new insights into the 1963 vajont slide using 2d and 3d distinct element method analyses the 1963 vajont rock slide is studied using the distinct element method dem two dimensional 2d and three dimensional 3d dem models were constructed based on information published in the literature in this study a strength reduction approach was used to calculate the slide surface friction angles required for stability the influence of several parameters was investigated in 2d namely the reservoir water level the shear stiffness of the slide surface the rock mass strength the rock mass deformability and rock joint patterns of the parameters which have been investigated the most important parameter was found to be the reservoir water level the rock mass deformability which is neglected by other investigators is also found to be important from the 3d analyses the failure friction angle was found to be sensitive to the assumptions made on the eastern boundary and could affect the failure friction angle by approximately 3 the slope was found to exhibit signs of failure beginning from s

simulation of a supercellular storm using a three dimensional mesoscale model with an explicit lightning flash scheme 1 a complete lightning flash scheme is implemented in the three dimensional 3 d nonhydrostatic mesoscale model meso nh of the french community the scheme which is part of the electrical scheme follows a new approach with two steps first lightning flashes are modeled as bidirectional leaders to mimic the vertical propagation of the initial discharge channels along the electric field then a probabilistic branching algorithm is adapted from the dielectric breakdown concept to reinforce the flash propagation toward distant regions of high charge density but immersed in a weak electric field this results in a high increase of the total length of the lightning flash channel and also in a better capture of the morphology of intracloud lightning flashes the electrification and lightning schemes are tested for an ideal case of a supercellular storm the model succeeds in reproducing the general features of a storm and the electric charge cycle sensitivity analyses show that the implementation of a branching stage is necessary and efficient enough to relax the growth of the electric field the intracloud discharges generated by the model look realistic with a two layer horizontal structure extending over tens of kilometers from the triggering area the lightning flash length and the quantity of charge neutralized are ten times more important when the branching algorithm is taken into account the main conclusion drawn from this study is the feasibility and the benefit of an advanced treatment of lightning flashes in 3 d numerical simulations with an electrification scheme

comparing rockfall scar volumes and kinematically detachable rock masses scenario based risk assessment for rockfalls requires assumptions for different scenarios of magnitude volume the magnitude of such instabilities is related to the properties of the jointed rock mass with the characteristics of the existing unfavourably dipping joint sets playing a major role the critical factors for the determination of the maximum credible rockfall volume in a study site the forat negre in andorra are investigated the results from two previous analyses for the rockfall size distribution at this site are discussed the first analysis provides the observed size distribution of the rockfall scars and it is an empirical evidence of past rockfalls the second one calculates the kinematically detachable rock masses indicating hypothetical rockfalls that might occur in the future the later gives a maximum rockfall volume which is one order of magnitude higher because the persistence of the basal planes is overestimated the tension cracks and lateral planes interrupt systematically the basal planes exerting a control over their persistence and restricting the formation of extensive planes and large rockfall failures nonetheless the formation of basal planes across more than one spacings of tension cracks is possible and small step path failures have been observed too concluding the key factor for the determination of the maximum credible volume at the study site is the maximum realistic length of the basal planes penetrating into the rock mass their spacing and if applied the contribution of the rock bridges to the overall rock mass resistance

geochemical and strontium isotopic characteristics of parental aleutian arc magmas evidence from the basaltic lavas of atka eighteen flows from a basal stratigraphic sequence on the aleutian island of atka were analyzed for major elements trace elements and initial 87sr 86sr ratios petrographically these lavas contain abundant plagioclase 24 45 and lesser amounts of olivine 7 magnetite and clinopyroxene phenocrysts compositionally the lavas are high alumina 20wt basalts 48 51 wt sio2 with low tio2 1 and mgo 5 within the section compositional variations for all major elements are quite small while mgo content correlates with olivine phenocryst contents no such relationship exists between the other oxides and phenocryst content these lavas are characterized by 8 10 ppm rb high sr 610 669 ppm 308 348 ppm ba and very constant zr 23 29 ppm and sc 23 29 ppm abundances ni and cr display extremely large compositional ranges 12 118 ppm and 12 213 ppm respectively no correlation exists between trace element concentrations and phenocryst contents strontium isotopic ratios show a small but significant range 0 70314 0 70345 and are slightly elevated with respect to typical morb no systematic correlation between stratigraphic position and petrography or geochemistry is evident ree abundances measured on six samples are lree enriched la yb n 2 20 2 81 and display similar chondrite normalized patterns one sample has a slight positive eu anomaly but the other lavas do not compared to other aleutian basalts of similar silica content these lavas are less lree enriched and have lower overall abundances the geochemical characteristics of these basalts suggest they represent true liquid compositions despite their highly porphyritic nature published phase relations indicate fractionation of a more mgo rich magma could not have produced these lavas the high al2o3 and low mgo and compatible element abundances suggest a predominantly oceanic crustal source for parental high alumina basalts

theory and observations of controls on lightning flash size spectra previous analyses of very high frequency vhf lightning mapping array lma observations relative to the location of deep convective updrafts have noted a systematic pattern in flash characteristics in and near strong updrafts flashes tend to be smaller and more frequent while flashes far from strong vertical drafts exhibit the opposite tendency this study quantitatively tests these past anecdotal observations using lma data for two supercell storms that occurred in oklahoma in 2004 the data support a prediction from electrostatics that frequent breakdown and large flash extents are opposed an energetic scaling that combines flash rate and flash area exhibits a 5 3 power law scaling regime on scales of a few kilometers and a maximum inflashenergyatabout10km thespectralshapeis surprisinglyconsistentacrossarangeofmoderatetolarge flash rates the shape of this lightning flash energy spectrum is similar to that expected of turbulent kinetic energy spectra in thunderstorms in line with the hypothesized role of convective motions as the generator of thunderstorm electrical energy the correspondence between kinematic and electrical energy spectra suggests that advection of charge bearing precipitation by the storm s flow including in turbulent eddies couples the electrical and kinematic properties of a thunderstorm

effects of charge and electrostatic potential on lightning propagation 1 three dimensional lightning mapping observations are compared to cloud charge structures and electric potential profiles inferred from balloon soundings of electric field in new mexico mountain thunderstorms for six individual intracloud and cloud to ground flashes and for a sequence of 36 flashes in one storm the comparisons consistently show good agreement between the altitudes of horizontal lightning channels and the altitudes of electric potential extrema or wells lightning flashes appear to deposit charge of opposite polarity in relatively localized volumes within the preexisting lower positive midlevel negative and upper positive charge regions associated with the potential wells the net effect of recurring lightning charge deposition at the approximate levels of potential extrema is to increase the complexity in the observed storm charge structure the midlevel breakdown of both normal intracloud flashes and negative cloud to ground flashes is observed to be segregated by flash type into the upper and lower parts of the deep potential well associated with the midlevel negative charge the segregation is consistent with perturbations observed in the bottom of the negative potential well due to embedded positive charge that was probably deposited by earlier flashes it is also consistent with an expected tendency for vertical breakdown to begin branching horizontally before reaching the local potential minimum the joint observations reconcile the apparent dichotomy between the complex charge structures often inferred from balloon soundings through storms and the simpler structures often inferred from lightning measurements

