empirical relationships among seismic velocity effective pressure porosity and clay content in sandstone we use a multivariate analysis to investigate the influence of effective pressure pe porosity and clay content c on the compressional velocity vp and shear velocity vs of sandstones laboratory measurements on water saturated samples of 64 different sandstones provide a large data set that was analyzed statistically for each sample relationships between effective pressure and vp and vs have been determined all samples were well fit by relationships that have an exponential increase in velocity at low pe tapering to a linear increase with pe for pe greater than 0 2 kbar there are differences in the pressure dependences of velocity for different rocks particularly at very low pressures however the differences cannot be attributed to or c for the combined set of measurements from all samples the best fitting formulations are vp 5 77 6 94 1 73c 0 446 pe e 16 7pe and vs 3 70 4 94 1 57c 0 361 pe e 16 7pe while this is admittedly a very simplified parameterization it is remarkable how well

geophysical geological transect and tectonic evolution of the swiss italian alps a complete alpine cross section integrates numerous seismic reflection and refraction profiles across and along strike with published and new field data the deepest parts of the profile are constrained by geophysical data only while structural features at intermediate levels are largely depicted according to the results of three dimensional models making use of seismic and field geological data the geometry of the highest structural levels is constrained by classical along strike projections of field data parallel to the pronounced easterly axial dip of all tectonic units because the transect is placed close to the western erosional margin of the austroalpine nappes of the eastern alps it contains all the major tectonic units of the alps a model for the tectonic evolution along the transect is proposed in the form of scaled and area balanced profile sketches shortening within the austroalpine nappes is testimony of a separate cretaceous age orogenic event west directed thrusting in these units is related to westward propagation of a thrust wedge resulting from continental collision along the meliata hallstatt ocean further to the east considerable amounts of oceanic and continental crustal material were subducted during tertiary orogeny which involved some 500 km of n s convergence between europe and apulia consequently only a very small percentage of this crustal material is preserved within the nappes depicted in the transect postcollisional shortening is characterized by the simultaneous activity of gently dipping north directed detachments and steeply inclined south directed detachments both detachments nucleating at the interface between lower and upper crust large scale wedging of the adriatic or apulian lower crust into a gap opening between the subduced european lower crust and the pile of thin upper crustal flakes alpine nappes indicates a relatively strong lower crust and detachment between upper and lower crust

the dav and periadriatic fault systems in the eastern alps south of the tauern window alpine deformation of austroalpine units south of the tauern window is dominated by two kinematic regimes prior to intrusion of the main periadriatic plutons at 30 ma the shear sense was sinistral in the current orientation with a minor north side up component sinistral shearing locally overprints contact metamorphic porphyroblasts and early periadriatic dykes direct rb sr dating of microsampled synkinematic muscovite gave ages in the range 33 30 ma whereas pseudotachylyte locally crosscutting the mylonitic foliation gave an interpreted 40ar 39ar age of 46 ma the transition from sinistral to dextral transpressive kinematics related to the periadriatic fault occurred rapidly between solidification of the earlier dykes and of the main plutons subsequent brittle ductile to brittle faults are compatible with n s to nnw sse shortening and orogen parallel extension antithetic riedel shears are distinguished from the previous sinistral fabric by their fine grained quartz microstructures with local pseudotachylyte formation one such pseudotachylyte from speikboden gave a 40ar 39ar age of 20 ma consistent with pseudotachylyte ages related to the periadriatic fault the magnitude of dextral offset on the periadriatic fault cannot be directly estimated however the jump in zircon and apatite fission track ages establishes that the relative vertical displacement was 4 5 km since 24 ma and that movement continued until at least 13 ma

