shear wave structure of the south indian lithosphere from rayleigh wave phase velocity measurements we investigate the upper mantle shear wave speed structure beneath the south indian shield by measuring and modeling fundamental mode rayleigh wave phase velocity dispersion observed phase velocities for the south indian shield closely match those observed for the canadian shield we constrain the south indian crust using published receiver function results and invert the dispersion data for upper mantle shear wave structure the 155 km thick seismic lithosphere of the south indian shield is composed of a 35 km thick two layer crust and a 120 km thick high velocity upper mantle lid beneath the moho the average sn wave speed is 4 7 km sec 1 both sn travel times data and the dispersion data suggest a positive sub moho shear wave speed gradient beneath the seismic lithosphere there is a low velocity layer where the shear wave speed drops to 4 4 km sec 1

sensitivities of a squall line over central europe in a convective scale ensemble abstractconvective scale ensemble simulations with perturbed initial and lateral boundary conditions are performed to investigate the mechanisms and sensitivities of a central european convection event from the convective and orographically induced precipitation study cops in this event a primary squall line developed ahead of a decaying mesoscale convective system mcs upstream of the vosges mountains france weakened over the rhine valley then regenerated as a secondary squall line over the black forest mountains germany all ensemble members captured the squall line evolution but most suffered from a delay in the onset of convection and positional errors of 50 150 km over the cops region these errors in the secondary initiation were linked to errors in the primary initiation detailed analysis revealed a similar primary initiation mechanism in all members in the ascending branch of a midlevel frontal circulation ahead of the mcs convection initiated within a mesoscale moisture anomaly

deep seismic investigation across the barents kara region and novozemelskiy fold belt arctic shelf abstract since 1995 sevmorgeo has collected wide angle reflection refraction profiling warrp multichannel seismic data mcs and seismoacoustic profiling along regional lines 1 ar 2 ar and 3 ar these lines cross the whole barents kara region and novozemelskiy fold belt as a result new geological data about the deep structure of the earth s crust have become available four main tectono stratigraphic units are distinguished in the section of the earth s crust 1 a sedimentary cover 2 the upper proterozoic mainly riphean for the barents plate and riphean paleozoic the south kara syneclise deformed and folded complexes 3 the upper crystalline crust granite gneissic metamorphic archean proterozoic complex 4 the lower crust basalt complex the barents kara region is characterized by moderately thinned continental and subcontinental crust with an average thickness of 37 39 km on islands and areas of uplifts with ancient massifs the thickness of the crust 38 42 km approaches the typical crust for a continental platform in the novozemelskiy fold belt the thickness of the crust reaches 40 42 km rift related grabens are characterized by significant crustal thinning with thicknesses of 33 36 km several grabens are revealed the riphean graben on the kola kanin monocline the lower paleozoic west kola graben the devonian demidovskiy aulacogen the upper paleozoic malyginskiy graben in the barents region and upper paleozoic triassic noyabr skiy and the chekinskiy grabens in the kara region data concerning the deep structure lead us to conclude that mainly destructive processes contributed to the dynamics of the forming of the barents kara region

seismic velocity model of the crust and uppermost mantle around the mirnyi kimberlite field in siberia abstract we present the first detailed seismic velocity models of the crust and uppermost mantle around the mirnyi kimberlite field in yakutia siberia we have digitized vintage seismograms that were acquired in 1981 and 1983 by use of taiga analogue seismographs along two perpendicular seismic profiles the 370 km long northwest striking profile i across the kimberlite pipe was covered by 41 seismographs which recorded seismic signals from 21 chemical shots along the line including one off end shot the perpendicular 340 km long profile ii across profile i ca 30 km to the south of the mirnyi kimberlite field was covered by 45 seismographs which recorded seismic signals from 22 chemical shots including four off end shots each shot involved detonation of between 1 5 and 6 0 tons of tnt distributed in individual charges of 100 200 kg in shallow water both velocity models show normal cratonic structure of the ca 45 km thick crust with only slight undulation of the moho however relatively small seismic velocity is detected to 25 km depth in a ca 60 km wide zone around the kimberlite pipe surrounded by elevated velocity 6 3 km s in the upper crust the lower crust has a relatively constant velocity of 6 8 6 9 km s it appears relatively unaffected by the presence of the kimberlite field extremely large p wave velocity 8 7 km s of the sub moho mantle is interpreted along profile i except for a 70 km wide zone with a normal pn velocity of 8 1 km s below the kimberlite profile ii mainly shows pn velocities of 8 0 8 2 km s with unusually large velocity 8 5 km s in two ca 100 km wide zones at its southwestern end one zone being close to the kimberlite field the nature of these exceptionally large sub moho mantle velocities is not yet understood the difference in velocity in the two profile directions indicates anisotropy but the effect of unusual rock composition e g from a high concentration of garnet cannot be excluded

lithospheric thinning in the eastern indian craton evidence for lithospheric delamination below the archean singhbhum craton abstract we herein present shear velocity structure extending down to 300 km depth below the archean singhbhum odisha craton soc and proterozoic chotanagpur granitic gneissic terrain cggt which has been obtained through the inversion modeling of p receiver functions we use three component broadband recordings of 200 teleseismic earthquakes 30 90 from a 15 station seismic network that has been operational in the eastern indian shield since february 2013 we obtain the thinnest crust of 35 km overlying a thin lithosphere of 78 km below the region near south singhbhum shear zone which could be attributed to the 1 6 ga plume activity associated with dalma volcanic however the thickest crust of 47 km overlying a thin lithosphere of 81 km is noticed below the region near the singhbhum granite of 3 6 ga this thinning of lithosphere could be attributed to the delamination of lithospheric root due to the himalayan orogeny with a shortening rate of 2 cm year this delamination model in soc gets further support from the densification of the lower crust which could result from repeated episodes of basaltic underplating associated with episodes related to dalma 1 6 ga and rajmahal 117 ma volcanisms this led to relatively more mafic heterogeneous and deformed crustal structure in soc as well as egmb with an average crustal vs of 4 0 km s in comparison to that in cggt with an average crustal vs of 3 9 km s as seen through our modeling results the thickest lithosphere of 100 km is observed in the southwestern soc as well as northeastern cggt we also notice that a sharp and flat moho in cggt which could be attributed to thermal reactivation and large volume melting of the mafic cratonic crust during the late archean subduction process and associated volcanism episodes this model gets further support from the estimated 169 km thick lower vs zone in the upper mantle below cggt our modeling results also support a northward subduction of archean soc under the proterozoic cggt during 1 0 1 6 ga as earlier proposed by the geological age data from the region

a low seismic wavespeed anomaly beneath northwestern india a seismic signature of the deccan plume abstract seismic tomography of the indian region using p wave arrival times reveals an approximately cylindrical region of lowered seismic velocities in the upper mantle to the north of the gulf of cambay and the present exposure of the deccan flood basalts this anomaly with low velocities interrupts the characteristically high seismic velocities in the lithosphere beneath peninsular india and extends from shallow depth down to a more extensive low velocity zone beneath 200 km the centre of the low velocity anomaly lies just below the earliest alkaline magmatism which has been directly associated with the deccan plume in the northern portion of the cambay graben these magmatic events precede the main deccan flood eruptions by at least 3 myr the lowered seismic wavespeeds link into the ancient narmada lineament and to some extent to the south but here unfortunately the tomographic image runs out of resolution synthetic tests indicate that such a zone of lowered wavespeeds can be recovered with some loss of amplitude towards the south the association of the current seismic anomaly with the deccan traps is intriguing since the cambay graben remains a place of raised heat flow one explanation would be that the seismic anomaly represents the signature of the initial conduit through which plume material forced its way through the lithosphere beneath the cambay rift the zone of lowered seismic velocities beneath the indian lithosphere might then represent the remains of the initial plume head which would need to have moved with india over the 65 myr since the deccan eruptions

heterogeneous lithosphere and the underlying mantle of the indian subcontinent abstract p and s receiver functions prfs and srfs respectively for 21 broad band seismograph stations of the india meteorological department imd illuminate lithosphere and the underlying mantle of some previously poorly sampled regions of the indian sub continent our analysis demonstrates that the archean and early proterozoic lithospheric keel of the indian shield has been reworked by younger processes we find very low s wave velocities in the uppermost mantle from 4 0 to 4 3 km s to the north of the deccan volcanic province kutch region and aravalli craton 1 in the south southern granulite terrain and sri lanka 2 and in the north east gangetic plane bengal basin and singhbuhm craton 3 the anomalies 1 and 2 may extend into the transition zone early arrivals of the s410p seismic phase are indicative of anomalously high vp vs ratio 1 9 in the upper mantle of the low velocity regions whereas late arrivals in the western himalaya ladakh and western tibet are consistent with the previously found indications of anomalously low vp vs ratio a transition from the high s velocity mantle lid to a layer of slightly lower velocity is seen in part of the data but a straightforward interpretation of this transition as the lithosphere asthenosphere boundary is problematic a mafic s velocity in the upper crust and a pronounced low s velocity layer in the lower crust beneath the eruptive center is practically the only specific feature in the lithosphere that may be linked to the deccan traps a separation in depths between the 410 km and 660 km discontinuities varies laterally in a range from 240 to 270 km the largest uplift of the 410 km discontinuity up to 390 km is observed beneath the foothills of the himalaya where it is caused by cooling of the transition zone by the ongoing continental collision

