shear wave splitting and subcontinental mantle deformation splitting observations are interpreted in terms of the strain induced lattice preferred orientation of mantle minerals especially olivine we consider three hypotheses concerning the origin of the continental anlsotropy 1 strain associated with absolute plate motion as in the oceanic upper mantle 2 crustal stress and 3 the past and present internal deformation of the subcontinental upper mantle by tectonic episodes it is found that the last hypothesis is the most successful namely that the most recent significant episode of internal deformation appears to be the best predictor of q for stable continental regions this is interpreted as fossil anisotropy whereas for presently active regions such as alaska the anisotropy reflects present day tectonic activity in the stable portion of north america there is a good correlation between delay time and lithospheric thickness this is consistent with the anisotropy being localized in the subcontinental lithosphere and suggests that intrinsic anisotropy is approximately constant the acceptance of this hypothesis has several implications for subcontinental mantle deformation first it argues for coherent deformation of the continental lithosphere crust and mantle during orogenies this implies that the anisotropic portion of the lithosphere was present since the deformational episode and rules out the addition of undeformed material to this layer by subsequent underplating or conductive growth of the thermal boundary layer one of the most important issues in the study of orogenies is the need to reconcile the formation of thickened lithosphere with the paradoxically high mantle temperatures often associated with orogenic episodes most efforts to date have focussed on modes of deformation whereby the cold lithospheric mantle is removed by convective instability or delamination and replaced by warm asthenosphere these models however are incompatible with the evidence for preserved coherent lithospheric deformation rather the deformed mantle appears to have been heated in place we suggest that the elevated mantle temperatures may be due to the strain heating accompanying the deformation

anisotropy of schists contribution of crustal anisotropy to active source seismic experiments and shear wave splitting observations we have made sets of five independent compressional and shear wave velocity measurements which with density allow us to completely characterize the transverse isotropy of samples from five metamorphic belts the haast schist terrane south island new zealand poultney slate chugach phyllite coldfoot schist and pelona schist united states these velocity measurements include compressional wave velocities for propagation parallel perpendicular and at 45 to the symmetry axis shear wave velocity for propagation and particle motion perpendicular to the symmetry axis and shear wave velocity for propagation parallel to the symmetry axis velocity measurements were made up to pressures of 1 gpa 35 km depth where microcracks are closed and anisotropy is due to preferred mineral orientation our samples exhibit compressional wave anisotropy of 9 20 as well as significant shear wave splitting metamorphic terranes that are anisotropic to ultrasonic waves may also be anisotropic at the scale of active and passive seismic experiments our data suggest that a significant thickness 10 20 km of appropriately oriented steeply dipping foliation schist in the crust could contribute as much as 45 of observed shear wave splitting our data set can also be used to model the effects of crustal anisotropy for active source seismic experiments in order to determine if the anisotropy of the terrane is significant and needs to be taken into account during processing and modeling of the data

intrinsic elasticity of a textured transversely isotropic muscovite aggregate comparisons to the seismic anisotropy of schists and shales 1 the anisotropic properties of phyllosilicate rocks are investigated through the modeling of the pore free intrinsic elasticity of a textured muscovite aggregate the elastic constants were calculated for textures as defined using orientation distribution functions odfs ranging from perfectly aligned to completely random the odfs were described using a gaussian distribution the width of which is controlled by the standard deviation of the orientations of the crystal c axis with respect to the sample foliation plane under the assumption that the sample has hexagonal transversely isotropic symmetry the values were obtained using the widely used voigt reuss hill averaging techniques as well as the geometric mean average gma the gma is more physically meaningful in that it requires that the elastic constants determined in either the stiffness or the compliance domains be invertible comparisons between these different averages indicate that strictly the voigt and reuss values do not necessarily provide the limiting bounds as is expected for the isotropic case despite this some characteristics of the elastic wave p wave anisotropy are only weakly dependent on the averaging procedure employed the calculated elastic constants are converted to the anisotropic and parameters in order to allow for comparison to existing measurements in the literature however these intrinsic results are not intended to provide a measure of the properties of phyllites per se but to provide a reference against which more sophisticated models that incorporate porosity layering and composition may be constructed