palinspastic reconstruction and topographic evolution of the eastern alps during late tertiary tectonic extrusion this paper presents a new palinspastic restoration of the eastern alps for neogene time and an attempt to reconstruct the neogene palaeogeology palaeotopography and palaeohydrography in connection with the structural evolution the eastern alps underwent radical horizontal displacement during the neogene due to large strike slip systems and formation of structural windows our palinspastic reconstruction considers a the rearrangement of tectonic units dismembered during tectonic extrusion b the tectonic denudation driven by displacement of the crystalline blocks c geochronological arguments and d the sedimentary record of the syn extrusion basins the rearrangement of tectonic blocks results in a remarkably good fit of highly dismembered zones both in crystalline and sedimentary areas and shows the pre miocene unstretched pattern of the eastern alps reduced to 65 of its present day e w elongation using this structural frame and considering the sedimentary record a set of palaeogeologic and palaeotopographic sketch maps with the palaeo river systems is presented for three time slices pre syn and post extension situation in late oligocene and early miocene times the western eastern alps were already mountainous whereas the eastern part of the orogen formed lowlands or hilly areas enhanced block movement in the course of the extrusion process around the early middle miocene boundary led to the formation of intramontane sedimentary basins and a fault induced reorientation of the drainage pattern which forms the basis of the modern river system in the area east of the tauern window this region where pre miocene land surfaces are preserved probably became a mountainous area not before late miocene time and never reached the elevations of the areas further west

v p v s in unconsolidated oil sands shear from stoneley the sdt a sonic tool was tested in a borehole in the orinoco heavy oil belt eastern venezuela the sonically slow reservoir consists of unconsolidated quartz sand interbedded with shale full waveform analysis yields both compressional and shear slownesses we calculated the shear wave slowness from the stoneley slowness compressional and stoneley slownesses were determined using modified semblance techniques the compressional velocity is relatively fast in the heavy oil pay zone compared to the remainder of the well heavy oil 8 api possesses a finite rigidity at sonic frequencies and the rigidity of the hydrocarbon adds to the stiffness of the poorly consolidated sand the sand would not otherwise yield such a high velocity compressional and shear velocities of samples from eight whole cores were measured in the laboratory and the core velocities were found to be consistent with the logs especially encouraging is the agreement of the laboratory shear with the shear log derived from stoneley th

states of paleostress north and south of the periadriatic fault comparison of the drau range and the friuli southalpine wedge this study focuses on the analysis of structures and kinematics of a n s profile along the axis of maximum shortening of the european eastern alps the area includes the southern austroalpine unit in the north and the southalpine unit which is a part of the adriatic indenter the stratigraphically different units are separated by the periadriatic fault the major strike slip fault within the alps in order to assess the kinematics of these units mainly fault slip data from north and south of the periadriatic fault were analyzed we distinguish a succession of five main kinematic groups in both units 1 n s compression 2 nw se compression 3 ne sw compression 3 changes gradually from subvertical to subhorizontal 4 n s compression and 5 nw se compression our study reveals that the deformation sequence on either sides of the paf is similar the mean orientations of the principal stress axes however show small but consistent differences the subhorizontal axes north of the periadriatic fault plunge northward in the south southward a counterclockwise ccw rotation of the southern part in respect to the north is evident and in line with the well known counterclockwise rotation of the adriatic indenter as well as dextral displacement of the n fanning stress field along the periadriatic fault opposing plunge directions are interpreted as a primary feature of the internal stress field within an orogenic wedge further increased during ongoing compression

compressional and shear wave velocities as a function of confining stress in dry sandstones a laboratory study was carried out to investigate the influence of confining stress on compressional and shear wave velocities for a set of rock samples from gas producing sandstone reservoirs in the cooper basin south australia the suite of samples consists of 22 consolidated sublitharenites with helium porosity ranging from 2 6 to 16 6 we used a pulse echo technique to measure compressional and shear wave velocities on dry samples cylindrical 4 6 2 cm at room temperature and at elevated confining stress 60 mpa compressional and shear wave velocities in samples increase non linearly with confining stress a regression equation of the form v a be dp gives a good fit to the measured velocities with improved prediction of velocities at high confining stresses compared with equations suggested by other studies the predicted microcrack closure stresses of the samples show values ranging from 70 mpa to 95 mpa and insignificant correlation with porosity permeability or clay content there is a positive correlation between change in velocity with core porosity and permeability but this association is weak and diminishes with increasing confining stress experimental results show that pore geometry grain contact type and distribution and location of clay particles may be more significant than total porosity and clay content in describing the stress sensitivity of sandstones at in situ reservoir effective stress the stress dependence of cooper basin sandstones is very large compared with data from other studies the implication of our study for hydrocarbon exploration is that where the in situ reservoir effective stress is much less than the microcrack closure stress of the reservoir rocks the variation of reservoir effective stress could cause significant changes in velocity of the reservoir rocks the velocity changes induced by effective stress in highly stress sensitive rocks can be detected at sonic log and probably surface seismic frequencies

