factors affecting the durability of selected weak and clay bearing rocks from turkey with particular emphasis on the influence of the number of drying and wetting cycles weathering can induce a rapid change of rock material from initial rock like properties to soil like properties the resistance of a rock to short term weathering is described through a durability parameter called the slake durability index as durability is an important engineering parameter particularly for weak and clay bearing rocks it was assessed by a number of tests the main purpose of this study is to assess the influence of the number of drying and wetting cycles and controls of mineralogical composition and strength on durability for this purpose 141 samples of different types of weak and clay bearing rocks were selected from different parts of turkey and relationships between the above mentioned rock characteristics were statistically investigated the samples were subjected to multiple cycle slake durability testing x ray diffraction xrd analysis and uniaxial compression testing in addition to assess the influence of mineralogical composition on durability the mineral contents of the original material and the material passing from the drum of the slake durability apparatus after each cycle were also determined by xrd the results indicate that the type and amount of clay minerals are the main factors influencing the variations of the slake durability index in all samples the durability of the clay bearing rocks studied correlates best with the amount of expandable clay minerals a strong relationship between the uniaxial compressive strength and the fourth cycle slake durability index is found only for the marls among the rock types studied assessment of gradation results of the spoil pile materials consisting of clay bearing rocks also reveals that the increase in percentage of fines in old piles is indicative of material degradation as is evident by multiple cycle slaking it is emphasized that two cycle conventional slake durability testing did not appear to offer an acceptable indication of the durability of weak and clay bearing rocks when compared with multiple cyclic wetting and drying comments on the performance of the test are made that aim to make the testing process and interpretation of the results more reliable

probabilistic rainfall thresholds for triggering debris flows in a human modified landscape abstract in the carrara marble basin cmb apuan alps italy quarrying has accumulated widespread and thick quarry waste lying on steep slopes and invading valley bottoms the apuan alps are one of the rainiest areas in italy and rainstorms often cause landslides and debris flows the stability conditions of quarry waste are difficult to assess owing to its textural geotechnical and hydrogeological variability therefore empirical rainfall thresholds may be effective in forecasting the possible occurrence of debris flows in the cmb three types of thresholds were defined for three rain gauges of the cmb and for the whole area rainfall intensity rainfall duration id cumulated event rainfall rainfall duration ed and cumulated event rainfall normalized by the mean annual precipitation rainfall intensity emapi the rainfall events recorded from 1950 to 2005 was analyzed and compared with the occurrence of debris flows involving the quarry waste they were classified in events that triggered one or more debris flows and events that did not trigger debris flows this dataset was fitted using the logistic regression method that allows us to define a set of thresholds corresponding to different probabilities of failure from 10 to 90 and therefore to different warning levels the performance of the logistic regression in defining probabilistic thresholds was evaluated by means of contingency tables skill scores and receiver operating characteristic roc analysis these analyses indicate that the predictive capability of the three types of threshold is acceptable for each rain gauge and for the whole cmb the best compromise between the number of correct debris flow predictions and the number of wrong predictions is obtained for the 40 probability thresholds the results obtained can be tested in an experimental debris flows forecasting system based on rainfall thresholds and could have implications for the debris flow hazard and risk assessment in the cmb

composition of back arc basin volcanics valu fa ridge lau basin evidence for a slab derived component in their mantle source abstract samples dredged from 2 localities near the crest of the valu fa ridge an active back arc basin spreading centre in the lau basin consist of highly vesicular lava fragments of andesitic composition the samples are characterized by rare euhedral an 85 plagioclase phenocrysts in a hypocrystalline groundmass of an 60 plagioclase laths brown glass and rare subhedral clinopyroxene samples from within and to a lesser extent between the dredge hauls show remarkable isotopic and chemical homogeneity with 87 sr 86 sr 0 70330 2 143 nd 144 nd 0 51303 2 206 pb 204 pb 18 65 2 207 pb 204 pb 15 55 1 208 pb 204 pb 38 34 4 sr 165 ppm rb 7 ppm cs 0 17 ppm k 3300 to 4200 ppm ba 96 ppm and ree lree depleted with 12 18 chondritic abundances on sr nd pb pb and sr pb plots the volcanics lie just within or on the edge of the morb fields overlapping with island arc volcanics from the marianas and tonga compared with morb and ocean island basalts the samples show alkali element enrichment relative to ree and higher cs relative to rb the isotopic and geochemical characteristics of the valu fa ridge volcanics clearly indicate a minor but significant slab derived component in the back arc basin mantle source

images of transequatorial f region bubbles in 630 and 777 nm emissions compared with satellite measurements images of transequatorial f region bubbles were obtained from magnetic field aligned airglow observations from haleakala hawaii for 9 nights in august 1988 bubbles of scale size 10 100 km were recorded with an intensified ccd detector attached to a filter wheel imager and sequential images were made in the plasma recombination emissions at 630 nm and 777 nm and in the background emissions the observations also yield information on the large scale structure of the ionosphere in the northern appleton anomaly region particularly on the latitude variations of plasma concentration and layer height measurements from the dmsp f8 and f9 satellites extend this to include the southern anomaly region the dmsp satellites were near 830 km in altitude and in near polar orbits at about 1800 and 2120 hours local time a comparison of the bubble images and the dmsp results with plasma concentration and drift velocities obtained from the san marco satellite allows us to put the measurements along the san marco track into the larger ionospheric context one to one correspondence is found between the presence of the optical bubbles and the presence of plasma depletions measured from the san marco satellite allowing identification on consecutive orbits of the same depletions this extends for up to 5 hours of the satellite measured information for individual depletions that is their vertical and horizontal drift velocities and the plasma concentration variations the images show the shapes of the depletions in apex height and longitude and their evolution horizontal drift velocities of the bubbles were determined by a correlation analysis bubble occurrence is compared with day to day changes in the equatorial fountain electric fields and transequatorial asymmetries caused by neutral winds and with measurements of radar backscatter from centimeter scale irregularities associated with bubbles in the kwajalein sector the development of 10 100 km scale size bubbles at a given time and location is clearly a consequence of the presence of even larger wavelike corrugations in the f layer provided there is also at least a moderately strong equatorial fountain

human induced hazardous debris flows in carrara marble basins tuscany italy in carrara marble basins the long and intensive quarrying activities which began in the first century bc have produced extensive dump deposits locally known as ravaneti ravaneti are of such large dimensions and diffusion as to make them a widespread landform of the apuane alps tuscany in recent years these quarry dump deposits have been affected by frequent debris flows more than 50 in 1996 97 this phenomenon is the most significant currently active geomorphological process in this landscape the evolution of quarrying techniques produced a variety of sedimentological compositions of ravaneti the debris flows analysed involve only the surface layers where debris is mixed with fine material with a lower permeability active ravaneti than the coarser underlying debris older ravaneti the presence of different permeability layers causes a wetting front to move downwards source area observations indicate a soil slip movement in the initial phases of the failure the transformation of landslides into debris flow occurs by means of both soil contractive failure and an increase of granular temperature the morphological and sedimentological analyses of depositional lobes resulted in a classification of three types of lobe based on fabric morphometry relationships allowing the identification of different flow dynamics 1 type a lobe platy form matrix supported and well developed fabric with general tendency of ab clast plane strikes to lie generally parallel to flow direction as a consequence of laminar flow 2 type b lobe elongated form clast supported and random fabric as a consequence of both turbulent flow and coarser composition of starting material 3 type c lobe intermediate type a b morphometry tendency for ab clast plane to lie in a semi circle around the main flow direction determined by the presence of secondary flow lines divergent from it in the stopping phase in carrara marble basins the anomalous frequency with which debris flows tend to be triggered by medium intensity rainstorms about 30 mm h 1 rainfall is due to the recent increases in silt dump produced by modern quarrying techniques this represents a significant example of debris flows as an environmental problem in major anthromorphized landscapes copyright 2000 john wiley sons ltd

investigation of the effect of aggregate shape and surface roughness on the slake durability index using the fractal dimension approach argillaceous rocks cover about one thirds of the earth s surface the major engineering problems encountered with weak to medium strength argillaceous rocks could be slaking erosion slope stability settlement and reduction in strength one of the key properties for classifying and determining the behavior of such rocks is the slake durability the concept of slake durability index sdi has been the subject of numerous researches in which a number of factors affecting the numerical value of sdi were investigated in this regard this paper approaches the matter by evaluating the effects of overall shape and surface roughness of the testing material on the outcome of slake durability indices for the purpose different types of rocks marl clayey limestone tuff sandstone weathered granite were broken into chunks and were intentionally shaped as angular subangular and rounded and tested for slake durability before testing the aggregate pieces of each rock type their surface roughness was determined by using the fractal dimension despite the variation of final values of sdi test results values of id the rounded aggregate groups plot relatively in a narrow range but a greater scatter was obtained for the angular and subangular aggregate groups the best results can be obtained when using the well rounded samples having the lowest fractal values an attempt was made to analytically link the surface roughness with the id parameter and an empirical relationship was proposed a chart for various fractal values of surface roughness to use as a guide for slake durability tests is also proposed the method proposed herein becomes efficient when well rounded aggregates are not available in such condition the approximate fractal value for the surface roughness profile of the testing aggregates could be obtained from the proposed chart and be plugged into the empirical relation to obtain the corrected id value the results presented herein represent the particular rock types used in this study and care should be taken when applying these methods to different type of rocks