application of geotechnical and geophysical field measurements in an active alpine environment abstract a gravelly scree slope in the meretschibach catchment a location in the swiss alps in the vicinity of agarn canton valais has been observed to deform downslope at up to 0 5 m p a the potential instabilities at this site include surficial landslides some of them originally thought to be triggered by an increase in pore water pressure with a subsequent loss of shear strength as a consequence of rainfall infiltration and rockfalls a programme consisting of monitoring laboratory testing and investigation was developed to perform a thorough soil characterisation needed in order to produce a realistic ground model the long term geotechnical monitoring included in situ soil temperature suction as well as volumetric water content measurements using dielectric permittivity and time domain reflectometry tdr sensors this data was complemented by electrical resistivity tomography ert to provide extensive knowledge on the depth to bedrock and to validate the volumetric water contents in specific locations the datasets are completed by recordings from two nearby weather stations seasonal changes of precipitation and temperature were reflected in corresponding trends in all measurements a comparison of volumetric water content records was obtained using capacitance and time domain reflectometry tdr sensors with ert yielding reasonable agreement the resulting ground model which integrates all currently available parameters delivers the essential information and boundary conditions for predicting and validating slope instabilities in the future using numerical and physical modelling

evolution of the total lightning structure in a leading line trailing stratiform mesoscale convective system over houston texas 1 line normal vertical cross sections of houston lightning detection and ranging ldar vhf radiation sources and radar reflectivity provide new insights into the three dimensional total lightning structure and evolution of a leading line trailing stratiform llts mesoscale convective system mcs over houston texas on 31 october 2005 previous research examining only the mature stage of an mcs showed that the overwhelming majority of vhf lightning sources occurred in the convective region with a lightning pathway extending rearward and descending in altitude into the stratiform region this descending pathway was most likely associated with small charged ice particles advected from the convective line unlike previous research the lightning pathway observed during the evolution of the mcs on 31 october 2005 initially extended rearward 40 km at a nearly constant height of 9 10 km in less than an hour the lightning pathway evolved into a sloped pathway similar to that found by previous research with a horizontal extent between 50 to 60 km and downward descent of 4 to 5 km during the lightning pathway evolution radar analysis showed an increase of reflectivity in the midlevels of the stratiform region consistent with increased depositional and aggregational growth above the melting layer broadening increased range of values of radar reflectivity above the melting layer was most likely an indication of a strengthening mesoscale updraft in the stratiform region this strengthening updraft may have contributed to an increase in the growth of the small charge carrying ice crystals giving them a greater fall speed in addition the mesoscale updraft may have promoted an environment conducive to local stratiform region charge generation in the mixed phase region just above the melting layer

regions where lightning flashes began regions where 773 flashes began during 13 thunderstorms were located by calculating centroids of the sources of the first six or 10 vhf pulses that were emitted by each flash sources were located by measuring differences in the times at which their pulses arrived at five widely spaced receivers stationed on the ground we found that the distribution of origin heights was bimodal with peaks at 5 3 and 9 2 km above mean sea level amsl standard errors in the coordinates of flash origins were estimated to be 20 80 m in x and y and 160 240 m in the height coordinate z there were 431 flashes in the lower group and 342 in the higher flashes in the lower group were more numerous in 10 storms in three storms high flashes were in the majority there was evidence to suggest that this condition depended partly on the phase of the host thunderstorm recorded e field changes produced by 165 flashes whose paths we had mapped convinced us that the vast majority of the 773 flashes including the 342 high flashes had also been negative flash origins tended to cluster in regions that were a few kilometers or less in horizontal diameter densities of flash origins in these regions ranged from 1 25 to 25 km 3 the origins of 658 flashes were mapped onto radar precipitation patterns of their host storms we found that 66 of the flashes began within one picture element approximately 270 m of the contours for 20 dbz 27 began inside these contours and most of these began at edges of high reflectivity cores the remaining 7 began outside the 20 dbz contours similar results 73 19 8 were obtained for 276 high flashes that began at heights above 7 4 km amsl but 195 ground flashes scored 54 36 9 and showed a greater tendency to begin inside the 20 dbz contours the distribution of distances between origins and their nearest 20 dbz contours showed a marked peak near zero we concluded that charge density in thunderclouds was affected by the presence of heavy precipitation and that 20 dbz surfaces enclosed regions that carried excess negative charge

quantification of degree of saturation at shallow depths of earth slopes using resistivity imaging technique abstractearthen slopes encountered in engineering practice typically consist of unsaturated or partially saturated soils during rainfall water infiltrates into the slope and causes a reduction in suction slope stability is affected by the increase in the degree of saturation as a result of the reduction in normal stress and cohesive strength along potential failure surfaces therefore to determine the geohazard potential it is important to know the degree of saturation within slopes at shallow depths resistivity imaging ri is one of the most convenient techniques available for geohazard studies however only qualitative saturation profiles can be obtained using this method quantification of the degree of saturation has become important for using ri in the evaluation of the geohazard potential of slope failures the objective of this study was to quantify the degrees of saturation at shallow depths using ri electrical resistivity tests were conducted in the laboratory on high plasticity clay ch