modelling the interseismic deformation of a thrust system seismogenic potential of the southern alps this article focuses on the montello thrust system in the eastern southern alps as a potential seismogenic source this system is of particular interest because of its lack of historical seismicity nevertheless the system is undergoing active deformation we developed a finite element model using visco elasto plastic rheology the free parameters of the model essentially the locking status of the three thrusts included in the study were constrained by matching the observed horizontal gps and vertical levelling data we show that the amount of interseismic fault locking and thus the seismic potential is not necessarily associated with the fastest slipping faults more specifically the locked bassano thrust has a greater seismic potential than the freely slipping montello thrust the findings suggest that faults with subtle evidence of quaternary activity should be carefully considered when creating seismic hazard maps

geomorphology and age of the marocche di dro rock avalanches trentino italy abstract the marocche di dro deposits in the lower sarca valley are some of the most distinctive rock avalanche deposits of the alps we use geomorphology and cosmogenic 36 cl exposure dating of boulders to divide the marocche di dro deposits into two rock avalanche bodies the marocca principale to the north and the kas to the south the deposits were previously undated and had been mapped as up to five different events the largest event marocca principale which comprises an estimated 1000 10 6 m 3 of predominantly rotzo formation limestones occurred 5300 860 yr ago the release area is located mainly in the alcove between mt casale and mt granzoline but likely extends all the way to mt brento the kas event took place 1080 160 yr ago with detachment below mt brento the kas debris with an estimated volume of 300 10 6 m 3 buried the southern third of the marocca principale deposit kas presents a barren stark landscape dominated by house sized tovel member rotzo formation boulders bearing distinctive chert lenses both the extreme relief of the rock wall more than 1300 m and the tectonic setting predispose the range front to massive failure for the two events initially translational movement likely quickly evolved into complex failure and massive collapse run out across the valley of several kilometers and run up on the opposite slope of hundreds of meters followed a summary of all dated and large historical landslides in the alps underlines the periods of enhanced slope activity discussed in the literature 10 9 kyr 5 3 kyr and 2 1 kyr the latter especially for the southern alps no deposits of the first temporal cluster are found at marocche di dro the age of marocca principale at 5300 860 yr suggests occurrence during the second period failure may have been related to the shift to wetter colder climate at the transition from the middle to the late holocene nevertheless a seismic trigger cannot be ruled out for the kas rock avalanche at 1080 160 yr ago we implicate the middle adige valley 1046 ce earthquake as trigger its epicentral distance is much closer to the sarca valley in comparison to that of the verona earthquake 1117 ce

use of psinsar data to infer active tectonics clues on the differential uplift across the giudicarie belt central eastern alps italy abstract the permanent scatterers synthetic aperture radar interferometry psinsar methodology provides high resolution assessment of surface deformations precision ranging from 0 8 to 0 1 mm year over long periods of observation hence it is particularly suitable to analyze surface motion over wide regions associated to a weak tectonic activity for this reason we have adopted the psinsar technique to study regional movement across the giudicarie belt a nne trending trust belt oblique to the southern alpine chain and presently characterized by a low to moderate seismicity over 11 000 ps velocities along the satellite line of sight los were calculated using images acquired in descending orbit during the 1992 1996 time span the psinsar data show a differential uplift of around 1 4 1 7 mm year across the most external wnw dipping thrusts of the giudicarie belt mt baldo mt stivo and mt grattacul thrusts alignment this corresponds to a horizontal contraction across the external part of the giudicarie belt of about 1 3 1 5 mm year