upper mantle beneath foothills of the western himalaya subducted lithospheric slab or a keel of the indian shield summary the fate of the mantle lithosphere of the indian plate in the india eurasia collision zone is not well understood tomographic studies reveal high p velocity in the uppermost mantle to the south of the western himalaya and these high velocities are sometimes interpreted as an image of subducting indian lithosphere we suggest that these high velocities are unrelated to the ongoing subduction but correspond to a near horizontal mantle keel of the indian shield in the south of the indian shield upper mantle velocities are anomalously low and relatively high velocities may signify a recovery of the normal shield structure in the north our analysis is based on the recordings of seismograph station nil in the foothills of the western himalaya the t component of the p receiver functions is weak relative to the q component which is indicative of a subhorizontally layered structure joint inversion of the p and s receiver functions favours high uppermost mantle velocities typical of the lithosphere of archean cratons the arrival of the ps converted phase from 410 km discontinuity at nil is 2 2 s earlier than in iasp91 global model this can be an effect of remnants of tethys subduction in the mantle transition zone and of high velocities in the keel of the indian shield joint inversion of sks particle motions and p receiver functions reveals a change in the fast direction of seismic azimuthal anisotropy from 60 at 80 160 km depths to 150 at 160 220 km the fast direction in the lower layer is parallel to the trend of the himalaya the change of deformation regimes at a depth of 160 km suggests that this is the base of the lithosphere of the indian shield a similar boundary was found with similar techniques in central europe and the tien shan region but the base of the lithosphere in these regions is relatively shallow in agreement with the higher upper mantle temperatures the ongoing continental collision is expressed in crustal structure the crust beneath nil is very thick 58 2 km and the s velocity in the intermediate and lower crust is around 4 0 km s 1 this anomalously large velocity and thickness can be explained by scraping off the lower crust when the indian lithosphere underthrusts the himalaya

field measurements of coastal waves and currents in portugal and greece abstract the mast ii wavemod project aimed at improving stochastic modelling of ocean waves and currents in coastal waters in order to supplement existing data two measurement campaigns were carried out one on the atlantic coast of portugal and secondly on the northern coast of crete in the mediterranean the portuguese measurements covered 7 months during winter 1993 1994 while off crete measurements started early in february 1994 and continued for 10 months in both sites two directional waveriders and one non directional waverider were deployed along a transect out from the coast in water depths between 10 and 100 m in addition the mediterranean site also incorporated measurements of mean current velocities available satellite data were analysed to supplement the buoy data in this paper both measurement campaigns are described together with a presentation of some of the data collected

modeling wind waves and wave exposure of nearshore zones in medium sized lakes we determine wind wave properties and estimate the wave exposure along the entire shore of lake uberlingen a subbasin of lake constance using a third generation spectral wave model swan and compare results to field data on surface waves at three different sites and to predictions from a simple fetch based model fetch forcing the models with local wind data measured at a meteorological station in the center of lake uberlingen provides better simulation results than a spatially resolved wind field obtained from the numerical weather system of the consortium for small scale modeling cosmo because wave diffraction is considered in swan but not in fetch swan provides on average higher wave heights than fetch and agrees better with observations for waves with heights above 0 15 m wave exposure that is the frequency of occurrence of wind waves with heights above 0 15 m varied substantially between different sites along the shore even at small spatial scales although the general pattern of wave exposure was similar for simulations with swan and fetch the model results differed at specific sites especially at bays and headlands and also with respect to the absolute values for wave exposure and its variation between sites simple fetch models may be insufficient to reliably quantify the spatial variability of wave exposure at small spatial scales and complex wave models such as swan may be required even in medium size lakes

stratigraphy structure and volcanology of the se deccan continental flood basalt province implications for eruptive extent and volumes the deccan volcanic province is one of the world9s largest continental flood basalt provinces and derives additional importance because its eruptions 64 67 ma straddle the cretaceous tertiary boundary to better assess the environmental impact of deccan volcanism and its possible effect upon cretaceous tertiary boundary biota it is necessary to document the stratigraphy chronology and volume of the eruptions new chemostratigraphical data permit mapping of the se deccan these data strengthen the likelihood that the rajahmundry traps of eastern india were originally fed by long distance flows and are an extension of the main deccan volcanic province an east west cross section reveals a depression or moat around the se periphery of the deccan volcanic province this provided a site in which shallow lakes initially formed and along which later lava eruptions became channelled and confined published palaeomagnetic data indicate that the lavas of the se deccan were erupted during chron 29r coeval with the cretaceous tertiary boundary and the chemostratigraphic data place the associated lake sediments i e lameta group beneath and within lavas of the wai subgroup finally these new map data are combined with previous work to provide a quantitative estimate for the original deccan volcanic province eruptive volume of c 1 3 10 6 km 3

deep crustal structure of the indian shield from joint inversion of p wave receiver functions and rayleigh wave group velocities implications for precambrian crustal evolution 1 the s wave velocity structure of the crust and uppermost mantle of the indian shield has been investigated by jointly inverting p wave receiver functions and rayleigh wave group velocities at 38 broadband stations in the subcontinent the indian shield is an amalgamation of several terranes of archean and proterozoic age that were partly flooded by deccan trap volcanism during cenozoic times and that make up a natural laboratory for assessing models of precambrian crustal evolution our results reveal significant variations in crustal thickness and deep crustal velocities 45 50 km thick under the archean west dharwar craton and southern granulite terrane with lower crustal velocities around 4 1 km s 32 35 km thick beneath the archean east dharwar and bundelkhand cratons with lower crustal velocities around 3 8 3 9 km s 50 65 km thick under the proterozoic bhandara craton with lower crustal velocities around 4 2 4 3 km s and 55 km thick under the proterozoic aravalli delhi belt with lower crustal velocities around 4 2 km s s velocities in the 4 1 4 3 km s range in the deep crust can be attributed to mafic lithologies suggesting there has been no secular change in the precambrian evolution of the south indian shield moreover pervasive mafic dike swarming throughout the indian shield suggests that the layer of mafic cumulates is 2 5 1 6 ga old and that it delaminated from some archean terranes our interpretation is that mafic underplating of the terranes making up the indian shield occurred in proterozoic times and that a refractory root developed under the archean terranes after the proterozoic event

pn arrivals and lateral variations of moho geometry beneath the kaapvaal craton abstract pn arrivals from mining induced earthquakes on the edge of the witwatersrand basin show that the p wavespeeds in the uppermost mantle are almost constant throughout most of the kaapvaal craton the presence of only small wavespeed variations allows the use of a simple method of estimating crustal thicknesses below the stations of the kaapvaal broad band network using pn times that has been compared with results from receiver functions one thousand three hundred thirty seven pn arrivals were used to derive crustal thicknesses at 46 stations on the kaapvaal craton the average crustal thicknesses for 19 centrally located stations on each of the northern and southern regions of the craton that yielded well constrained thicknesses were 50 52 0 88 km and 38 07 0 85 km respectively in contrast the corresponding average thicknesses determined from receiver functions were 43 58 0 57 km and 37 58 0 70 km respectively the systematically lower values for receiver functions in the northern part of the kaapvaal craton that was affected by the bushveld magmatism at 2 05 ga suggest that the receiver functions do not enable the petrological crust mantle boundary to be reliably resolved due to variations in composition and metamorphic grade in a mafic lower crust the pn times also suggest pervasive azimuthal anisotropy with maximum wavespeeds of about 8 40 km s at azimuths of about 15 and 217 in the northern and southern regions of the craton respectively and minimum wavespeeds of about 8 25 km s

hindcast of the wave conditions along the west iberian coast this paper describes the development of a wave prediction system for the west iberian coast the implemented wave prediction system is based on two state of the art spectral wave models wam for the ocean area and swan for the nearshore however because of its extended geographical space the swan model will include some generation effects in the coarse swan simulations complemented by wave transformation effects near the coast the system was validated by means of extended hindcast runs in various regions belonging to the continental portuguese coastal environment which were compared with buoy data focusing on the extreme energetic events and both direct comparisons and statistical results are presented

sensitivity of deep convection to terrain forcing over mediterranean islands the influence of mountainous islands on the initiation of deep convection is investigated using the consortium for small scale modeling cosmo model a case study and sensitivity analysis is performed for 26 august 2009 when moist convection occurred over both corsica and sardinia islands in the western mediterranean sea sensitivity runs with systematically modified topography are explored to evaluate the relative importance of the land sea contrast and the terrain height for convection initiation whereas no island precipitation is simulated when the islands are completely removed all simulations that represent these land surfaces develop convective precipitation although convection initiates progressively earlier in the day over taller islands the precipitation rates and accumulations do not show a fixed relationship with terrain height this is due to the competing effects of different physical processes firstly whereas the forcing for low level ascent increases over taller islands the boundary layer moisture supply decreases which diminishes the conditional instability and precipitable water secondly whereas taller islands enhance the inland propagation speeds of sea breeze fronts they also block these fronts mechanically and prevent them from reaching the island interior as a result the island precipitation is rather insensitive to island terrain height except for one particular case in which the island precipitation increases considerably due to an optimal superposition of the sea breeze and upslope flow comparing the two islands convective precipitation develops earlier over corsica due to its increased terrain height and reduced convective inhibition however precipitation amounts are substantially larger over sardinia where a stronger land sea contrast gives rise to a more intense and organized line of sea breeze convergence these results demonstrate the complexity of interactions between sea breezes and orography and reinforce that an adequate representation of detailed topographic features is necessary to account for thermally induced wind systems that initiate deep convection

crustal shear velocity structure of the south indian shield 1 the south indian shield is a collage of precambrian terrains gathered around and in part derived from the archean age dharwar craton we operated seven broadband seismographs on the shield along a n s corridor from nanded nnd to bangalore bgl and used data from these to determine the seismic characteristics of this part of the shield surface wave dispersion and receiver function data from these sites and the geoscope station at hyderabad hyb give the shear wave velocity structure of the crust along this 600 km long transect inversion of rayleigh wave phase velocity measured along the profile shows that the crust has an average thickness of 35 km and consists of a 3 66 km s 1 12 km thick layer overlying a 3 81 km s 1 23 km thick lower crust at all sites the receiver functions are extremely simple indicating that the crust beneath each site is also simple with no significant intracrustal discontinuities joint inversion of the receiver function and surface wave phase velocity data shows the seismic characteristics of this part of the dharwar crust to be remarkably uniform throughout and that it varies within fairly narrow bounds crustal thickness 35 2 km average shear wave speed 3 79 0 09 km s 1 and vp vs ratio 1 746 0 014 there is no evidence for a high velocity basal layer in the receiver function crustal images of the central dharwar craton suggesting that there is no seismically distinct layer of mafic cumulates overlying the moho and implying that the base of the dharwar crust has remained fairly refractory since its cratonization index terms 7203 seismology body wave propagation 7205 seismology continental crust 1242 7255 seismology surface waves and free oscillations keywords continental crust archean crust receiver function indian shield