process of slip surface development and formation of slip surface clay in landslides in tertiary volcanic rocks japan abstract once landslide movement has been initiated the sliding mass tends to move toward a more stable position however landslides that have occurred in some tertiary volcanic rocks in japan show recurrent movement a possible reason for this behavior is that the mineral composition and properties of slip surface materials results in better lubrication along the slip surface as movement continues in order to determine the causes five landslides in japanese tertiary volcanics with different movement histories were studied based on geological investigation the results presented in this paper were obtained by studying the development process and formation of slip surfaces and clays in landslides in these volcanics for rocks of similar types and mineralogies the clay content of slip surface materials can be directly related to the displacement and history of slide movement this study indicates that the type of slip surface ranges from 1 striation type showing only striations on bedrock without clay to 2 brecciated type clayey breccia 3 mylonite type clay with breccia and to 4 clay type clay without breccia if the slip surface occurs in tuff or tuffaceous materials and is subjected to increasing slide movement the smectite content in the slip surface clay increases while the silicate mineral content decreases furthermore the smectite content is observed to increase within the same landslide from the head to the toe portion of the landslide direction of groundwater flow the groundwater along the slip surface above the impervious zone contains an increased concentration of ca ions as the concentration of hco3 ions exceeds 40 mg l an environment is created that promotes the formation of smectite this process indicates that there is an active ion exchange within the groundwater near the slip surface that forms smectite thus the formation of smectite in the slip surface requires the presence of tuff and a sufficient concentration of hco3 ions in the groundwater the study results presented here indicate that frictional resistance decreases as clay content increases the reason for repeated movement of japanese landslides in tertiary tuffs or tuffaceous rocks at or in the immediate vicinity of the slip surface is attributed to 1 an increase in clay materials along the slip surface as the slide movement is repeated and 2 the presence of groundwater that promotes the formation of smectite as is commonly known smectite is one of the clay minerals that has lowest frictional resistance

effect of fines and confining stress on undrained shear strength of silty sands a silty sand is considered as a delicate composite matrix containing a sand grain matrix and a silt matrix large strain undrained shear strength sus data in triaxial compression for a particular host sand mixed with different amounts of nonplastic fines are presented results indicate that the intergranular void ratio es which is the void ratio of the sand grain matrix given by e fc 1 fc where fc is the silt content fraction by weight plays an important role on sus of silty sands at the same void ratio e a silty sand shows low sus compared to that of the host sand however when compared at the same es provided that it is less than the maximum void ratio of the host sand emax hs both the silty sand and the host sand show similar sus that is fairly independent of the initial confining stress when es of the silty sand is in the vicinity of or exceeds emax hs the sus depends on the initial effective confining stress at such loose states sus normalized with respect to the initial con

geochemical characteristics of the slip zones of a landslide in granitic saprolite hong kong implications for their development and microenvironments geochemical investigations of the slip zones of a landslide in granitic saprolite revealed that they have signatures distinct from their host materials these distinctions include stronger si depletion higher al enrichment greater loi significant fixations of mn ba and ce stronger negative eu anomalies and greater accumulations of other rare earth elements ree altogether these geochemical characteristics indicate that a the slip zones have greater abundance of clays consistent with field and microscopic observations b concentration of clay size particles within the slip zones may have been from downward leaching and deposition and lateral transportation of al si solutions and colloids through pores and fractures within the saprolite and c there were prevailing oxidation and poor drainage and occasional reduction conditions within the slip zones it was concluded that geochemical analyses could be effective in gathering clues for understanding the development and nature of slip zones in landslide investigations

origin and weathering of landslide material in a loess area a geochemical study of the kulcs landslide hungary geochemical characteristics of sediments are responses to physical and chemical alteration in landslides however consequences of in situ interactions associated with landslides are difficult to distinguish from those related to long term weathering in young soft sediments such as loess in this study geochemical characteristics of the kulcs landslide in hungary are studied to identify the provenance of the loess paleosol red clay sequence and geochemical signatures that can potentially be attributed to the effects of landsliding results indicate that sliding is largely initiated by the lithological changes within the landslide body sediments above the sliding zone closely resemble the non slipped pleistocene old loess deposits from hungary it is also confirmed that the sliding zone develops in old paleosols in the loess sequence and red clays at its base which are all characterized by the enrichment of al k na h2o and considerable depletion in ca and mg associated with carbonates altogether these geochemical characteristics indicate that chemical weathering trend of unconsolidated landslide sediments is slightly modified by the redistribution of carbonates and decomposition of plagioclase it is assumed that the distribution of mn and ba is modified by the water sediment interaction in the landslide

application of a two dimensional electrical tomography technique for investigating landslides along the amman dead sea highway jordan electrical tomography geophysical surveys were conducted with the syscal r2 resistivity instrument at the location of instantaneous rock failure of a few 1 000s m3 along the amman dead sea highway jordan providing a ground image for investigating landslide sites which caused material damage and closed the road this slide occurred along two major fault planes after heavy rainfall in a rock consisting of a succession of shale marl and marly limestone layers which were folded tilted and fractured three electrical tomography profiles were performed along the axis of the slope to assess the landslide risk in such potential unstable areas the results obtained based on two dimensional inversion of field data have allowed mapping of the shale zones at depths which are characterized by a lower resistivity value and have demonstrated that the rupture was initiated at the contact between the shale mass black colored and the massive limestone white yellowish brown colored