segmentation and configuration of subducted lithosphere in italy an important control on thrust belt and foredeep basin evolution the apennine foredeep basin system located on continental crust consists of four roughly parallel basin segments each containing a flexural outer rise and an inner trough that deepens continuously toward the thrust belt flexural modeling of subsidence data across the basin indicates that this foredeep basin results mainly from deep subsurface loads acting on the subducted slab from within the subduction zone rather than from the topographic load of the apennine mountains the geometry of the four basin segments observed within the apennine foredeep is thus inferred to reflect subduction of segmented lithosphere where each lithospheric segment corresponds to a segment of the foredeep basin beneath the basin and in the foreland the lithosphere is continuous segmentation occurs only at depth beneath the thrust belt this pattern olf segmentation of the subducted lithosphere at depth is reflected in the large scale geometry of the outer part of the apennine thrust belt and appears to control it similarly the pattern of segmentation also appears to control the position of the eastern limit of back arc type extension in western italy these relations strongly suggest a genetic relation between subduction zone processes foredeep basin geometry and thrust belt evolution in which the configuration of the subducted lithosphere largely controls the large scale surface deformation observed in the apennine system

seismic attenuation and velocity dispersion in heterogeneous partially saturated porous rocks summary using a numerical approach we explore wave induced fluid flow effects in partially saturated porous rocks in which the gas water saturation patterns are governed by mesoscopic heterogeneities associated with the dry frame properties the link between the dry frame properties and the gas saturation is defined by the assumption of capillary pressure equilibrium which in the presence of heterogeneity implies that neighbouring regions can exhibit different levels of saturation to determine the equivalent attenuation and phase velocity of the synthetic rock samples considered in this study we apply a numerical upscaling procedure which permits to take into account mesoscopic heterogeneities associated with the dry frame properties as well as spatially continuous variations of the pore fluid properties the multiscale nature of the fluid saturation is taken into account by locally computing the physical properties of an effective fluid which are then used for the larger scale simulations we consider two sets of numerical experiments to analyse such effects in heterogeneous partially saturated porous media where the saturation field is determined by variations in porosity and clay content respectively in both cases we also evaluate the seismic responses of corresponding binary patchy type saturation patterns our results indicate that significant attenuation and modest velocity dispersion effects take place in this kind of media for both binary patchy type and spatially continuous gas saturation patterns and in particular in the presence of relatively small amounts of gas the numerical experiments also show that the nature of the gas distribution patterns is a critical parameter controlling the seismic responses of these environments since attenuation and velocity dispersion effects are much more significant and occur over a broader saturation range for binary patchy type gas water distributions this analysis therefore suggests that the physical mechanisms governing partial saturation should be accounted for when analysing seismic data in a poroelastic framework in this context heterogeneities associated with the dry frame properties which do not play important roles in wave induced fluid flow processes per se should be taken into account since they may determine the kind of gas distribution pattern taking place in the porous rock

kinematics seismotectonics and seismic potential of the eastern sector of the european alps from gps and seismic deformation data abstract we present a first synoptic view of the seismotectonics and kinematics of the eastern sector of the european alps using geodetic and seismological data the study area marks the boundary between the adriatic and the eurasian plates through a wide zone of deformation including a variety of tectonic styles within a complex network of crustal and lithospheric faults a new dense gps velocity field new focal mechanisms and seismic catalogues with uniformly re calibrated magnitudes from 1005 are used to estimate geodetic and seismic deformation rates and to develop interseismic kinematic and fault locking models kinematic indicators from seismological and geodetic data are remarkably consistent at different spatial scales in addition to large scale surface motion gps velocities highlight more localized deformation features revealing a complex configuration of interacting tectonic blocks for which new constraints are provided in this work accounting for elastic strain build up at faults bonding rotating blocks the geodetic and seismological data highlight two belts of higher deformation rates running wsw ene along the eastern southern alps esa in italy and e w in slovenia where deformation is more distributed the highest geodetic strain rates are observed in the montello cansiglio segment of the esa thrust front for which the higher density of the gps network provides indications of limited interseismic locking most of the dextral shear between the eastern southern alps and the eastern alps blocks is accommodated along the fella sava fault rather than the periadriatic fault in northern croatia and slovenia geodetic and seismological data allow constraining the kinematics of the active structures bounding the triangular shaped region encompassing the sava folds which plays a major role in accommodating the transition from adria to pannonian like motion trends the analysis of the seismic and geodetic moment rates provides new insights into the seismic potential along the esa front

