also appears to commence near the ground weak drainage flow forms late in the night the causes o

monitoring the monsoon in the himalayas observations in central nepal june 2001 abstract the monsoon himalayan precipitation experiment mohprex occurred during june 2001 along the south slopes of the himalayas in central nepal radiosondes were launched around the clock from two sites one in the marsyandi river basin on the eastern footslopes of the annapurna range and one farther to the southwest near the border with india the flights supported rainfall and other hydrometeorological observations including surface winds from the marsyandi network that has been operated in this region since the spring of 1999 the thermodynamic profiles obtained from the soundings support the observed nocturnal maximum in rainfall during the monsoon with total column moisture and instability maximized just before rainfall peaks coinciding with the appearance of a monsoon depression over central india the onset of the monsoon in this region was characterized by a weeklong weakening of the upper level westerlies and an increase in moisture and convective instability the vertical structure of

seismic velocity structure of the crust and shallow mantle of the central and eastern united states by seismic surface wave imaging seismic surface waves from the transportable array of earthscope s usarray are used to estimate phase velocity structure of 18 to 125 s rayleigh waves then inverted to obtain three dimensional crust and upper mantle structure of the central and eastern united states ceus down to 200 km the obtained lithosphere structure confirms previously imaged ceus features e g the low seismic velocity signature of the cambrian reelfoot rift and the very low velocity at 150 km depth below an eocene volcanic center in northwestern virginia new features include high velocity mantle stretching from the archean superior craton well into the proterozoic terranes and deep low velocity zones in central texas associated with the late cretaceous travis and uvalde volcanic fields and beneath the south georgia rift which contains jurassic basalts hot spot tracks may be associated with several imaged low velocity zones particularly those close to the former rifted laurentia margin

pre mesozoic geology of the western and north western irish continental shelf exploration wells drilled offshore west and north west of ireland penetrated a c 3 7 m cumulative thickness of permo carboniferous sediments overlying dalradian metasediments intruded by caledonian granitic plutons in the north late tournaisian to early visean clastics were deposited coeval with the rheic transgression upon an emergent craton in a continental to marginal marine environment they record an increasing marine influence upwards with the establishment of a carbonate shelf in the asbian clastic carbonate sedimentation which became cyclical in late visean to early namurian temporally correlates with the yoredale cyclothems younger namurian sediments are not preserved sedimentation in early westphalian progressed from prodelta to coal enriched delta top and abandonment facies and is conformably succeeded by brackish to freshwater sediments that contain evidence for local marine incursions of stephanian age an autuno silesian section that is preserved offshore may also have been deposited onshore prior to erosion seismic data enable partial delineation of n s and ne sw early sub basins marginal to the main porcupine basin these sub basins which contain silesian sediments may have styled successive extensional episodes in the basin and augment support for rift models of carboniferous basin development in the north atlantic nw european domain birps data provide supporting evidence for the offshore prolonga tion of pre mesozoic basement fault zones

rugose coral biostromes in the late visean mississippian of nw ireland bioevents on an extensive carbonate platform abstract the extensive upper visean asbian platform carbonates in nw ireland bricklieve limestone fm glencar limestone fm and dartry limestone fm contain distinctive rugose coral biostromes which are dominated by different species of the genus siphonodendron these are in stratigraphic sequence pauciradiale biostrome oldest martini biostrome and several junceum biostromes youngest they represent bioevents caused by special short lasting ecological conditions and can be used as approximately synchronous horizons to correlate within the region the pauciradiale biostrome is the thickest laterally most persistent and most variable in facies and biotic composition of all biostromes it formed on a tectonically influenced platform with a landward seaward zonation from northwest to southeast mainly above storm wave base and below fair weather wave base the northwestern streedagh facies is characterized by the presence of clusters of large sheet like colonies of s pauciradiale the intermediate o donnell s rock facies is unique for the predominance of the fasciculate genus solenodendron the southeastern bricklieve facies represents the amalgamation of autochthonous and allochthonous coral debris and bioclastic debris with localized small patches of coral boundstone mass occurrences of fasciculate rugose corals re appear in the martini biostrome this biostrome developed in a shallower water setting just above fair weather wave base on a levelled carbonate platform the junceum biostromes are thinner decimetre to some metres thick and less persistent they formed in deeper water mostly below storm wave base except for the composite 2nd junceum biostrome of the bricklieve mountains which records a period of shallowing according to facies and coral morphologies which were compared with modern scleractinian growth forms sea level variation exerted one of the strong controls on the rise and decline of the biostromes the pauciradiale biostrome formed during an extended shallowing upward cycle in a depth interval leading to the climax of siphonodendron pauciradiale the cycle ended with the development of the martini biostrome in shallow water its demise is probably caused by drowning during the late asbian sea level rise during that time slice the junceum biostromes flourished in deeper water on the platform coral growth ceased almost completely after formation of the junceum biostromes during the falling sea level of the latest asbian siliciclastic input and resulting turbidity as well as turbulence formed a complex cascade of ecological constraints in addition to the local tectonic influences they combined to result in the depth factor which controlled the distribution of predominating coral populations and the succession of the different biostromes in the asbian of nw ireland

