an automated time window selection algorithm for seismic tomography we present flexwin an open source algorithm for the automated selection of time windows on pairs of observed and synthetic seismograms the algorithm was designed specifically to accommodate synthetic seismograms produced from 3 d wavefield simulations which capture complex phases that do not necessarily exist in 1 d simulations or traditional traveltime curves relying on signal processing tools and several user tuned parameters the algorithm is able to include these new phases and to maximize the number of measurements made on each seismic record while avoiding seismic noise our motivation is to use the algorithm for iterative tomographic inversions in which the synthetic seismograms change from one iteration to the next hence automation is needed to handle the volume of measurements and to allow for an increasing number of windows at each model iteration the algorithm is sufficiently flexible to be adapted to many tomographic applications and seismological scenarios including those based on synthetics generated from 1 d models we illustrate the algorithm using data sets from three distinct regions the entire globe the japan subduction zone and southern california

thermal response of the mantle following the formation of a super plate 1 evidence indicating that the mantle below pangea was characterized by elevated temperatures supports the widely held view that a supercontinent insulates the underlying mantle implementing a 3d model of mantle convection featuring distinct oceanic and continental plates we explore different effects of supercontinent formation on mantle evolution we find that a halt in subduction along the margins of the site of the continental collision is sufficient to enable the formation of mantle plumes below a composite super plate and that the addition of continental properties that contribute to insulation have little effect on sub continental temperature our findings show that the mean temperature below a supercontinent surpasses that below the oceanic plates when the former is a perfect insulator but that continental thermal insulation plays only a minor role in the growth of sub supercontinent mantle plumes we suggest that the growth of a super oceanic plate can equally encourage the appearance of underlying upwellings

high resolution mapping of tio2 abundances on the moon using the hubble space telescope 1 samples of the lunar regolith returned by apollo astronauts show large variations 0 to 10 wt in tio2 abundance indicating complex compositional zonation within the lunar mantle a long held goal of the lunar science community is the accurate determination of tio2 abundances on the lunar surface through remote sensing methods to date only limited progress has been made in this area using spacecraft spectral measurements acquired in visible through near infrared wavelengths here we show that variations in the ratios of ultraviolet uv to visible vis reflectances in images taken by the hubble space telescope indicate a strong correlation with tio2 abundances determined from returned samples at the apollo 17 landing site and little correlation with the maturity of lunar soils these new findings imply that uv vis observations may lead to an alternate and improved method of remotely mapping tio2 bearing materials probably as ilmenite across the lunar surface and enable more refined studies of lunar crustal composition surface volcanism and subsurface magma evolution processes additionally accurate identification and quantification of tio2 rich deposits serves to guide future human exploration of the moon

back analysis of an excavated slope failure in highly fractured rock mass the case study of kargar slope failure iran this paper examines the failure of kargar cut slope located at the south part of esfahan subway using analytical and numerical back analysis methods the excavated trench has 27 m depth with near vertical walls due to the space limitation around it the geology of the area comprises weathered and heavily jointed shale and sandstone overlaid by alluvium deposits despite the slope being supported by shotcrete and fully grouted rock bolts a catastrophic failure occurred at the east wall due to the uncertainty about the causes of failure initiation back analyses have been performed via both the limit equilibrium and numerical method for considering various probable mechanisms in the back analysis with limit equilibrium method the rock mass is assumed as an equivalent continuum and hoek brown failure criterion and geological strength index gsi are applied to calculate the shear strength parameters the results show that gsi value was 33 in the failed mass in the numerical back analysis the distinct element method is applied to study the contribution of rock joints to the failure and progressive rock mass strength degradation until failure the results show that threshold values of joint cohesion and friction were 0 2 mpa and 30 respectively also the modeled slip surface being step shaped agrees with the observed one

analysis of the bedding landslide due to the presence of the weak intercalated layer in the limestone analysis and research results show that the sliding plane of jiudingshan landslide is along the weak intercalated layer clay filled in the limestone and the sliding block is separated by the tension crack on the slope crest the earlier study results show that for the rough ups and downs structural plane when i is greater than 2 0 the shear strength of the structural surface is intensely close to the strength of the filling by the earlier theory this failure must be through the clay filling in this study the failure is back analyzed and the shear strength of the infilling is tested by the laboratory direct shear tests for which samples were retrieved in the field the failure cannot be explained by the laboratory results of shear strength parameters to simulate the field conditions the real strength parameters of sliding surface are measured by the in situ shear tests for the weak intercalated layer by the in situ tests it is shown that the failure initiates along the contacts between the clay infilling and the limestone boundaries but not through the clay itself though the contact surface is the interface of the clay limestone the cohesion is not 0 and it is not negligible too

developments in the characterization of complex rock slope deformation and failure using numerical modelling techniques recent advances in the characterization of complex rock slope deformation and failure using numerical techniques have demonstrated significant potential for furthering our understanding of both the mechanisms processes involved and the associated risk this paper illustrates how rock slope analyses may be undertaken using three levels of sophistication level i analyses include the conventional application of kinematic and limit equilibrium techniques with modifications to include probabilistic techniques coupling of groundwater simulations and simplistic treatment of intact fracture and plastic yield such analyses are primarily suited to simple translational failures involving release on smooth basal rear and lateral surfaces where the principle active damage mechanisms are progressive failure and or asperity breakdown level ii analyses involve the use of continuum and discontinuum numerical methods in addition to simple translation level ii techniques can be applied to complex translational rock slope deformations where step path failure necessitates degradation and failure of intact rock bridges along basal rear and lateral release surfaces active damage processes in this case comprise not only strength degradation along the release surface e g asperity breakdown but also a significant component of brittle intact rock fracture level iii analyses involve the use of hybrid continuum discontinuum codes with fracture simulation capabilities these codes are applicable to a wide spectrum of rock slope failure modes but are particularly well suited to complex translation rotational instabilities where failure requires internal yielding brittle fracturing and shearing in addition to strength degradation along release surfaces through a series of rock slope analyses the application of varied numerical methods are discussed particular emphasis is given to state of the art developments and potential use of level iii hybrid techniques d 2005 elsevier b v all rights reserved

investigation of the failure mechanism and stabilization of a landslide in weathered tuffite giresun northeastern turkey this study investigates the causes and failure mechanism of the aksu landslide that occurred during the construction of the giresun espiye road between km 1 030 1 170 in northern turkey and recommends proper stabilization techniques for the purpose of investigating the causes and mechanism of this slope failure engineering geological mapping geotechnical investigation and rock mass characterization were performed from top to bottom weathered tuffite tuffite flysch and dacitic tuffite were the major units in the study area the disturbance of the slope by the excavations performed at the toe of the slope i e due to the foundation excavation for the tunel restaurant building and for the road cut led to a translational slide the translational slide occurred in completely weathered tuffite due to the disturbance of the stability of the slope by the excavations performed at the toe of the slope particularly for the foundation excavation of the tunel restaurant building and for the road cut along the giresun espiye road the rise in the groundwater level was also another important factor that has contributed to the occurrence of the landslide after establishing the geometry of the landslide in detail the shear strength parameters of the failure surface were determined by the back analysis method sensitivity analyses were performed and landslide failure mechanisms were modeled to quantify the contributing factors that have caused the formation of the aksu landslide the influence of an earthquake was investigated through pseudostatic slope stability analysis toe buttressing ground water drainage and surface water drainage alternatives were considered for stabilizing the slope