active intraplate deformation within adria examples from the adriatic region abstract recent seismicity recorded in the adriatic region suggests that active deformation occurs within the adria plate earthquakes are common in the adjoining chains and in particular along the northern apennines in the southern alps and along the dinaric albanian hellenic thrust fronts in addition medium to low grade seismicity also affects the foreland and is clustered along two main transects through the centre of the adriatic region the two zones of active deformation correspond to the mid adriatic ridge and the gargano region and approximately trend nw se and e w respectively several interpretations have been proposed to explain the deformation observed within the adriatic foreland including a variety of contrasting kinematic and geodynamic models we attempted to unravel the complicated structural evolution of the central adriatic region by interpreting industrial and ministerial shallow and deep seismic profiles and the recent seismicity recorded in the adriatic the subsurface study allowed us to better understand the structural style timing and rates of deformation affecting the mid adriatic ridge and the gargano region and to unravel the relationships of active deformation with respect to the adjacent chains the results of our study indicate that the structural setting and type of seismicity of the central adriatic can be explained in terms of active intraplate deformation with the reactivation of inherited discontinuities

lateral extrusion in the eastern alps part 1 boundary conditions and experiments scaled for gravity lateral extrusion encompasses extensional collapse gravitational spreading away from a topographic high in an orogenic belt and tectonic escape plane strain horizontal motion of wedges driven by forces applied to their boundaries in the eastern alps it resulted from 1 an overall northerly compression apulia against eurasia 2 a strong foreland bohemian massif 3 lack of constraint along a lateral boundary carpathian region and 4 a previously thickened gravitationally unstable thermally weakened crust eastern alpine orogenic belt six indentation experiments reproduce lateral extrusion at lithospheric scale the models have two to four lithospheric layers with a mohr coulomb rheology for the upper and a viscous rheology for the lower crust the lithosphere rests upon a low viscosity asthenosphere a broad indenter a narrow deformable area and a weakly constrained eastern margin fullfill as closely as possible conditions in the eastern alps indentation produces both thickening in front of the indenter and escape of triangular wedges lateral variations in crustal thickness become attenuated by gravitational spreading the overall fault pattern includes domains of reverse strike slip oblique normal and pure normal faults strike slip faults in conjugate sets develop serially the narrow width of the deformable area and the strength of the foreland determine the angles between the sets gravitational spreading produces a rhombohedral pattern of oblique and pure normal faults along the unconstrained margin opposite the unconstrained margin the indenter front shows thrusts and folds intersecting with the conjugate strike slip sets a triangular indenter favors spreading high velocity of indentation favors escape high confinement limits lateral motion inhibits spreading and favors thickening lateral extrusion in the eastern alps is best modeled by 1 a weak lateral confinement 2 a broad and straight indenter 3 a narrow width of the deformable area and 4 a rigid foreland crustal thickening lateral escape and gravitational spreading all contribute to the overall deformation