crustal structure of the siberian craton and the west siberian basin an appraisal of existing seismic data abstract we present a digital model sibcrust of the crustal structure of the siberian craton sc and the west siberian basin wsb based on all seismic profiles published since 1960 and sampled with a nominal interval of 50 km data quality is assessed and quantitatively assigned to each profile based on acquisition and interpretation method and completeness of crustal model the database represents major improvement in coverage and resolution and includes depth to moho thickness and average p wave velocity of five crustal layers sediments and upper middle lower and lowermost crust and pn velocity maps and cross sections demonstrate strong crustal heterogeneity which correlates weakly with tectono thermal age and strongly with tectonic setting sedimentary thickness varies from 0 3 km in stable craton to 10 20 km in extended regions typical moho depths are 44 48 km in archean crust and up to 54 km around the anabar shield 40 42 km in proterozoic orogens 35 38 km in extended cratonic crust and 38 42 km in the west siberian basin average crustal vp velocity is similar for the sc and the wsb and shows a bimodal distribution with peaks at ca 5 4 km s in deep sedimentary basins and 6 2 6 6 km s in parts of the wsb and sc exceptionally high basement vp velocities 6 8 7 0 km s at the northern border between the sc and the wsb indicate the presence of magmatic intrusions and are proposed to mark the source zone of the siberian lip the cratonic crust generally consists of three layers and high velocity lowermost crust vp 7 4 km s is observed only locally pn velocities are generally 8 2 km s in the sc and wsb and abnormally high 8 6 8 9 km s around kimberlite fields we discuss the origin of crustal heterogeneity and link it to regional crustal evolution

on thermally forced circulations over heated terrain abstracta combination of analytical and numerical models is used to gain insight into the dynamics of thermally forced circulations over diurnally heated terrain solutions are obtained for two layer flows representing the boundary layer and the overlying free troposphere over an isolated mountainlike heat source a scaling based on the linearized boussinesq system of equations is developed to quantify the strength of thermally forced updrafts and to identify three flow regimes each with distinct dynamics and parameter sensitivities this scaling closely matches corresponding numerical simulations in two of these regimes the first characterized by a weakly stable boundary layer and significant background winds and the second by a strongly stable boundary layer in the third regime characterized by weak winds and weak boundary layer stability this scaling is outperformed by a fundamentally different scaling based on thermodynamic heat engines within this regime the inability of wind ventilation or

a new tectonic model for the laurentia avalonia baltica sutures in the north sea a case study along mona lisa profile 3 abstract we present a new model for the lithospheric structure of the transitions between laurentia avalonia and baltica in the north sea northwestern europe based on 2 d potential field modelling of mona lisa profile 3 across the central graben with constraints from seismic p wave velocity models and the crustal normal incidence reflection section along the profile the model shows evidence for the presence of upper and lower palaeozoic sedimentary rocks as well as differences in crustal structure between the palaeo continents laurentia avalonia and baltica our new model together with previous results from transformations of the gravity and magnetic fields demonstrates correlation between crustal magnetic domains along the profile and the terrane affinity of the crust this integrated interpretation indicates that a 150 km wide zone characterized by low grade metamorphosis and oblique thrusting of avalonia crust over baltica lower crust is characteristic for the central north sea area the magnetic susceptibility and the density across the coffee soil fault range from almost zero and 2715 kg m3 in avalonia crust to 0 05 si and 2775 kg m3 in baltica crust the model of mona lisa profile 3 indicates that the transition between avalonia and baltica is located beneath the central graben with a ramp flat ramp geometry our results indicate that the initial rifting of the central graben and the viking graben was controlled by the location of the caledonian collisional suture located at the coffee soil fault and that the deep crustal part of baltica extends further to the west than hitherto believed

4 d evolution of se asia s mantle from geological reconstructions and seismic tomography abstract how the collision between india and asia is related to processes deeper in the mantle is unclear here we compare geological reconstructions of block motions within asia since 50 ma with the tomographically imaged three dimensional 3 d morphology of subducted lithosphere to obtain insight into the spatiotemporal evolution of mantle structure past positions of the convergent margin show remarkable similarities with slab geometry at specific depths the striking change in slab geometry from a linear structure beneath 1100 km to an increasingly distorted shape at depths of less than 700 km results from collision the slab contours match the progressive deformation of asia s margin including india s indentation and sundaland s extrusion ever since the onset of collision the indian plate appears to have overridden its own sinking mantle and it does not seem at present to underthrust tibet significantly north of the zangbo suture if correct this observation would provide further evidence against models of plateau build up involving indian lithosphere the tomographic images beneath india confirm that asian deformation has absorbed at least 1500 km of convergence since collision began from the match between the southeastward motion of sundaland between 40 and 20 ma and the principal change in slab structure between 700 and 1100 km depths we infer that lateral advection in the mantle is small and that the sinking rate beneath sunda was 2 cm yr in the lower mantle and 5 cm yr above the transition zone

moho depth and crustal composition in southern africa abstract we present new results on structure thickness and composition of the crust in southern africa based on 6300 seismic receiver functions at 85 stations application of hk stacking to the entire sase dataset and use of multi frequency bands improve resolution substantially we observe a highly heterogeneous crustal structure with short wavelength variations in thickness h vp vs ratio composition and moho sharpness which defines 20 blocks that do not everywhere coincide with surface tectonic features in the zimbabwe craton the tokwe block has h 35 38 km and vp vs 1 74 1 79 whereas the thicker crust in the tati block h 47 51 km may be related to deformation of the archean crust along the cratonic margin two distinct crustal blocks with similar crustal thickness 42 46 km but significantly different vp vs ratios are recognized in the limpopo belt extreme values of 1 90 1 94 at the dyke swarms in eastern limpopo and 1 84 at the olifants river dyke swarm and easternmost bushveld intrusion complex bic indicate voluminous magmatic intrusions in the whole crust we find no evidence for magmatic intrusions in the central inferred part of bic where the crust is thick 45 50 km and vp vs is low 1 68 1 70 this thick crustal root may have deflected rising magmas to form the two bic lobes most of central kaapvaal has thin 35 40 km crust and vp vs 1 74 these characteristics are similar to the tokwe block in zimbabwe craton and may indicate delamination of pre existing lower crust which is further supported by a very sharp moho transition the exposed cross section in the vredefort impact crater is non representative of cratonic crust due to shallow moho 34 km and high vp vs 1 80 attributed to shock metamorphism high vp vs 1 76 is typical of the witwatersrand basin and anomalously low vp vs 1 66 1 67 marks the kaapvaal kheis namaqua transition highly heterogeneous crust both in thickness and vp vs ratio is typical of the namaqua natal and cape fold belts

a review of crust and upper mantle structure beneath the indian subcontinent this study has been supported by a grant from the ministry of earth sciences moes iitkgp ckh

observation of convection initiation processes with a suite of state of the art research instruments during cops iop 8b in the afternoon of 15 july 2007 a thunderstorm was initiated within a line of cumulus clouds which formed parallel to the crest of the black forest mountains during the intensive observation period iop 8b of the convective and orographically induced precipitation study cops this paper extends the analysis of processes that led to convection initiation ci i e the transition from shallow to deep convection on this day with the data from several cops instruments that have not been considered in previous studies in particular the boundary layer structure lids and the water vapour field in the pre convective environment of the event are discussed for this purpose we investigated measurements of water vapour lidars temperature lidars and wind lidars profiles from radiosondes in situ aircraft data and gridded data of weather stations as well as gps integrated water vapour data and satellite imagery thermally driven circulation systems formed over both the black forest and the vosges mountain ranges which resulted in local convergence zones these superimposed with the large scale convergence in the black forest area in the presence of sufficient moisture and updraught clouds formed close to the mountain crests the related latent heat release allowed larger thermals to be produced which may have had a positive feedback on stabilizing these convergence zones as a whole we believe that differences in the moisture field explain why convection remained shallow and sparse over the vosges mountains because these differences were responsible for differences in convective inhibition cin the stationary location of the convergence zone over the southern black forest was probably decisive for ci because it constantly transported sensible and latent heat into the area in which ci took place

the timing of crustal extension and the eruption of continental flood basalts the association between mantle plumes continental flood basalt eruption and the extension and rifting of the crust is well recognized1 3 but there has always been controversy as to whether the plume or the rifting was the initiating factor4 5 was rifting triggered by doming above the thermal plume2 3 6 or was rifting the driving force preceding the associated volcanicity7 8 here i show that recent flow by flow mapping of two continental flood basalt provinces the columbia river basalt group and the deccan basalt group allows one to infer the relative timing of volcanicity and crustal extension in both provinces eruption of the main tholeiitic phase preceded significant extension and crustal thinning this suggests that the primary event in the formation of these provinces was the upwelling of a mantle plume and that the subsequent crustal extension rifting and decompression was in part a consequence of the initiation of that plume