hydroclimatic seasonality recorded by tree ring δ18o signature across a himalayan altitudinal transect abstract water stable isotope ratios of tropical precipitation predominantly reflect moisture source and precipitation intensity trees can incorporate the isotopic signals into annual tree ring cellulose records permitting reconstruction of the temporal changes of hydroclimate over decades to millennia this is especially valuable in the himalayas where the understanding of monsoon dynamics is limited by the lack of a dense and representative observational network we have analyzed tree ring 18 o records from two distinct physiographic sites along the upper kali gandaki valley in the central nepal himalayas representing the wet high himalayas and the trans himalayan dryland to the north empirical correlations and regression analyses were compared to an in situ calibrated oxygen isotope fractionation model exploring the relationships between tree ring 18 o and seasonal mean variability of hydroclimatic forcing at the different locations for this purpose gridded precipitation data from the asian rain gauge dataset aphrodite as well as high resolution onsite observations relative humidity air temperature 18 o of precipitation and radial tree growth were used we found that two distinct sets of meteorological values reflecting pre monsoon and monsoon conditions are needed to reproduce the measured tree ring 18 o values from the high himalayan site but that a single set of monsoonal values performs best for the trans himalayan site we conclude that trans himalayan trees capture long term changes in strength of the indian summer monsoon in contrast high himalayan tree ring 18 o records a more complex hydro climatic signal reflecting both pre monsoon and monsoon seasons with very contrasting isotopic signatures of precipitation this difference in the two hydroclimatic proxy records offers an opportunity to reconstruct first order hydroclimate conditions such as local precipitation rates and to gain new insights into monsoon timing and seasonal water source determination across the himalayan orographic region

diurnal winds in the himalayan kali gandaki valley part ii modeling abstract the penn state ncar mesoscale model mm5 is used to simulate and better understand the wind observations in the kali gandaki valley reported in the first part of this paper the kali gandaki river originates in nepal near tibet flows southward through the mustang basin crosses the himalayas in a gorge and descends to the lowlands of nepal extremely strong diurnal upvalley flow in the gorge and the basin alternates with rather weak drainage flow in the night as proposed in part i the mustang basin and the tibetan plateau can be considered as an elevated heat source driving the upvalley flow during the day however the extreme strength of the diurnal upvalley winds and the order of magnitude asymmetry between day and night cannot be explained with a simple plateau circulation theory the model is successful in simulating almost all aspects of the observations the simulations strongly suggest that the observed acceleration of the upvalley winds near the entrance to the mustang basin is linked

the impact of a buried high velocity layer in the seismic site amplification of the city of llolleo chile programa de riesgo sismico prs at the university of chile comision nacional de investigacion cientifica y tecnologica conicyt 2017 21171480 fondo nacional de desarrollo cientifico y tecnologico fondecyt 1170430 advanced mining technology center amtc fb0809 pia conicyt

regional crustal imaging by inversion of multimode rayleigh wave dispersion curves measured from seismic noise application to the basque cantabrian zone n spain