empirical models of storm time equatorial zonal electric fields ionospheric plasma drifts often show highly complex and variable signatures during geomagnetically active periods due to the effects of different disturbance processes we describe initially a methodology for the study of storm time dependent ionospheric electric fields we present empirical models of equatorial disturbance zonal electric fields obtained using extensive f region vertical plasma drift measurements from the jicamarca observatory and auroral electrojet indices these models determine the plasma drift perturbations due to the combined effects of short lived prompt penetration and longer lasting disturbance dynamo electric fields we show that the prompt penetration drifts obtained from a high time resolution empirical model are in excellent agreement with results from the rice convection model for comparable changes in the polar cap potential drop we also present several case studies comparing observations with results obtained by adding model disturbance drifts and season and solar cycle dependent average quiet time drift patterns when the disturbance drifts are largely due to changes in magnetospheric convection and to disturbance dynamo effects the measured and modeled drift velocities are generally in good agreement however our results indicate that the equatorial disturbance electric field pattern can be strongly affected by variations in the shielding efficiency and in the high latitude potential and energy deposition patterns which are not accounted for in the model these case studies and earlier results also suggest the possible importance of additional sources of plasmaspheric disturbance electric fields

on post midnight field aligned irregularities observed with a 30 8 mhz radar at a low latitude comparison withf layer altitude near the geomagnetic equator 1 we investigated the relationship between post midnightf region field aligned irregularities fais andf layer altitude by analyzing data of a 30 8 mhz radar installed 5at kototabang indonesia 0 2 s 100 3 e geomagnetic latitude 10 4 s and an ionosonde installed at chumphon thailand 10 7 n 99 4 e geomagnetic latitude 3 3 n chumphon is located near the geomagnetic equator on approximately the same meridian as kototabang case studies show that the altitude of thef layer rose at chumphon a half hour before the post midnight fais appeared at kototabang the doppler velocity of thee region fais observed simultaneously by the 30 8 mhz radar was downward indicating that thef layer uplift was not caused by the electric field we also investigated seasonal variations of the post midnight fai occurrence and thef layer altitude both the post midnight fais and the uplift of thef layer were frequently seen around midnight between may and august the seasonal variation of the midnightf layer uplift around the geomagnetic equator coincided with that of the post midnight fai occurrence at kototabang these results suggest that the uplift of thef layer would play an important role in the generation of post midnight fais we evaluated the linear growth rate of the rayleigh taylor instability based on the altitude of thef layer observed at chumphon the result shows that the uplift of thef layer can enhance the growth rate because gravity driven eastward electric current increases therefore we interpret that the observed fais were accompanied by plasma bubble the growth rate of which was reinforced by the upliftedf layer

spoil pile instabilities with reference to a strip coal mine in turkey mechanisms and assessment of deformations with the increasing adoption of the surface mining of coal problems associated with spoil pile instability which affects resource recovery mining cost and safety and presents environmental hazards have become a matter of prime concern to mine planners and operators the study of geotechnical aspects is thus very important in the rational planning for the disposal reclamation treatment and utilization of spoil material a strip coal mine one of the largest open pit mines in turkey is located in central anatolia and provides coal to a thermal power station coal production is carried out in two adjacent open pits the central pit and south pit a large scale spoil pile instability over an area of 0 3 km2 occurred within the dumping area of the central pit in addition small scale movement occurred in the outside dumping area this paper outlines the results of field and laboratory investigations to describe the mechanisms of the spoil pile instabilities and to assess deformations monitored over a long period following the failure shear test results indicate that the interface between the floor and spoil material dumped by dragline has a negligible cohesion and is the most critical plane of weakness for spoil pile instability back analyses based on the method of limit equilibrium and the numerical modelling technique and observations in the pit revealed that failure occurred along a combined sliding surface consisting of a circular surface through the spoil material itself and a planar surface passing along the interface between the spoil piles and floor the analyses also indicated that pore water pressure ratios of about 0 25 satisfy limiting equilibrium condition and that rainfall about one month before the failure may be a contributing factor to the instability movement monitoring data obtained following the failure over a 1 5 year period suggested that the ongoing deformations were mainly due to compaction of the spoil material based on the monitoring data and the results of the analyses the failure mode of the local instability occurring at the outside dumping area was considerably similar to that of the large instability

experimental tests for the assessment of the shear strength of marble waste dumps the large dumps of waste material called ravaneti from marble quarrying activities in alpi apuane basin are distinguished features of the local landscape they are strongly heterogeneous never compacted and frequently subject to local instabilities the access roads to the marble quarries cross the dumps therefore it is concern of the local authorities to hinder such phenomena in this respect it is of paramount importance to evaluate the shear strength of the material comprising the dumps at the proper scale in this note the results of in situ direct shear and tilt tests on samples of metric size are illustrated together with the interpretation according to a strength criterion relative to rockfills the results of a series of lab tests on the finer fraction of the waste material are also described and interpreted finally qualitative considerations on the local and global stability of the waste dumps related to their shear strength are reported

evidence for late paleocene to late eocene seafloor in the southern new hebrides basin abstract we interpret marine magnetic anomaly data from the southern part of the new hebrides basin as showing that a fragment of late paleocene late eocene oceanic crust is preserved between the new caledonia loyalty islands platform and the new hebrides island arc trench system the magnetic lineations which trend about ne sw are interpreted as anomalies 18 through 23 42 55 m y b p with the inferred crustal ages increasing to the north drilling at dsdp site 286 which is located on oceanic crust slightly older than 55 m y according to our magnetic anomaly identifications revealed mid eocene sediments overlying igneous basement

lithological and seasonal control on rainfall thresholds for the possible initiation of landslides in central italy we compiled a catalogue of 442 rainfall events with landslides in the abruzzo marche and umbria regions central italy between february 2002 and august 2010 for each event we determined the duration d in hours and the cumulated total event rainfall e in mm using rainfall measurements obtained from a dense network of 150 rain gauges landslides were mapped as single points using google earth and were attributed a level of mapping accuracy p in four classes p1 1 km2 p10 10 km2 p100 100 km2 p300 300 km2 using this information we determined cumulated event rainfall rainfall duration ed thresholds which are entirely equivalent to rainfall intensity duration id thresholds and avoid unnecessary conversions to determine the ed thresholds we modified a statistical method first proposed to determine id thresholds adopting a bootstrapping statistical technique we expanded the method to determine the uncertainty associated with the parameters that define the power law threshold model and the sensitivity of the thresholds to the number of d e data points in the empirical data set we determined ed thresholds for 1 and 5 exceedance probability levels i for the entire study area and for the three individual regions in the study area abruzzo marche and umbria ii for three main lithological domains in the study area post orogenic sediments flysch deposits carbonate rocks and iii for two seasonal periods may september october april comparison of the ed thresholds indicates that the cumulated amount of rainfall necessary to trigger landslides in flysch deposits is larger than in post orogenic sediments and carbonate rocks however the ed thresholds for post orogenic sediments and carbonate rocks were statistically indistinguishable in the study area also the seasonal thresholds were statistically different for rainfall durations shorter than 12 h and longer than 100 h but were indistinguishable in the range 12 d 100 h the results obtained are directly applicable to landslide forecasting based on empirical rainfall thresholds and have implications for landslide hazard and risk assessment as well as for landslide erosion and landscape evolution studies both in the study area and in the neighboring regions

spread f occurrence over a southern anomaly crest location in brazil during june solstice of solar minimum activity 1 we present a study of spread f occurrence over a location under the southern crest of the equatorial ionization anomaly cachoeira paulista 22 7 s 45 0 w mag lat 16 s dip angle 32 3 brazil during the last solar cycle which presented an extended solar minimum activity after analyzing hundreds of ionograms obtained with a digital ionosonde dgs 256 between 2001 and 2010 we verified high spread f occurrence around midnight postmidnight during june solstice southern hemisphere winter with a peak occurrence between 2006 and 2009 when the solar flux has reached very low values 70 sfu at the brazilian sector the occurrence of spread f is known to be associated with equatorial plasma bubbles epbs and is observed mainly between september and march on the other hand epbs are rarely observed over cachoeira paulista hereafter referred as cp during june solstice because of the weak magnitudes of the equatorial electric field prereversal enhancement an essential condition to the development of the large scale irregularities at the equatorial region despite the rarity of epbs we observed several strong spread f events occurring under low plasma densities conditions which can extend for several hours we have found evidences that the spread f events over cp during june solstices of low solar activity can be caused by ionospheric disturbances that are unrelated to equatorial processes finally we present a statistical analysis of the events and we suggest that traveling ionospheric disturbances could be one of the main sources of these nonequatorial spread f events

stability of waste spoils in an area strip mine geological and geotechnical considerations results of investigations into the stability of coal mine spoil consisting of thick clay saturated sand and shale overburden in an areal strip mine are presented atterberg limits particle size distributions and compaction tests were performed to provide index characteristics of the materials unconsolidated undrained and consolidated undrained triaxial compression test results on 10 2 cm diameter samples of compacted shale and shale soil mixtures were used to investigate the short term and the long term conditions respectively of the spoil slope there is evidence that the failure envelope of mine spoil made up of shale or shale soil mixture is curved however stability analyses reveal that the use of strength parameters defined by a linear mohr coulomb envelope yields results that are comparable with those obtained when the non linear failure envelope is used provided that such strength parameters are defined at the operating normal stress level on the failure surface the study illustrates a very good case of spoil instability resulting from very thick overburden soils of low strength and high water content results show that the key to achieving stability in such areas lies in an almost total segregation of the soils from the rocks