developments in the analysis of footwall slopes in surface coal mining abstract surface mining of coal particularly in areas of mountainous topography often involves the formation of extensive footwall slopes parallel to the strata dip due to structural deformation steep dips on the limbs of folds may be encountered in association with thrust faults jointing and residual shear strength conditions such an environment necessitates a rigorous assessment of footwall stability in order to ensure safe and economic exploitation of the coal this paper provides a detailed review of the factors influencing footwall slope instability in surface coal mining and the major instability mechanisms which have been recognized within the published literature the analysis of footwalls in the design stage and the back analysis of footwall slope failures has in general been undertaken using predominantly two dimensional limit equilibrium techniques often incorporating a simplistic elastic column analysis the application of numerical modelling techniques to surface coal mine footwalls has received little attention in this paper the authors attempt to illustrate the potential for investigating footwall failure mechanisms and stability using principally the distinct element method

compositional and temporal investigation of exposed lunar basalts in the mare imbrium region abstract this paper presents an updated stratigraphical and compositional study of the exposed maria within the imbrium basin on the moon clementine multispectral data were employed to derive tio2 and feo wt abundance estimates of potentially distinct basaltic flows additionally nasa lunar orbiter images were used to estimate flow ages using crater count statistics mare imbrium shows evidence of a complex suite of low to high ti basaltic lava units infilling the basin over an 800 million year timescale more than a third 37 of identified mare basalts were found to contain 1 3 wt tio2 two other major mare lithological units representing about 25 of the surface each show tio2 values between 3 5 and 7 9 wt the dominant fraction 55 of the sampled maria contain feo between 16 and 18 wt followed by 27 of maria having 18 20 wt and the remaining 18 14 16 wt feo a crater frequency count for diameters 500 m shows that in three quarters of the sampled mare crater counts range between 3 5 and 5 5 10 2 per km2 which translates according to a lunar cratering model chronology into estimated emplacement ages between 3 3 and 2 5 ga a compositional convergence trend between the variations of iron and titanium oxides was identified in particular for materials with tio2 and feo content broadly above 5 and 17 wt respectively suggesting a related petrogenesis and evolution according to these findings three major periods of mare infill are exposed in the imbrium basin despite each period showing a range of basaltic compositions classified according to their tio2 content it is apparent that at least within these local geological settings the igneous petrogenesis generally evolved through time towards more tio2 and feo rich melts

numerical analysis of initiation and progressive failure in natural rock slopes the 1991 randa rockslide the 1991 randa rockslide in the swiss alps involved several complex mechanisms relating to geological mechanical and hydrological processes for which no clear trigger can be asserted this paper investigates the concept of progressive failure and the numerical modelling of rock mass strength degradation in natural rock slopes using the randa rockslide as a working example results from continuum i e finite element modelling are presented to illustrate a hypothesis suggesting that initiation of a progressive rock mass degradation process ultimately leading to failure began following deglaciation of the valley below discontinuum distinct element modelling is then applied to investigate the underlying mechanisms contributing to the episodic nature of the rockslide finally the use of a hybrid method that combines both continuum and discontinuum techniques to model fracture propagation are discussed in the context of modelling progressive slide surface development linking initiation and degradation to eventual catastrophic failure

identifying crack initiation and propagation thresholds in brittle rock recent work at the underground research laboratory of atomic energy of canada limited in pinawa manitoba has shown that high compressive stresses near the tunnel face significantly contribute to

using seismic waves to image earth s internal structure seismic waves generated in earth s interior provide images that help us to better understand the pattern of mantle convection that drives plate motions

analysis of spalling failure in marble rock slope a case study of neyriz marble mine iran the expansion of the neyriz marble mine into deeper levels caused an unexpected failure particularly in the toes of lower benches this phenomenon can impact the overall stability of the quarry and results in undesirable environmental and technical consequences to understand the failure mechanism a comprehensive study including laboratory testing in situ field testing and theoretical analyses are carried out the theory of the brittle failure which was mainly developed based on the experiences gained during excavation in granite rocks is adopted and augmented in this study to explain the governing mechanism of failure mechanical properties of the marble are determined using conventional rock mechanics tests and the in situ stress field was evaluated using a modified under coring test analyzing the laboratory and field data with the available empirical criteria for brittle failure shows that the level of stress in the lower bench is high enough to initiate the brittle failure finally constitutive models developed for this failure mode are adopted in conjunction with numerical modeling to investigate the observed failure in the quarry two modeling strategies based on elastic and elastic plastic analyses are considered comparing the predicted failure surface with the observed failure profile it can be concluded that the brittle failure criteria can very well capture the failure mechanism in this marble quarry this shows that the criteria proposed to describe spalling failure around underground excavation in granite can be effectively employed for assessing the brittle failure in deep open cast and quarry mines in good quality rocks such as marble

the pandemonium creek rock avalanche british columbia in 1959 a rock spur became detached from the headwall of a cirque near pandemonium creek in the southern coast mountains of british columbia approximately 5 000 000 cu m of blocky gneissic quartz diorite debris travelled 9 0 km along a highly irregular path descending a vertical distance of 2 km to the valley of south atnarko river the high mobility of the rock avalanche is manifested by superelevation in valley bends two run ups and two right angle changes in flow direction this mobility is due in part to 1 peculiarities in the path of the landslide lateral moraines for example funnelled and accelerated the debris and 2 travel over a glacier below the detachment zone although most of the debris came to rest on the upper part of a fan at the mouth of pandemonium creek one lobe traversed the fan and entered knot lakes where it generated displacement waves that destroyed trees along the shore run up and superelevation data indicate that the debris was moving between 81 and 100 m s as it entered the run up zone at pandemonium creek and 21 38 m s in pandemonium valley to the east these velocities were analysed by applying the dynamic model of h j korner rock mechanics 1976 8 225 256 to the path of the landslide the analysis suggests that the rock avalanche had two phases a very rapid initial phase from detachment to the beginning of the run up and following sudden energy losses at the run up a second phase involving much lower velocities the pandemonium creek landslide is similar in many respects to much larger highly mobile rock avalanches in other parts of the world for example huascaran peru and little tahoma peak washington u s a although much less common than rockfalls and debris flows rock avalanches are capable of far greater damage this is a consequence of their size and the fact that they travel great distances at high velocities the potential exists for other highly mobile landslides of the pandeminium creek type in the mountains of western canada highlighting the need for caution in the future development of this region