surface wave tomography from microseisms in southern california received 5 april 2005 revised 23 may 2005 accepted 9 june 2005 published 26 july 2005 1 since it has already been demonstrated that point topoint seismic propagation green functions can be extracted from seismic noise it should be possible to image earth structure using the ambient noise field seismic noise data from 148 broadband seismic stations in southern california were used to extract the surface wave arrival times between all station pairs in the network the seismic data were then used in a simple but densely sampled tomographic procedure to estimate the surface wave velocity structure within the frequency range of 0 1 0 2 hz for a region in southern california the result compares favorably with previous estimates obtained using more conventional and elaborate inversion procedures this demonstrates that coherent noise field between station pairs can be used for seismic imaging purposes citation sabra k g p gerstoft p roux w a kuperman and m c fehler 2005 surface wave tomography from microseisms in southern california geophys res lett 32 l14311 doi 10 1029 2005gl023155

p and s wave tomography of the mantle beneath the united states mantle seismic structure beneath the united states spanning from the active western plate margin to the passive eastern margin was imaged with teleseismic p and s wave traveltime tomography including usarray data up to may 2014 to mitigate artifacts from crustal structure 5 40 s rayleigh wave phase velocities were used to create a 3 d starting model major features of the final p and s models include two distinct low velocity anomalies at depths of 60 300 km beneath the central and northern appalachians and passive margin the central appalachian low velocity anomaly coincides with eocene basaltic magmatism and the northern anomaly is located along the cretaceous track of the great meteor hot spot at depths of 300 700 km beneath the central and eastern u s large high velocity anomalies are inferred to be remnants of the farallon slab that subducted prior to 40 ma during the laramide orogeny

3 d upper mantle shear velocity model beneath the contiguous united states based on broadband surface wave from ambient seismic noise ambient noise seismic tomography has been widely used to study crustal and upper mantle shear velocity structures most studies however concentrate on short period 50 s surface wave from ambient noise while studies using long period surface wave from ambient noise are limited in this paper we demonstrate the feasibility of using long period surface wave from ambient noise to study the lithospheric structure on a continental scale we use broadband rayleigh wave phase velocities to obtain a 3 d vs structures beneath the contiguous united states at period band of 10 150 s during the inversion 1 d shear wave velocity profile is parameterized using b spline at each grid point and is inverted with nonlinear markov chain monte carlo method then a 3 d shear velocity model is constructed by assembling all the 1 d shear velocity profiles our model is overall consistent with existing models which are based on multiple datasets or data from earthquakes our model along with the other post usarray models reveal lithosphere structures in the upper mantle which are consistent with the geological tectonic background e g the craton root and regional upwelling provinces the model has comparable resolution on lithosphere structures compared with many published results and can be used for future detailed regional or continental studies and analysis

crust and upper mantle structure associated with extension in the woodlark rift papua new guinea from rayleigh wave tomography the woodlark seafloor spreading center is propagating westward into the australian plate near the d entrecasteaux islands di papua new guinea generating an active transition zone from continental rifting to seafloor spreading from march 2010 to july 2011 we deployed 31 on shore and 8 offshore broadband seismic stations around the di region to explore the dynamic processes of the lithosphere extension and the exhumation of the high pressure terranes exposed on those islands we measure the multiband 10 60 s rayleigh wave phase velocities from both ambient noise and earthquake signals these measurements are then inverted for a three dimensional shear velocity model for the crust and upper mantle the results indicate that the lithosphere extension is localized near the rift axis beneath the di with a shear velocity structure in the upper mantle that is similar to mid ocean ridges beneath the kiribisi basin west of di an ultraslow shear velocity anomaly 4 0 km s is observed at shallow mantle depth 30 60 km which can be interpreted either by the presence of excess partial melt due to slow melt extraction or by the existence of felsic crustal material buried to mantle depth and not yet exhumed