the problem of the deep structure of the southern alps 3 d material balance considerations and regional consequences abstract the lombardic southern alps are a typical thin skinned frontal fold and thrust belt although this recent reassessment is widely accepted figures for shortening and schemes for transfer of shortening at their eastern end in the giudicarie vary exact section balancing is not feasible because of insufficient information but approximate shortening is on an order probably exceeding 100 km with about 80 100 km attributable to the middle to late miocene milan belt acceptance of this quantitative conclusion has farreaching consequences transfer of the milan belt shortening in the east follows the lateral edge of the allochthon which is sinistrally transpressive the giudicarie line with its sedimentary decollement zone the giudicarie belt the pre existing adamello intrusions and the jorio tonale line are part of the thrust masses and consequently allochthonous transfer of shortening across the insubric line into the tauern antiform and associated structures of neo alpine compression in the eastern alps resulted in the sinistral dissection of the insubric line at the giudicarie line superposition of this compression on pannonian stretching east of and transtensive motion at the brenner line west of the tauern produced a confusing structural pattern whose quantitative kinematics have not been worked out another sinistral probably compressive transfer zone is postulated at the western end of the milan belt retrodeformation leads simultaneously to both a straightening of the insubric line and the connection of the canavese line with the villalvernia varzi levanto line to define the boundary of the adriatic block at the beginning of neo alpine deformation

focal mechanism inversion in the giudicarie lessini seismotectonic region southern alps italy insights on tectonic stress and strain abstract a set of 41 focal mechanisms 1989 2006 from p wave first polarities is computed from relocated seismic events in the giudicarie lessini region southern alps estimated hypocentral depths vary from 3 1 to 20 8 km for duration magnitudes md in the range 2 7 5 1 stress and strain inversions are performed for two seismotectonic zones namely g giudicarie and l lessini this subdivision is supported by geological evidence seismicity distribution and focal mechanism types the available number of data 16 in g 22 in l does not make possible any further subdivisions seismotectonic zones g and l are undergoing different kinematic regimes thrust with strike slip component in g and strike slip in l principal stress and strain axes in each sub region show similar orientations the direction of maximum horizontal compressive stress is roughly perpendicular to the thrust fronts along the giudicarie belt in zone g and compatible with right lateral strike slip reactivation of the faults belonging to the schio vicenza system in zone l on the whole kinematic regimes and horizontal stress orientations show a good fit with other stress data from focal mechanisms and breakouts and with geodetic strain rate axes

thermochronological record of thrusting and strike slip faulting along the giudicarie fault system alps northern italy the giudicarie fault system represents the central approximately ne sw trending segment of the periadriatic fault system based on new fission track data the near surface evolution of the units bordering the giudicarie fault system gfs is analysed new and published zircon fission track zft data are compiled in an age contour map of the area and depict some first order features of cooling and exhumation pattern out of the three main permian plutons located in the footwall of the gfs the northern brixen pluton and southernmost kreuzberg pluton yielded zft ages of about 100 ma while the intermediate ifinger pluton cooled through the zircon partial annealing zone only in the miocene the ifinger granodiorite overthrusts the southalpine basement and the permian rocks of the athesian volcanic district along the nw dipping brittle naif fault across this thrust an important age jump from miocene to permian zft ages is observed suggesting that the deformation has jumped towards the southeast thus deactivating the related segment of the gfs the most eye catching feature of the age contour map is the corridor of young miocene zft ages from small tonalitic intrusions along the northern giudicarie fault this corridor connects early miocene 17 23 ma zft ages of the ne adamello with the middle late miocene 19 9 ma zft ages of the meran mauls basement and the western tauern window and provides evidence for a polyphase deformation along the gfs a three step evolution model is proposed for the gfs a shearing of the northern rim of the adamello batholith along the dextral strike slip periadriatic fault system b bending of the central part of the fault to a ne direction together with the adjacent intrusive rocks c dissection of the bend part meran mauls fault by the sinistral transpressive northern giudicarie fault and exhumation of small tonalitic bodies along this structure highlights different exhumation history for permian intrusions along the giudicarie fault system very consistent zft ages of 15 ma for the entire meran mauls basement corridor of miocene zircon fission track ages along the giudicarie fault system evidence for a polyphase deformation along the giudicarie fault system