groundmass crystallization of mount st helens dacite 1980 1986 a tool for interpreting shallow magmatic processes the 1980 1986 eruption of mount st helens volcano provides an unprecedented opportunity to observe the evolution of a silicic magma system over a short time scale groundmass plagioclase size measurements are coupled with measured changes in matrix glass plagioclase and fe ti oxide chemistry to document increasing groundmass crystallinity and thus to better constrain proposed physical models of the post may 18 1980 magmatic reservoir measurements of plagioclase microlite and microphenocryst sizes demonstrate that relatively rapid growth approximately 10 9 cm s of groundmass plagioclase occurred immediately subsequent to may 18 relatively rapid plagioclase growth continued through the end of 1980 at an average rate of 3x10 11 cm s plagioclase growth rates then decreased to 1x10 11 cm s through 1986 changes in groundmass crystallinity are reflected in changes in both matrix glass and plagioclase microphenocryst rim chemistry although the matrix glass composition appears to have remained approximately constant from 1981 1986 after a rapid compositional change from may 18 until the end of 1980 plagioclase microphenocrysts show increasingly more complex zoning patterns with time microphenocryst core compositions are commonly positively correlated with crystal size both of these observations indicate continuous groundmass plagioclase growth through 1986 magmatic temperatures estimated from fe ti oxide pairs are approximately constant through 1981 at eruption temperatures of 930 c and at log fo2 of 10 8 by 1985 1986 oxide temperatures decreased to 870 c chemical and textural changes can be explained by 1 rapid degassing and crystallization in response to the intrusion of magma into a shallow 4 5 km reservoir toward the end of the may 18 1980 eruption 2 continued crystallization at a much reduced rate through 1986 due to slow cooling of the shallow magma reservoir growth rates and consequent chemical changes appear to decrease at the end of 1980 this is coincident with the change in eruption style from explosive eruptions sometimes followed by dome growth to solely extrusive dome building events and can be explained by the expected viscosity increase of both degassing and increasing crystallinity the model of twostage crystallization of magma in a shallow reservoir is consistent with conclusions from gas studies casadevall et al 1983 gerlach and casadevall 1986 a b patterns of crater deformation chadwkck et al 1988 and post 1980 seismicity endo et al 1990 although it does not explain the experimental data of hill and rutherford 1989 on the growth rate of amphibole reaction rims textural measurements on mount st helens dacite can also be used to evaluate crystallization kinetics in silicic magmas systems for which experimental data is almost non existent plagioclase growth rates are 5 10 times slower than estimated plagioclase growth rates in basaltic systems a result consistent with the higher viscosity of a more silicic melt furthermore patterns of textural change both average crystal size and number density are similar to those observed during the 1984 mauna loa eruption by lipman and banks 1987 suggesting that the only modification to the crystallization behavior of plagioclase required in extrapolation from basaltic systems is a moderate decrease in rates such that the rate of crystallization scales with the melt viscosity

lightning and precipitation in a small multicellular thunderstorm radio images of 26 consecutive lightning flashes are described in relation to radar pictures of the storm these flashes all started in two vertical turrets where reflectivity factors exceeded 25 dbz five large cloud flashes pervaded an almost horizontal plume or low level anvil and ground flashes occurred on the opposite side in the propagating flank of this storm observers on the ground reported a light hailfall and copious rain most of the lightning occurred in a region that was 3 5 km above ground agl flashes originated at heights that ranged from 3 1 km where the environmental air temperature was 5 c to 5 1 km agl 16 c and they began at a mean height of 3 94 km agl 10 c the standard deviation of 26 heights at which flashes began was 440 m recorded electric field changes showed that the channels were charged negatively and we inferred that negative charge had accumulated at these heights in the vertical turrets and that the paths followed by cloud flashes were influenced by positive charge which had accumulated in a plume that was nearly horizontal and which had formed on the flank opposite to the propagating flank of the storm the estimated total length of 18 consecutive lightning flashes that had occurred during a 3 min interval was 486 km measurements of electric field change magnitudes were used to estimate totals of 440 c and 106 c that had been discharged in 180 s from two cells whose volumes enclosed by 30 dbz surfaces were 260 and 80 km3 respectively this paper also describes the geometries of stepped leaders that cause electric field changes of the bil form it discusses a continuing current which was carried by a cloud flash

analysis of acoustic emission patterns for monitoring of rock slope deformation mechanisms acoustic emission ae is generated in soil and rock materials by rearrangement of particles during displacement or increasing damage in the microstructure preceding a collapse therefore ae is appropriate for estimation of slope degradation to overcome the high attenuation that characterise geological materials and thus to be able to monitor ae activity a system that makes use of a waveguide to transmit ae waves from a deforming zone to a piezoelectric transducer was developed the system quantifies acoustic activity as ring down count rdc rates in soil applications rdc rates have been correlated with the rate of deformation whereas the recent application to rock slopes requires new interpretation strategies in order to develop new strategies the system was installed at two rock slope trial sites in italy and austria rdc rates from these sites which have been measured over 5 and 1 5 years respectively are analysed and clear and recurring trends are identified the comparison of ae trends with response from a series of traditional instruments available at the sites allows correlation with changes in external slope loading and internal stress changes ae signatures from the large rock slope in italy have been identified as generated in response to variations in the groundwater level and snow loading at the slope in austria ae signatures include the detachment of small boulders from the slope surface caused by the succession of freeze thaw cycles during winter time the work reported in this paper is contributing to the development of ae monitoring and interpretation strategies for rock slopes the longer term aim is to identify approaching failures and derive rules for setting thresholds that can be used to give warning of rock slope failures in time to enable action to be taken

experimental and numerical investigations of dyke failures involving soft materials abstract this paper presents the results of an experimental and numerical investigation on the collapse of dykes involving soft soils nine centrifuge tests were carried out to investigate the dyke subsoil interaction the tests consisted in placing a dyke made out of speswhite clay or baskarp sand on a subsoil the dykes and the subsoils were alternatively changed to explore the different contrast in stiffness ranging from stiff dykes on soft subsoil to soft dykes on stiff subsoils the small scale models were placed in the centrifuge and were progressively accelerated up to a maximum of 100 g the recordings which were then processed by particle image velocimetry piv offered an insight onto the deformation and failure mechanisms the results showed that dykes placed on a stiff subsoil underwent brittle failures with the development of slip surfaces whereas the same dyke placed on a soft subsoil underwent large deformation which presented a serviceability issue these tests were then modelled with the material point method mpm which is a continuum based method for numerical simulation dedicated for large deformation problems simple constitutive models were used for which the parameters could be estimated using state indices

mapping deeply buried geothermal faults using microtremor array analysis summary in this paper the spatial autocorrelation microtremor array analysis is utilized to map deeply buried subtle faults that have primary controls on geothermal reservoirs we identified a low velocity anomaly which is approximately 50 m wide at about 550 1400 m deep a well drilled based on this anomaly later successfully produced hot water and further proved that the low velocity anomaly was caused by a highly fractured zone at depths from 700 to 1500 m our results clearly demonstrate that the microtremor survey method can be effectively utilized to map deeply buried faults and structures for geothermal energy exploration the most effective way to increase the drilling success rate and hence reduce the geothermal exploration risk seems to be the development of new exploration methods and the integration of various geophysical technologies