lake van southeastern turkey experiment receiver function analyses of lithospheric structure from teleseismic observations the p and s wave receiver functions and their joint inversions are used to study the lithosphere beneath the lake van region using approximately 600 teleseismic earthquake data mw 5 8 at different azimuths collected from 10 permanent broadband stations operated by kandilli observatory and earthquake research institute and disaster and emergency management authority in the region the dataset is taken from the european integrated data archive the simulated annealing method is used for the joint inversion of p wave and s wave receiver functions since the p410s phase cannot be detected reliably in the depth stacks this may be due to the low olivine content and high basalt content at this depth the inversion process is therefore performed without travel time residuals the crustal thickness is observed at nearly 45 km in all the velocity models obtained from the inversion the relatively low velocity layer vs 3 4 km s at depths of the middle crust may be associated with volcanic centers near nemrut in the west of the region additionally another low velocity layer vs 3 0 km s is observed in the upper crust around the suphan volcano also vp vs and poisson s ratios are calculated for the study area their high values vp vs 1 85 and 0 285 correspond to the partial melting of the lower crust in the region according to velocity models obtained from the inversion results the most important outcome is that the average variance of the moho discontinuity 45 km and lithosphere asthenosphere boundary 90 km under the seismograph stations can be interpreted as a likely part of the arabian oceanic plate in relation to the collision zone

relationship between atmospheric blocking and warm season thunderstorms over western and central europe a statistically significant link is presented between atmospheric blocking located over the eastern north atlantic and northern europe and warm season thunderstorm activity over western and central europe lightning data from 2001 to 2014 were used to identify thunderstorm days and blocking events were extracted from the era interim reanalysis using an objective identification algorithm the statistical link between the two phenomena is established through odds ratio analysis two areas one over the eastern part of the north atlantic and one over the baltic sea were identified as locations where blocking influences the occurrence of deep moist convection in parts of western and central europe based on the mean ambient conditions on days with blocking in these two areas well known dynamic and thermodynamic mechanisms supporting or suppressing the development of thunderstorms were confirmed the anticyclonic circulation of a block over the eastern part of the north atlantic leads to a northerly to northwesterly advection of dry and stable air masses into europe on the eastern flank of the block in addition these environmental conditions are on average associated with large scale subsidence of air masses convection inhibiting conditions in contrast the southerly to southwesterly advection of warm moist and unstable air masses on the western flank of a block over the baltic sea results in convection favouring conditions over western and central europe both blocking situations are on average associated with weak wind speeds at mid tropospheric levels and with weak wind shear as a consequence thunderstorms related to atmospheric blocking over the baltic sea tend to be on average less organised

phanerozoic hot spot traces and paleogeographic reconstructions of the siberian continent based on interaction with the african large low shear velocity province abstract we review intraplate magmatism in siberia and its folded surroundings from 480 ma to the present we describe several large igneous provinces lips and the intervals in which they were continuously formed within the limits of the siberian continent the altay sayan early paleozoic magmatic area 598 446 ma the altay sayan lip 408 393 ma the viluy lip 380 350 ma the barguzin vitim lip 310 275 ma the late paleozoic rift system of central asia 318 242 ma the siberian traps and west siberian rift system 250 249 ma the east mongolian and west trans baikalian lip 228 195 ma and a number of various aged late mesozoic and cenozoic rift zones and magmatic areas from 160 ma to the present day following lawver and muller 1994 kharin 2000 lawver et al 2002 and chernysheva et al 2005 we accept the position of the icelandic hot spot under the siberian trap area at the permo triassic boundary that enables us to estimate the geographic coordinates of the siberian trap location at 250 ma they are the same as iceland today presently the icelandic hot spot is situated above the african large low shear velocity province llsvp that indicates a hot mantle plume we suggest a set of paleogeographic reconstructions of the siberian continent for which we evaluate the paleolatitude based on the paleomagnetic data and estimate the paleolongitude position by placing siberia above the african llsvp furthermore we estimate the geographic coordinates for other ancient hot spots in the framework of the african llsvp that we consider to be responsible for the intraplate magmatism during different time periods in the phanerozoic eon available rare element and isotopic characteristics of the intraplate magmatic rocks of siberia enable us to determine three primary sources moderately depleted mantle prema enriched mantle em i and em ii of the mantle origin magma we propose that the model explains the interaction of the hot mantle plume including hot spots plume tails with the siberian intraplate magmatism areas throughout the phanerozoic eon

super mobility of hot indian lithosphere negi j g pandey o p and agrawal p k 1986 super mobility of hot indian lithosphere tectonoph vsics 131 147 156 the great mobility of the indian subcontinent during the last 180 million years 9000 km of south north motion with an anticlockwise rotation of about 60 o has long been a major puzzle for theorists of plate tectonics a relative analysis of the available heat flow data the estimated temperature depth regime of india and the gravity anomalies reveals that the indian lithosphere does not have the characteristics of a typical shield zone and that it has higher radioactivity smaller viscous drag decidedly low viscosity of 10 p lower density and a well defined low velocity zone as compared to other shield areas of the world these factors appear to contribute significantly to the faster northward movement of the thin indian lithosphere as compared to the almost immobile african plate

tectonic inheritance of the indian shield new insights from its elastic thickness structure abstract a new evaluation of the elastic thickness te structure of the indian shield derived from isotropic fan wavelet methodology documents spatial variations of lithospheric deformation in different tectonic provinces correlated with episodic tectono thermal events the te variations corroborated by shear velocity crustal thickness and seismogenic thickness reveal the heterogeneous rheology of the indian lithosphere the thinned attenuated lithosphere beneath peninsular india is considered to be the reason for its mechanically weak strength

impacts of human interventions on the evolution of the ria formosa barrier island system s portugal abstract human interventions on sandy barriers disturb natural barrier dynamics to the extent of having become key forces in modifying geomorphological evolution this work identifies natural and human induced drivers and analyses their importance to the multi decadal evolution of the ria formosa barrier island system in south portugal aerial photographs from the last six decades and historical maps are used to assess changes in cross shore rates morphological characteristics barrier and dune widths inlet morphology and migration and barrier areas through systematic methods that can be easily transferred to other barrier systems interventions and especially hard engineering ones jetties inlet stabilisations affected barrier evolution trends shore perpendicular works increased shoreline progradation updrift and initiated coastal retreat downdrift with strongest erosive impacts along the edges of the system inlet stabilisations changed tidal inlet hydrodynamics and initiated ebb shoal attachment to the barriers on either side of a non migrating inlet that experienced loss of tidal prism this shoal attachment was the main factor for the increase in total barrier area of ria formosa during the 60 years of analysis barrier growth after 2005 was slower which could indicate that the system is reaching morphodynamic stability

lithosphere and asthenosphere of the tien shan imaged by s receiver functions 1 the s receiver function technique was applied to the recordings from 36 broad band stations in the tien shan the results reveal a pronounced difference in the properties of the lithosphere asthenosphere of the tien shan and those of the neighboring platforms beneath the tien shan an upper mantle lid with an s velocity of about 4 5 km s is underlain at a depth of about 90 km by a low velocity zone where the s velocity drops to 4 1 4 2 km s trends of p and s travel time residuals are consistent with the presence of melt or other liquids in this zone there is no evidence of any similar layer beneath the platforms the crust is 55 65 km thick beneath most of the tien shan and 45 km below the platforms although it thins to about 45 km near the naryn basin in the central tien shan

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

initiation of convective storms at radar observed boundary layer convergence lines abstract the origin of 653 convective storms occurring over a 5000 km2 area immediately east of the colorado rocky mountains from 18 may to 15 august 1984 was examined seventy nine percent of the 418 storms that initiated within the study area occurred in close proximity to radar observed boundary layer convergence lines this percentage increased to 95 when only the more intense storms 60 dbze were considered colliding convergence lines initiated new storms or intensified existing storms in 71 of the cases a new storm took a median time of 24 min to grow to 30 dbz following line collision the convergence lines ranged in length between ten and several hundred kilometers both radar and mesonet stations indicated that the primary convergence was concentrated in a zone 0 5 to 5 km in width these lines were characterized on doppler radar as thin lines of enhanced reflectivity between 0 and 20 dbze and as a line of strong radial or azimuthal gradient in doppler velocity these lines were observed ev

the laptev sea rift abstract in north eastern siberia the active mid ocean gakkel ridge interacts with the continental shelf of the laptev sea extension has affected the shelf since at least the early tertiary and has resulted in the formation of a complex horst and graben system we present new seismic data from the laptev sea including deep seismic soundings the most prominent rift basin is the ust lena rift with a minimum e w width of 300 km at latitude 75 n and a cenozoic infill up to 13 km in thickness the asymmetric shape of the basin and conclusive evidence for a detachment imply a simple shear geometry the suggested rift model combines a ramp and flat geometry for the detachment with ductile stretching beneath the detachment a major west dipping hingeline listric fault separates the ust lena rift from the laptev horst the 100 150 km wide laptev horst is subdivided into three units by narrow rift grabens another prominent rift graben is the anisin basin which is located in the northern shelf area though the laptev sea rift formed in interaction with an active mid oceanic ridge there are indications that the laptev sea rift is of the passive rift type the rift was developed east of a sw ne trending transfer zone which links the gakkel ridge to the laptev sea rift

lithospheric mantle deformation beneath the indian cratons abstract the nature of deformation of the deep continental roots beneath the archean early proterozoic terrains opens the question whether these ancient terrains have had stable roots since the precambrian or whether recent plate motions have deformed them in view of this we make an attempt to study the thermal structure beneath the cratonic regions of the indian shield which vary in lithospheric thickness from 65 km in the singhbhum craton to 148 km in the archean dharwars the average depth of 104 km to the top of the underlying asthenosphere is consistent with other termination methods and is in fact less than half the 200 400 km depth found in other stable areas of the earth similarly the average reduced heat flow of about 35 mw m2 and moho temperature of about 550 c range 400 730 c for the indian cratons are also much higher than their counterparts elsewhere our study indicates a large scale deformation of the cratonic mantle lithosphere beneath the indian shield since the mesoproterozoic c