geotechnical and geoenvironmental characteristics of man made underground structures in cappadocia turkey underground cities and semi underground settlements most of which are 1500 years at least exist in the cappadocia region of turkey these man made rock structures are carved in soft tuffs and the best examples of long term performance of man made structures in the field of rock engineering the tuffs also have good thermal isolation properties to be used as housing and storage of foods in this article the authors are only concerned with physical and short term mechanical characteristics due to the wide spectrum of the theme and the in situ characterization of the cappadocia tuffs and the results of investigations are presented in addition a critical overview on possible engineering geological problems at cappadocia with mechanical aspects of historical and modern rock structures and their implications in rock engineering is made from the experimental results in the field it is evident that the engineering characteristics of these rocks do not show significant changes in vertical and horizontal directions however they are prone to atmospheric conditions in addition temperature and humidity measurements at different floors of the underground cities and various parts of semi underground settlements indicated that variations in climatic conditions of the openings are very small when compared to those outside the ground surface

de 2 observations of morningside and eveningside plasma density depletions in the equatorial ionosphere the occurrence of equatorial density depletions in the nightside f region ionosphere has been investigated by using observations gathered by the polar orbiting dynamics explorer 2 satellite from august 1981 to february 1983 a variety of electric field plasma drift patterns were observed within these depletions including updrafting downdrafting bifurcating converging subsonic and supersonic flows the depletions 116 events in total are distributed over two groups group i eveningside depletions consists of the events in the 1900 2300 mlt sector and group ii morningside depletions are the events in the 2300 0600 mlt sector a statistical analysis reveals clear differences in the density depletion occurrence rates between the two groups magnetic activity appears to suppress the generation of eveningside depletions with a delay of 2 3 hours in the morningside the probability of observing depletions increases instantly with increasing magnetic activity yet the best correlation is found with a 2 hour delay this indicates that in the premidnight sector the substorm induced dynamo and prompt penetration electric fields induce westward electric fields in the equatorial ionosphere 2 hours after the onset in the auroral region in the postmidnight sector high latitude ionospheric disturbances induce instantly equatorial eastward electric fields that move the f layer to higher altitudes where it can become unstable to the rayleigh taylor instability eveningside depletions were observed at all longitudes except those over the pacific ocean while the morningside depletions occurred mostly over the pacific and atlantic african sectors

subaqueous calderas in the archean abitibi greenstone belt an overview and new ideas abstract the 300 700 km abitibi greenstone belt in canada contains numerous world class archean volcanogenic massive sulfide vms deposits yet documentation of archean subaqueous calderas hosting such deposits is lacking the modern sunrise deposit in the myojin knoll caldera of the izu bonin arc shows that submarine calderas are first order sites for vms the hunter mine and normetal calderas as well as the blake river megacaldera complex are reviewed with respect to geometry regional geology physical volcanology dyke emplacement and hydrothermal carbonate alteration these subaqueous calderas are placed into the geodynamic context of the abitibi greenstone belt the abitibi belt displays a complex history of oceanic arc formation evolution collision and fragmentation with numerous types of volcanic edifices and sedimentary basins controlled by oblique subduction and mantle plumes analogue models yielding new insights into the sequence of caldera forming events and their synvolcanic fault patterns are applied to explain archean examples underpressure experiments develop a consistent sequence of fault patterns that compare favourably with natural caldera events during subsidence two sets of faults propagate from the magma chamber margin 1 early reverse outward dipping faults and 2 normal inward dipping faults the largest massive sulfide deposits form preferentially at the caldera margin based on experimental studies and detailed facies mapping the hunter mine caldera is of the segmented piecemeal variety and the normetal caldera is akin to a piston structure the blake river megacaldera contains 1 the e w trending misema 2 the nw trending new senator and 3 the ne trending noranda calderas with the latter two being nested graben type calderas consistent with oblique archean subduction the poorly documented hydrothermal carbonate alteration is discussed and a new exploration model for calderas is presented the alteration study was evaluated at three levels microprobe analysis geochemical staining of drill core and whole rock analyses there were two principal stages of alteration related to vms formation an early silicification phase developed either at depth and or at the seawater interface whereby silicification was bedding parallel in fine grained volcaniclastic deposits near the water surface a pervasive and extensive semi conformable carbonate alteration zone with a discordant focused root zone along faults evolved subsequently three distinct carbonate pairings were observed 1 proximal siderite sideroplesite fe ankerite next to the vms deposit 2 an intermediate ankerite fe dolomite zone and 3 a distal calcite dolomite zone the carbonate phase is associated with the mineralizing event transitions between carbonate species are subtle and changes are indicated by mineral assemblage overlap the silica carbonate hydrothermal alteration pattern is a replacement product and is far more widespread than has been documented this alteration can be easily confused with primary carbonates and chemical precipitation deposits e g banded iron formation if detailed volcano sedimentary facies mapping with alteration has not been conducted and if outcrop is insufficient

a physically based model for the topographic control on shallow landsliding a model for the topographic influence on shallow landslide initiation is developed by coupling digital terrain data with near surface through flow and slope stability models the hydrologic model topog o loughlin 1986 predicts the degree of soil saturation in response to a steady state rainfall for topographic elements defined by the intersection of contours and flow tube boundaries the slope stability component uses this relative soil saturation to analyze the stability of each topographic element for the case of cohesionless soils of spatially constant thickness and saturated conductivity the steady state rainfall predicted to cause instability in each topographic element provides a measure of the relative potential for shallow landsliding the spatial distribution of critical rainfall values is compared with landslide locations mapped from aerial photographs and in the field for three study basins where high resolution digital elevation data are available tennessee valley in marin county california mettman ridge in the oregon coast range and split creek on the olympic peninsula washington model predictions in each of these areas are consistent with spatial patterns of observed landslide scars although hydrologic complexities not accounted for in the model e g spatial variability of soil properties and bedrock flow control specific sites and timing of debris flow initiation within areas of similar topographic control

coordinated study of coherent radar backscatter and optical airglow depletions in the central pacific 1 equatorial plasma depletions have well known seasonality and solar cycle behavior except for a few well instrumented sectors much of these data have come from satellite sounding and in situ observations we present a climatology of optical airglow images and 50 mhz coherent backscatter from the pacific sector from solar maximum january 2002 to solar minimum january 2009 in contrast to in situ observations we find that depletion activity remains quite high into solar minimum however the depletions and associated backscatter appear later in the evening and backscatter persists longer at solar minimum furthermore we present individual nights that illustrate the day to day variability of depletion formation and their relationship to coherent backscatter echoes the echoes originate from the depleted regions early in the evening but disappear as the night progresses

engineering geological characterization of coal mine waste material and an evaluation in the context of back analysis of spoil pile instabilities in a strip mine sw turkey abstract coal mine waste material which usually consists of a mixture of coarse grained particles to rock fragments grading to fine grained particles causes geotechnical and environmental problems on disposal a study of the geotechnical aspects of the problem is therefore important in rational planning for the disposal reclamation treatment and use of such material spoil pile instability has been a continuing problem in the eskihisar strip coal mine of southwestern turkey particularly shallow seated circular failures appearing along the haul road and instabilities covering large agricultural areas outside the dumping yard increase the importance of spoil pile stability the fact that the height of spoil piles dumped by trucks on both sides of the haul road will increase much more in the future has focused the attention of the miners to this problem this study outlines the geotechnical characteristics of waste material from the tertiary coal bearing rocks derived from field and laboratory investigations and describes the causes and mechanism of spoil instabilities which threaten the safety of the haul road and the agricultural areas in the vicinity of the pit gradation results suggest that fines and coarser material were approximately equally represented in the spoil the percentage of fines is indicative of material degradation as evidenced by slaking tests site observations and numerous back analysis of investigated failures reveal that the failures do not penetrate the foundation material and only occur along circular surfaces through the spoil material it is also noted that surface water infiltration reducing the effective shear strength of the spoil material contributes to failures shear test results indicate that the spoil is a nearly cohesionless material with a residual internal friction angle of about 33 which confirms the values derived from standard penetration tests it is also noted from back analyses that the spoil material exhibits a shear strength at or approaching the residual value at the time of failure the use of shear strength parameters defined by the linear mohr coulomb envelope yields results that are comparable with those obtained when the non linear failure envelope is used provided that such strength parameters were defined at the operating normal stress levels on the failure surfaces

modelling of the initiation of rainfall induced debris flows in the cardoso basin apuan alps italy abstract a case study is being carried out in relation to the event of june 19 1996 when an intense rainstorm hit the cardoso area in the apuan alps italy the catastrophe triggered several gravitational movements mainly characterized by soil slip debris flows a dataset coming from field and laboratory surveys allowed a complete parameterization of the event and consequently the realization of a physically based dynamic model related to the initiation of the rainfall induced landslides the aim of the study is to analyze the processes involved in the light of the modelling results and to assess the spatio temporal activity of the landslides both in terms of location of the triggering sites and of determination of the critical rainfall conditions the critical rainfall input thresholds obtained with a deterministic approach are then compared with the thresholds obtained by an empirical analysis of the main rainfall events occurred in the southern apuan area in the period from 1975 to 2002

effective parameters for the particle breakage of calcareous sands an experimental study abstract calcareous sediments have different behavior under monotonic and cyclic loadings compared to that of terrigenous soils particle breakage is considered the most important feature of calcareous soils and has been used in many experimental investigations recently this phenomenon affects some characteristics of carbonate sediments such as compressibility shearing strength and permeability in this study experiments were conducted to evaluate the parameters that affect the particle breakage of calcareous sands including confining pressure relative density axial strain drainage conditions and grain size distribution the input energy per unit volume of the soil was also calculated to analyze the effect of this parameter on the particle breakage in the testing program two calcareous sands from different locations in the persian gulf namely bushehr port bp and hormuz island hi sands were used for the triaxial compression tests the experimental results showed that the input energy played an important role in the particle breakage behavior of used soils in comparison to other parameters considered in this study axial strain as a representation of the effect of deviatoric loading had major influences on the amount of crushing the results also indicated that hi sand particles yielded at a higher stress than bp sand