the western end of the eoalpine high pressure belt texel unit south tyrol italy eclogites in the texel unit eastern alps south tyrol italy represent the westernmost outcrops of the e w striking eoalpine high pressure belt ehb east of the tauern window the ehb forms part of a cretaceous intracontinental south dipping subduction collision zone however the same nappe stack displays a northwest dip at its western end this prominent change in dip direction gave rise to discussions on the general setting of the eoalpine collision based on our own observations and literature data we present a new tectonic model for the western end of the ehb due to the special situation of this area at the tip of the southalpine indenter originally south east dipping structures became overturned and former thrusts appear as normal faults e g schneeberg fault zone while former normal faults presently display thrust geometries e g jaufen fault thus we explain the current configuration with a coherent eoalpine subduction direction

a classification for the pressure sensitivity properties of a sandstone rock frame a three parameter formula is proposed to describe the sensitivity of the bulk modulus or shear rigidity for a sandstone rock frame under applied isotropic loading the theoretical basis for this relation is the use of excess compliance as a pseudo function to describe all internal weaknesses in the rock regardless of their origin the law is fitted to 179 sets of laboratory measurements on unsaturated reservoir core and outcrop sandstones that have low to moderate porosity and a range of clay fractions and cementation a stress index defined to quantitatively rank the reservoir sands indicates that laboratory derived pressure sensitivity is highest 10 per mpa maximum for the clean moderate porosity paleocene sands from the forties formation and west of shetlands whereas the lower porosity cemented and more consolidated permian sands rank as least pressure sensitive 1 per mpa maximum higher porosity sands are stress sensitive because of the overall rock frame compressibility all of t

eoalpine and mesoalpine tectonics in the southern alps according to structural and stratigraphic data eoalpine and mesoalpine tectonics can be clearly recognized in the southern alps and distinguished from the better known neoalpine deformation

microcrack induced elastic wave anisotropy of brittle rocks the failure of brittle rocks during compression is preceded by the formation growth and coalescence of microcracks elastic wave velocities are reduced in the presence of open microcracks and fractures and may therefore be used to monitor the progressive damage of the rock in general these microcracks are not randomly oriented and the rock displays an elastic anisotropy the elastic anisotropy due to cracks can be expressed in terms of a second rank and fourth rank crack density tensor for open cracks the contribution of the fourth rank crack density tensor to the elastic wave velocities is small these results are compared with recent measurements of the ultrasonic compressional and shear wave velocities for propagation parallel and perpendicular to an increasing axial stress applied at constant confining stress to berea sandstone inversion of the velocity measurements indicates that the microcracks propagate parallel to the maximum compressive stress in agreement with current rock mechanics theory a reasonable fit to the data is obtained using only the second rank crack density tensor even though at high confining stress the cracks are expected to be in partial contact along their length this is consistent with the model of elastic wave propagation in a medium containing partially contacting fractures published by white however measurements of off axis wave velocities are required to fully quantify the contribution of the fourth rank crack density tensor

effects of diagenesis and clays on compressional velocities in rocks experimental results at ultrasonic frequencies in brine or water saturated samples cut perpendicular to bedding demonstrate that compressional velocities vary linearly with porosity and volume fraction clay in detrital silicate rocks characterized by pores with low aspect ratios p wave velocity is more sensitive to porosity than clay content obeying the empirically derived expression vp 2 4c 8 6 5 8 at 800 bars confining pressure and 400 bars pore pressure where the units of vp are kilometers per second is the volume fraction pores and c is the volume fraction clay deviations from this equation are less than 2 with the exception of the high pore aspect ratio st peter sandstone which has a compressional velocity that is 17 higher than the predicted value the equation is insensitive to the chemical compostion of the dominant clay mineral and apparently insensitive to the location of the clay grains with respect to the mineral framework e g in free pore space or in contact zones between mineral grains of lower compressibilities