hydrogeological assessment of a deep seated coastal landslide based on a multi disciplinary approach abstract this study focuses on the understanding of the hydrogeological functioning of a complex landslide affecting the coastal municipality of villerville normandy france we wish to provide a conceptual model of functioning using a multi disciplinary approach a set of geomorphological geological and hydrological data as well as in situ observations were first used to understand the main landslides processes new acquisitions were then carried out to strengthen our hypotheses thanks to passive geophysics sp and the characterization of physicochemical parameters of surface waters the joint analysis of former ert surveys and sp results is of significant interest for correlating hydrokinetic information measured at the surface with resistivity tomograms which provide internal information this study highlights 1 a division of the behaviour into three parts from east to west 2 variable internal dynamics highlighted by geology and electric fields 3 a preferential discharge of the continental water table upstream of the central area of the landslide this work tends to demonstrate that on the basis of initial in situ knowledge available on many study areas the understanding of the hydrogeological functioning can be substantially improved by implementing light and inexpensive surveys also suitable for large and complex landslides

spherule layers records of ancient impacts abstract a large extraterrestrial object striking earth at cosmic velocity melts and vaporizes silicate materials which can condense into highly spheroidal sand size particles that get deposited hundreds to thousands of kilometers from the point of impact these particles known as impact spherules have been detected in great abundance in a relatively small number of thin discrete layers ranging in age from less than a million years to 3 47 billion years unaltered impact spherules consist entirely of glass microtektites or a combination of glass and crystals grown in flight microkrystites impact spherule layers form very rapidly and can be very extensive even global in extent e g the cretaceous tertiary k t boundary layer so they form excellent time stratigraphic markers because they are always found in a stratigraphic context spherule layers are probably superior to terrestrial craters and related structures for assessing the environmental and biotic effects of large impacts a reco

shallow and deep seated regolith slides on deforested slopes in canakkale nw turkey abstract this study deals with the stripping of regolith on a steep slope by surface wash and shallow landslides and a deep seated landslide at a lower slope that took place on 17 february 2003 at the village of mazilik east of canakkale turkey soil loss and shallow slides dominate on the deforested steep slopes in the study area and occur preferentially along slope parallel sub horizontal joint planes with clay coatings particularly oxyhydroxides that are rich in fe but poor in mn as a result of weathering under well drained conditions gully erosion also occurs where the regolith cover is relatively thick up to 4 m the area of the deep seated landslide however is dominated by silty clay 46 a geoelectrical resistivity survey revealed a clay rich zone at depths of 3 10 m corresponding to the slip surface of the slide which was associated with excessive water content after the snowy day of 14 february 2003 with a daily precipitation of 16 4 mm based on thornthwaite s water budget analysis the study area has a slide prone condition with excess soil moisture content heavy rainfall events snow accumulation and snow melting in winter months and low soil permeability also favouring slope instability

upper mantle p wave velocities in the southeast north island new zealand abstract reversed pn velocities have been determined from regional earthquake sources for the wairarapa region in the southeast north island new zealand values were 8 64 0 13 km s in the easternmost part of the region and 8 90 0 13 km s in the central wairarapa which are consistent with subducted pacific plate lying at shallow depth under the region a value of 8 22 km s between wellington and the wairarapa region is interpreted as a possible difference in the velocity structure above the refractor between the two localities

noble metal abundances in an early archean impact deposit we report detailed analyses on the concentrations of the noble metals pd os ir pt and au in an early archean spherule bed s4 of probable impact origin from the lower fig tree group barberton greenstone belt south africa compared to other sedimentary deposits of known or suspected impact origin some noble metals are present in exceptionally high concentrations noble metal abundances are fractionated relative to abundances in chondrites with ratios of osir ptir pdir and auir at only 80 80 41 and 2 of these values in ci chondrites although an extraterrestrial source is favored for the noble metal enrichment the most plausible cause of the fractionation is by regional hydrothermal metasomatic alteration