a slope movement in a complex rock formation deformation measurements and dem modelling abstract the case history of a deep seated slope movement in a complex rock formation marly arenaceous formation is analyzed the movement monitored for more than 20 years was recognized after the discovery of intense cracking in the concrete lining of a hydraulic tunnel running across the slope the time history of displacements shows that the ongoing deformation process is essentially a stationary creep phenomenon also influenced by transient variations in pore pressure distribution the shearing zone is mainly formed by tectonized clay gouge and is characterized by a mobilized strength close to residual the slope has been modelled by dem approach as a complex blocky structure defined by several joint sets bedding planes inclined and sub vertical joints different hypotheses about the geometry of the slip surface compatible with field evidences are discussed as well as their influence on the critical friction angle of the slope the type of model adopted for rock mass with continuous or staggered joints influences the pre failure deformation mode but the failure conditions are not as much affected finally the response of dem models to the increase in water level at the toe of the slope and to the rise of the groundwater table inside the slope has been analyzed the results of simplified models without flow calculation and coupled hydro mechanical analyses are compared finding some relevant differences

using lightning observations as a volcanic eruption monitoring tool lightning commonly occurs in the eruption columns produced by explosive volcanic eruptions there are several different kinds of lightning detection instruments that could be employed to help monitor volcanoes each with their own advantages and disadvantages very low frequency vlf instruments have the ability to detect lightning at long ranges but tend to have low sensitivity due to network geometry and typically can provide only the time and 2 d location of a cloud to ground return stroke or similar high amplitude pulse produced by an intracloud discharge low frequency lf and medium frequency mf instruments typically have more sensitivity than a vlf network but can only be used for detection on a regional scale very high frequency vhf lightning mapping instruments also provide only regional coverage but detect all lightning within their range during the 2009 eruption of redoubt volcano alaska usa each of these types of instruments detected lightning from redoubt s ash plume the vhf system consistently detected lightning before the other two during each distinct explosive event and also detected more lightning than the others by one or two orders of magnitude lightning observations could be used to confirm and in some cases detect explosive volcanic activity the rapid response provided by lightning monitoring is a valuable tool for fast identification of potentially hazardous ash clouds

layered lightning activity the horizontal extent of lightning channels reconstructed acoustically from several storms is significantly larger than the vertical extent furthermore an examination of all the reconstructed lightning structure in each of three storms one in arizona one in colorado and one in florida shows that the lightning activity tends to occur in layers 2 3 km thick in the arizona and florida storms there were two layers of activity temperatures at the lower boundary of the layers were near 4 c and 18 c in the arizona storm and 11 c and 39 c in the florida storm in the colorado storm there was a single layer having a lower boundary near the 0 c isotherm our interpretation is that each of the two layers in the arizona and florida storms is associated with a corresponding charged region in the dipole of the thundercloud charge distribution we suggest that the single layer in the colorado storm was a result of the dipolar regions being closer together in altitude

multi technique approach to rockfall monitoring in the montserrat massif catalonia ne spain abstract montserrat mountain is located near barcelona in catalonia in the northeast of spain and its massif is formed by conglomerate interleaved by siltstone sandstone with steep slopes very prone to rockfalls the increasing number of visitors in the monastery area reaching 2 4 million per year has highlighted the risk derived from rockfalls for this building area and also for the terrestrial accesses both roads and the rack railway a risk mitigation plan has been launched and its first phase during 2014 2016 has been focused largely on testing several monitoring techniques for their later implementation the results of the pilot tests performed as a development from previous sparse experiences and data are presented together with the first insights obtained these tests combine four monitoring techniques under different conditions of continuity in space and time domains which are displacement monitoring with ground based synthetic aperture radar and characterization at slope scale with an extremely non uniform atmospheric phase screen due to the stepped topography and atmosphere stratification terrestrial laser scanner surveys quantifying the frequency of small or even previously unnoticed rockfalls and monitoring rock block centimetre scale displacements the monitoring of rock joints implemented through a wireless sensor network with an ad hoc design of zigbee loggers developed by icgc and finally monitoring singular rock needles with total station

a general analytical solution for the evolution of cliffs accounting for strength degradation seismic action formation of tension cracks and seepage abstract the evolution of natural slopes over time is ruled by several concurrent physical phenomena namely the strength of its component geomaterials and their weakening over time due to weathering processes the occurrence of seismic events seepage and the formation of tension cracks the paper presents analytical solutions obtained considering a succession of discrete failure events landslides progressively altering the slope morphology over time the model derived in the framework of limit analysis assuming plane strain conditions provides a tool for the assessment of whether manufacts and or infrastructures located on a slope subject to various natural degradation phenomena will be affected by the occurrence of failures unlike current empirical and semi empirical models of slope evolution the analytical solution that is here presented is derived by applying principles of soil and rock mechanics therefore it is of general validity so that no ad hoc calibration against past observations of the evolving slope is needed this analytical technique only requires knowledge of the geotechnical parameters characterising the geomaterials comprising the slope of interest namely angle of shearing resistance cohesion c tensile strength unit weight together with knowledge of the relevant seepage scenarios strength degradation processes and seismic events likely to occur results show that that earthquake loading and seepage can substantially decrease slope stability increase the volume of material sliding away during each landslide event and alter the evolution of the slope over time while tensile strength exhibits a less strong influence especially as strength degradation progresses dimensionless ready to use charts are provided for the benefit of practitioners

two simultaneous charge structures in thunderstorm convection 1 a pair of simultaneous horizontally displaced thunderstorm electric field soundings are used to investigate an existing conceptual model of thunderstorm charge structure the soundings show that two different vertical charge structures one in the updraft and one outside the updraft can exist at the same time inside a storm as depicted in the existing model the data suggest that the two charge structures can be relatively close together since the soundings are separated by only 3 to 8 km horizontally in the convective region of the storm horizontal extent of the charge structures is estimated to be at least 4 km 4 km the differences in the two charge structures are coincident with substantial differences over this same 3 to 8 km horizontal distance in the reflectivity structure updraft speed and lightning activity of the convection the nonupdraft sounding was made through the intense reflectivity core found at middle levels in the convection additional electric field complexity and additional charge regions were found in the nonupdraft sounding and the lightning related electric field changes tended to be larger in magnitude and more numerous in that sounding than in the updraft sounding

coordinated lightning balloon borne electric field and radar observations of triggered lightning flashes in north florida this study examines coordinated storm and triggered lightning observations made in july august 2013 at the international center for lightning research and testing to determine why triggered flashes in florida typically transition from an upward vertical channel entering the cloud to horizontal structure near the storm s melting level data from a balloon borne electric field meter a mobile 5 cm wavelength radar and a small baseline vhf lightning mapping array acquired during a period in which three flashes were triggered on 1 august confirmed the hypothesis that the transition to horizontal lightning structure just above the melting level occurred in a layer of negative charge this experiment was the first to provide vertical profiles of the electric field in florida storms from which their vertical charge distribution could be inferred three dissipating storms observed on different days all had negative charge near the melting level but a growing mature storm had positive charge there