apollo 17 landing site topography photometric corrections and heterogeneity of the surrounding highland massifs 1 a high resolution digital elevation model for the apollo 17 landing site 20 n 31 e and surrounding region is used to correct the photometry of clementine ultraviolet visible multispectral data to standard viewing and illumination geometry on a pixel by pixel basis feo and tio2 concentrations were derived from these topographic photometrically corrected data and steep sloped highland massifs are used to assess the magnitude of the effects of the correction the effects are significant yielding errors as high as 5 wt feo and 4 wt tio2 absolute on 30 slopes the magnitude of the correction varies for sun facing versus anti sun slopes with greater changes on anti sun slopes because most of the apollo 17 sample stations were on surfaces with low slope values 5 the topography has only a small effect on the use of the apollo 17 site for calibration of feo and tio2 parameters topographically corrected data and derived compositional information are used to show accurately the variation in composition of the highland units such as the massifs and the sculptured hills on a fine scale massif compositions are consistent with mixtures of noritic impact melt and feldspathic granulitic material plus variable amounts of high ti basalt on flanks at low elevations and pyroclastic deposits at high elevations as surmised from previous studies an unexpected enrichment in feo at intermediate elevations in some places where massif surfaces have not been covered by mass wasting of impact melt rich material signals an older volcanic component not previously recognized this component may be correlative with an old high plains volcanic unit exposed northeast of the landing site and north of the sculptured hills downslope movement of regolith on steep slopes appears to have resulted in compositional or grain size sorting leading to an apparent enrichment in feo and tio2 from volcanic glass in valleys and draws the sculptured hills have highly variable compositions ranging from feldspathic patches to exposures of mafic rocks a strong but localized mafic anomaly within the sculptured hills may be a small postbasin volcanic feature consisting of very low ti basalt

space weathering on airless bodies resolving a mystery with lunar samples using new techniques to examine the products of space weathering of lunar soils we demonstrate that nanophase reduced iron npfe0 is produced on the surface of grains by a combination of vapor deposition and irradiation effects the optical properties of soils both measured and modeled are shown to be highly dependent on the cumulative amount of npfe0 which varies with different starting materials and the energetics of different parts of the solar system the measured properties of intermediate albedo asteroids the abundant s type asteroids in particular are shown to directly mimic the effects predicted for small amounts of npfe0 on grains of an ordinary chondrite regolith this measurement and characterization of space weathering products seems to remove a final obstacle hindering a link between the abundant ordinary chondrite meteorites and common asteroids

stability of rock slopes in valles marineris mars 1 new slope measurements from the mars orbiter laser altimeter mola in conjunction with the rock mass rating system rmr permit inversions of slope height and angle from wallrock and interior deposits within valles marineris troughs for strength and lithology wallrock 50 rmr 65 is stronger than interior deposits 30 rmr 55 these values are consistent with layered igneous rock beneath wallrock slopes with interior deposits consistent with partially indurated sedimentary or volcaniclastic rocks larger volumes of landslide debris relative to terrestrial slides are related to the reduced martian gravity seismicity along trough bounding normal faults likely triggered the landslides in the adjacent wallrock the weaker interior deposits are located sufficiently far from a border fault and on its hangingwall to have remained stable during the seismogenic faulting in valles marineris

a practical procedure for the back analysis of slope failures in closely jointed rock masses abstract where closely jointed rock masses are encountered in slopes failure can occur both through the rock mass as a result of combination of macro and micro jointing and through the rock substance determination of the strength of this category of rock mass is extraordinarily difficult since the size of representative specimens is too large for laboratory testing this difficulty can be overcome by using a non linear rock mass failure criterion or by back analysis of such slopes to estimate the rock mass strength in this paper a practical procedure and a computer program are presented for the back determination of shear strength parameters mobilized in slopes cut in closely jointed rock masses which obey a non linear failure criterion rather than a linear one the procedure shows that the constants to derive normal stress dependent shear strength parameters of the failed rock masses can be determined by utilizing a main cross section and without a pre determined value of rock mass rating rmr trials are made for different rmr m and rmr s values corresponding to various possible combinations of the constant m and s which are used in the hoek brown failure criterion satisfying the limit equilibrium condition it is also noted that the procedure provides a quick check for the rock mass rating obtained from the site investigations the method is used in conjunction with the bishop s method of analysis based on circular slip surfaces the procedure outlined in this paper has also been satisfactorily applied to documented slope failure case histories in three open pit mines in turkey

geomechanical characterisation of rock masses in alpine regions the basque arc basque cantabrian basin northern spain the geomechanical characterisation of rock masses in alpine regions is one of the main challenges currently facing rock mechanics these rock masses made up of very different materials and frequently tectonically disturbed are affected by engineering works giving rise to potentially important problems thus in the basque country these materials are at the cause of important fatalities occurring in recent years in this context we aim at characterising these materials with the ultimate purpose of predicting their behaviour the characterisation is initially approached based on the gsi mi and ci parameters following the hoek brown failure criterion this information is supplemented with field and laboratory measurements and by obtaining the rqd and rmr indices using the information obtained from 99 metering stations we develop a graphic classification procedure which allows us to distinguish materials based on their characteristics behaviour type and degree of associated problems and type and effectiveness of solutions provided eight classes of material are established

evolution of gravity driven rock slope failure and associated fracturing geological analysis and numerical modelling abstract an accurate analysis of fracture and cleavage anisotropies along two landslides in the argentera massif french southern alps was performed in order to relate the fracturing mode to the rock slope failure state the mature la clapiere landslide and the incipient isola landslide were investigated in both cases the gneissic rock schistosity was found sub horizontal in the vicinity of the landslides at shallow depths while it was sub vertical elsewhere at the massif s scale in addition to the well known regional tectonic fracture sets we identified in both cases a new family of vertical valley parallel vp fractures the vp fractures were only observed on the lower part of slopes affected by landslides where schistosity was found sub horizontal the vp fractures are clearly related to the decrease in schistosity dip and correspond to fold extrado like joints the proximity of the schistosity folds and the associated vp joints to the landslides suggests that they are gravity driven the presented 2 d finite difference models of the slope destabilisation in the la clapiere site shade light on possible mechanisms of the indicated gravity induced processes a progressive degradation of the material strength was imposed in these models to simulate the weathering effect which led to inelastic deformation damage at the lower part of slope this was followed by the formation of dense sub vertical deformation bands and then by the initiation of a landslide in the area corresponding to the actual position of the la clapiere landslide it is suggested that the gravity induced damage in the lower part of slope increases the permeability and thereby accelerates the weathering that causes a more rapid strength reduction the latter results in the tilting folding of pre existing fabrics and the related vp fracturing the la clapiere landslide is initiated in the upper part of this zone

testing the relation between uv vis color and tio2 content of the lunar maria reflectance spectroscopy is important for placing lunar samples into a regional and global geologic context to this end the ultraviolet visible uv vis color ratio used to estimate the tio2 composition of mature mare basalts has been one of the most widely used spectral parameters in lunar exploration we examine the correlation between uv vis color and tio2 content using a combination of clementine lunar prospector and sample data to document the extent to which color is dependent upon tio2 examination of the remotely sensed data reveals that the correlation between uv vis ratio and tio2 composition is best represented by a sigmoidal trend rather than the canonical linear or curvilinear correlation with this information we are then able to evaluate between two models that propose different explanations for the relationship between uv vis color and tio2 the first model attributes the correlation between tio2 and uv vis color to spectrally neutral opaques i e ilmenite while the other emphasizes the effect of fe ti charge transfer in lunar glasses and dual scattering mechanisms between high and low ti basalts we do not find evidence in the spectral data to support the occurrence of fe ti charge transfer in lunar glass as the principal cause for color in high ti basalts the data also do not substantiate the existence of different scattering mechanisms e g volume v surface scattering between high and low tio2 basalts instead our analyses substantiate that the spectral effects of ilmenite exhibit a major influence over the uv vis ratio by including sample data we find that in addition to ilemenite tio2 content factors such as feo content ilmenite grain size modal abundance of plagioclase and the olivine to pyroxene ratio in a mare soils can influence the uv vis continuum these findings point to promising avenues of research that future uv vis spectral techniques can exploit in order to yield more accurate tio2 estimates and potentially additional petrologic information