depth variable crustal anisotropy patterns of crustal weakness and destructive earthquakes in canterbury new zealand abstract low strain rate areas of the earth are often host to long recurrence but damaging earthquake cycles in many cases these events occur on reactivated and previously unrecognized faults noise based imaging of seismic anisotropy is capable of revealing the seismic fabric of inherited structures as well as the preferred orientation of pervasive cracking in the upper crust both features with a potential relationship to failure on faults causing catastrophic earthquakes by understanding the orientation of seismic weaknesses seismic hazard in areas of low strain rate can be better understood the geometric relation of crustal anisotropy and the 3 d crustal stress tensor has the potential to qualitatively inform us of the location and or orientation of large crustal earthquakes in regions with little previously recorded seismicity but known tectonic loading directions in this study noise cross correlation techniques were used to measure surface wave dispersion these measurements were inverted to solve for azimuthal anisotropy of fundamental mode rayleigh waves in the canterbury region of the south island of new zealand the results of passive imaging show a distinct difference in magnitude and azimuth of surface wave anisotropy at different depths within the crust across the region we suggest that the approximately east west fast axis orientation at upper crustal depths reflects the cretaceous faulting of the impacting chatham rise and the approximately northeast southwest fast axis orientation at lower crustal depths reflects the present plate boundary strain direction the upper crust fast axis parallels the surface rupturing greendale fault which gave rise to the ongoing destructive canterbury earthquake sequence we suggest that the upper crust azimuthal anisotropy measured using ambient noise is capable of revealing dominant patterns of crustal weaknesses in regions like canterbury which are prone to low recurrence but highly damaging earthquakes

origin of small scale segmentation and transpressional thrusting along the alpine fault new zealand the alpine fault is the major structural feature of the australian pacific plate boundary in the south island of new zealand geologic evidence suggests that half to three quarters of the plate boundary displacement is accommodated by movement on the fault detailed investigation of the central section of the alpine fault has revealed that it consists of oblique thrust sections striking 020 050 that are linked by subvertical right lateral faults striking between 065 and 090 the segmentation is on a scale of 1 10 km similarly oriented right lateral faults are abundant southeast of the alpine fault and are consistent with stresses induced in an elastic layer by an oblique slip ductile fault zone below propagation of the fault to the surface is predicted to result in an en echelon arrangement of strike slip and thrust segments it is suggested that the spatial distribution of segments is affected by the existence of deeply incised valleys in the hanging wall that disturb the stress field to depths of 1 4 km the segmentation is near surface and does not appear to act as a barrier to the propagation of large earthquakes

absent anisotropy the paradox of the southern alps orogen 1 a high resolution active source dataset recorded across the southern alps of new zealand displays unusually strong s wave phases which show minimal shear wave splitting a suite of methods was used to analyse the data to minimize the uncertainty in the anisotropy measurements we use the silver and chan 1991 method cross correlation of stacked data and deconvolution in combination with the other methods the results were consistent at each station but differed between stations fault parallel fast directions with delay times of 0 0 08 s were calculated from the most impulsive s wave arrivals the crustal rocks from the southern alps are strongly anisotropic in the laboratory contrasting with results shown here the minimal delay times suggest that the shear waves are affected by multiple phases of deformation in the crust

isotopic evidence for the cretaceous tertiary impactor and its type high precision mass spectrometric analysis of chromium in sediment samples from the cretaceous tertiary k t boundary coincident with the extinction of numerous organisms on earth confirms the cosmic origin of the k t phenomenon the isotopic composition of chromium in k t boundary samples from stevns klint denmark and caravaca spain is different from that of earth and indicates its extraterrestrial source the chromium isotopic signature is consistent with a carbonaceous chondrite type impactor the observed differences in the chromium isotopic composition among various meteorite classes can serve as a diagnostic tool for deciphering the nature of impactors that have collided with earth during its history

upper mantle anisotropy in the new zealand region shear wave splitting parameters of fast polarization direction and delay time t are determined using data from the southern alps passive seismic experiment sapse on the south island of new zealand and in the surrounding region our results clearly show that are subparallel to trends of the alpine and marlborough faults and to the pacific australian plate boundary the t values range from 0 6 2 2 s with an average value of 1 6 s the largest values are from the central south island the main source of the observed shear wave splitting is an anisotropic region between 40 400 km the width of the zone is approximately 200 km we attribute the coincidence of surface structural trends with the measured and the large t values to significant shear deformation in a 200 km thick zone along the plate boundary extending from the surface to deep within the upper mantle

application of electrical resistivity tomography technique for investigation of landslides a case from turkey electrical resistivity imaging is a widely used tool in near surface geophysical surveys for investigation of various geological environmental and engineering problems including landslide in this study an electrical resistivity tomography ert survey was conducted in a landslide area located in the soke district of aydin turkey in 2003 the neogene aged units on the slope next to a newly built school building became unstable due to an excavation work and moved after a heavy rainfall the resulting landslide partly covered the school the authors carried out a 2 d resistivity survey along three profiles over the landslide mass using a wenner configuration it yielded useful information about the geometry and characteristics of the landslide in addition a 2 d synthetic resistivity modelling study was carried out to understand the response of the resistivity method to a landslide problem before the field surveys eight boreholes were also drilled in the landslide area both the drilling and resistivity results indicated the presence of a fault in the site also the resistivity data from the line measured along the axis of the landslide revealed the surface of rupture