formation of charge structures in a supercell abstract lightning mapping electric field and radar data from the 26 may 2004 supercell in central oklahoma are used to examine the storm s charge structure an initial arc shaped maximum in lightning activity on the right flank of the storm s bounded weak echo region was composed of an elevated normal polarity tripole in the region of precipitation lofted above the storm s weak echo region later in the storm two charge structures were associated with precipitation that reached the ground to the left of the weak echo region six charge regions were inferred with positive charge carried on hail at the bottom of the stack farther forward in the storm s precipitation region four charge regions were inferred with negative charge at the bottom of the stack there were different charge structures in adjacent regions of the storm at the same time and regions of opposite polarity charge were horizontally adjacent at the same altitude flashes occasionally lowered positive charge to ground from the forwa

trends in large deformation analysis of landslide mass movements with particular emphasis on the material point method traditional geotechnical analyses for landslides involve failure prediction i e onset of failure and the design of structures that can safely withstand the applied loads the analyses provide limited information on the post failure behaviour modern numerical methods are able to simulate large mass movements and there is an opportunity to utilise such methods to evaluate the risks of catastrophic damage if a landslide occurs in this paper various large deformation analysis methods are introduced and their applicability for solving landslide problems is discussed since catastrophic landslides often involve seepage forces consideration of the coupled behaviour of soil and pore fluid is essential two approaches to model soil pore fluid coupling in large deformation analysis using the material point method mpm are introduced an example simulation is presented for each approach one on a model levee failure and the other on a natural cut slope failure the selborne experiment conducted by cooper and co workers in 1998 in the levee failure case mpm simulation was able to capture a complex failure mechanism including the development of successive shear bands the simulation was also able to predict excess pore pressure generation during the failure propagation and the subsequent consolidation stage the simulations demonstrated the importance of the dilation characteristics of soil as well as changes in geometry for the post failure behaviour in the selborne case mpm was able to simulate the progressive failure of brittle overconsolidated clay the evolution of shear stresses along the failure surface was also captured by the mpm the changes in the pore pressure and the actual shape of the failure surface were simulated by the mpm the importance of accurately modelling the shear band within the mpm framework is highlighted

statistical analysis of storm electrical discharges reconstituted from a lightning mapping system a lightning location system and an acoustic array in the framework of the european hydrological cycle in the mediterranean experiment project a field campaign devoted to the study of electrical activity during storms took place in the south of france in 2012 an acoustic station composed of four microphones and four microbarometers was deployed within the coverage of a lightning mapping array network on the 26 october 2012 a thunderstorm passed just over the acoustic station fifty six natural thunder events due to cloud to ground and intracloud flashes were recorded this paper studies the acoustic reconstruction in the low frequency range from 1 to 40 hz of the recorded flashes and their comparison with detections from electromagnetic networks concurrent detections from the european cooperation for lightning detection lightning location system were also used some case studies show clearly that acoustic signal from thunder comes from the return stroke but also from the horizontal discharges which occur inside the clouds the huge amount of observation data leads to a statistical analysis of lightning discharges acoustically recorded especially the distributions of altitudes of reconstructed acoustic detections are explored in detail the impact of the distance to the source on these distributions is established the capacity of the acoustic method to describe precisely the lower part of nearby cloud to ground discharges where the lightning mapping array network is not effective is also highlighted

lightning activity and severe storm structure space time mapping of vhf sources from four severe storms on 19 june 1980 reveals that lightning processes for cloud to ground cg and large intracloud ic flashes are confined to an altitude below about 10 km and closely associated with the central regions of high reflectivity another class of ic flashes produces a splattering of sources within the storms main electrically active volumes and also within the large divergent wind canopy aloft there is no apparent temporal association between the small high altitude ic flashes that occur almost continuously and the large ic and cg flashes that occur sporadically in the lower portions of storms

crystal size distributions and scaling laws in the quantification of igneous textures this study demonstrates the value of the combined use of scaling of the chemical evolution of cooling magmas have investigated the detailed relationships between temanalysis and crystal size distribution csd measurements in the interpretation of igneous textures and outlines applications of these perature phase abundance and phase composition the reaction series bowen 1922 and the cipw norm cross methods to other fundamentally important problems theoretical calculations and measurements of natural samples are used to et al 1903 have been supplemented by modern thermodynamic models that predict the compositions and abundcharacterize the relationship between igneous texture and cooling history the total number nt and mean length l of crystals ances of minerals in equilibrium with melt of a given composition and temperature e g ariskin et al 1993 in a sample are correlated through a scaling relationship of the form n t l this proportionality depends on the mineralogy ghiorso sack 1995 although there are a few areas of uncertainty the chemistry of igneous petrogenesis is of the rock and so a modal normalization factor c is introduced the csd slope s and intercept ln n are uniquely related to fairly well understood but chemical models cannot address the central probeach other through the equation ln n 4ln s ln c where s l this overall relationship allows the texture of a rock lem of igneous crystallization which is the physical process of generating a set of crystals from magma two to be related to the local duration of cooling through an arbitrary crystal growth model quantification of the link between the texture magmas with the same composition will normally produce the same minerals in the same proportions however of a rock and its cooling history makes it possible to predict spatial variations in texture we show an example of this method using depending on their thermal histories these two magmas can solidify into rocks with drastically different physical the sudbury igneous complex canada additional applications include relating the textures of volcanic rocks to spatial and temporal appearances e g basalt and gabbro the set of minerals is the same but what distinguishes them is the abundance variations in the magma chamber and extracting kinetic parameters from suites of comagmatic rocks and size of the constituent crystals the fine grained rocks in the chilled margins of most basic intrusions cooled rapidly and the coarse grained rocks in the interiors of plutons cooled slowly this has