mantle discontinuities beneath the deccan volcanic province abstract mantle discontinuities beneath the deccan volcanic province dvp are imaged using about 900 seismograms from a network of six broadband stations deployed in the dvp along a 350 km long north south profile paralleling the west coast of india teleseismic receiver function analysis of the data enabled distinct identification of the moho 410 and 660 km discontinuities presence of sub moho low velocity zones with velocity reductions in the range of 0 1 0 4 km s have been brought out through modeling of receiver function stacks at individual stations the arrival times of p410s and p660s are normal as predicted by the iasp91 model and the mantle transition zone thickness is 252 km which is close to the global average this study reveals that the upper mantle beneath dvp south of the narmada rift does not exhibit any anomalous signatures associated with a mantle plume a shield like lithosphere coupled with the presence of an upper mantle low velocity zone confined to shallow depths beneath dvp imposes constraints on the mechanisms feasible for deccan volcanism the present study does not favour the plume impact plume incubation models instead necessitates searching for clues offshore west coast of india and exploring alternate mechanisms

receiver function tomography of the central tien shan abstract to obtain an image of the deep structure of the tien shan in central asia we invert p and s receiver functions jointly for almost 40 local broad band seismograph stations the inversion is performed using a simulated annealing technique the combined inversion is an improvement on earlier studies where p and s receiver functions were inverted separately using this approach we deal with structural imaging problems that are usually investigated with teleseismic body wave and surface wave tomography techniques we demonstrate that the uppermost mantle in the north of the central tien shan is composed of a high velocity lid a few tens of kilometers thick above a pronounced low velocity zone the crustal structure in this region provides evidence of magmatic underplating these features are likely related to a small plume that is manifested by basaltic eruptions of cretaceous paleogene age the low velocity layer is also found in a southeast trending corridor which may correspond to the bachu uplift in the tarim basin crustal thickness beneath the orogen varies from about 45 to about 70 km the smallest values most likely inherited from the pre orogenic era are found in a neighborhood of the talas fergana fault similar values are characteristic of the kazakh shield in the north and the tarim basin in the south the largest values are found beneath the bounding ranges we infer that uplift of the central tien shan is unlikely to be caused by crustal shortening alone

observations of s410p and s350p phases at seismograph stations in california 1 we analyze a new set of seismic data from seismograph stations in california this data set consists of nearly 5000 s receiver functions for 47 seismograph stations as a rule the stacked srfs display a distinct s410p seismic phase s wave converted to p at the 410 km discontinuity the wave paths of s410p sample the upper mantle beneath california and the neighboring region of the pacific in northernmost california the s410p travel times are close to those of the iasp91 global model further south s410p usually arrives about 2 s earlier than predicted by the iasp91 model this early arrival can be explained either by an anomalously high vp vs velocity ratio 1 9 in a 125 km thick layer of the upper mantle versus 1 8 in iasp91 by a depression of the 410 km discontinuity of 15 km or by a combination of both effects with smaller amplitudes we observe systematically s350p phase which is converted from a negative discontinuity with a lower s velocity at the lower side near a depth of 350 km the observations of s350p are indicative of a low s velocity layer a few tens of kilometers thick atop the 410 km discontinuity beneath southern california and the neighboring oceanic region some receiver functions also display s480p phase which is interpreted as evidence of an intermittent low velocity layer in the transition zone

deep seismic structure of the indian shield western himalaya ladakh and tibet abstract p and s receiver functions from seismograph stations in the indian shield western himalaya ladakh and tibet are processed with a method which provides estimates of the p and s velocities and their ratio as a function of depth the time difference between the p660s and p410s phases in the north of the indian shield and the lesser himalaya is 1 0 1 5 s larger than the normal 24 s this is an effect of a low temperature with implication that the consumed material of the indian shield has reached the transition zone the waveforms of the p410s and s410p phases at some stations in the indian shield are indicative of a thin a few tens of kilometers low s velocity layer atop the 410 km discontinuity which is usually related to mantle upwelling the mantle s velocity under the indian shield at depths less than 180 km is 4 4 4 5 km s much lower than the 4 7 km s typical for precambrian shields we explain this low s velocity mainly by a recent tertiary metasomatic alteration of the high velocity mantle keel beneath the western himalaya ladakh and western tibet but not eastern tibet the s velocity in the mantle at depths less than 100 150 km is around 4 7 km s vp vs is anomalously low and we argue that this high velocity layer is a remnant of the mantle lithosphere of the northern greater india at most locations in the indian shield high s velocities 3 5 km s and more are dominant in the middle and lower crusts and the elevated s velocity is accompanied by an increased vp vs ratio 1 8 2 1 versus the standard 1 73 in the foothills of the himalaya the crust is 50 55 km thick and consists almost entirely of a high s velocity 3 7 km s and more rock with the increased vp vs ratio in the middle and the standard vp vs ratio in the lower crust this observation suggests that the upper crust of the indian plate is scraped off in the collision zone whereas the high velocity lower crust is subducted jointly with the mantle lithosphere the high velocities are responsible for the p wave teleseismic travel time anomaly of 1 s relative to ladakh under the himalaya the vp vs ratio in the crust is normal which suggests a change in composition relative to the crust of the indian shield under ladakh and tibet the anomalously high vp vs ratio in the crust is observed again beneath tibet our analysis reveals a low velocity crustal zone of partial melt between the 20 km and 45 km depths previously the 45 km discontinuity was interpreted as the effect of eclogitization

lithosphere of the dharwar craton by joint inversion of p and s receiver functions summary the archean dharwar craton in south india is known for long time to be different from most other cratons specifically at station hyderabad hyb the ps converted phases from the 410and 660 km mantle discontinuities arrive up to 2 s later than in other cratons of comparable age which implies lower upper mantle velocities to resolve the unique lithosphere asthenosphere system of the dharwar craton we inverted jointly p and s receiver functions and teleseismic p and s traveltime residuals at 10 seismograph stations this method operates in the same depth range as long period surface waves but differs by much higher lateral and radial resolution we observe striking differences in crustal structures between the eastern and western dharwar craton edc and wdc respectively crustal thickness is of around 31 km with predominantly felsic velocities in the edc and of around 55 km with predominantly mafic velocities in the wdc in the mantle we observe significant variations in the p velocity with depth practically without accompanying variations in the s velocity in the mantle s velocity there are azimuthdependent indications of the hales discontinuity at a depth of 100 km the most conspicuous feature of our models is the lack of the high velocity mantle keel with the s velocity of 4 7 km s 1 typical of other archean cratons the s velocity in our models is close to 4 5 km s 1 from the moho to a depth of 250 km there are indications of a similar upper mantle structure in the northeast of the indian craton and of a partial recovery of the normal shield structure in the northwest a division between the high s velocity western tibet and low s velocity eastern tibet may be related to a similar division between the northeastern and northwestern indian craton

3d lithosphere density structure of southern indian shield from joint inversion of gravity geoid and topography data abstract we present the 3d crustal and lithospheric structure and crustal average density distribution of southern indian shield south of 18 n sri lanka and adjoining oceans the model is based on the assumption of local isostatic equilibrium and is derived from joint inversion of free air gravity and geoid anomalies and topography data the derived crustal thickness of 10 25 km in the oceanic region increases to 34 35 km along the coast a crustal thickness of 34 38 km is obtained beneath the eastern dharwar craton and 36 45 km beneath the western dharwar craton and the southern granulite terrain sri lanka has a thinner crust of 30 35 km the lithosphere asthenosphere boundary is located at depths of 70 120 km under oceanic regions and 150 180 km below the dharwar craton and the northern block of southern granulite terrain a notably thinned lithosphere of 130 km near bangalore in the eastern dharwar craton 140 km beneath the southern block of southern granulite terrain and 130 km in sri lanka is observed the thickness of the lithosphere 130 km near bangalore is inferred as the frozen in signature of a small fossil mantle plume and or tectono compositional effect of a rifted margin and a suture considerable stretching and or convective removal of pristine lithosphere in the southern block of southern granulite terrain and adjoining sri lanka before disappearing completely in the archaean northern block of southern granulite terrain and dharwar craton is suggested

velocity structure composition and discrimination of crustal provinces in the former soviet union significant progress had been made over the last two decades in seismic refraction wide angle reflection investigations of continental russia highlights of this progress include the determination of crustal thickness lithospheric body wave velocities compressional and shear wave attenuation and existence of deeply penetrating dipping reflectors these new multiwave deep seismic sounding dss data recorded along geotraverses crossing precambrian cratons pc provinces of cenozoic basin deposition cb and palaeozoic fold belts pb provide a basis for the study of eurasian continental structure and tectonics interpretation of dss data has shown that geological provinces of different age and tectonic history can be distinguished by the relationship between vp vs and the crystalline crustal thickness h there are two primary relationships in the vp vs vs h function in the first characteristics of pc vp vs is directly proportional to crustal thickness in the second relationship observed in cb and pb vp vs is inversely proportional to crustal thickness province boundaries are imaged as dipping reflectors through analysis of the wave field of three component records using special velocity filtering dynamic features of these reflections suggest that these boundaries are detachment faults separating relatively thin layers with complicated fine structure the composition of the crystalline crust determined from body wave velocities varies significantly over the transition zone from one geological province to another mapping of regions according to the vp vs vs h function shows a correlation of the known mineral oil and gas deposits with province boundaries

stratification of the earth beneath the azores from p and s receiver functions abstract seismic recordings of iris ida gsn station cmla and of several temporary stations in the azores archipelago are processed with p and s receiver function prf and srf techniques contrary to regional seismic tomography these methods provide estimates of the absolute velocities and of the vp vs ratio up to a depth of 300 km joint inversion of prfs and srfs for a few data sets consistently reveals a division of the subsurface medium into four zones with a distinctly different vp vs ratio the crust 20 km thick with a ratio of 1 9 in the lower crust the high vs mantle lid with a strongly reduced vp vs velocity ratio relative to the standard 1 8 the low velocity zone lvz with a velocity ratio of 2 0 and the underlying upper mantle layer with a standard velocity ratio our estimates of crustal thickness greatly exceed previous estimates 10 km the base of the high vs lid the gutenberg discontinuity is at a depth of 80 km the lvz with a reduction of s velocity of 15 relative to the standard iasp91 model is terminated at a depth of 200 km the average thickness of the mantle transition zone tz is evaluated from the time difference between the s410p and sks660p seismic phases that are robustly detected in the s and sks receiver functions this thickness is practically similar to the standard iasp91 value of 250 km and is characteristic of a large region of the north atlantic outside the azores plateau our data are indicative of a reduction of the s wave velocity of several percent relative to the standard velocity in a depth interval from 460 to 500 km this reduction is found in the nearest vicinities of the azores in the region sampled by the prfs but as evidenced by srfs it is missing at a distance of a few hundred kilometers from the islands we speculate that this anomaly may correspond to the source of a plume which generated the azores hotspot previously a low s velocity in this depth range was found with srf techniques beneath a few other hotspots