aleutian island arc magma production rates and primary controlling factors abstract island arc magmatism is considered a major mechanism of continental crustal growth hence the variation in island arc magma production rates and its influencing factors are of great importance the along arc strike variation in the island arc magma production rate is important for elucidating whether the subduction zone temperature is a controlling factor on arc magmatism no back arc spreading or ridge subduction is occurring in the intraoceanic subduction region of the aleutian subduction zone and the along arc temperatures vary due to differences in the subducting plate age convergence rate and slab dip therefore this is an ideal region to study the correlation between magma production rates and subduction zone temperatures however previous studies estimated the magma production rates at only a few locations due to the insufficient coverage of seismic data here we employ the gravity inversion method based on density modelling and seismic data constraints to calculate the present day arc crustal thickness and then obtain the magmatic thickness by removing the pre existing crustal thickness from the present day arc crustal thickness finally the magma production rates along the main intraoceanic subduction region of the aleutian arc are mapped by estimating the island arc magmatic thickness and the most recent subduction inception dating result in addition the subduction zone temperatures and mantle melt amounts along five profiles across the aleutian arc are calculated the magma production rate variation is highly correlated with the mantle melt amount the slab temperature controls the extent of the slab dehydration which is essential for mantle wedge melting and the mantle wedge temperature controls the size of the hydrated mantle melting region and the melting fraction therein therefore as the subduction zone temperature controls the mantle melt amount we suggest that the subduction zone temperature is the first order controlling factor on the magma production rate

a method for the study of crack propagation in rock structures a method is presented for analysing the stability of rock structures based on the propagation of geological discontinuities discontinuities are modelled as flat cracks and their propagation is analysed using fracture mechanics methods as rock structures are brittle these phenomena can be studied using linear elastic fracture mechanics lefm problems in the application of lefm methods are analysed with regard to the states of compressive stress present in rock a numerical procedure is described which simulates the propagation of natural discontinuities in rock the crack propagation trajectories determined from this analysis are compared with experimental results obtained on mortar specimens the applicability of the method to the study of rock mass stability is shown with reference to the behaviour of rock slopes l article presente une methode permettant d analyser la stabilite de structures rocheuses cette methode est fondeve sur petude de la propagation de discontinuites geologiques ces discon

mars surface mineralogy from hubble space telescope imaging during 1994 1995 observations calibration and initial results visible to near infrared observations of mars were made with the hubble space telescope hst during 1994 1995 with the goals of monitoring seasonal variability of the surface and atmosphere and mapping specific spectral units to constrain the planet s surface mineralogy this paper presents the details of the collection and calibration of the data concentrating specifically on the near ir data that were obtained exclusively for the surface mineralogy aspect of our hst mars observing program we also present some initial results from the calibrated data set our calibration procedures included the standard pipeline processing steps supplemented by special procedures required for use with the linear ramp filters on the wide field planetary camera 2 instrument and an additional point spread function deconvolution procedure applied in order to realize the full potential spatial resolution of the images 23 to 64 km pixel between august 1994 and august 1995 the calibration results in a set of images projected onto a standard map grid and presented in radiance factor i f units having an estimated 5 photometric accuracy based on the performance of hst and comparisons with previous ground based and spacecraft mars spectra initial scientific analyses of these data reveal 1 distinct red blue color units within the classical bright regions similar to those seen in viking orbiter images and possibly related to variations in nanophase and or crystalline ferric mineral abundance 2 near ir spectral slope variations correlated with albedo on a large scale darker is bluer near ir slope but exhibiting wider variations among many of the small scale features visible in the data 3 an absorption at 860 nm that occurs in all regions but which is 3 to 5 stronger in many of the classical dark regions than in the bright regions possibly because of a greater abundance of a well crystalline ferric phase like hematite or a very low ca pyroxene or opx cpx mixture and 4 an absorption from pyroxene at 953 nm with a band depth that is inversely correlated with albedo bright regions 0 to 5 deep dark regions 7 to 15 deep and which shows the highest band depth values in individual craters calderas and other small geologic units that are resolved in the images

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

insights on the kinematics of the india eurasia collision from global geodynamic models the eocene india eurasia collision is a first order tectonic event whose nature and chronology remains controversial we test two end member collision scenarios using coupled global plate motion subduction models the first conventional model invokes a continental collision soon after 60 ma between a maximum extent greater india and an andean style eurasian margin the alternative scenario involves a collision between a minimum extent greater india and a neotethyan back arc at 60 ma that is subsequently subducted along southern lhasa at an andean style margin culminating with continent continent contact at 40 ma our numerical models suggest the conventional scenario does not adequately reproduce mantle structure related to tethyan convergence the alternative scenario better reproduces the discrete slab volumes and their lateral and vertical distribution in the mantle and is also supported by the distribution of ophiolites indicative of tethyan intraoceanic subduction magmatic gaps along southern lhasa and a two stage slowdown of india our models show a strong component of southward mantle return flow for the tethyan region suggesting that the common assumption of near vertical slab sinking is an oversimplification with significant consequences for interpretations of seismic tomography in the context of subduction reference frames

reliability back analysis of landslide shear strength parameters based on a general nonlinear failure criterion abstract the shear strength parameters of a sliding surface are important parameters for the stability evaluation and engineering design of a landslide to consider the randomness uncertainty and the nonlinear characteristics of the geotechnical the reliability back analysis method of determining shear strength parameters of a landslide based on nonlinear mohr coulomb failure criteria is proposed in this study by analyzing a slope with linear failure surface the feasibility and validity of the proposed method are discussed in an engineering case the proposed method provides a new choice and reference for the determination of the shear strength parameters of the sliding surface of a landslide

crustal thickness over the nw pacific and its tectonic implications abstract igneous emplacement on the nw pacific oceanic crust via mantle activity such as hot spots and mantle plumes results in perturbations of crustal thickness therefore mapping crustal thickness variations is key for understanding these mantle structures and processes improvements in resolution and accuracy of marine gravity anomalies promote the use of moho gravity inversion effects especially for large scale applications for improving the moho gravity inversion accuracy density variations of the lithospheric mantle are modelled via lithospheric age temperature density relationship since age grid with a resolution of 2 arc minutes is available and density variations of the mantle beneath lithosphere are modelled via seismic wave velocity density relationship since velocity structure with penetration to 700 km is available comparisons between the moho geometries by gravity inversion and seismic interpretation demonstrate that the mantle density modelling improves the moho inversion accuracy our crustal map shows that 1 the crustal thickness of 26 of the nw pacific region is thicker than 7 km 2 the southern end of the emperor seamounts was emplaced on the western flank of the hess rise and a part of the central hawaiian seamounts was emplaced on the eastern end of the mid pacific mountains 3 the magma production of hawaiian seamounts is greater than that of the emperor seamounts 4 the leakiness of the fracture along which the line islands formed decreases in the order of the central southern and northern segments