salt water intrusion mapping by geoelectrical imaging surveys the geoelectrical imaging method is a tool for mapping the intrusion boundary between fresh water and saline water due to its inherent capability to delineate the lateral changes in pore water salinity a new field survey technique that can be used for environmental and geotechnical investigations has been developed this study evaluates the multiscale survey technique as a tool employed in electrical imaging to detect the salt water intrusion boundary in yan state of kedah northwest malaysia the technique was incorporated into these surveys and it has proved to be a robust method for accurately mapping the fresh water saline water boundary the resulting resistivity sections from these surveys were consistent with both the available geological and borehole information from the area and the previous resistivity surveys conducted by the geological survey of malaysia at those sites

rapid least squares inversion of apparent resistivity pseudosections by a quasi newton method1 a fast inversion technique for the interpretation of data from resistivity tomography surveys has been developed for operation on a microcomputer this technique is based on the smoothness constrained least squares method and it produces a two dimensional subsurface model from the apparent resistivity pseudosection in the first iteration a homogeneous earth model is used as the starting model for which the apparent resistivity partial derivative values can be calculated analytically for subsequent iterations a quasi newton method is used to estimate the partial derivatives which reduces the computer time and memory space required by about eight and twelve times respectively compared to the conventional least squares method tests with a variety of computer models and data from field surveys show that this technique is insensitive to random noise and converges rapidly this technique takes about one minute to invert a single data set on an 80486dx microcomputer

offshore rayleigh group velocity observations of the south island new zealand from ambient noise data we thank captain and crew of the r v thomas g thompson cruise tn229 the r v roger revelle cruise rr1002 and the sio obsip facility for expert assistance at sea the obs instruments used in this field program were provided by the u s national ocean bottom seismic instrumentation pool http www obsip org moana seismic data are archived at the iris data management center the collection of ocean bottom seismic data was funded by the national science foundation under grants ear 0409564 ear 0409609 and ear 0409835 new zealand onshore seismic data made available by the geonet project sponsored by eqc gns science and linz j stachnik acknowledges support from the cires postdoctoral fellowship program f c lin was supported by nsf grant cybersees 1442665 and the king abdullah university of science and technology kaust under award ocrf 2014 crg3 2300 we thank martha savage dan zietlow justin ball craig jones bill fry and peter molnar for valuable comments and discussion and john collins for leading the moana obs experiment we thank two anonymous reviewers and editor mike ritzwoller for their constructive comments

groundwater flow after heavy rain in landslide slope area from 2 d inversion of resistivity monitoring data in the interest of monitoring the flow of groundwater from heavy rains we conducted surface resistivity tomography through the vadose zone over several days the measured data were modeled by 2 d inversion a laboratory experiment was carried out to estimate the difference in geological characteristics we measured the effects of groundwater fluctuation using two tank models one using sand and one using bricks which represent unconsolidated sediments and jointed rocks respectively in the sand model we succeeded in monitoring water level fluctuation as the change in resistivity over time in the brick model the water level did not appear as a distinct boundary field experiments were carried out in an area in which the near surface conditions consisted of heavily weathered rocks with an extensive shear zone several tens of meters thick measurements were performed over 42 days during which we observed changes in resistivity associated with heavy rainfall it became clear that resistivity decreases of up to 8 were present in highly porous zones in heavily weathered layers this result suggests a connection between a decrease in resistivity and the infiltration of rainwater in particular a pronounced zone of minimum resistivity may indicate infiltration of rainwater into the vadose zone the relationship between resistivity changes and rainfall was inferred to depend on the permeability of geological structure

case history of controlling a major landslide at karandu turkey abstract landslides are the major geotechnical problems in highway projects the trinity consisting of water discontinuity and clay wdc is the major driving force behind any landslide a detailed model study including geology hydrogeology engineering geology and geotechnics enables the geotechnical designer to alleviate a slide problem the karandu landslide with a mass of over 100 million m 3 forms a transportation bottleneck from ankara and istanbul to sinop in turkey the artesian pressure in the slide mass is greater than 2 bars well developed and outsloping discontinuities have conveyed infiltrating groundwater towards the slide area high clay content of the slide mass derived from an underlying unit of claystone and siltstone reduced the shear strength considerably in addition to surface drainage a subsurface drainage system consisting of water wells and trenches have reduced the water table and piezometric level appreciably they formed a comprehensive network to mitigate the adverse effect of the wdc thus the minimum factor of safety increased 30 or more this solution allowed the designer to cross the slide area and to follow the best alignment for the given corridor thus construction costs have reduced to one third of rehabilitation costs for the existing road also transportation time was reduced from 2 5 h to 50 min