love and rayleigh phase velocity maps 5 40 s of the western and central usa from usarray data abstract continuous data recorded on more than 1600 usarray seismic stations operating in the western and central us between 2006 and 2012 are used to map phase velocities of love and rayleigh waves at short periods 5 40 s using a noise correlation technique vertical and transverse records for all station pairs separated by less than 600 km are cross correlated in 4 h long segments and the resulting spectra are stacked for the time period of station operation dispersion curves are determined from the locations of zeros in the real component of the correlation spectra using a method based on that of aki 1957 phase velocity maps expanded on a 0 25 by 0 25 pixel grid are estimated by inversion of the phase velocity measurements comparison with predicted phase velocity maps based on the crustal model crust2 0 combined with the mantle model nd08 shows good agreement at the longer periods strong slow anomalies 25 in the short period maps are geographically correlated with basins and regions of thick sedimentary cover the strength of these anomalies is not well predicted by existing crustal velocity models

strike slip terranes and a model for the evolution of the british and irish caledonides evidence is presented that many of the major strike faults in the british and irish caledonides were active as sinistral strike slip zones in the end silurian to pre mid devonian period some such as the highland boundary fault moved in this way at an earlier stage in the ordovician these data allow the caledonian rocks lying between the laurentian miogeocline whose basement is represented by the lewisian moine and possibly the dalradian and the gondwanaland miogeocline midland platform and welsh basin to be re analysed as a group of disorganized terranes which originated to the southwest in north america and southwest europe africa prior to the silurian the highland border terrane and northern belt terrane are interpreted as duplicated pieces of a mid ordovician sequence which was a back are to northwest subduction the midland valley terrane is interpreted as a slice of laurentian foreland onto which ophiolites were obducted in the lower ordovician but which became the basement of a continental margin arc to northwest subduction in the mid ordovician the cockburnland terrane is inferred to be part of the same arc repeated and then broken up and dispersed by continuing strike slip the connemara terrane is regarded as an allochthonous piece of the dalradian miogeocline and the south mayo terrane as a remnant of an early ordovician arc and fore arc which in mid ordovician times became a back arc marginal basin to northwest subduction the lake district wexford terrane is part of an arc to southeast subduction under gondwanaland whose activity climaxed in the mid ordovician the central terrane is interpreted as a silurian overstep assemblage which blankets the junction between laurentian and gondwanaland derived oceanic terranes and therefore iapetus is regarded as an ordovician ocean which closed prior to the silurian the model suggests that at the end of the silurian a clockwise rotating gondwanaland having carried laurentia into collision with baltica broke free and created a major sinistral strike slip zone which disrupted the ordovician palaeogeography in the british isles north american sector of iapetus

an introduction to the special issue of earth and planetary science letters on usarray science abstract the usarray observatory a component of the earthscope science initiative has provided a geophysical dataset that densely samples the continental us with unprecedented scale and resolution the major scientific target of the multidisciplinary earthscope project is an understanding of the structure dynamics and evolution of the north american continent with emphasis on imaging the continental crust and lithosphere as well as illuminating dynamic processes in the deep earth this special issue of earth and planetary science letters presents a collection of papers that leverage data from the usarray observatory to provide fundamental insights into earth s structure and dynamics here we present an overview of the papers in this issue on a range of topics including the nature of crustal and mantle heterogeneity across north america the dynamics of the subcontinental mantle the assembly and preservation of continental interiors and the physics of earthquakes and faulting

surface wave tomography of eastern and central tibet from two plane wave inversion rayleigh wave and love wave phase velocity mapssurface wave tomography of eastern and central tibet from two plane wave inversion rayleigh wave and love wave phase velocity maps

how does the tibetan plateau affect the transition of indian monsoon rainfall abstract the roles of the tibetan plateau tp upon the transition of precipitation in the south asian summer monsoon are investigated using a simplified regional climate model before the onset of the south asian monsoon descending flow in the midtroposphere which can be considered as a suppressor against precipitation prevails over northern india as revealed by the ncep ncar reanalysis data the descending motion gradually weakens and retreats from this region before july consistent with the northwestward migration of the monsoon rainfall to examine a hypothesis that the dynamical and thermal effects of tp cause the midtropospheric subsidence and its seasonal variation a series of numerical experiments are conducted using a simplified regional climate model the mechanical effect of the tp generates robust descending flow over northern india during winter and spring when the zonal westerly flow is relatively strong but the effect becomes weaker after april as the westerly flow tends to be weaker