coal mining under difficult geological conditions the can lignite open pit canakkale turkey abstract this paper describes the slope instability problems in the can canakkale northwestern turkey coal mine slope instabilities have been one of the major problems in the pit mine since the beginning of mining activities in particular the west and east sector panels in front of the tki turkish coal enterprises buildings and the seramic factory located in the vicinity of the pit mine have been suffering from slope instability problems to assess the instabilities field data collection from boreholes surface sampling and monitoring studies were performed deterministic stability analyses such as limit equilibrium sensitivity and back analyses were applied based on the results the active passive wedge type of failure was determined as the most dominant instability type based on the back analysis results mean values of residual shear strength parameters were determined as c 42 kpa o 8 the results also indicate that the excessive excavation of the toe along the huge lignite open pit was the main cause of the instability the weak contacts between the lithological units were also an important factor taking into consideration the results of the analyses some remedial measures were also suggested for the coal mine such as decreasing the inclination of the toe safe benching and effective drainage of surface water and groundwater

the distribution and origin of lunar light plains around orientale basin abstract lunar light plains are relatively flat smooth to gently rolling deposits that occur in crater floors and other topographic lows in the lunar highlands with albedo values comparable to surrounding highland terrain once interpreted to be the product of highland volcanism apollo 16 samples from the light plains of the cayley formation led to the interpretation that most light plains form from the deposition of fluidized basin ejecta conflicting relative age estimates suggest that light plains are ejecta from the orientale and imbrium basins or from a larger number of impact events combined with possible volcanic eruptions here we examine the distribution variability and origin of light plains associated with the orientale basin using data from the lunar reconnaissance orbiter camera lroc we find that the distribution composition and age of the light plains to the north and northwest of the orientale basin are consistent with an origin with the formation of orientale in this case the orientale basin forming impact significantly altered the surface within four basin radii from the rim

space weathering from mercury to the asteroid belt the variety of evidence bearing on the nature of space weathering is reviewed the effects of space weathering include spectral darkening reddening and subdued absorption bands and the distinctive magnetic electron spin resonance caused by single domain metallic iron particles ever since the apollo missions two paradigms have dominated the thinking of the planetary science community concerning space weathering 1 the optical effects are caused by impact vitrified glass in agglutinates and 2 the submicroscopic metallic iron results from the reduction of ferrous iron by the impact melting of minerals whose surfaces have been saturated with hydrogen from the solar wind however studies carried out since the apollo program showed that both of these paradigms are invalid a hypothesis first suggested by the author and his colleagues 26 years ago but not generally accepted at that time now appears to be essentially correct both the optical and magnetic effects are caused by metallic iron particles smaller than the wavelength in ubiquitous vapor deposited coatings on soil particle surfaces and inside agglutinates the vapor is generated by both solar wind sputtering and micrometeorite impact vaporization and injected preferentially downward into the porous regolith the iron is reduced by a physical process the selective loss of oxygen that occurs during deposition of the vapor and does not require heating melting or a reducing environment a mathematical theory that describes the optical effects of the submicroscopic iron quantitatively is derived and applied to the regoliths of the moon mercury and an s asteroid

seismic evidence for deep water transportation in the mantle we report seismic evidence for the transportation of water into the deep mantle in the subduction zone beneath northeastern japan our data indicate that water is released from the hydrated oceanic crust at shallow depths approximately 100 kilometers and then forms a channel of hydrated mantle material on top of the subducting plate that is the pathway for water into the deep mantle our result provides direct evidence that shows how water is transported from the ocean to the deep mantle in a cold subduction zone environment

a new general empirical approach for the prediction of rock mass strengths of soft to hard rock masses abstract it is almost impossible to prepare representative cores of rock masses including discontinuities patterns for laboratory studies to overcome these difficulties researchers have focused on developing empirical equations for estimating of the stress strain behavior of a rock mass including measurements of the discontinuity patterns as can be seen in the literature the uniaxial compressive strength value of rock mass ucs rm can be estimated by reducing the uniaxial compressive strength of intact rock material ucs i based on the quality of a rock mass represented by variables such as rock mass rating rmr geological strength index gsi and q value for this reason a unique reducing curve form empirical equation has limited application and generally cannot be applied to all kind of rock masses from particularly soft to hard rock masses in this study a new general empirical approach is constructed to estimate the strength of rock masses of varying hardness the new empirical equations have been calibrated using data from five slope failures and four sets of uniaxial compressive strength data of rock masses in the new empirical equations the ucs i is considered not only to be a scale parameter used in the strength reduction but also used to adjust the degree of strength reduction in conjunction with elastic modulus of the rock material e i the disturbance factor on the rock mass is taken into consideration by two separate reduction factors applied to the structure rating sr to capture increasing joint density and to the s and m b parameters of the hoek brown criterion to decrease the degree of interlocking hence non interlocked cohesionless under zero normal stress rock masses such as spoil piles can also be modeled in the new empirical approach

influence of structural heterogeneities and of large scale topography on imbricate gravitational rock slope failures new insights from 3 d physical modeling and geomorphological analysis initial topography and inherited structural discontinuities are known to play a dominant role in rock slope stability previous 2 d physical modeling results demonstrated that even if few preexisting fractures are activated propagated during gravitational failure all of those heterogeneities had a great influence on mobilized volume and its kinematics the question we address in the present study is to determine if such a result is also observed in 3 d as in 2 d previous models we examine geologically stable model configuration based upon the well documented landslide at randa switzerland the 3 d models consisted of a homogeneous material in which several fracture zones were introduced in order to study simplified but realistic configurations of discontinuities e g based on natural example rather than a parametric study results showed that the type of gravitational failure deep seated landslide or sequential failure and resulting slope morphology evolution are the result of the interplay of initial topography and inherited preexisting fractures orientation and density the three main results are i the initial topography exerts a strong control on gravitational slope failure indeed in each tested configuration even in the isotropic one without fractures the model is affected by a rock slide ii the number of simulated fracture sets greatly influences the volume mobilized and its kinematics and iii the failure zone involved in the 1991 event is smaller than the results produced by the analog modeling this failure may indicate that the zone mobilized in 1991 is potentially only a part of a larger deep seated landslide and or wider deep seated gravitational slope deformation

upper mantle density modelling for large scale moho gravity inversion case study on the atlantic ocean moho geometry is an important parameter in geodynamic understanding seismic methods can provide accurate burial depths but the coverage is low the widely used crust1 0 model under oceans is greatly restricted by a low coverage of seismic data gravity inversion can provide high coverage of moho undulations but the accuracy is relatively low observed gravity anomalies integrate gravity effects induced by 3 d density perturbations in the earth for studies of the geometry of a specific density interface based on gravity all gravity effects caused by other interfaces should be removed from the total anomaly map based on 3 d density distributions we use temperature based and velocity based methods to model the lithospheric upper mantle density two temperature calculation parameter models psm and gdh1 three thermal expansion coefficients alpha and three scaling ratio models are tested for each method psm and gdh1 result in a similar mantle gravity anomaly mga pattern but different mga average values when the alpha model is the same different alpha and scaling ratio models result in different moho inversion results and the optimal result from the temperature based method has an rms of 3 2 km with the crust1 0 model a comparison between this inversion result and the crust1 0 model shows that the temperature based method performs well in reproducing moho geometry in the main part of the atlantic ocean especially in the central basin the optimal result from the velocity based method has an rms of 4 3 km with the crust1 0 model compared with the temperature based method the velocity based method performs worse in the central basin but better in regions with low velocity and low density mantle away from the mid ocean ridge