reply to comments by s yagiz on determination of strength parameters and quality assessment of denizli travertines sw turkey by ibrahim cobanoglu and sefer beran celik engineering geology 129 130 2012 38 47

geomagnetic conjugate observations of equatorial airglow depletions 1 we report for the first time large scale equatorial f region airglow depletions extending to low midlatitudes in both hemispheres the observational sites were located at low midlatitude geomagnetic conjugate points clear depletions of 630 0 nm airglow intensity due to equatorial plasma bubbles were simultaneously observed with two all sky imagers at sata japan magnetic latitude 24 n and its geomagnetic conjugate point darwin australia magnetic latitude 22 s on the night of november 12 2001 airglow depletion regions with east west scale sizes of 40 100 km extend poleward the maximum apex altitude of the plasma bubbles is about 1 700 km over the geomagnetic equator the depletions move eastward at about 100 m s without changing their structures the darwin depletion structures mapped onto the northern hemisphere along the geomagnetic field coincide closely with structures in the sata images even for the 40 km structure these observations indicate that plasma depletions in the equatorial ionosphere elongate along the geomagnetic field lines

stratigraphy of eastern bay of exploits newfoundland fossils from the fanners island formation new name show that southwest of new world island newfoundland a thick over 3 km sequence of late llandeilo turbidites and basalts overlies the dunna

the influence of the geological and geomorphological settings on shallow landslides an example in a temperate climate environment the june 19 1996 event in northwestern tuscany italy on june 19 1996 an extremely heavy rainstorm hit a restricted area in the apuan alps northwestern tuscany italy its max intensity concentrated over an area of about 150 km2 astride the apuan chain where 474 mm was recorded in about 12 h 21 of the mean annual precipitation with an intensity up to 158 mm h the storm caused floods and hundreds of landslides and debris flows which produced huge damage hundreds of millions of euros partially destroyed villages and killed 14 people this paper reports the results obtained from a detailed field survey and aerial view interpretation in the most severely involved area 647 main landslides were investigated mapped and related to the geologic geomorphic and vegetational factors of the source areas this was in order to define the influence of these factors and contribute to an evaluation of the landslide hazard in the study area an assessment was also made of the total area and volume of material mobilised by landsliding the study area about 46 km2 wide includes three typically mountainous basins characterised by narrow deep cut valleys and steep slopes where many rock types outcrop most of the landslides were shallow and linear referable to complex earth and debris translational slide which quickly developed into flow soil slip debris flow usually they involved colluvium and started in hollows underlain by metamorphic rock metasandstone and phyllite often dipping downslope therefore bedrock lithology and impermeability appeared to be important factors in the localisation of the landslide phenomena the investigation of the geomorphic and land use features in the source areas also frequently highlighted a rectilinear profile of the slope a high slope gradient 31 45 and dense chestnut wood cover in the area about 985 000 m2 2 1 of 46 km2 was affected by landsliding and about 700 000 m2 of this area was covered by chestnut forest the landslides removed about 7000 trees the volume of mobilised material was about 1 360 000 m3 about 220 000 m3 remained on the slopes while the rest poured into the streams in addition about 945 000 m3 was mobilised by the torrential erosion in the riverbeds

coordinated observations of postmidnight irregularities and thermospheric neutral winds and temperatures at low latitudes we investigated a post midnight field aligned irregularity fai event observed with the equatorial atmosphere radar at kototabang 0 2 s 100 3 e dip lat 10 4 s in indonesia on the night of 9 july 2010 using a comprehensive dataset of both neutral and plasma parameters we examined the rate of total electron content change index roti obtained from gps receivers in southeast asia airglow images detected by an all sky imager and thermospheric neutral winds and temperatures obtained by a fabry perot interferometer at kototabang altitudes of the f layer h f observed by ionosondes at kototabang chiang mai and chumphon were also surveyed we found that the post midnight fais occurred within plasma bubbles and coincided with kilometer scale plasma density irregularities we also observed an enhancement of the magnetically equatorward thermospheric neutral wind at the same time as the increase of h f at low latitude stations but h f at a station near the magnetic equator remained invariant simultaneously a magnetically equatorward gradient of thermospheric temperature was identified at kototabang the convergence of equatorward neutral winds from the northern and southern hemispheres could be associated with a midnight temperature maximum occurring around the magnetic equator equatorward neutral winds can uplift the f layer at low latitudes and increase the growth rate of rayleigh taylor instabilities causing more rapid extension of plasma bubbles the equatorward winds in both hemispheres also intensify the eastward pedersen current so a large polarization electric field generated in the plasma bubble might play an important role in the generation of post midnight fais

the determination of statistical and deterministic hydrological landslide triggering thresholds hydrological landslide triggering thresholds separate combinations of daily and antecedent rainfall or of rainfall intensity and duration that triggered landslides from those that failed to trigger landslides they are required for the development of landslide early warning systems when a large data set on rainfall and landslide occurrence is available hydrological triggering thresholds are determined in a statistical way when the data on landslide occurrence is limited deterministic models have to be used for shallow landslides directly triggered by percolating rainfall triggering thresholds can be established by means of one dimensional hydrological models linked to the infinite slope model in the case of relatively deep landslides located in topographic hollows and triggered by a slow accumulation of water at the soil bedrock contact simple correlations between landslide occurrence and rainfall can no longer be established therefore real time failure probabilities have to be determined using hydrological catchment models in combination with the infinite slope model

palaeozoic arc growth deformation and migration across the lachlan fold belt southeastern australia abstract the palaeozoic lachlan fold belt lfb is a low pressure metamorphic belt characterized by greenschist facies rocks and infolded volcanic sequences which indicate that the belt has not undergone substantial uplift at any stage porphyroblast matrix relationships in one of the highest grade metamorphic zones of the lfb the omeo complex indicate that the thermal peak was reached before or was synchronous with the earliest deformation similar to that in high grade metamorphic zones of the northern arunta inlier central australia in both areas the metamorphism is of low p high t type centred on major granite intrusions as regional aureoles and characterized by anti clockwise p t t paths however in the outer lower grade parts of the aureoles peak metamorphic conditions post date the earliest deformation this diachronous relationship indicates that 1 outward migration of a thermal front was centred on major granitoid intrusions batholiths 2 deformation propagated outward more rapidly than migration of the thermal front and 3 plastic and ductile deformation began only after heating around the batholiths thus orogeny was initiated after and localized by heat focusing in the mid crust associated with batholith emplacement therefore the early deformation is a result of thermal softening it is typically subhorizontal ductile shear at mid crustal levels but is characterized by upright to inclined folds at upper crustal levels in the latter environment the typically discordant contact aureole plutons are often interpreted as post tectonic granitoids but they were part of the ongoing mid crustal thermal perturbation that induced regional greenschist facies metamorphism which overprinted the early formed upright folds as it migrated to upper crustal levels orogeny migrated generally eastward through the lfb it began with the early silurian benambran orogeny centred on the wagga metamorphic belt wmb and terminated with the carboniferous kanimblan orogeny which was most intense in the hill end trough eastward migration of orogeny across central victoria part of the west lfb began in the ballarat bendigo zone during the early devonian and terminated in the melbourne zone in the middle devonian orogeny was centred on the meridional batholiths of the lfb each of which are considered to represent the transitory axis of an ancient magmatic arc stepwise but generally eastward arc migration caused the eastward migration of orogeny a tectonic model based on the modern southwest pacific arc system can be applied to the lfb following cambrian intra oceanic arc growth associated with west dipping subduction an ordovician marginal sea developed partly on stretched cambrian crust and was flooded by an extensive turbiditic wedge closure of the eastern part the east lfb began in the early silurian after a magmatic arc developed over the wmb possibly associated with an east dipping subduction zone after re establishment of west dipping subduction in the middle silurian absolute motion retreat of the upper australian plate caused by oblique plate convergence resulted in dextral transtension and the generation of siluro devonian inter arc and back arc basins transient compression resulted in deformation along the magmatic arc and induced formation of a new outboard eastward arc system periodic compression within the evolving arc and back arc system resulted in a series of east younging east verging linear siluro devonian fold and thrust belts which were localized adjacent to elongate batholiths that represent the relict arc systems local westward jumps in deformation and plutonism occurred the most significant is the 600 km westward jump into the west lfb caused by closure of the remainder of the passive ordovician back arc basin melbourne and bendigo ballarat zones west dipping subduction beneath the basin produced a low pressure fold thrust belt similar to the east lfb though the granitoids have a more primitive isotopic character indicating closure of thin dominantly oceanic crust in the early to middle devonian localized deformation induced by thermal softening of the crust within magmatic arcs that have developed on earlier passive margins is likely to produce anticlockwise p 7 t paths and may be a typical feature of southwest pacific style tectonism