relationship between plagioclase crystallization and cooling rate in basaltic melts rock textures commonly preserve a record of the near surface crystallization history of volcanic rocks under conditions of simple cooling without convection or mixing textures will reflect sample cooling rate the temperature at which crystallization was initiated and the distribution of mineral phase precipitation across the crystallization interval compilation of plagioclase size and number density data on natural dike sill and lava lake and experimental samples suggests that 1 growth and nucleation rates of plagioclase in natural basaltic samples are a predictable function of cooling rate and 2 the observed crystallization rate dependence on cooling rate is similar to that observed in experiments initiated at subliquidus temperatures comparison of natural and experimental samples thus suggests that most basalts crystallize under conditions of heterogeneous nucleation with the number density of preexisting nucleii partially controlling textural responses to cooling rate changes time scales of crystallization and cooling in magmatic systems are intimately linked through a balance between heat removal from the system and heat evolved through crystallization evaluation of textural data in the context of recent numerical models of crystallization in simple one and two component systems provides new insight into regularities in the crystallization behavior of basaltic magmas for example the rate of change in crystal size and number density as dictated by mass balance has been used as a measure of the relative importance of time scales of crystallization and cooling in numerical models of crystallizing systems in natural samples plagioclase size scales with the length scale of cooling such that a logarithmic plot of grain size as a function of normalized distance across the dike has a slope that appears approximately independent of dike width solidification time comparison with available textural data for other phenocryst phases suggests that the same may be true for pyroxene and magnetite crystallization with each phase having a characteristic slope probably controlled by the thermodynamic properties of the crystallizing phase measured crystal size distributions are unimodal and show maximum frequencies in the smaller size classes distributions broaden and the grain size at peak frequency increases with increasing crystallization times decreasing cooling rates in contrast partially crystallized makaopuhi lava lake samples have crystal size distributions that decrease exponentially with increasing crystal size measured size distributions in dikes can be explained by late stage modification of makaopuhi type distributions through loss of small crystals possibly the consequence of growth without nucleation finally this compilation of the textural response of basaltic magmas to changes in cooling rate suggests that empirical calibrations of crystallization rate dependence on cooling rate from natural samples provide a reasonable model for plagioclase crystallization in near surface basaltic systems predicted growth rates will be slow and relatively constant 10 10 10 11 cm s for crystallization times expected in most shallow volcanic systems 1000 years

characteristics of infrasound from lightning and sprites near thunderstorm areas 1 research about thunder was mainly performed 20 30 years ago but has been renewed in recent years due to new interest about infrasound in the framework of the verification of the compliance of the comprehensive nuclear test ban treaty during the eurosprite 2005 campaign an infrasound miniarray has been set up in france to measure the characteristics of infrasound from lightning and sprites when these kinds of sources were close to the sensors that is for lightning distances lower than 100 km and sprite distances lower than 300 km for two large thunderstorms which passed over the station detection conditions of infrasound from lightning are detailed and some characteristics are thoroughly described e g amplitude variation with distance and spectrum of an individual event in the frequency range from 0 01 to 10 hz the locations of infrasound sources are determined using a 3 d inversion infrasound signals from sprites have also been detected and the 3 d inversion method used for lightning infrasound has been adapted to locate the sources of infrasound from sprites four different sprite infrasound events are analyzed in this way the infrasound source corresponds well to the sprite spatial characteristics deduced from camera observations questions about generation mechanisms of infrasound from lightning and sprites still remain these new results should help us to understand the sound generation processes

vhf radio pictures of lightning flashes to ground we present information obtained from vhf radio pictures of 47 lightning flashes that struck ground 1430 m above mean sea level msl to the north of johannesburg over a period of 16 years radio pictures were obtained using a hyperbolic method i e by taking differences between times at which radio noise from lightning arrived at five widely spaced stations these data were supplemented by recordings of electric field change we found that stepped leaders and intracloud streamers emitted pulses and progressed at speeds that averaged 1 6 105 ms 1 stepped leaders ranged in length from 3 to 13 km bil breakdown intermediate leader waveforms of electric field change were caused by stepped leaders whose branched channels followed complicated paths the electric field changes they recorded in an effective bandwidth of 3 5 khz could be reproduced faithfully by calculations based on an assumption that the radio sources became charged at the expense of a region near the origin of each leader some return strokes radiated trains of noise called q noise whose sources extended at speeds near 108 ms 1 sources of this q noise retraced leader channels before extending them at these high speeds interstroke processes radiated q noise whose sources extended at speeds that averaged 8 7 107 ms 1 most q sources 98 were directed vertically but they pervaded regions that retrogressed at speeds that averaged 2 2 104 ms 1 in directions away from the starting points of the flashes this retrogression was directed horizontally but the vertical q streamers caused j changes to have positive or negative slopes according to the relative positions of q sources and the reversal cone sixty percent of our sample of ground flashes were endowed with portions that were cloud flashes or were themselves minor components of cloud flashes a more detailed summary appears at the end of the paper

investigation of a shallow slope failure on expansive clay in texas abstract highway slopes constructed with highly plastic clay soils undergo shrink swell cycles during the wet dry season which usually soften the soil and may cause failure a few years following construction there are two major wet dry cycles in texas where summer to early fall is categorized as the dry period and late fall to spring is categorized as the wet period during this study the failure of a highway slope located in fort worth texas was investigated and the effect of rainfall on the slope failure was evaluated the failure of the slope was investigated using soil test borings geophysical testing laboratory testing slope stability analysis and unsaturated flow analysis the site investigation included sample collections from different depths of borings determination of the soil index properties and various shear strength testing to determine soil strength parameters the obtained test results were further utilized in slope stability and flow analyses using the finite element method fem in plaxis the study indicated that both a fully softened condition and rainfall were responsible for the slope failure the fully softened condition provided a factor of safety of 1 46 whereas the perched water condition after rainfall provided a nearly failing factor of safety of 1 05

electrical and polarimetric radar observations of a multicell storm in telex abstract on 28 29 june 2004 a multicellular thunderstorm west of oklahoma city oklahoma was probed as part of the thunderstorm electrification and lightning experiment field program this study makes use of radar observations from the norman oklahoma polarimetric weather surveillance radar 1988 doppler three dimensional lightning mapping data from the oklahoma lightning mapping array lma and balloon borne vector electric field meter efm measurements the storm had a low flash rate 30 flashes in 40 min four charge regions were inferred from a combination of lma and efm data lower positive charge near 4 km and midlevel negative charge from 4 5 to 6 km msl from 0 to 6 5 c were generated in and adjacent to a vigorous updraft pulse further midlevel negative charge from 4 5 to 6 km msl and upper positive charge from 6 to 8 km from 6 5 to 19 c were generated later in quantity sufficient to initiate lightning as the updraft decayed a negative screening layer was present near the storm top

crystallization history of the 1984 mauna loa lava flow during a 3 week eruption in 1984 mauna loa produced vent lavas that increased in crystallinity from 1 to 30 and 27 km long flows that increased in crystallinity as they moved downstream we examined the crystallization history of these lavas using crystal size distribution csd analysis to study the rates of crystallization viscosity increase and latent heating typical average growth and nucleation rates were 5 10 9 cm s 1 and 5 cm 3 s 1 for microphenocrysts 20 to 500 m size crystals nucleated in the rift zone and 5 10 8 cm s 1 and 5 104 cm 3 s 1 for microlites 1 to 20 m size crystals nucleated in the channel these crystallization rates are high compared with those found in other csd studies of igneous rocks probably due to highly nonequilibrium conditions brought on by rapid degassing in the rift zone and cooling in the lava channel growth and nucleation rates decreased with time at the vent and with distance downstream the maximum downstream total crystallinity measured is 39 25 microlites 14 microphenocrysts in a quenched sample 14 km from the vent growth and nucleation rates cannot be calculated for postemplacement samples but they place upper limits of 53 58 on the amount of crystallization in the channel 9 20 km from the vent crystallization could have been mostly responsible for the 105 fold downstream increase in apparent viscosity although degassing and increasing incorporation of solid lava fragments also contributed another effect of crystallization on the lava flow was the sizeable latent heating 0 01 j g 1 s 1 over the first half of the flow length if the crystallinity of downstream quench samples is representative of the hot fluid core which may have been counteracted by entrainment of cooler material measurements of crystallization are shown to be crucial in the study of lava flow emplacement dynamics