new insights into the basement structure of the west siberian basin from forward and inverse modeling of grace satellite gravity data 1 the oil and gas rich west siberian basin is underlain by a layer of flood basalts of late permian triassic age that are coeval with the siberian traps the extent and thickness of the basalts are unknown but knowing their thickness is important for discussions on the end permian mass extinction because basalt volume constrains estimates of emitted volatiles we have used grace satellite and terrestrial gravity data to study the structure of the crust and basalt distribution published seismic sections are used to constrain the sediment isopachs and to estimate a depth density function we use published models of crustal thickness and basement depth to reduce the observed gravity field to the basement level the resulting three dimensional density model gives information on density anomalies in the lower crust and upper mantle and on the basalt thickness we identify several rift graben structures that are presumably filled with basalt the lower crust below the west siberian basin shows considerable density variations and these variations allow the region to be divided into four major blocks the eastern part of the basin toward the siberian platform shows an arch shaped density increase in the lower crust that is accompanied by a linear high density anomaly at shallower depths our work demonstrates the way in which the grace gravity field can be applied to map geological structures like buried rifts and large basins the same techniques can be used for other large remote basins such as those in cratonic south america

high resolution downscaled ocean waves dow reanalysis in coastal areas abstract large scale wave reanalysis databases 0 1 1 spatial resolution provide valuable information for wave climate research and ocean applications which require long term time series 20 years of hourly sea state parameters however coastal studies need a more detailed spatial resolution 50 500 m including wave transformation processes in shallow waters this specific problem called downscaling is usually solved applying a dynamical approach by means of numerical wave propagation models requiring a high computational time effort besides the use of atmospheric reanalysis and wave generation and propagation numerical models introduce some uncertainties and errors that must be dealt with in this work we present a global framework to downscale wave reanalysis to coastal areas taking into account the correction of open sea significant wave height directional calibration and drastically reducing the cpu time effort about 1000 by using a hybrid methodology which combines numerical models dynamical downscaling and mathematical tools statistical downscaling the spatial wave variability along the boundaries of the propagation domain and the simultaneous wind fields are taking into account in the numerical propagations to performance similarly to the dynamical downscaling approach the principal component analysis is applied to the model forcings to reduce the data dimension simplifying the selection of a subset of numerical simulations and the definition of the wave transfer function which incorporates the dependency of the wave spatial variability and the non uniform wind forcings the methodology has been tested in a case study on the northern coast of spain and validated using shallow water buoys confirming a good reproduction of the hourly time series structure and the different statistical parameters

shear velocity structure of the laterally heterogeneous crust and uppermost mantle beneath the indian region abstract the shear velocity structure of the indian lithosphere is mapped by inverting regionalized rayleigh wave group velocities in time periods of 15 60 s the regionalized maps are used to subdivide the indian plate into several geologic units and determine the variation of velocity with depth in each unit the hedgehog monte carlo technique is used to obtain the shear wave velocity structure for each geologic unit revealing distinct velocity variations in the lower crust and uppermost mantle the indian shield has a high velocity 4 4 4 6 km s upper mantle which however is slower than other shields in the world the central indian platform comprised of proterozoic basins and cratons is marked by a distinct low velocity 4 0 4 2 km s upper mantle lower crustal velocities in the indian lithosphere generally range between 3 8 and 4 0 km s with the oceanic segments and the sedimentary basins marked by marginally higher and lower velocities respectively a remarkable contrast is observed in upper mantle velocities between the northern and eastern convergence fronts of the indian plate the south bruma region along the eastern subduction front of the indian oceanic lithosphere shows significant velocity enhancement in the lower crust and upper mantle high velocities 4 8 km s are also observed in the upper mantle beneath the ninetyeast ridge in the northeastern indian ocean

tethyan subducted slabs under india abstract tomographic imaging of the mantle under tibet india and the adjacent indian ocean reveals several zones of relatively high p wave velocities at various depths under the hindu kush region in northeastern afghanistan and southern tajikistan a regional northward dipping slab is seen in the entire upper 600 km of the mantle and is apparently still attached to the lithosphere of the indian plate under northern pakistan this same slab shows a roll over structure with the deeper portion overturned and dipping southward as can also be seen in the distribution of earthquake hypocenters farther east southeast e g in the vicinity of nepal a well resolved anomaly below 450 km depth is connected to the slab under the hindu kush but seems to be separated from the lithosphere above 350 km these upper mantle anomalies are interpreted as the remnants of delaminated sub continental lithosphere that went down when greater india continued to converge northward with asia after 45 ma the deeper high velocity anomalies under the indian sub continent appear clearly separated from the shallower ones as well as from each other and are inferred to represent remnants of oceanic lithospheric slabs that have sunk into the lower mantle and were subsequently overridden by the indian plate they occur at depths between 1000 and 2300 km and occasionally descend down to the core mantle boundary the anomalies form three parallel wnw ese striking zones we interpret the two southern zones as remnants of oceanic lithosphere that was subducted when the neo tethys ocean closed between india and tibet in the cretaceous and earliest tertiary the northern deep mantle zone under northern afghanistan the himalayas and the lhasa block in southern tibet may represent the last subducted remnant of the paleo tethys ocean which is thought to have closed before the hauterivian stage of the early cretaceous the middle zone continues southeastward as a rather straight high velocity zone towards sumatra where it becomes convex southward and parallel to the subduction zone under the sunda arc comparison of this straight middle zone near india with the shallower upper 600 1000 km northern zone which displays a cusp like shape near the yunnan sw china syntaxis of the eastern himalayas supports the notion that the shallow northern zone represents later subduction than the deeper middle zone the suggestion of a counterclockwise rotation 20 of the indian plate during tertiary indentation of asia is supported by these features the present day latitudes of 5 35 n of the deep slabs under india and adjacent areas correspond to the approximate paleolatitudes of the cretaceous subduction zones the slab remnants in the middle mantle occur therefore near the ancient locations where they started their downward journey which implies that lateral movements in the deeper mantle were not large

numerical simulation of present day tectonic stress across the indian subcontinent in situ measurements of maximum horizontal stress shmax in the indian subcontinent are limited and do not present regional trends of intraplate stress orientation the observed orientations of shmax vary considerably and often differ from the plate velocity direction we have simulated orientation and magnitude of shmax through finite element modeling incorporating heterogeneities in elastic property of the indian continent and plain stress approximation to understand the variability of shmax four different scenarios are tested in simulation 1 homogeneous plate with fixed plate boundary 2 homogeneous plate with boundary forces 3 heterogeneous plate with fixed boundary 4 heterogeneous plate with boundary forces the estimated orientation and magnitude of shmax with a heterogeneous plate with boundary forces in the himalayan region and an eastern plate boundary comprising the indo burmese arc and andaman subduction zone are consistent with measured maximum horizontal stress this study suggests that plate boundary force varies along the northern indian plate margin and also provides a constraint on the intraplate stress field in the indian subcontinent

formation of an archaean continent about 30 of the earth is covered by continents but only about 10 small kernels of these continentsae known as archaean cratonsae are continental fragments formed before 2 5 gyr ago the kaapvaal craton of south africa which formed and stabilized between 3 7 and 2 7 gyr ago is one of the oldest reasonably sized examples of these continental fragments it consists of a mosaic of subdomains that have been welded together by processes similar to those of modern day plate tectonics the earliest subdomains may have owed their origin to the onset of efficient recycling from the earth s hydrosphere into the mantle

44 year wave hindcast for the north east atlantic european coast this paper describes a 44 year from 1958 to 2001 wave hindcast conducted for the north atlantic using a fine grid in the north east atlantic coastal areas of europe the wind fields were obtained by a local area model that was applied in the areas adjacent to the european coasts which was forced by the results of the ncep reanalysis while the ncep results have a spatial distribution of 2 and a time step of 6 h the wind fields produced by the local area model have a spatial resolution of 0 5 and a time step of 1 h which is important for accurate descriptions of the conditions in coastal areas and in rapidly changing storms a version of the wam model that allowed two way nesting was adopted and calculations were made with nested grids allowing a fine resolution in the coastal areas of europe this paper includes the description of the set up of the wave model and the validation performed vs in situ measurements so as to allow assessments of the quality of the data produced in this study

seismic signatures of detached lithospheric fragments in the mantle beneath eastern himalaya and southern tibet abstract in this study we investigate the mantle transition zone mtz structure beneath eastern himalaya and southern tibet using 9000 high quality receiver functions from 96 broadband stations spanning the entire region the pervasive early arrival times 1 7 s compared to iasp91 of the p to s conversions from the 410 km discontinuity are attributed to the high shear wave velocities associated with the subducted indian and asian lithosphere s global and regional shear wave velocity models obtained from seismic tomography evince such high velocity anomalies both in the uppermost mantle and within the mtz in this complex collision environment in contrast the conversions from the 660 km discontinuity are either normal or delayed up to 1 s providing evidences for a thickened mtz beneath most of the study region although presence of water in the mtz can result in such a thickening issues like 1 low amplitudes of the p410s and p660s conversions 2 small dependence of their amplitudes with frequency 3 absence of a detectable low velocity layer atop 410 and 4 lack of evidence for a 520 km discontinuity preclude such an interpretation instead we attribute this thickening to lowered temperatures affected by the possible presence of detached cold and dense lithospheric slabs within the mtz such a detachment might have been facilitated either by convection or gravity removal of the lithosphere thickened due to continued subduction of the indian plate since the mesozoic