a distributed slope stability model for steep forested basins a distributed physically based slope stability model dslam based on an infinite slope model a kinematic wave groundwater model and a continuous change vegetation root strength model is presented it is integrated with a contour line based topographic analysis and a geographic information system gis for spatial data extraction and display the model can be run with either individual rainfall events or long term sequences of storms these inputs can be either actual storm records or synthesized random events based on monte carlo simulation the model is designed to analyze rapid shallow landslides and the spatial distribution of safety factor fs in steep forested areas it can investigate the slope stability problem in both temporal and spatial dimensions for example the impact of timber harvesting on slope stability either at a given time or through an extended management period the probability of landslide occurrence for a given year and the delivery of landslide sediments to headwater streams the dslam model was applied in a steep forested drainage of cedar creek in the oregon coast ranges using actual spatial patterns of timber harvesting and measured rainfall during a major storm which triggered widespread landslides in that area in 1975 simulated volume and number of failures were 733 m3 and 4 respectively these values agreed closely with field measurements following the 1975 storm however the effect of parameter uncertainty may complicate this comparison for example when soil cohesion values of 2 0 and 3 0 kpa were used the failure volume changed by factors of 2 04 and 0 41 respectively compared with the average condition of 2 5 kpa used in the simulation for soil depths 30 higher and lower than the standard condition the failure volume changed by factors of 2 0 and 0 27 respectively when maximum root cohesion changed from 12 5 kpa average condition to 10 kpa the failure volume increased 1 73 fold for the case of 15 kpa the failure volume changed by a factor of 0 55 the simulated failures caused by the storm were mostly in hollows the simulations show that the spatial distribution of fs is controlled mainly by topography and timber harvesting patterns and is greatly affected by groundwater flow patterns during major rainstorms most areas with fs 3 0 corresponded with the distribution of blocks clear cut in 1968 and all elements with fs 2 0 were in areas clear cut in 1968 areas with low fs 1 0 1 6 expanded dramatically during the rainstorm and decreased at a slow rate after the storm factors of safety in hollows declined sharply during the storm

new approaches to the characterization of clay bearing densely jointed and weak rock masses various classification systems for rock masses have been used in engineering applications however these systems are not sufficient to classify clay bearing densely jointed and weak rock masses among the factors that cause this deficiency are the damaging effect of water on rocks which has not sufficiently been described in the existing classification systems this factor was allowed for by the inclusion of new parameters in the modified rock mass classification m rmr system developed in recent years the aim of this study is to make contributions to the m rmr classification system and to overcome the difficulties encountered in the classification procedure for this purpose data were collected for rock mass classification from 13 clay bearing densely jointed and weak rock masses in four regions yatagan soma baskoyak and guvenc located in the western and middle parts of turkey the discontinuity data were collected by the line survey technique and evaluated by statistical methods in addition to the uniaxial compressive strength test for the determination of the rating for intact rock strength the block punch index test was also considered as an alternative parameter and the slake durability index test and x ray diffraction analyses were performed on 104 samples collected from the studied rock masses further the weathering coefficient wc determined by schmidt hammer was considered as an alternative parameter for the determination of the rating for joint weathering as a result of statistical evaluation of data obtained from the field and laboratory studies it has been concluded that the block punch index bpi could be used as an alternative parameter for the determination of the rating for intact rock strength in the m rmr classification system it was also found that the slake durability index id determined at the fourth cycle would be a more effective approach than the second cycle index that has previously been used to express the unfavourable effect of water on the rock mass the propositions made in the present work to contribute to the m rmr system were tested in back analyses of three previously failed slopes and the performance of the system with the newly introduced improvements appeared to be satisfactory

geotechnical characterization of mining rock waste dumps in central evia greece open pit mining using drill and blast has been taking place in central evia greece for many decades this is so due to the presence of ferronickel ores in the area as a consequence of the mining activity large volumes of overburden upper cretaceous limestone are being annually extracted and deposited at predefined sites creating rock waste dumps or embankments in the context of optimum land surface use and better stability conditions a geotechnical characterization of these waste dumps has taken place and is presented in the current paper first image analyses are performed on fragmented limestone muckpiles and the degree and intensity of rock fragmentation due to blasting is assessed results compare reasonably well with computations based on the kuz ram empirical model for fragmentation analysis overall muckpiles on excavation faces consist of boulders and cobbles by 80 90 per weight following a laboratory investigation program is executed on samples retrieved from the waste dumps based on the results the dumps consist of heavily coarse grain material mostly classified as gc according to modified proctor tests and in situ density tests using the troxler device compaction on the crest of the dumps is characterized as very high while permeability is empirically considered as medium to high as far as the friction angle of the waste dump material is concerned this is estimated based on observations i e recorded inclinations of existing dumps combined with an empirical model from the literature generally it is considered that the friction angle varies considerably with the overburden pressure within the dump s body nonetheless if a single value approach is necessary for simplicity purposes and stability considerations then a friction angle of about 40 characteristic value is suggested as a reasonable assumption

the opening of the woodlark basin subduction of the woodlark spreading system and the evolution of northern melanesia since mid pliocene time abstract magnetic anomaly and seismological data define segments of active seafloor spreading and associated magnetic lineations trending ene in the woodlark basin the total opening rate has been approximately 6 cm yr for the last 1 m y spreading rates diminish by over 10 from east to west along the woodlark spreading system implying a pole of current opening 15 20 to the west commencement of seafloor spreading in the basin has apparently been time transgressive beginning prior to 3 5 m y in the east and at successively later times to the west earthquake focal mechanisms and geological evidence suggest that the land areas bounding the western end of the woodlark basin are undergoing tensional deformation we believe that eventually the woodlark basin plate boundary will propagate westward through the d entrecasteaux islands into the papuan peninsula hitherto unreported shallow seismicity associated with the northern margin of the ne trending section of the woodlark rise probably reflects partial decoupling of the woodlark and solomon basins possibly due to mechanical difficulties in subducting the young woodlark lithosphere analysis of the relative motions between the solomon indo australian and pacific plates shows that the woodlark spreading system has been subducted at high rates 10 cm yr beneath the solomon islands during the opening of the woodlark basin several tectonic and geological features limited to the region of interaction of the woodlark basin with the solomon trench and arc may be symptomatic of ridge subduction these features include high heat flow in the solomon trench which shoals to 4 km low levels of seismicity and only shallow hypocenters and voluminous eruptions of high k 2 o tio 2 olivine basalts and basaltic andesites extremely close to the trench axis this close association in space and time of an unusual volcanic suite with ridge subduction implies a strong dependence of the petrogenesis on the tectonic regime a combination of this study of the woodlark basin and the previous study of the bismarck basin taylor 1979 provides a reconstruction of the positions of the continents ocean basins and island chains in northern melanesia for mid pliocene time in accepting the existence of a solomon plate we can explain the trench like structure off the trobriand margin of new guinea the occurrence of late cenozoic calc alkaline volcanism along the papuan peninsula and the presence of intermediate depth seismicity beneath the north papuan peninsula the rapid changes in relative motions along or across the new ireland solomons chain over the past 3 5 m y may explain the spatial and temporal changes in igneous activity observed on these islands

data compilation from large drained compression triaxial tests on coarse crushable rockfill materials abstractinvestigating the mechanical properties of rockfills requires laborious time consuming and expensive large scale testing therefore practitioners frequently adopt design parameters based

geotechnical characterization of lignite bearing horizons in the afsin elbistan lignite basin se turkey abstract the afsin elbistan lignite deposit with its 3 4 billion metric tons of reserves is the biggest lignite basin and one of the most important resources for electrical energy production in turkey kislakoy mining field was selected as the first opencast mine to feed four power station blocks of 300 mw each slope instability has been a continuing problem in the kislakoy opencast mine particularly complex failures along a noncircular failure surface appearing at the final slope stage and covering large areas in the mine increase the importance of slope stability this study outlines the geotechnical characteristics of the lignite bearing horizons and describes the causes and mechanisms of slope instabilities which threaten the safety of the mine quantitative x ray diffraction xrd analyses were carried out using an interactive data processing system siroquant based on rietveld interpretation methods parametric slope stability analysis and backanalysis were carried out for the failure that occurred at the northwestern final slope stage of the mine the spencer wright limiting state equilibrium method was used in order to determine with confidence the most representative values of regional shear strength parameters to explain the failure mechanism and to assess the conditions at the time of failure in the analysis phreatic and piezometric surfaces were considered site observations and numerous backanalyses of the slope failure reveal that a compound slide occurred where gyttja contact zone layers rest directly on the lignite gyttja contact zone contains the weakest material within the system the analysis showed that the main cause of the northwestern slope instability was the presence of the groundwater flow within a quaternary aquifer through buried valleys reducing the effective shear strength of the slope materials it is also noted from backanalysis that the gyttja contact zone layer presents a shear strength at or approaching the residual value at the time of failure

observations of f layer electron density profiles modulated by planetary wave type oscillations in the equatorial ionospheric anomaly region 1 a digital ionosonde of the type known as the canadian advanced digital ionosonde cadi is operational at sao jose dos campos 23 2 s 45 9 w brazil this ionospheric sounding station is located under the southern crest of the ionospheric equatorial anomaly the f layer electron density profile presents considerable day to day variability even during undisturbed conditions and this variability is still one of the less understood aspects of the physics of the ionosphere the propagation of waves into the ionosphere may play an important role in this day to day ionospheric variability in this paper we present a new technique that uses multifrequency virtual height variations from ionospheric sounding observations at this low latitude station to investigate how the f layer is modulated by planetary wave type oscillations we have also considered the possible influence of oscillations due to solar origin solar rotation variation in the present study observations during the months of june to september 2003 season of low range type equatorial spread f occurrence at this location have been used the present study indicates the presence of 2 day the observed 3 day periods are possibly associated with the quasi 2 day oscillations 5 day 10 day and 16 day periods related to planetary wave type oscillations due to tropospheric sources during all the day also it appears that during the day and dusk times the longer periods 24 30 days are related to solar rotation 27 days whereas the shorter periods 9 17 days have possibly some influence from half solar rotation 13 5 days during the nighttime possibly the short period oscillations 3 9 days may have some influence from the geomagnetic disturbances