glassy microspherules microtektites from an upper devonian limestone the properties of microspherules recovered from an upper devonian marine limestone immediately overlain by a geochemical anomaly of siderophile and chalcophile elements are similar to those of impact derived microtektites these microspherules are glass have splash form shapes contain spherical vesicles and lechatelierite inclusions and show oxide compositional variations similar to those in known microtektites these characteristics suggest that these upper devonian microspherules have an impact origin a bolide impact may have occurred about 365 million years ago on the south china plate and caused a faunal extinction on eastern gondwana

electrical resistivity tomography technique for landslide investigation a review abstract in the context of in situ geophysical methods the electrical resistivity tomography ert is widely used for the near surface exploration of landslide areas characterized by a complex geological setting over the last decade the technological improvements in field data acquisition systems and the development of novel algorithms for tomographic inversion have made this technique more suitable for studying landslide areas with a particular attention to the rotational translational and earth flow slides this paper aims to present a review of the main results obtained by applying ert for the investigation of a wide spectrum of landslide phenomena which affected various geological formations and occurred in different geographic areas in particular significant and representative results obtained by applying 2d and 3d ert are analyzed highlighting the advantages and drawbacks of this geophysical technique finally recent applications of the time lapse ert tl ert for landslide investigation and the future scientific challenges to be faced are presented and discussed

electrical imaging in archaeology abstract a field data acquisition system has been developed to enable an electrical image of the subsurface to be produced rapidly and effectively under computer control the unprocessed measured apparent resistivity data give a very approximate but nevertheless useful picture of the subsurface and an example section across the ramparts of salmonsbury fort gloucestershire england illustrates this a section measured across the mediaeval site at rocester derbyshire england demonstrates how the data may also be modelled using modern finite element computer software however the sharpest images are produced by a newly developed and completely automatic computer inversion process the technique is illustrated with an image of true resistivity measured across a burnt mound in birmingham

microstructural study of a natural slip zone quantification and deformation history abstract microstructure of a natural slip zone was comprehensively examined using a combination of images captured systematically by optical microscopy opm and backscattered electron microscopy bem techniques microstructural features identified on these images were processed and evaluated using an advanced image analysis system which proved that quantitative analyses could considerably enhance the understanding of shear behavior of slip zones it was found that variations of porosity abundance of platy clay particles and alignments of particles are significant indicators revealing nature of deformation processes these indicators show that global mechanical behavior of the investigated slip zone can be conceptualized as that of normally consolidated clayey soils under drained conditions the geometric patterns of the microstructure of the slip zone are similar to the s c fabrics seen in tectonic shear zones it is suggested that combined progressive bulk simple shear and pure shear modes enable to realistically reconstruct the kinematic history of the slip zone through which particle movements and microstructural evolution were accomplished via various types of particulate flows the results of this study show that clay mineralogy plays a more important role in the development of the slip zone than abundance of clay size particles while both clay mineralogy and relative proportions of each particle size fraction control the response of particles to shear deformation among the fractions present in the slip zone fine silts are the strongest indicator of global shear stress characterized by their highest degree of alignment whereas clay particles are the weakest highest degree of shape preferred orientation is also found within fine silt domains

investigation of the nature of slip surface using geochemical analyses and 2 d electrical resistivity tomography a case study from lapseki area nw turkey the nature and subsurface structure of the slip surface of a landslide was studied on the basis of geochemical analyses and 2 d electrical resistivity tomography ert survey head scarp and lateral slip surfaces of the landslide marked by clear slickensided shear planes were composed of the average amounts of clayey silt 32 5 and sand 67 5 energy dispersive x ray spectroscopy edx data revealed the enrichment of si 23 24 fe 12 2 al 9 51 and c 8 34 in the elemental composition of the disturbed slip surface from x ray diffractometry xrd data six main clay types were determined such as volkonskoite halloysite ferrosilite saponite illite and nontronite the ert survey displayed that the landslide developed as a reactivation on the upper part of an old landslide body

geological record and reconstruction of the late pliocene impact of the eltanin asteroid in the southern ocean in 1995 an expedition on board the research vessel fs polarstern explored the impact site of the eltanin asteroid in the southern ocean the only known asteroidimpact into a deep ocean basin analyses of the geological record of the impact region place the event in the late pliocene 2 15 myr and constrain thesize of the asteroid to be 1 km the explosive force inferred for this event places it at the threshold of impacts believed to have global consequences and its studyshould therefore provide a baseline for the reconstruction and modelling of similar events which are common on geological timescales