high velocity anomaly under the deccan volcanic province abstract tomographic modelling of p wave residuals at 22 vertical component seismograph stations operated in the deccan volcanic province dvp in west central india and the dharwar craton point to the existence of a large deep at least 300 km high velocity anomaly 1 3 faster directly beneath most of the dvp and dharwar craton there is also marginal evidence that the westernmost part of the dvp may be characterised by low velocity up to 1 5 to a depth of about 200 km this coherent high velocity anomaly under the dvp and its extension into the south indian shield is viewed as a lithospheric root an architecture characteristic of precambrian shields

teleseismic travel time residuals in north america and anelasticity of the asthenosphere abstract the slope a of the relation t s a t p b for the teleseismic s and p travel time residuals t s and t p is practically the only robust observational value that is equally sensitive to the lateral s and p velocity variations in the upper mantle published estimates of a for north america are about twice higher than those at ultrasonic frequencies in olivine at comparable pressures and temperatures in our study lateral variations of the s residuals in north america are found not from the s wave readings which can be easily biased but from accurately determined delays relative to p of the ps phases converted from 410 km and 660 km discontinuities nevertheless the estimates of a thus derived are close to the values obtained with the standard technique the discrepancy between the ultrasonic and seismic estimates of a can be explained by physical velocity dispersion on the assumption of a single absorption band our value of a is consistent with the published values of q in the seismic frequency band and velocities in the ultrasonic range if the high frequency cutoff of the absorption band in the upper mantle beneath western north america is on the order of several hundred hertz however in the literature there are indications of a cutoff at around 1 hz then our data imply the presence of another absorption band at high frequencies outside the seismic frequency band this band may correspond to the viscous dissipation in the walsh walsh j b 1969 a new analysis of attenuation in partially melted rock j geophys res 74 4333 4337 model of penny shaped inclusions of melt

seismic reflection fabrics of continental collision and post orogenic extension in the middle urals central russia abstract deep seismic reflection surveys in the middle urals central russia provide the basis for a revised structural and tectonic interpretation of late paleozoic continental collision and early mesozoic post orogenic extension in this orogen these profiles esru 93 and esru 95 form a transect from the former east european platform margin in the west to accreted island arc and oceanic terranes in the east crossing the main uralian fault muf the principal suture zone in the urals the foreland of the middle urals is characterized by a fold and thrust belt developed above a gently e dipping detachment at 10 km depth and a deeper presumably older and previously unrecognized detachment system of probable late proterozoic baikalian age a large 5 km frontal ramp marks the axis of the regional kvarkush anticlinorium which dominates the foreland structure reflectivity in the middle and lower crust of the east european platform is inferred to be primarily a precambrian fabric based on correlation of the seismic data with surface geology the muf is redefined spatially seismically and structurally as the top of an 40 e dipping reflective package placing it 1 at the boundary between upper greenschist to amphibolite facies rocks of continental affinity to the west and unmetamorphosed to lower greenschist facies rocks of the tagil island arc to the east 2 at the primary topographic break in the middle urals and 3 10 km further east at this latitude than recent interpretations but consistent with previous russian maps at depth the muf appears to merge in a listric fashion with a zone of subhorizontal mid crustal reflectivity 15 20 km depth that truncates a series of large scale antiforms and associated w dipping e vergent shear zones of inferred paleozoic age across the uralian hinterland these relationships suggest that the muf was reactivated as a normal fault during late to post orogenic evolution of the orogen based on interpretation of the moho as the base of lower crustal reflectivity crustal thickness varies from 48 to 51 km 14 15 s across the esru 93 profile in concert with existing russian studies showing a thickened crust beneath the urals to the east on the esru 95 profile beneath the tagil island arc a strongly w dipping reflective package in the lower crust suggests abrupt thinning of the crust to 45 km 13 s consistent with nearby wide angle reflection data at the surface this crustal thinning coincides with the triassic imenovskii graben we interpret these collective observations as evidence for post orogenic extension of the middle urals in early mesozoic time in association with reactivation of the muf as a breakaway normal fault at the westernmost boundary of the west siberian basin extensional province in contrast results from the urseis 95 experiment indicate that the southern urals are largely unextended implying that post orogenic evolution varied along strike within the orogen

cloud resolving simulations of deep convection over a heated mountain abstract cloud resolving numerical simulations of airflow over a diurnally heated mountain ridge are conducted to explore the mechanisms and sensitivities of convective initiation under high pressure conditions the simulations are based on a well observed convection event from the convective and orographically induced precipitation study cops during summer 2007 where an isolated afternoon thunderstorm developed over the black forest mountains of central europe but they are idealized to facilitate understanding and reduce computational expense in the conditionally unstable but strongly inhibited flow under consideration sharp horizontal convergence over the mountain acts to locally weaken the inhibition and moisten the dry midtroposphere through shallow cumulus detrainment the onset of deep convection occurs not through the deep ascent of a single updraft but rather through a rapid succession of thermals that are vented through the mountain convergence zone into the deepening cloud mass emerging t

crust and mantle beneath western himalaya ladakh and western tibet from integrated seismic data abstract to understand deep structure of the western himalaya ladakh and western tibet we conduct an integrated analysis of teleseismic body wave recordings from the linear array of 16 portable broadband seismographs along a profile running through the himalaya to the karakoram the database includes p and s receiver functions teleseismic p and s residuals and observations of shear wave splitting in sks the analysis reveals beneath the himalaya a cold region at a depth of several hundred kilometers this anomaly can be caused by remnants of tethys subduction and perhaps is unrelated to the ongoing process the present day process is reflected in velocities beneath the lesser himalaya intermediate between those of the crust and the upper mantle this observation can be explained by scraping off the ductile lower crust of the underthrusting indian plate and accumulation of the high velocity crustal material in the frontal region of the thrust zone a representative value of the crustal thickness at the profile is 65 km and at most stations there is no evidence for a low velocity layer at mid crustal depths which makes crustal channel flow unlikely seismic waves in the upper 200 km of the mantle are faster than in global iasp91 model and the structure includes a low velocity layer sandwiched between two high velocity layers we interpret the lower layer as an image of subducted mantle lithosphere of the indian plate shear wave splitting is different in the south and the north in the south the fast direction of anisotropy is normal to the trend of the himalaya and can be interpreted as an effect of the ne motion of the indian lithosphere in the north the fast direction is oriented e w and can be explained by the fabric left in the presently extinct subduction zones in eastern tibet a similar analysis of the p and s receiver functions reveals upper mantle with the s velocities about 5 lower than in the west the mantle in the vicinity of station lsa lhasa contains a low s velocity layer between 160 km and 230 km depths with a velocity reduction of 0 2 km s underlain by the lehmann discontinuity

the nature of the crust in southern india implications for precambrian crustal evolution 1 we present crustal thickness and poisson s ratio determinations from receiver function analyzes at 32 sites on the archaean and proterozoic terrains of south india the crustal thickness in the late archaean 2 5 ga eastern dharwar craton varies from 34 39 km similar crustal thickness is observed beneath the deccan volcanic province and the cuddapah basin the most unexpected result is the anomalous present day crustal thickness of 42 51 km beneath the mid archaean 3 4 3 0 ga segment of the western dharwar craton since the amphibolite grade metamorphic mineral assemblages 5 7 kbar paleopressures in this part of western dharwar craton equilibrated at the depths of 15 20 km our observations suggest the existence of an exceptionally thick 57 70 km crust 3 0 ga ago beneath the exhumed granulite terrain in southernmost india the crustal thickness varies between 42 60 km the poisson s ratio ranges between 0 24 0 28 beneath the precambrian terrains indicating the presence of intermediate rock type in the lower crust these observations of thickened crust suggest significant crustal shortening in south india during the archaean

low velocity layers in the subcrustal lithosphere beneath the deccan traps region of western india abstract travel times and relative amplitude modeling of a seismic record section from the koyna dss profile in the deccan traps region has yielded a velocity model for the indian continental subcrustal lithosphere the observed record section assembled with a reduction velocity of 6 km s 1 and using digitized data from analog deep seismic sounding dss recorders reveals a prominent wave group with an apparent velocity similar to but about 3 s after the reflected p phase from the moho pmp at a reduced time of 7 5 to 6 5 s and recording distance range from 70 to 95 km we interpret this strong amplitude phase as the reflection from an interface in the subcrustal lithosphere comparison of synthetic seismograms for a range of velocity models with the observed record section shows that the observed phase under investigation cannot be explained either by a reflected phase from a subcrustal velocity discontinuity with a single velocity increase or by the p to s converted phase pms from the moho subcrustal velocity models with a single low velocity layer lvl do not seem to give a satisfactory fit to the amplitude observations on the field record section we prefer a subcrustal velocity model with alternating lvl at least two with a velocity of 7 0 7 4 km s 1 separated by a thin high velocity layer in this model the synthetic amplitudes of the reflected phase from the top of the deeper lvl at 56 km depth well match those of the observed reflection phase it is inferred that the continental subcrustal lithosphere in this region of the indian shield has a lamellar structure with significant vertical variation of structural and mechanical properties the alternating lvl occurring at relatively shallow depths below the moho velocity decreasing from 8 3 to 7 4 km s 1 may be associated with zones of weakness and lower viscosity the lvl in the subcrustal lithosphere as well as the lvl inferred in the upper and the lower crust krishna et al 1989 together with the observed depth distribution of seismicity in this region suggest a well defined rheological stratification of the continental lithosphere with varying material properties