calibration and validation of rainfall thresholds for shallow landslide forecasting in sicily southern italy abstract empirical rainfall thresholds are tools to forecast the possible occurrence of rainfall induced shallow landslides accurate prediction of landslide occurrence requires reliable thresholds which need to be properly validated before their use in operational warning systems we exploited a catalogue of 200 rainfall conditions that have resulted in at least 223 shallow landslides in sicily southern italy in the 11 year period 2002 2011 to determine regional event duration cumulated event rainfall ed thresholds for shallow landslide occurrence we computed ed thresholds for different exceedance probability levels and determined the uncertainty associated to the thresholds using a consolidated bootstrap nonparametric technique we further determined subregional thresholds and we studied the role of lithology and seasonal periods in the initiation of shallow landslides in sicily next we validated the regional rainfall thresholds using 29 rainfall conditions that have resulted in 42 shallow landslides in sicily in 2012 we based the validation on contingency tables skill scores and a receiver operating characteristic roc analysis for thresholds at different exceedance probability levels from 1 to 50 validation of rainfall thresholds is hampered by lack of information on landslide occurrence therefore we considered the effects of variations in the contingencies and the skill scores caused by lack of information based on the results obtained we propose a general methodology for the objective identification of a threshold that provides an optimal balance between maximization of correct predictions and minimization of incorrect predictions including missed and false alarms we expect that the methodology will increase the reliability of rainfall thresholds fostering the operational use of validated rainfall thresholds in operational early warning system for regional shallow landslide forecasting

development of new zealand according to the fore arc model of crustal evolution abstract analysis of new zealand geology using a fore arc model crook 1980a leads to the recognition of four arc terrains the west facing tuhua volcanic arc was active from the late proterozoic until the middle or late cambrian post subduction sediments neritic in the east and flysch in the west accumulated on the tuhua accretionary prism from the late cambrian until the early devonian thermal equilibration metamorphism granitoid plutonism and penetrative deformation occurred in the middle to late devonian a small area of permian platform cover has escaped later erosion the east facing rangitata terrain records subduction from early permian to late early cretaceous much of its accretionary prism consists of a submarine fan complex derived from western antarctica and carried sideways into the trench the accretionary prism is thick and completely kratonized in southern new zealand but the thickness is more variable northwards there the overlying upper cretaceous to upper oligocene post subduction sequence comprises shelf sediments implying an intermediate thickness prism or flysch followed by shelf sediments implying a thin prism during the accumulation of this sequence the rangitata terrain was a passive continental margin the south facing jurassic late oligocene northland terrain collided with this passive margin in northern new zealand at the end of the oligocene forming the northland allochthon subduction then flipped and the oldest part of the kaikoura terrain volcanic arc formed on the outer part of the northland terrain originally this terrain faced northeast and consumed the southwestern part of the south fiji basin crust but during the miocene the arc migrated clockwise to assume its present northeastern orientation the fore arc model employed here satisfactorily explains most first order and many second order features of new zealand geology without requiring modification thus attesting to the model s versatility and robustness new zealand provides a basis for elaborating some aspects of the model particularly the transition from the syn to post subduction phases of fore arc evolution combination of this study with a similar study of the southeastern australian paleozoic yields insights into the phanerozoic evolution of the australian pacific plates active margin

observations and modeling of the coupled latitude altitude patterns of equatorial plasma depletions 1 the equatorial ionosphere is host to the most dramatic and enigmatic plasma instability mechanism in the geospace environment equatorial spread f esf was discovered in early ionosonde measurements and interpreted theoretically using rayleigh taylor theory subsequent diagnostic and modeling advances have improved substantially our understanding of esf onset and evolution and its associated effects on the ionosphere throughout the low latitude domain the degree to which esf mechanisms penetrate into the lower midlatitudes is a topic of current study a reverse of the familiar concept of high to low latitude coupling for space weather phenomena optical diagnostic systems first ground based and now space based reveal the presence of esf structures via images of airglow depletions that are aligned in the approximately north south direction spanning the geomagnetic equator ground based all sky camera systems used to capture the two dimensional horizontal patterns of airglow depletions are the main source of observations showing that esf processes intrude to midlatitudes in the l 1 5 domain in this paper we review the process of mapping airglow depletions along geomagnetic field lines to the equatorial plane hence defining the maximum apex heights achieved a case study comparison of simultaneous radar backscatter data from kwajalein with optical data from wake island sites that share common magnetic meridians in the pacific section confirms the utility of the approach and its applicability to sites at other longitudes modeling studies based on buoyancy arguments using flux tube integrated mean density values versus l shell apex heights show that instability induced plasma depletions starting at f layer bottomside heights easily reach altitudes above 2000 km in the equatorial plane implying that esf intrusions to lower midlatitudes should be a relatively frequent occurrence

an effective antecedent precipitation model derived from the power law relationship between landslide occurrence and rainfall level abstract antecedent rainfall is an important predisposing factor in triggering landslides because it reduces soil suction and increases the pore water pressure in soils the existing approaches to quantify the antecedent rainfall were derived from empirical methods used to develop rainfall runoff models in which the daily decays of rainfall within a given period preceding a given day are considered as independent processes in this study a methodology accounting for the effective antecedent rainfall that influences landslide occurrence is developed from a power law relationship between the frequency of landslide occurrence and the landslide triggering rainfall level in this model the decay rate of the daily rainfall is related to a scaling exponent defined by the power law relationship the decay process of daily rainfall within a given period preceding a given day is not independent but is interrelated and the impact of rainfall in the preceding k days on soil moisture is associated with the precipitation from the preceding k 1 days

magnetic anomalies and tectonic fabric of marginal basins north of new zealand detailed airborne magnetic studies conducted over the region of the s w pacific marginal basins extending from the solomon islands to new zealand suggest that three major phases of basin formation and island arc development have occurred in this region development of the tasman sea took place during the late cretaceous paleocene development of the basins to the east of the tasman sea occurred predominantly during the oligocene as well as during the upper miocene to recent the south fiji basin consisting of the kupe and minerva abyssal plains is marked by the presence of possibly two rrr triple junction spreading centers that were active between the times of anomalies 13 to 7 36 25 5 m y the kupe abyssal plain shows the presence of residual magnetic anomalies 7 to 13 of the eastern limb of the proposed spreading center the western limb appears to have been subducted beneath the present site of the three kings rise this seafloor spreading phase calculated half spreading rate of 35 mm yr was coincident with the overthrusting phase of the new caledonia ultramafic rocks during that period active volcanism along the then continuous solomons new hebrides fiji lau island arc was taking place magnetic anomalies from 1 to 4 0 8 m y b p are seen to extend along a clearly defined lineation pattern over the north fiji basin analysis of the magnetic anomalies suggests that during the upper miocene at about the time of magnetic anomaly 4 8 m y the solomons lau island arc commenced breaking up through the development of an active spreading center calculated half spreading rate of 35 mm yr located between the new hebrides and fiji portions of the island arc portions of the northeastern sector of the minerva abyssal plain were subducted beneath the north fiji basin during this period between 0 8 m y b p at the time of about anomaly 3 to 2 4 5 3 5 m y the development of the north fiji basin extended into the lau basin and havre trough thus separating the tonga and lau ridges as a result a distinct series of active spreading centers developed southward along the axis of the havre trough lau basin the havre trough is marked by present seismic and submarine volcanic activity residual magnetic anomalies 1 2 0 1 8 m y b p form a symmetrical pattern around the axis of the trough extending south from the lau basin to the active taupo white island volcanic zone of new zealand phases of development of the marginal basins described in this paper may be correlated with phases of changes in the direction and rate of pacific plate motion

global distribution of density irregularities in the equatorial ionosphere we analyzed measurements of ion number density made by the retarding potential analyzer aboard the atmosphere explorer e ae e satellite which was in an approximately circular orbit at an altitude near 300 km in 1977 and later at an altitude near 400 km large scale 60 km density measurements in the high altitude regions show large depletions of bubble like structures which are confined to narrow local time longitude and magnetic latitude ranges while those in the low altitude regions show relatively small depletions which are broadly distributed in space for this reason we considered the altitude regions below 300 km and above 350 km and investigated the global distribution of irregularities using the rms deviation n n over a path length of 18 km as an indicator of overall irregularity intensity seasonal variations of irregularity occurrence probability are significant in the pacific regions while the occurrence probability is always high in the atlantic african regions and is always low in the indian regions we find that the high occurrence probability in the pacific regions is associated with isolated bubble structures while that near 0 longitude is produced by large depletions with bubble structures which are superimposed on a large scale wave like background considerations of longitude variations due to seeding mechanisms and due to f region winds and drifts are necessary to adequately explain the observations at low and high altitudes seeding effects are most obvious near 0 longitude while the most easily observed effect of the f region is the suppression of irregularity growth by interhemispheric neutral winds

the highland border rocks and their relation to marginal basin development in the scottish caledonides it has long been known that the highland border includes an assemblage of altered serpentinites gabbros spilitic lavas ferruginous and manganiferous cherts black phyllites quartzose clastics and amphibolites new work confirms that many of these rocks represent a dismembered tectonically emplaced ophiolite of caledonian age which originated in a narrow oceanic basin within or bordering the dalradian sedimentary pile the ophiolitic rocks were expelled from the basin as thrust sheets transecting d1 structures studies in the sw highlands suggest emplacement during d2 synchronous with se translation of the tay nappe this implies that the ophiolite originated in the n the highland border rocks are seen as marginal to a long lived northward dipping subduction zone within the southern uplands the evolution of the ballantrae ophiolitic complex the midland valley and the dalradian sedimentary basin are considered within this framework