aerial seismology using balloon based barometers seismology on venus has long eluded planetary scientists due to extreme temperature and pressure conditions on its surface which most electronics cannot withstand for mission durations required for ground based seismic studies we show that infrasonic low frequency pressure fluctuations generated as a result of ground motion produced by an artificial seismic source known as a seismic hammer and recorded using sensitive microbarometers deployed on a tethered balloon are able to replicate the frequency content of ground motion we also show that weak artificial seismic activity thus produced may be geolocated by using multiple airborne barometers the success of this technique paves the way for balloon based aero seismology leading to a potentially revolutionary method to perform seismic studies from a remote airborne station on the earth and solar system objects with substantial atmospheres such as venus and titan

numerical methods in rock mechanics the purpose of this civilzone review paper is to present the techniques advances problems and likely future development directions in numerical modelling for rock mechanics and rock engineering

analysis of a rock slope with internal dilation a class of rock slope failures exists in which the mode of failure requires the existence or creation of internal shears to accommodate large internal slide mass distortion these internal displacements are required to allow motion along the basal slip surface this paper demonstrates that the more traditional limit equilibrium methods of analysis are often conservative when used to assess the stability of slopes with this failure mechanism as a result back analysis may overestimate the available shear resistance a method of analysis capable of handling this failure mechanism was proposed by s k sarma a case history from the revelstoke hydroelectric project british columbia is used to demonstrate that these internal shears were required for movement to occur and that passive anchors inside the sliding rock mass can be used to improve the overall slope stability no attempt is made to evaluate the actual factor of safety of the three dimensional slide mass key words rock slope foliation shear s

numerical analysis of a large landslide induced by coal mining subsidence mining induced subsidence is one of the challenging problems in geotechnical engineering the surface topography of the ground over mining excavations plays a key role in the mechanism of subsidence when a mining operation is performed beneath mountainous or hilly terrain it may trigger landslides this study therefore aims to analyse the impacts of underground mining on the stability of slopes by using numerical modelling a coal mining induced landslide at nattai north australia is investigated as a typical case study in this area mining operations beneath the sydney basin escarpments initiated the largest contemporary landslide and mass movement known in australia cunningham 1988 discontinuous numerical modelling is employed to analyse the mechanisms of the ground movements leading to this landslide the role of geological and geotechnical factors such as rock mass characteristics bedding and joints are discussed through the numerical modelling the outcomes of the analyses reveal that mining induced stresses lead to the shear and compressive failure of weak strata at the escarpment base particularly around its toe the failure of the base materials as well as the caving of the overlaying bedded rocks into the extracted panel facilitated the detachment of the massive sandstone this rock column ahead of the escarpment was overlaying the weak strata the numerical results also indicate that the aforementioned rock column remained almost unaffected during mining however the failure of the weak strata at the toe of the escarpment initiated the simultaneous forward sliding and toppling of the rock column this mode of failure which is known as ski jump type of failure was previously observed and explained by pells et al 1987

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

imaging of lunar surface maturity the physical evolution of the lunar surface with exposure to the space environment is termed maturation and maturity is the degree to which a particular lunar soil possesses quantitative characteristics consistent with that exposure several quantitative measures or indices of maturity have been proposed and employed including the abundance of solar wind gas abundance of various types of agglutinates various measures of grain size and is feo among the changes attendant with space exposure are striking changes in the optical characteristics of soils mature lunar soils are dark red and exhibit reduced spectral contrast relative to immature soils this paper presents an optical maturity index that quantifies the spectral effects of maturation we show that this optical maturity index correlates with other maturity indices about as well as the accepted maturity indices correlate among themselves and is only weakly coupled to composition the modest correlations among maturity indices suggest important controls on individual maturity indices other than age uncorrelated variations in the rates of accumulation of individual indicators or variations in depths over which indicators are emplaced in addition to mixing these effects conspire to reduce the equivalence of maturity and duration of surface exposure optical maturity illustrates some of these effects showing that ejecta of large and small craters mature at different rates and that the interiors and ejecta of large craters exhibit systematically different optical maturities the same or analogous effects are likely to influence other maturity indices

age evaluation and causation of rock slope failures along the western margin of the antrim lava group alg northern ireland based on cosmogenic isotope 36cl surface exposure dating the temporal pattern of postglacial rock slope failure in a glaciated upland area of ireland the western margin of the antrim lava group was evaluated using both 36cl exposure dating of surface boulders on run out debris and 14c dating of basal organic soils from depressions on the debris the majority of the 36cl ages 21 15 ka indicate that major failures occurred during or immediately following local deglaciation 18 17 ka other ages 14 9 ka suggest some later smaller scale failures during the lateglacial and or early holocene the 14c ages 2 36 0 15 cal ka bp indicate the very late onset of organic accumulation and do not provide close limiting age constraints rock slope failure during or immediately following local deglaciation was probably in response to some combination of glacial debuttressing slope steepening and paraglacial stress release later failures may have been triggered by seismic activity associated with glacio isostatic crustal uplift and or permafrost degradation consequent upon climate change the 36cl ages support the findings of previous studies that show the deglacial lateglacial period in northwest ireland and scotland to have been one of enhanced rock slope failure

postperovskite phase transition and its geophysical implications 1 the stability of mg fe sio3 perovskite in the deep lower mantle has long been uncertain recently a phase transition from perovskite to postperovskite was discovered through a significant change in the x ray diffraction pattern at high pressure and high temperature conditions corresponding to the core mantle boundary region this phase transition was also confirmed by first principles calculations these suggest that mg fe sio3 postperovskite is the predominant mineral in the lowermost mantle called the d layer and phase transition from perovskite to postperovskite has significant geophysical implications for its nature and dynamics the postperovskite phase may account for the large seismic anomalies observed in the d region such as the d discontinuity s wave anisotropy and anticorrelation between the anomalies in s wave and bulk sound velocities in addition this phase transition is a strongly exothermic reaction it destabilizes the thermal boundary layer at the base of the mantle and should promote the formation of high temperature upwelling plumes

high resolution seismic array imaging based on an sem fk hybrid method we demonstrate the feasibility of high resolution seismic array imaging based on teleseismic recordings using full numerical wave simulations we develop a hybrid method that interfaces a frequency wavenumber fk calculation which provides analytical solutions to 1 d layered background models with a spectral element sem numerical solver to calculate synthetic responses of local media to plane wave incidence this hybrid method accurately deals with local heterogeneities and discontinuity undulations and represents an efficient tool for the forward modelling of teleseismic coda including converted and scattered waves we benchmark the accuracy of the sem fk hybrid method against fk solutions for 1 d media we then compute sensitivity kernels for teleseismic coda waves by interacting the forward teleseismic waves with an adjoint wavefield produced by injecting coda waves as adjoint sources based on adjoint techniques these sensitivity kernels provide the basis for mapping variations in subsurface discontinuities density and velocity structures through non linear conjugate gradient methods we illustrate various synthetic imaging experiments including discontinuity characterization volumetric structural inversion for the crust or subduction zones these tests show that using pre conditioners based upon the scaled product of sensitivity kernels for different phases combining finite frequency traveltime and waveform inversion and or adopting hierarchical inversions from longto short period waveforms could reduce the non linearity of the seismic inverse problem and speed up its convergence the encouraging results of these synthetic examples suggest that inversion of teleseismic coda phases based on the sem fk hybrid method and adjoint techniques is a promising tool for structural imaging beneath dense seismic arrays