formation of spinels in cosmic objects during atmospheric entry a clue to the cretaceous tertiary boundary event abstract magnetic spinels produced by oxidation of extraterrestrial objects in the atmosphere have a composition distinct from terrestrial spinels they are characterized by a high iron oxidation state arising from crystallization under high oxygen fugacities and a high nickel concentration due to the relatively high abundance of this element in extraterrestrial material the iron oxidation state increases from micrometeorites to meteoroid ablation material and to impact generated products this reflects a progressive increase of the oxygen fugacity corresponding to decreasing altitudes of crystallization spinels found at the cretaceous tertiary boundary are similar to those that crystallized from meteoroid ablation material and impact generated products supporting the view that a collisional event did occur at the end of the cretaceous

dynamics of a complex mass movement triggered by heavy rainfall a case study from nw turkey abstract following a period of heavy precipitation a large and complex mass movement namely the dagkoy landslide occurred in the west black sea region of turkey on may 21 1998 this paper describes the conditioning factors of the landslide and interprets the mass transport processes in terms of a movement scenario geology geomorphology and vegetation cover were considered as the conditioning factors of the failure observations showed that the gently sloping about 10 area is mostly covered by dense forest trees at the crown where the motion initiated significant intersection of the collapsed slope with dip of the local marls seems to have contributed to the formation and geometry of the landslide the distance from the crown down to the toe of the landslide measured more than 600 m with about 0 6 km 3 total earth material displaced the landslide has both a block sliding characteristics in the upper portions and a debris flow soil flow component around the margins of the sliding blocks in the middle parts and at the toe the proposed scenario for the landslide reveals that the movement was initiated near crown as a result of the excess water content in the marls at the end of 3 days of heavy rainfall the early perturbations transverse cracks ridges etc lasted for 6 7 h after which the central part of the zone started to move as a soil flow in which very large intact blocks were transported even though the movement was very rapid 1 2 m min there was no loss of life however the movement destroyed 38 houses one mosque and a considerable amount of farmland

kinematics of oblique collision and ramping inferred from microstructures and strain in middle crustal rocks central southern alps new zealand the hanging wall of the alpine fault near franz josef glacier has been exhumed during the past similar to2 3 m y providing a sample of the ductilely deformed middle crust of a modem obliquely convergent orogen presently exposed rocks of the pacific plate are inferred to have undergone several phases of ductile deformation as they moved westward above a mid crustal detachment initially they were transpressed across the outboard part of the orogen resulting in oblate fabrics with a down dip stretch later they encountered the alpine fault experiencing an oblique slip backshearing on vertical planes this escalator like deformation tilted and thinned the incoming crust onto that crustal scale oblique ramp this style of hanging wall deformation may affect only the most rapidly uplifting central part of the southern alps because of the low flexural rigidity of the crust in that region and its displacement over a relatively sharp ramp angle at depth a 3d transpressive flow affected mylonites locally near the fault but their shear direction remained parallel to plate motion ruling out ductile extrusion as an important process in this orogen outside the mylonite zone late cenozoic shortening is inferred to be modest 30 40 as measured from deformation of younger biotite grains oblique collision is dominated by translation on the alpine fault and rocks migrate rapidly through the deforming zone preventing the accumulation of large finite strains transpression may play a minor role in oblique collision c 2001 elsevier science ltd all rights reserved

the influence of crenulation cleavage development on the bulk elastic and seismic properties of phyllosilicate rich rocks abstract the anisotropy of seismic wave propagation is strongly influenced by the mineralogy and microstructure of rocks phyllosilicates are elastically highly anisotropic and are therefore thought to be important contributors to seismic anisotropy in the continental crust crenulation cleavage is one of the most common microstructural fabrics found in multiply deformed phyllosilicate rich crustal rocks we calculated the bulk elastic properties and resulting wave velocities for rock samples that preserved three different stages of crenulation cleavage development an initial planar foliation a moderately developed crenulation cleavage and a well developed crenulation cleavage mineral orientation maps were obtained using electron backscatter diffraction and calculations were made using asymptotic expansion homogenization combined with the finite element method the difficulties involved with sample preparation and data acquisition of phyllosilicate rich rock samples are also discussed we compare our results to more conventional methods for calculating an aggregate stiffness matrix from a mineral orientation map namely voigt and reuss averages these averages do not account for grain scale interactions and therefore deviate from the results calculated using asymptotic expansion homogenization our results show that the rocks characterized by a planar foliation and a moderately developed crenulation cleavage are highly anisotropic with p wave anisotropies up to 30 9 and s wave anisotropies up to 34 2 whereas the rock characterized by a well developed crenulation cleavage is only mildly anisotropic with a p wave anisotropy of 15 5 and s wave anisotropy of 10 7 progressive development of the fabric also causes the orientations of p and s wave velocity maxima and s wave polarization directions to change markedly despite the high anisotropy imparted by a planar schistosity the variety of folds and fabrics typically found in phyllosilicate rich rocks within larger scale crustal volumes will tend to mute the anisotropy possibly to the point of appearing nearly isotropic