le terrane de slide mountain cordilleres canadiennes une lithosphere oceanique marquee par des points chauds the slide mountain terrane consists of devonian to permian siliceous and detrital sediments in which are interbedded basalts and dolerites locally ultramafic cumulates intrude these sediments the slide mountain terrane is considered to represent a back arc basin related to the quesnellia paleozoic arc terrane however the slide mountain mafic volcanic rocks exposed in central british colombia do not exhibit features of back arc basin basalts babb but those of mid oceanic ridge morb and oceanic island oib basalts the n morb type volcanic rocks are characterized by light rare earth element lree depleted patterns la nb ratios ranging between 1 and 2 moreover their nd and pb isotopic compositions suggest that they derived from a depleted mantle source the within plate basalts differ from those of morb affinity by lree enriched patterns higher tio2 nb ta and th abundances lower end values and correlatively higher isotopic pb ratios the nd and pb isotopic compositions of the ultramafic c

longitudinal variability of annual changes in activity of equatorial spread f and plasma bubbles global distribution maps of equatorial spread f esf activity for various annual periods were derived from the topside soundings by the ionosphere sounding satellite b iss b in 1978 1980 the esf activity during the northern winter period reveals maximum enhancement at the atlantic longitudes of large westward geomagnetic declination and during the northern summer at the pacific longitudes of large eastward declination on several orbits passing over the region of the esf activity enhancement abrupt depletions of the electron density or equatorial plasma bubbles were observed at the satellite altitude of about 1100 km it has also been found that the background electron density distributions tend to be symmetric with respect to the magnetic equator in the region of the enhanced esf activity and asymmetric in the region of the suppressed esf activity these observations are taken account of by the influence of a transequatorial thermospheric wind upon the suppression of the rayleigh taylor type plasma instability

paleogeographic and paleotectonic evolution of a basement controlled archean supracrustal sequence chibougamau caopatina quebec the 7 14 km thick archean volcano sedimentary sequence in the chibougamau caopatina region ccr composed of two mafic to felsic cycles and two thick essentially epiclastic successions is divided into a southern caopatina segment scs and northern chibougamau segment ncs the sedimentary units which evolved after cycle 1 volcanic rocks in the scs and after the combined cycles 1 and 2 in the ncs document a diachronous sedimentary basin evolution this criterion has been employed to distinguish an early evolutionary stage in the south and a late evolutionary stage in the north in each segment the basin episode represents a unique extensional event volcanism preceded the major sedimentary rifting event in both segments composition of sediments and sedimentary facies correlated with the interpreted basin margin faults support the interpretation of two phases of crustal extension volcanic construction and sill intrusion were the prevalent factors governing emergence of volcanic islands in the cc

airglow characteristics of equatorial plasma depletions a new low light level all sky 6300 a airglow imaging system has been developed for ground based studies of the optical signatures of equatorial plasma depletions the system was designed for narrowband interference filters 6 a full width at half power with interchangeable all sky 180 and narrow field 60 lenses and records images photographically by using a standard 35 mm camera a field test of the apparatus was conducted on ascension island 8 0 s 14 4 w from january 24 to february 10 1981 the photographs were analyzed for broad morphological characteristics by using simple overlay techniques augmented by digital image processing methods to extract more quantitative detail the initial results to come from these observations show that airglow depletions occur most often during the 2030 2330 lt period often covering one fourth of the visible sky they extend from the magnetic equator to beyond the crest of the equatorial anomaly with east west cross sections of 100 km to several hundred kilometers they are usually not aligned with magnetic meridians showing a progressive skewness to the west at further distances from the equator several cases of apparently twisting overlapping and bifurcating depletions were observed the depletions drifted to the east with speeds that decreased from 190 m s at 2100 lt to 80 m s at 0100 lt the airglow intensities within depletions were typically 40 50 of the background levels and the western walls of the depletions usually had a steeper gradient than the corresponding eastern walls

orogenesis without collision stabilizing the terra australis accretionary orogen eastern australia the neoproterozoic to end paleozoic terra australis orogen extended along the gondwana margin of the paleo pacific ocean and it now provides a detailed record of orogenic activity and continental stabilization within an ongoing convergent accretionary plate margin new geochronological data from end paleozoic plutonic and volcanic rocks associated with the gondwanide orogeny in the new england region of eastern australia integrated with information on the nature and timing of associated sedimentation deformation and metamorphism allow resolution of a high fidelity record of orogenesis at the end of the carboniferous around 305 ma convergent margin magmatism which had been active along the western margin of the new england region terminated and was followed by a short pulse of regional compressional deformation and metamorphism marking the commencement of the tablelands phase of gondwanide orogenesis deformation was almost immediately followed by the onset of clastic sedimentation and local calc alkaline volcanism dated at 293 ma in the extensional barnard basin emplacement of the two new england s type granitic suites the bundarra and the hillgrove suites along with localized high temperature low pressure metamorphism was essentially contemporaneous ranging in age from 296 to 288 ma and overlapped in time with i type magmatism and the switch from regional compression to extension and barnard basin rifting the hunter bowen phase of the gondwanide orogeny commenced with contractional deformation resulting in termination of sedimentation in the barnard basin and regional deformation and metamorphism across new england and into the sydney and gunnedah basins to the west at around 265 260 ma contractional loading of the sydney and gunnedah basins resulted in their conversion from extensional to foreland basins which received ongoing pulses of sediment from the new england orogenic welt until 230 ma the hunter bowen phase was associated with widespread i type plutonism and volcanic activity in new england that ceased around 230 ma marking the termination of gondwanide orogenesis orogenesis occurred in an evolving convergent plate margin setting s and i type magmatic activity ranging in age from ca 300 to 230 ma represents a stepping out of arc magmatism from the western margin of new england prior to 305 ma into the preexisting arc trench gap there is no evidence that deformation was related to the collision of the convergent margin with a major lithospheric mass and the widespread development of extensional basins in the eastern third of australia in the early permian indicates control by phenomena acting on a continental scale probably changing plate kinematics associated with the amalgamation of pangea

an investigation of landslide problems in spoil piles in a strip coal mining area west virginia u s a abstract spoil piles in coal mine areas in north central west virginia suffer from numerous landslide problems an investigation to determine the causes of these slides showed that the stratigraphic composition the nature of the foundation soils the seasonal high water table and the mining technique contributed to the instability the presence of red shales is identified as a key problem several models of failure were investigated based on inclinometer data these data suggest that multiple failure surfaces may develop in spoil piles in such cases the initial failure surface is better defined than other movement surfaces which either represent subsequent failures that occur in response to placement of additional spoil materials or are shear zones of readjustment following initial failure results show that failures are most likely initiated along the spoil natural ground interface and propagate slowly into the spoil mass

geochemistry of 1 9 ga morb and oib like basalts from the amisk collage flin flon belt canada evidence for an intra oceanic origin subaqueously erupted basalts that occur in kilometre scale allochthons within the 1 9 ga flin flon belt canada appear to have been generated at oceanic ridges and possibly oceanic plateaus remote from archean cratons the ocean floor basalts fall into two categories 1 n type resembling n morbs and mariana type back arc basin basalts depleted to flat ree patterns high zrnb variable thnb and initial nd 3 3 to 5 4 2 e type resembling transitional and plume morbs slightly enriched ree patterns lower zrnb initial nd 3 1 to 4 5 in the largest and best studied allochthon the elbow athapapuskow assemblage mixing between depleted n morb and enriched oib sources or melts coupled with variable addition of a subduction lile component can explain the chemical variations in the basalts zircon u pb dates of 1904 ma for a syn volcanic diabase sill and 1901 6 5 ma for a gabbro peridotite cumulate complex demonstrate that crystallization of the ocean floor basalts overlapped with in part eruption of the tectonically juxtaposed 1 90 1 88 ga arc volcanic rocks the elbow athapapuskow allochthon is interpreted as back arc basin crust that developed simultaneously with flin flon arc magmatism subaerially erupted basalts that chemically resemble tholeiitic oibs 8 14 mgo relative hree depletion initial nd 2 2 to 3 4 occur in tectonic contact with the elbow athapapuskow assemblage the oibs may have been generated by deeper garnet residue melting of enriched mantle tapped during extension in the elbow athapapuskow back arc basin and were possibly erupted onto a remnant arc deeper mantle melting is also indicated by the presence of the lree enriched oceanic plateau like basalts of the sandy bay assemblage the back arc 01b and plateau volcanic assemblages were jux taposed against ca 1 9 ga arc assemblages in a philippines like intraoceanic accretionary complex by 1 87 ga

effect of geomagnetic activity on equatorial radio vhf scintillations and spread f the paper discusses the occurrence of scintillations of ats 3 137 mhz beacons recorded at huancayo on geomagnetically quiet and disturbed days during the years 1969 1976 and compares the results with the corresponding occurrence of range and frequency spread f at huancayo during the equinoctial months and the december solsticial months the geomagnetic activity reduces the equatorial scintillations during premidnight hours but increases their occurrence during the postmidnight hours these features are very similar to the effect of geomagnetic activity on the occurrence of the range type of equatorial spread f rather than on the occurrence of frequency spread which decreases for any hour of the night during geomagnetic active periods during the june solsticial months the occurrence of both scintillations and spread f is very much reduced however both the phenomena are more frequent on disturbed than on quiet days for any of the hours of the night these effects are consistently the same for any of the years within the solar cycle it is suggested that the equatorial radio scintillations at 137 mhz during the nighttime are produced primarily by the occurrence of the range type of spread f the geomagnetic effects are due to the modifications of the equatorial electric field by the geomagnetic disturbance and thereby affect the development of f region irregularities causing scintillations