magma dynamics beneath kameni volcano thera greece as revealed by crystal size and shape measurements size distributions of plagioclase crystals in series of recent porphyritic dacite lavas from kameni volcano greece can be modelled by mixing two populations of crystals each with overlapping linear crystal size distributions csd termed microlites and megacrysts the magmas bearing the microlites and megacrysts started to crystallise 6 13 and 24 96 years respectively before each eruption the dates of initiation of crystallisation of the megacrysts indicate that they are left overs of earlier injections of new magma into a shallow chamber some magma remains after each eruption and continues to crystallise new magma with few or no crystals is then introduced and the microlites crystallise from the mixed magma eruption followed 6 13 years after mixing such a model would suggest that some porphyritic magmas are products of a shallow magma chamber that is never completely emptied just topped up from time to time

an integrated geophysical approach for investigating hydro geological characteristics of a debris landslide in the wenchuan earthquake area debris landslides are one of the most widely distributed types of landslides in the wenchuan earthquake area the hydro geological structure characteristics are the fundamental basis for stability evaluation performing protection and administration of a landslide the rock and soil mass of a debris landslide was highly non uniform and preferential seepage paths were normally developed in it therefore in situ identification of the underground water seepage system became particularly important recently investigations on the seepage paths of underground water in debris landslides were restricted to indoor model testing and site observation which were far from meeting the actual demand for landslide prevention and mitigation to locate the seepage paths we conducted survey work on a debris landslide seated in the xishan village li county sichuan province china by combing four different geophysical methods they were multichannel analysis of surface wave masw electrical resistivity tomography ert ground penetrating radar gpr and microtremor survey method msm the geophysical interpretation was verified with field engineering surveys and monitoring data the results suggested that a dendritic pipe network seepage system usually developed in debris landslides varisized infiltration pipes showed the characteristics of inhomogeneity and concentration of the seepage this work highlighted that geophysical parameters shear wave velocity vs dielectric constant e and resistivity value could provide reliable qualitative and quantitative information about the colluvial layer bedrock interface potential sliding surface and underground water seepage system of a landslide the optimum combination of geophysical methods was suitable to survey the hydro geological characteristics of debris landslides in the wenchuan earthquake area

recrystallized impact glasses of the onaping formation and the sudbury igneous complex sudbury structure ontario canada abstract the origin of the sudbury structure and of the associated heterolithic breccias of the onaping formation and the sudbury igneous complex have been controversial while an impact origin of the structure has gained wide acceptance over the last 15 years the origin of the recrystallized onaping formation glasses and of the igneous complex is still being debated recently the interpretation of the breccias of the onaping formation as suevitic fall back impact breccias has been challenged the igneous complex is interpreted either as a differentiated impact melt sheet or as a combination of an upper impact melt represented by the granophyre and a lower impact triggered magmatic body consisting of the norite sublayer formations the onaping formation contains glasses as fluidal and nonfluidal fragments of various shapes and sizes they are recrystallized and our research indicates that they are petrographically heterogeneous and span a wide range of chemical compositions these characteristics are not known from glasses of volcanic deposits this suggests an origin by shock vitrification an interpretation consistent with their association with numerous and varied country rock clasts that exhibit microscopic shock metamorphic features the recrystallized glass fragments represent individual solid state and liquid state vitrified rocks or relatively small melt pods the basal member lies beneath the gray and black members of the onaping formation and where not metamorphic has an igneous matrix igneous textured melt bodies occur in the upper two members and above the basal member a comparison of the chemical compositions of recrystallized glasses and of the matrices of the basal member and the melt bodies with the components and the bulk composition of the igneous complex is inconclusive as to the origin of the igneous complex basal member matrix and melt bodies on average are chemically similar to the granophyre of the sudbury igneous complex suggesting that they are genetically related our chemical results allow interpretation of the entire igneous complex as a differentiated impact melt however they are also consistent with the granophyre alone being the impact melt and the norite and quartz gabbro beneath it representing an impact triggered magmatic body this interpretation is preferred as it is consistent with a number of field observations a re evaluation and extension of structural field studies and of geochemical data as well as a systematic study of the contact relationships of the various igneous phases of the igneous complex are needed to establish a sudbury impact model consistent with all data and observations

lightning location relative to storm structure in a supercell storm and a multicell storm relationships between lightning location and storm structure are examined for one radar volume scan in each of two mature severe storms one of these storms had characteristics of a supercell storm and the other was a multicell storm data were analyzed from dual doppler radar and dual vhf lightning mapping systems the distributions of vhf impulse sources were compared with radar reflectivity vertical air velocity and their respective gradients in the supercell storm lightning tended to occur along streamlines above and downshear of the updraft and reflectivity cores vhf impulse sources were most concentrated in reflectivities between 30 and 40 dbz and were distributed uniformly with respect to updraft speed in the multicell storm on the other hand lightning tended to coincide with the vertical reflectivity and updraft core and with the diverging streamlines near the top of the storm the results suggest to us that the location of lightning in these severe storms was most directly associated with the wind field structure relative to updraft and reflectivity cores since the magnitude and vertical shear of the environmental wind are fundamental in determining the reflectivity and wind field structure of a storm we suggest that these environmental parameters are also fundamental in determining lightning location

novel approach for health monitoring of earthen embankments abstractthis paper introduces a novel modular approach for the monitoring of desiccation induced deterioration in earthen embankments levees which are typically used as flood defense structures the approach is based on the use of a combination of geotechnical and noninvasive geophysical probes for the continuous monitoring of the water content in the ground the level of accuracy of the monitoring is adaptable to the available financial resources the proposed methodology was used and validated on a recently built 2 km long river embankment in galston scotland united kingdom a suite of geotechnical probes was installed to monitor the seasonal variation of water content over a 2 year period most devices were calibrated in situ a novel procedure to extrapolate the value of water content from the geotechnical and geophysical probes at any point of the embankment is shown desiccation fissuring degrades the resistance of embankments against several failure mechanisms an index of susceptibility is