age of initiation of collision between india and asia a review of stratigraphic data abstract the collision of india with asia is perhaps the most profound tectonic event to have occurred in past 100 ma it is responsible for the uplift of the himalayas and tibetan plateau and has been argued to have been responsible for geological geochemical and climatological consequences of global extent yet the age of initiation of this collision remains poorly constrained the literature is replete with estimates that range from the late cretaceous 65 ma to latest eocene

seismic lamination and anisotropy of the lower continental crust abstract seismic lamination in the lower crust associated with marked anisotropy has been observed at various locations three of these locations were investigated by specially designed experiments in the near vertical and in the wide angle range that is the urach and the black forrest area both belonging to the moldanubian a collapsed variscan terrane in southern germany and in the donbas basin a rift inside the east european ukrainian craton in these three cases a firm relationship between lower crust seismic lamination and anisotropy is found there are more cases of lower crustal lamination and anisotropy e g from the basin and range province western us and from central tibet not revealed by seismic wide angle measurements but by teleseismic receiver function studies with a p s conversion at the moho other cases of lamination and anisotropy are from exhumed lower crustal rocks in calabria southern italy and val sesia and val strona ivrea area northern italy we demonstrate that rocks in the lower continental crust apart from differing in composition differ from the upper mantle both in terms of seismic lamination observed in the near vertical range and in the type of anisotropy compared to upper mantle rocks exhibiting mainly orthorhombic symmetry the symmetry of the rocks constituting the lower crust is either axial or orthorhombic and basically a result of preferred crystallographic orientation of major minerals biotite muscovite hornblende we argue that the generation of seismic lamination and anisotropy in the lower crust is a consequence of the same tectonic process that is ductile deformation in a warm and low viscosity lower crust this process takes place preferably in areas of extension heterogeneous rock units are formed that are generally felsic in composition but that contain intercalations of mafic intrusions the latter have acted as heat sources and provide the necessary seismic impedance contrasts the observed seismic anisotropy is attributed to lattice preferred orientation lpo of major minerals in particular of mica and hornblende but also of olivine a transversely isotropic symmetry system such as expected for sub horizontal layering is found in only half of the field studies azimuthal anisotropy is encountered in the rest of the cases this indicates differences in the horizontal components of tectonic strain which finally give rise to differences in the evolution of the rock fabric

lithospheric seismic structure beneath two broadband station sites of the eastern part of chhotanagpur plateau new constraints from receiver functions and dispersion curves abstract the chhotanagpur plateau in eastern india was formed due to the severe upheaval of tectonic forces deep inside the earth the deep geological processes associated with its subsurface along with geodynamical rationales are never understood properly due to the dearth of good quality geophysical data we use high quality teleseismic earthquakes waveforms 5 5 m 8 0 recorded at two seismic stations ism and bokr located in dhanbad and bokaro respectively these data are used to jointly model discrete but complementary datasets such as ps and sp receiver functions and rayleigh wave group velocity dispersion curves via very fast simulated annealing vfsa a two step optimization procedure is carried out to find the best fitting models and associated uncertainties in terms of posterior probability density ppd functions our results reveal that on an average the eastern part of chhotanagpur plateau which is mostly composed of granite gneiss complex with high heat flow is characterized by the thick crust for ism station up to 150 km depth vp and vs vary between 6 1 km s 8 4 km s and 3 3 km s 4 8 km s respectively we observe that vp and vs ranges between 6 2 km s to 8 3 km s and 3 2 km s to 4 6 km s respectively for seismic station bokr we find that the crustal thickness beneath seismic stations ism and bokr is 43 and 44 km respectively the higher values of poisson s ratio 0 25 for station ism and bokr are 0 30 and 0 29 respectively which may indicate the presence of partial melt present in the lower crust

initiation of deep convection at marginal instability in an ensemble of mesoscale models a case study from cops the present study investigates the initiation of precipitating deep convection in an ensemble of convection resolving mesoscale models results of eight different model runs from five non hydrostatic models are compared for a case of the convective and orographically induced precipitation study cops an isolated convective cell initiated east of the black forest crest in southwest germany although convective available potential energy was only moderate and convective inhibition was high measurements revealed that due to the absence of synoptic forcing convection was initiated by local processes related to the orography in particular the lifting by low level convergence in the planetary boundary layer is assumed to be the dominant process on that day the models used different configurations as well as different initial and boundary conditions by comparing the different model performance with each other and with measurements the processes which need to be well represented to initiate convection at the right place and time are discussed besides an accurate specification of the thermodynamic and kinematic fields the results highlight the role of boundary layer convergence features for quantitative precipitation forecasts in mountainous terrain

a hybrid efficient method to downscale wave climate to coastal areas long term time series of sea state parameters are required in different coastal engineering applications in order to obtain wave data at shallow water and due to the scarcity of instrumental data ocean wave reanalysis databases ought to be downscaled to increase the spatial resolution and simulate the wave transformation process in this paper a hybrid downscaling methodology to transfer wave climate to coastal areas has been developed combining a numerical wave model dynamical downscaling with mathematical tools statistical downscaling a maximum dissimilarity selection algorithm mda is applied in order to obtain a representative subset of sea states in deep water areas the reduced number of selected cases spans the marine climate variability guaranteeing that all possible sea states are represented and capturing even the extreme events these sea states are propagated using a state of the art wave propagation model the time series of the propagated sea state parameters at a particular location are reconstructed using a non linear interpolation technique based on radial basis functions rbfs providing excellent results in a high dimensional space with scattered data as occurs in the cases selected with mda the numerical validation of the results confirms the ability of the developed methodology to reconstruct sea state time series in shallow water at a particular location and to estimate different spatial wave climate parameters with a considerable reduction in the computational effort

upper mantle stratification by p and s receiver functions summary seismic stratification of the upper mantle is investigated by applying two complementary techniques to the records of the graefenberg array in southern germany the anisotropic p receiver function technique kosarev et al 1984 vinnik montagner 1996 is modified by using summary seismic events instead of individual events and different weighting functions instead of the same function for the harmonic angular analysis of the sv and t components of the pds phases the summary events provide better separation of the second azimuthal harmonic than the individual events the parameters of the second harmonics of sv and t thus evaluated should be similar if they reflect the effects of azimuthal anisotropy this can be used as a criterion to identify the anisotropy to detect the sdp phases and their azimuthal variations caused by azimuthal anisotropy we have developed a stacking technique which can be termed the s receiver function technique it includes axis rotation to separate interfering p and s arrivals determination of the principal m component of the s wave motion deconvolution of the p components of many recordings by their respective m components and stacking of the deconvolved p components with weights depending on the level of noise and the angle between the m direction and the backazimuth of the event both techniques yield consistent results for the graefenberg array as indicated by the p receiver functions the upper layer of the mantle between the moho and 80 km depth is anisotropic with dvs vs around 0 03 and the fast direction close to 20 clockwise from north the fast direction of anisotropy below this layer is around 110 the boundary between the upper and the lower anisotropic layers is manifested by the detectable pds and sdp converted phases shear wave splitting in sks is strongly dominated by azimuthal anisotropy in the lower layer asthenosphere

crustal structure variations in south central mexico from receiver functions mexico has a complex geological history that is typified by the distinctive terranes that are found in the south central region crustal thickness variations often correlate with geological terranes that have been altered by several processes in the past for example aerial or subduction erosion underplating volcanic material or rifting but few geophysical studies have locally imaged the entire continental crust in mexico in this paper the thickness of three layers of the crust in south central mexico is determined to do this we use p and s wave receiver functions rf from 159 seismological broad band stations thanks to its adaptive nature we use an empirical mode decomposition emd algorithm to reconstruct the rfs into intrinsic mode functions imf in order to enhance the pulses related to internal discontinuities within the crust to inspect possible lateral variations the rfs are grouped into quadrants of 90 and their amplitudes are mapped into the thickness assuming a three layer model using this approach we identify a shallow sedimentary layer with a thickness in the range of 1 4 km the upper crust was estimated to be of a few kilometers 10 km thick near the pacific coast and thicker approximately 15 km in central oaxaca and under the trans mexican volcanic belt tmvb close to the pacific coast we infer a thin crust of approximately 16 0 9 km while in central oaxaca and beneath the tmvb we observe a thicker crust ranging between 30 and 50 km 2 0 km we observe a crustal thinning of approximately 6 km from central oaxaca 37 1 9 km towards the gulf of mexico under the veracruz basin where we estimate a crustal thickness of 31 6 1 9 km the boundary between the upper and lower crust in comparison with the surface of the moho do not show significant variations other than the depth difference we observe small crustal variations across the different terranes on the study area with the thinnest crust located at the pacific coast and gulf of mexico coast the thickest crust is estimated to be in central oaxaca and beneath the tmvb

convergence behavior of idealized convection resolving simulations of summertime deep moist convection over land convection resolving models crms can explicitly simulate deep convection and resolve interactions between convective updrafts they are thus increasingly used in numerous weather and climate applications however the truncation of the continuous energy cascade at scales of mathcal o 1 km poses a serious challenge as in kilometer scale simulations the size and properties of the simulated convective cells are often determined by the horizontal grid spacing delta x in this study idealized simulations of deep moist convection over land are performed to assess the convergence behavior of a crm at delta x 8 4 2 1 km and 500 m two types of convergence estimates are investigated bulk convergence addressing domain averaged and integrated variables related to the water and energy budgets and structural convergence addressing the statistics and scales of individual clouds and updrafts results show that bulk convergence generally begins at delta x 4 km while structural convergence is not yet fully achieved at the kilometer scale despite some evidence that the resolution sensitivity of updraft velocities and convective mass fluxes decreases at finer resolution in particular at finer grid spacings the maximum updraft velocity generally increases and the size of the smallest clouds is mostly determined by delta x a number of different experiments are conducted and it is found that the presence of orography and environmental vertical wind shear yields more energetic structures at scales much larger than delta x sometimes reducing the resolution sensitivity overall the results lend support to the use of kilometer scale resolutions in crms despite the inability of these models to fully resolve the associated cloud field