seismic anisotropy in western tibet 1 teleseismic sks data collected by a temporary broadband array across western tibet are analysed to constrain shear wave splitting parameters small delay anisotropy is detected with a rotation of the fast axis azimuth from 40 e in the tarim basin west of yecheng to more easterly values between hotien and shiquanhe a large contribution of crustal anisotropy would be required to link fast axis directions orthogonal to the kunlun and karakorum ranges with crustal shear due to underthrusting the fast axes north of yecheng may instead reflect frozen proterozoic strain in the tarim lithosphere the e w direction south of hotien may be related to sinistral shear along the altyn tagh fault it is possible that fast axes directions south of this fault reflect northeastwards motion of tibet relative to asia

the fracture criticality of crustal rocks summary the shear wave splitting observed along almost all shear wave ray paths in the earth s crust is interpreted as the effects of stress aligned fluid filled cracks microcracks and preferentially oriented pore space once away from the free surface where open joints and fractures may lead to strong anisotropy of 10 per cent or greater intact ostensibly unfractured crustal rock exhibits a limited range of shear wave splitting from about 1 5 to 4 5 per cent differential shear wave velocity anisotropy interpreting this velocity anisotropy as normalized crack densities a factor of less than two in crack radius covers the range from the minimum 1 5 per cent anisotropy observed in intact rock to the 10 per cent observed in heavily cracked almost disaggregated near surface rocks this narrow range of crack dimensions and the pronounced effect on rock cohesion suggests that there is a state of fracture criticality at some level of anisotropy between 4 5 and 10 per cent marking the boundary between essentially intact and heavily fractured rock when the level of fracture criticality is exceeded cracking is so severe that there is a breakdown in shear strength the likelihood of progressive fracturing and the dispersal of pore fluids through enhanced permeability the range of normalized crack dimensions below fracture criticality is so small in intact rock that any modification to the crack geometry by even minor changes of conditions or minor deformation particularly in the presence of high pore fluid pressures may change rock from being essentially intact below fracture criticality to heavily fractured above fracture criticality this recognition of the essential compliance of most crustal rocks and its effect on shear wave splitting has implications for monitoring changes in any conditions affecting the rock mass these include monitoring changes in reservoir evolution during hydrocarbon production and enhanced oil recovery and in monitoring changes before and after earthquakes amongst others

three dimensional geophysical anatomy of an active landslide in lias group mudrocks cleveland basin uk a geoelectrical investigation of a slow moving earth slide earth flow in lower jurassic lias group rocks of the cleveland basin uk is described these mudrock slopes are particularly prone to failure and are a major source of lowland landslides in the uk but few attempts have been made to spatially or volumetrically characterise the subsurface form of these slides the primary aim of this study was to consider the efficacy of fully three dimensional geoelectrical imaging for landslide investigation with reference to a geological setting typical of lias group escarpments the approach described here included a reconnaissance survey phase using two dimensional electrical resistivity tomography ert resistivity mapping self potential sp profiling and mapping followed by a detailed investigation of an area of the landslide using three dimensional 3d ert and self potential tomography spt interpretation of the geophysical data sets was supported by surface observations aerial lidar and differential gps geomorphological surveys and intrusive investigations boreholes and auger holes the initial phase of the study revealed the existence of a strong sp signature at the site consistent with a streaming potential source and established the relationships between the main geological units the geomorphologic expression of the landslide and the resistivity of the materials in and around the study area the 3d spt model generated during the second phase of the study indicated drainage patterns across the landslide and preferential flow from the low permeability mud rocks into the underlying more permeable sandstone formation because of favourable resistivity contrasts between the clay rich whitby mudstone formation landslide material and the underlying staithes sandstone formation the volumetric 3d ert image allowed a number of surface and subsurface landslide features to be identified and spatially located these included the lateral extent of slipped material and zones of depletion and accumulation the surface of separation and the thickness of individual earth flow lobes and the dipping in situ geological boundary between the whitby mudstone and staithes sandstone bedrock formations