effect of water in depleted mantle on post spinel transition and implication for 660 km seismic discontinuity abstract we have determined the post spinel transition boundary in anhydrous and hydrous mg2sio4 in a temperature range from 1173 to 2023 k at 19 3 25 4 gpa using synchrotron in situ x ray diffraction measurements the phase boundary in mg2sio4 is located at 22 gpa and 1800 k and 22 1 gpa and 1500 k which is slightly lower 0 3 0 5 gpa than that determined in the previous in situ measurements using the same pressure scale e g katsura et al 2003 post spinel transition in mg2sio4 determined by high p t in situ x ray diffractometry phys earth planet inter 136 11 24 the clapeyron slope of mg2sio4 was found to be gentle i e between 0 4 and 0 7 mpa k which is also consistent with previous in situ measurements but inconsistent with diamond anvil cell experiments and theoretical estimations the phase boundary in mg2sio4 2 wt h2o which is relevant to fe free depleted harzburgitic composition is located between 23 4 and 23 6 gpa and 1500 k which shifts the hydrous boundary to the higher pressures relative to anhydrous mg2sio4 from 1 3 to 1 0 gpa the result for hydrous mg2sio4 shows steeper clapeyron slope between 3 2 and 3 1 mpa k compared with anhydrous mg2sio4 and hydrous pyrolite system the present data suggest that water has a strong influence on 660 km discontinuity and the depressions observed at this boundary in several regions especially related to subduction zones can be explained by the presence of water in depleted harzburgite component

shdiff svdiff splitting in an isotropic earth 1 the vertically polarized svdiff seismic phase sometimes arrives later than the horizontally polarized shdiff both phases propagate in the d layer at the base of the mantle and the difference in their arrival times is usually interpreted in terms of seismic anisotropy in d using numerical simulations we demonstrate that a significant 1 s delay of svdiff relative to shdiff is present even in the iasp91 isotropic reference earth model and in a model with a high s velocity in d relative to iasp91 the delay is accompanied by strong amplitude decay of svdiff with distance this relationship resembles the effect of anelasticity in a model with a low s velocity in d the waveform of svdiff can be very different from shdiff and this difference can be mistaken for a delay of shdiff relative to svdiff in a laterally heterogeneous isotropic d svdiff can also be delayed because unlike shdiff svdiff has strong amplitude decay along fast paths its traveltime is thus dominated by slow propagation paths and tends to be positively biased for d models with an s velocity difference of 3 between two hemispheres there are regions where shdiff arrives up to 15 s earlier than the first clearly visible svdiff this is observed in a corridor several hundred kilometers wide if these effects are misinterpreted in terms of d anisotropy in actual seismic data estimates of anisotropy are biased and may contribute to the idea of seismic anisotropy being different in high and low s velocity regions of d

large fluctuations of shallow seas in low lying southeast asia driven by mantle flow the sundaland continental promontory as the core of southeast asia is one of the lowest lying continental regions with half of the continental area presently inundated by a shallow sea the role of mantle convection in driving long wavelength topography and vertical motion of the lithosphere in this region has often been ignored when interpreting regional stratigraphy including a widespread late cretaceous eocene unconformity despite a consensus that southeast asia is presently situated over a large amplitude dynamic topography low resulting from long term post pangea subduction we use forward numerical models to link mantle flow with surface tectonics and compare predicted trends of dynamic topography with eustasy and regional paleogeography to determine the influence of mantle convection on regional basin histories a late cretaceous collision of gondwana derived terranes with sundaland choked the active margin leading to slab breakoff and a 10 15 myr long subduction hiatus slab breakoff likely resulted in several hundred meters of dynamic uplift and emergence of sundaland between 80 and 60 ma and may explain the absence of a late cretaceous eocene sedimentary record renewed subduction from 60 ma reinitiated dynamic subsidence of sundaland leading to submergence from 40 ma despite falling long term global sea levels our results highlight a complete down up down dynamic topography cycle experienced by sundaland with transient dynamic topography manifesting as a major regional unconformity in sedimentary basins

stress field variations in the swiss alps and the northern alpine foreland derived from inversion of fault plane solutions 1 this study is devoted to a systematic analysis of the state of stress of the central european alps and northern alpine foreland in switzerland based on focal mechanisms of 138 earthquakes with magnitudes between 1 and 5 the most robust feature of the results is that the azimuth of the minimum compressive stress s3 is generally well constrained for all data subsets and always lies in the ne quadrant however within this quadrant the orientation of s3 changes systematically both along the structural strike of the alpine chain and across it the variation in stress along the mountain belt from ne to sw involves a progressive counterclockwise rotation of s3 and is most clear in the foreland where it amounts to 45 50 this pattern of rotation is compatible with the disturbance to the stress field expected from the indentation of the adriatic block into the central european plate possibly together with buoyancy forces arising from the strongly arcuate structure of the moho to the immediate west of our study area across the alps the variation in azimuth of s3 is defined by a progressive counterclockwise rotation of about 45 from the foreland in the north across the helvetic domain to the penninic nappes in the south and is accompanied by a change from a slight predominance of strike slip mechanisms in the foreland to a strong predominance of normal faulting in the high parts of the alps the observed rotation can be explained by the perturbation of the large scale regional stress by a local uniaxial deviatoric tension with a magnitude similar to that of the regional differential stress and with an orientation perpendicular to the strike of the alpine belt the tensile nature and orientation of this stress is consistent with the spreading stress expected from lateral density changes due to a crustal root beneath the alps

deterministic stability and sensitivity analyses of slopes in jointed rock masses abstract the paper describes a deterministic stability analysis together with a sensitivity analysis of slopes in heavily jointed rock mass with planar circular or combined modes of failure this approach is based on the modified sarma method of analysis in which the strength parameters are derived from the rock mass classification rmr system and applied to the hoek and brown rock failure criterion the results of the analysis are presented as a plot of factor of safety f against acceleration k which shows the effect of vibrations blasting earthquake etc and acceleration on the factor of safety of slopes the paper also considers the influence of various strength parameters on the factor of safety and the acceleration k application of this technique is illustrated with the aid of an example of a slope in an iron ore mine

engineering characteristics of ankara greywacke under the foundation of the beytepe open air theatre ankara turkey the construction of a large open air theatre having with an audience capacity of 7 000 is planned at the beytepe campus of hacettepe university located near ankara turkey in the heart of anatolia the foundation of the open air theatre is composed of weak and heavily jointed ankara greywacke an estimation of the strength and deformation of the ankara greywacke was required for assessments of short and long term stability accordingly rock mass characterization of the ankara greywacke was investigated in detail by scan line surveys and back analyses of in situ tests performed on the excavated surface of the rock mass the final version of the hoek and brown criterion hoek et al in proceedings of the north american rock mechanics society meeting toronto canada pp 1 6 2002 together with and improvements proposed by sonmez and gokceoglu int j rock mech min sci 43 671 676 2006 were considered together for the back analyses of small slope benches subjected to plate loading test loaded to failure in addition the plate loading test data were used with some well known empirical equations for predicting of deformation modulus of rock masses to calculate ranges of values of the geological strength index gsi the static and pseudostatic slope stabilities of the audience seating structures to be supported by benches excavated into the rock were also analyzed the stability assessments revealed the unlikelihood of large rock mass failures for the short term construction stages or for the long term as constructed conditions under static or pseudo static conditions additionally the analyses showed that there was no need for anchors between the concrete seating structures and greywacke rock mass