magnitude frequency relation for rockfall scars using a terrestrial laser scanner abstract the analysis of the three dimensional rockfall scar geometry provides clues for the understanding of the failure mechanisms acting on cliffs of the conditioning factors and on the frequency of the events in this paper a supervised step by step methodology is presented for establishing the statistical magnitude frequency relation of rockfall scar volumes using a point cloud from terrestrial laser scanner tls data the methodology includes a procedure for identifying discontinuity surfaces calculating the areas of those which are exposed and the height of rockfall scars in the estimation of the rockfall scar volume a key issue is the consideration of the minimum spacing of the discontinuity sets to differentiate between step path surfaces and undulated ones having obtained the distributions of both the basal area and height of the scar across the slope the volume of the rockfall scars is calculated stochastically by multiplication of these two parameters by means of a monte carlo simulation both distributions of the basal area and of the rockfall scar volume are found to be power law with the exponent b ranging from 0 9 to 1 2 the relation obtained might be used as a first approach of rockfall magnitude frequency curves in large cliffs

lightning location relative to storm structure in a leading line trailing stratiform mesoscale convective system 1 horizontal and line normal vertical cross sections and composite images of dallas fort worth lightning detection and ranging ldar ii vhf radiation sources and radar reflectivity over a 30 min period provide a unique perspective on lightning pathways within a leading line trailing stratiform llts mesoscale convective system mcs on 16 june 2002 the overwhelming majority of vhf lightning sources occurred within the leading convective line in a bimodal pattern in the vertical assuming that vhf source density maxima were most likely associated with positive charge then the ldar ii observations suggest that the gross charge structure of the convective region of the mcs was characterized by a tripole with net positive charge centered at 4 5 km agl 3 c and 9 5 km agl 35 c and net negative charge centered roughly in the relative minimum of the vhf source density maximum at 7 km agl 17 c a persistent lightning pathway and inferred positive charge zone sloped rearward by 40 50 km and downward by 4 5 km from the upper vhf source maximum in the convective line through the transition zone and into the radar bright band of the stratiform region in the stratiform region vhf lightning sources and inferred positive charge were concentrated in three layers centered at 4 5 6 and 9 km agl 2 c 11 c and 31 c respectively consistent with past electric field studies of symmetric llts mcss positive cloud to ground lightning flashes in the stratiform region were initiated in the convective line and followed the slanting pathway from the top of convective cores to the stratiform precipitation where they were horizontally extensive layered and highly branched the sloping lightning pathway was identical to hypothetical trajectories taken by snow particles these observations provide further support for the advection of charge on snow along the sloping pathway and the in situ generation of charge in the horizontal lightning layers as primary contributors to electrification and positive lightning production rearward of the convective line

storm structure during aircraft lightning strike events a small set of in situ aircraft and ground based radar data acquired during the 1981 and 1982 joint agency turbulence experiment is used to study the relationship of aircraft lightning strikes to storm precipitation turbulence severity and wind shear the strikes were found to be strongly correlated with vertical drafts predominantly downdrafts strikes were also well correlated with regions of strong turbulence however since most strong turbulence episodes encountered by the aircraft were not associated with lightning use of lightning location methods to map hazardous turbulence within storms is considered unreliable the strikes occurred in storm regions having a radar reflectivity factor between 25 and 35 dbz dbz represents 10 log z where z is the reflectivity factor these regions were generally on the boundaries of the dominant storm precipitation cores storm wind shear was frequently high in regions near aircraft strikes

combined effect of hysteresis and heterogeneity on the stability of an embankment under transient seepage the stability of most earth embankments is strongly influenced by the water content of the soil the water content directly influences the suction or pore pressure in the soil as well as the mass of material thereby affecting the stress state and strength and leading to changes in the stability these aspects are coupled by the so called soil water retention behaviour which is observed to be a hysteretic phenomenon moreover soils are known to be spatially variable or heterogeneous in nature which can lead to preferential flow paths and stronger or weaker zones in this paper the behaviour of a heterogeneous earth embankment subjected to cyclic water level fluctuation including the impact of hysteresis is investigated the soil property values governing the unsaturated hydraulic response of the embankment are considered as spatially random variables with the mechanical property values considered deterministic in order to isolate the impact of the hydraulic behaviour the monte carlo method mcm is used to conduct probabilistic analyses and an assessment of the relative influence of material properties illustrates that the saturated hydraulic conductivity ksat plays a dominant role in the slope stability moreover in the initially drying condition the average factor of safety fos and the 95th percentile fos of the slope considering hysteresis are smaller than those without considering hysteresis at all times while the variability of the fos considering hysteresis is larger than that when not considering hysteresis in practice this means that slopes under seepage conditions which are assessed to have a low fos should be assessed including the hysteretic behaviour to ensure stability

evolution of lightning activity and storm charge relative to dual doppler analysis of a high precipitation supercell storm abstracta high precipitation tornadic supercell storm was observed on 29 30 may 2004 during the thunderstorm electrification and lightning experiment observational systems included the oklahoma lightning mapping array mobile balloon borne soundings and two mobile c band radars the spatial distribution and evolution of lightning are related to storm kinematics and microphysics specifically through regions of microphysical charging and the location and geometry of those charge regions lightning flashes near the core of this storm were extraordinarily frequent but tended to be of shorter duration and smaller horizontal extent than typical flashes elsewhere this is hypothesized to be due to the charge being in many small pockets with opposite polarities of charge close together in adjoining pockets thus each polarity of lightning leader could propagate only a relatively short distance before reaching regions of unfavorable electric potential in the anvil however lightning extended tens of kilome

infrasound pulses from lightning and electrostatic field changes observation and discussion 1 narrow 1 2 s infrasound pulses that followed with 11 to 50 s delays rapid changes of electrostatic field were observed by a microbarometer array in the czech republic during thunderstorm activity a positive pressure fluctuation compression phase always preceded decompression the compression was usually higher than the decompression the angles of arrival azimuth and elevation were analyzed for selected distinct events comparisons of distances and azimuths of infrasound sources from the center of microbarometer array with lightning locations determined by the european cooperation for lighting detection lightning detection network show that most of the selected events can be very likely associated with intracloud ic discharges the preceding rapid changes of electrostatic field their potential association with ic discharges and high elevation angles of arrival for near infrasound sources indicate that an electrostatic mechanism is probably responsible for their generation it is discussed that distinguishing the relative role of thermal and electrostatic mechanism is difficult and that none of the published models of electrostatic production of infrasound thunder can explain the presented observations precisely a modification of the current models based on consideration of at least two charged layers is suggested further theoretical and experimental investigations are however needed to get a better description of the generation mechanism