radar and satellite global equatorial f region vertical drift model we present the first global empirical model for the quiet time f region equatorial vertical drifts based on combined incoherent scatter radar observations at jicamarca and ion drift meter observations on board the atmospheric explorer e satellite this analytical model based on products of cubic b splines and with nearly conservative electric fields describes the diurnal and seasonal variations of the equatorial vertical drifts for a continuous range of all longitudes and solar flux values our results indicate that during solar minimum the evening prereversal velocity enhancement exhibits only small longitudinal variations during equinox with amplitudes of about 15 20 m s is observed only in the american sector during december solstice with amplitudes of about 5 10 m s and is absent at all longitudes during june solstice the solar minimum evening reversal times are fairly independent of longitude except during december solstice during solar maximum the evening upward vertical drifts and reversal times exhibit large longitudinal variations particularly during the solstices in this case for a solar flux index of 180 the june solstice evening peak drifts maximize in the pacific region with drift amplitudes of up to 35 m s whereas the december solstice velocities maximize in the american sector with comparable magnitudes the equinoctial peak velocities vary between about 35 and 45 m s the morning reversal times and the daytime drifts exhibit only small variations with the phase of the solar cycle the daytime drifts have largest amplitudes between about 0900 and 1100 lt with typical values of 25 30 m s we also show that our model results are in good agreement with other equatorial ground based observations over india brazil and kwajalein

geomechanical characterization of the volcaniclastic material involved in the 2002 landslides at stromboli during the 2002 eruption the nw flank of stromboli volcano southern italy experienced large landslides that produced tsunami waves with a maximum runup of 10 m in height this paper focuses on the geomechanical behavior of the loose volcaniclastic layers the weakest component of the deposit forming the volcano flank tests on the coarse grained volcaniclastic soil and on the rock material forming the grains were conducted in dry conditions a feature of the subaerial slope the rock material in spite of its high porosity exhibits relatively high stiffness and strength due to the remarkable continuity of the solid skeleton accordingly the volcaniclastic soil is characterized by high shear strength during shear tests however significant grain crushing occurs which partly explains the nonlinear shear strength envelope and the strain softening associated with contractive behavior grain crushing was also found to affect compressibility and its time dependency investigated under oedometric conditions

scintillations plasma drifts and neutral winds in the equatorial ionosphere after sunset an equatorial campaign was conducted during september 25 to october 7 1994 to investigate the neutral and plasma dynamics in the equatorial ionosphere after sunset in relation to the day to day variability of the occurrence of equatorial spread f esf the campaign was organized under the auspices of national science foundation s multi instrumented studies of the equatorial thermosphere aeronomy program miseta which included the jicamarca radar spaced antenna satellite scintillation digisonde all sky imager and fabry perot interferometer fpi measurements near the magnetic equator in peru during a part of the period september 27 to october 3 the geophysics directorate of phillips laboratory performed measurements away from the magnetic equator at aguaverde chile magnetic latitude 11 s located 800 km to the east of the jicamarca meridian using geostationary and gps satellite scintillation digisonde and all sky imager systems the incoherent scatter radar results indicate that the postsunset enhancement of upward plasma drift even though of the order of only 20 m s 1 during the solar minimum period is a necessary condition for the generation of esf in view of the extreme difficulty of determining the neutral wind speed during the early evening hours by the fpi due to low airglow intensity it was not possible to unequivocally associate the observed postsunset enhancements with strong eastward neutral winds however considering a few observations contiguous to the campaign period it appears that such a causal relationship may exist the scintillation drift measurements in peru and chile indicated that the zonal irregularity drift was smaller away from the magnetic equator implying a variation of neutral wind with latitude this is reproduced in the altitude variation of zonal drift observed by the jicamarca radar during a magnetic storm scintillation measurements indicated that eastward drifts near the magnetic equator are accompanied by westward drifts near the anomaly peak which is consistent with the effects of a disturbance dynamo the campaign results indicate that in order to resolve the variability of esf a careful probing of neutral dynamics as a function of latitude needs to be undertaken during the postsunset period

age constraints and characteristics of subaqueous volcanic construction the archean hunter mine group abitibi greenstone belt the archean hunter mine group hmg is a 6 7 km thick south facing volcanic sequence at the southern limit of the northern volcanic zone abitibi greenstone belt the hmg is composed of 1 felsic lava flows and endogenous and exogenous domes with autoclastic breccia deposits 2 pyroclastic fire fountain products and high to low concentration volcaniclastic sediment gravity flows of autoclastic and pyroclastic origin interstratified with iron formation 3 mafic pillowed and brecciated flows 4 a prominent felsic dyke swarm and 5 abundant mafic intrusions the stratigraphy is complex as inferred by detailed volcano sedimentary facies mapping a 5 7 km wide n trending felsic dyke swarm coupled with abundant synvolcanic and synsedimentary faults chaotic breccias and mineralization suggest a central volcanic depression which is consistent with a caldera structure voluminous effusive activity and explosive fire fountaining eruptions contributed to caldera development rifting of this arc edifice is supported by the presence of felsic dykes and mafic tholeiitic sills the lithofacies and overlying komatiites flows are consistent with a deep water marine setting u pb age determinations help constrain the hmg caldera formation to 6 million years the sampled quartz feldspar phyric dykes yielded u pb zircon ages of 2728 3 4 3 4 and 2728 9 0 8 ma and together with a previously published dyke age of 2729 6 1 4 ma from the same dyke swarm a case is made that the swarm evolved over 1 million years 2728 6 2729 6 ma a lobate flow and flow breccia revealed similar ages of 2724 6 4 6 1 7 and 2727 6 4 2 2 0 ma whereas the up to 1 km thick gabbro diorite roquemaure sill precedes both felsic dykes and flows as indicated by the 2731 8 2 2 2 0 ma age the 2706 4 5 7 4 3 ma feldspar quartz phyric dykes occurred late in the history of the hmg and were not associated with subaqueous volcanic construction the 207pb 206pb ages of analyzed zircon fractions have an inherited component within error of the oldest crystallization ages obtained for the hmg complex collectively these age determinations and inheritance as well as stratigraphy support a tripartite division into a 2734 2730 ma lower formational stage a 2732 ma middle formational stage and a 2730 2728 ma upper formational stage the study shows that age constraints without detailed facies mapping may lead to erroneous conclusions on volcanic construction and that felsic volcanic dykes and flows may inherit an earlier component of their own volcanic edifice

analysis of regional gullies within noachis terra mars a complex relationship between slope surface material and aspect abstract the precise mechanisms by which martian hillside gullies erode and their dependence on the local environment remain subjects of debate we studied three sharp rimmed craters in noachis terra and 37 gully profiles using context camera ctx mars orbiter laser altimeter mola and high resolution stereo camera hrsc data we analysed the gully topographic profiles of seven gullies and nine dry ravines we measured slope properties using hrsc elevation data and used thermal inertia to infer material types of the gully sites we compared these with three nearby noachian age craters possessing crater wall slope angles within the range of previously observed gully formations in line with previous findings on individual gullies we found that the slope angles of gullies in our study area consistently reflect the inherited slope angles of the host escarpment suggesting that traditional slope based evidence of fluvial activity in martian gullies needs to be placed in context of its local environment we also observed a direct relationship between gully morphology and local composition of surface units martian gully features and possibly method of erosion appeared heavily influenced by changes in underlying geology and presence of erodible sediment examples included gully shape changing in accordance with type of erodible sediment we suggest that the degraded rims of gully free noachian craters precluded slope angles high enough to trigger creation of precursors to alcoves through mass wasting lack of these hollows has probably prevented the accumulation of enough ice rich sediment for gullies to form in our analysis reveals that there is a complex interdependence between slope processes and the local environment and global martian gully models may not work at the local scale

diachronous variscan late orogenic collapse as a response to multiple detachments a view from the internides in france to the foreland in the irish sea

the significance of a reliable ordovician age for some highland border rocks in central scotland a lower arenig fauna with north american affinities has been rediscovered at dounans aberfoyle central scotland this discovery makes part of the highland border complex younger than the adjacent dalradian rocks and suggests a provenance from the s

shear strength of rockfill a practical method for estimating the shear strength of rockfill is developed the peak drained friction angle prime is found to be closely related to that of rock joints in both cases the values of prime are dependent on sample size stress level surface roughness and on the uniaxial compression strength of the rock friction angles are therefore higher for smaller samples and very high where stresses are low as at the toe or near the face of a rockfill dam test data reviewed shows that the value of prime for rockfill can be quantified by a equivalent roughness r and an equivalent particle strength s the value of r depends on the porosity following compaction and on the degree of particle roundedness and surface smoothness a practical method is proposed for physically measuring the full scale shear strength of in place compacted rockfill

case study of slope failure during construction of an open pit mine in indonesia this paper presents back analyses of a failed slope at an open pit lignite mine in muara enim indonesia the slope which was being raised by the dumping of excavated material failed at a dump he

modern sand rich and mud rich siliciclastic aprons alternative base of slope turbidite systems to submarine fans base of slope aprons that lack significant channel development and are fed by multiple sediment sources i e numerous slope failures or debris chutes represent an alternative facies organization to submarine fans that possess channels and are fed by canyon point sources of allochthonous sediment two styles of base of slope apron deposition are evident 1 sand rich aprons with rhythmic gradational sand and gravel sheets that evolve to basin plain turbidites as exemplified by crater lake aprons and 2 mud rich aprons composed of chaotic sediment flow lobes without gradation as exemplified by ebro margin aprons