seismostratigraphy and thermal structure of earth s core mantle boundary region we used three dimensional inverse scattering of core reflected shear waves for large scale high resolution exploration of earth9s deep interior d and detected multiple piecewise continuous interfaces in the lowermost layer d beneath central and north america with thermodynamic properties of phase transitions in mantle silicates we interpret the images and estimate in situ temperatures a widespread wave speed increase at 150 to 300 kilometers above the coremantle boundary is consistent with a transition from perovskite to postperovskite internal d stratification may be due to multiple phase boundary crossings and a deep wave speed reduction may mark the base of a postperovskite lens about 2300 kilometers wide and 250 kilometers thick the core mantle boundary temperature is estimated at 3950 200 kelvin beneath central america a site of deep subduction the d is relatively cold t 700 100 kelvin accounting for a factor of two uncertainty in thermal conductivity core heat flux is 80 to 160 milliwatts per square meter mw m 2 into the coldest d region and 35 to 70 mw m 2 away from it combined with estimates from the central pacific this suggests a global average of 50 to 100 mw m 2 and a total heat loss of 7 5 to 15 terawatts

lunar iron and titanium abundance algorithms based on final processing of clementine ultraviolet visible images the clementine mission to the moon returned global imaging data collected by the ultraviolet visible uvvis camera this data set is now in a final state of calibration and a five band multispectral digital image model dim of the lunar surface will soon be available to the science community we have used observations of the lunar sample return sites and stations extracted from the final dim in conjunction with compositional information for returned lunar soils to revise our previously published algorithms for the spectral determination of the feo and tio2 content of the lunar surface the algorithms successfully normalize the effects of space weathering so that composition may be determined without regard to a surface s state of maturity these algorithms permit anyone with access to the standard archived dim to construct high spatial resolution maps of feo and tio2 abundance such maps will be of great utility in a variety of lunar geologic studies

an inverted continental moho and serpentinization of the forearc mantle volatiles that are transported by subducting lithospheric plates to depths greater than 100 km are thought to induce partial melting in the overlying mantle wedge resulting in arc magmatism and the addition of significant quantities of material to the overlying lithosphere asthenospheric flow and upwelling within the wedge produce increased lithospheric temperatures in this back arc region but the forearc mantle in the corner of the wedge is thought to be significantly cooler here we explore the structure of the mantle wedge in the southern cascadia subduction zone using scattered teleseismic waves recorded on a dense portable array of broadband seismometers we find very low shear wave velocities in the cold forearc mantle indicated by the exceptional occurrence of an inverted continental moho which reverts to normal polarity seaward of the cascade arc this observation provides compelling evidence for a highly hydrated and serpentinized forearc region consistent with thermal and petrological models of the forearc mantle wedge this serpentinized material is thought to have low strength and may therefore control the down dip rupture limit of great thrust earthquakes as well as the nature of large scale flow in the mantle wedge

assessment of the failure mechanism of a highwall slope under spoil pile loadings at a coal mine abstract the design of a highwall in coal mining involves the consideration of many factors the evaluation of a lignite strip coal mine at yatag an in southwest turkey has provided an opportunity to combine both qualitative and quantitative factors in highwall design in this paper an attempt has been made to illustrate an instability problem that occurred in a highwall externally loaded by a spoil pile in the southern part of the pit geotechnical data with slope monitoring information were evaluated and shear strength of the highwall material was determined using non linear failure criterion for jointed rock masses in conjunction with rock mass classification using a model for the loaded highwall these studies were complemented by limit equilibrium back analysis and finite element stress analysis incorporating the effect of the spoil pile loadings the results of the back analysis and numerical modelling which confirmed each other and detailed examination of geotechnical data with movement monitoring records indicate that the instability occurred by shallow seated circular failures mainly caused by the stresses exerted by the pile the progressive failure developed through a combination of sliding along structural discontinuities and failure through the moderate quality low strength rock mass in addition the calculated slip surfaces match the actual slip surfaces and the non linear shear strength failure criterion confirmed that the mobilized shear strength appears realistic for design purposes

evolution and effect of the stress concentration and rock failure in the deep multi seam coal mining supports crushing accident occasionally occurs in the protected seam exploitation of deep multi seam coal mining structure and results in adverse effect to the production to prevent its recurrence in a newly developed working field a 3d numerical extraction model was built based on the geologic and mining conditions of jining coal mine to evolve the changes state and characteristics of the reconstructed vertical and lateral stress in rock interlayer after protective seam exploitation stress release and increase zones of this mining structure were separated mining induced localized stress concentration and the interlayer rock failure behavior were explored the action of concentrated stress on the hydraulic supports in protected seam was discussed upon the major stress redistribution using the infinitesimal strain method a mechanical model was created to further explore from the vertical and lateral directions the cause and mechanism of localized stress concentration and rock failure behavior in rock interlayer the field investigation was finally performed to verify the numerical and mechanical results and the essential control measures were proposed to prevent this accident key findings of this study bring some new insights into the deep multi seam coal extraction and help to promote a more reliable underground mining

outcrop scale physical properties of burns formation at meridiani planum mars 1 a rock mass rating rmr analysis was performed on an outcrop of burns formation at meridiani planum mars rmr values were calculated for the present dry conditions rmr 63 and past wet conditions rmr 52 for present day dry conditions the rock mass has an in situ modulus of deformation e of 21 1 gpa cohesive strength c 0 of 4 64 mpa and tensile strength t 0 of 0 24 mpa these values were reduced by at most 50 during previous water saturated conditions the critical grain crushing pressure p for dry conditions is 19 5 gpa with an uncertainty of about an order of magnitude analysis of the rover observations indicates that the physical properties of burns formation are in the range of analogous terrestrial porous rock masses such as sandstone and shale

on the potential of recording earthquakes for global seismic tomography by low cost autonomous instruments in the oceans 1 we describe the development and testing of an autonomous device designed to revolutionize earth structure determination via global seismic tomography by detecting earthquakes at teleseismic distances in the oceans one prototype mermaid short for mobile earthquake recording in marine areas by independent divers was constructed and tested at sea the instrument combines two readily available relatively low cost but state of the art components a sounding oceanographic lagrangian observer or solo float and an off the shelf hydrophone with custom built data logging hardware we report on the development of efficient wavelet based algorithms for the detection and discrimination of seismic events and analyze three time series of acoustic pressure collected at a depth of 700 m in pilot experiments conducted offshore san diego ca in these tests over 120 hours of data were gathered and five earthquakes of which one was teleseismic were recorded and identified quantitative estimates based on these results suggest that instruments of the mermaid type may collect up to a hundred tomographically useful teleseismic events per year the final design will also incorporate a global positioning system receiver onboard signal processing software optimized for low power chips and high throughput satellite communication equipment for telemetered data transfer with these improvements we hope to realize our vision of a global array of autonomous floating sensors for whole earth seismic tomography