the effect of clay distribution on the elastic properties of sandstones the shape and location of clay within sandstones have a large impact on the p wave and s wave velocities of the rock they also have a large effect on reservoir properties and the interpretation of those properties from seismic data and well logs numerical models of different distributions of clay structural laminar and dispersed clay can lead to an understanding of these effects clay which is located between quartz grains structural clay will reduce the p wave and s wave velocities of the rock if the clay particles become aligned or form layers the velocities perpendicular to the alignment will be reduced further s wave velocities decrease more rapidly than p wave velocities with increasing clay content and therefore poisson s ratios will increase as the velocities decrease these effects are more pronounced for compacted sandstones small amounts of clay that are located in the pore space will have little effect on the p wave velocity due to the competing influence of the density effect and pore fluid stiffening the s wave velocity will decrease due to the density effect and thus the poisson s ratio will increase when there is sufficient clay to bridge the gaps between the quartz grains p wave and s wave velocities rise rapidly and the poisson s ratios decrease these effects are more pronounced for under compacted sandstones these general results are only slightly modified when the intrinsic anisotropy of the clay material is taken into account numerical models indicate that there is a strong nearly linear relationship between p wave and s wave velocity which is almost independent of clay distribution s wave velocities can be predicted reasonably accurately from p wave velocities based on empirical relationships however this does not provide any connection between the elastic and petrophysical properties of the rocks numerical modelling offers this connection but requires the inclusion of clay distribution and anisotropy to provide a model that is consistent with both the elastic and petrophysical properties if clay distribution is ignored predicting porosities from p wave or s wave data for example can result in large errors estimation of the clay distribution from p wave and s wave velocities requires good estimates of the porosity and clay volume and verification from petrographic analyses of core or cuttings for a real data example numerical models of the elastic properties suggest the predominance of dispersed clay in a fluvial sand from matching p wave and s wave velocity well log data using log based estimates of the clay volume and porosity this is consistent with an interpretation of other log data

the alpine evolution of the southern alps around the giudicarie faults a late cretaceous to early eocene transfer zone abstract data supporting relevant late cretaceous early eocene sinistral displacement along the giudicarie fault zone and a minor neogene dextral displacement along the periadriatic lineament are discussed the pre adamello structural belt is present only in the internal lombardy zone located w of the adamello massif this belt is unknown in the dolomites and surrounding areas located to the e of the giudicarie lineament upper cretaceous early eocene thick syntectonic flysch deposits of lombardy and giudicarie are well preserved along the southern and eastern border of the pre adamello belt s vergent alpine orogen towards the e in the dolomites and in the carnic alps and external dinarides only incomplete remnants of flysch deposits aptian albian and turonian maastrichtian in age are present they can be considered as equivalent to those of lombardy and giudicarie formerly in connection to each other along the n giudicarie corridor to the s the syntectonic flysch deposits are laterally replaced by the calcareous red pelagites of the scaglia rossa and by the carbonate shelf deposits of the friuli to the e and bagnolo to the s carbonate platforms the different location in the southern structural accretion of the eastern and western opposite blocks the dolomites versus the pre adamello belt can be related to the cretaceous eocene convergence in this frame the n giudicarie fault has been considered as part of a former transfer zone which produced the sinistral lateral displacement of the southern alps front for an amount of some 50 km during the late eocene to early oligocene the transfer zone was mostly sealed by the paleogene adamello batholith oligocene to neogene compressional evolution inverted the n giudicarie fault into a backthrust of the austroalpine units over the south alpine chain

strike slip movements and thrusting along a transpressive fault zone the north giudicarie line insubric line northern italy this paper analyzes the kinematic evolution and the deformation partitioning within an important transpressive fault zone located in the central part of the alpine chain the north giudicarie line is a nne trending fault which offsets the dextral insubric line with an apparent left lateral displacement of about 70 km the main fault plane of the north giudicarie line dips about 35 45 to the nw the footwall is characterized by n s striking strike slip faults which reactivate extensional faults of early jurassic to late cretaceous age the early deformation history of the north giudicarie line is revealed by basement and limestone mylonites shear sense of mylonites indicates on average top to the east thrusting these movements took place during the late oligocene early miocene when the insubric line was active as a right lateral strike slip fault therefore in this time span the north giudicarie line can be interpreted as a dextral transpressive bend of the insubric line mylonites have later been overprinted by brittle faults related to top to the se thrusting of middle late miocene age during this event the shape of the insubric line was strongly modified by left lateral transpression along the giudicarie fault zone deformation was partitioned between prevailing compression along the giudicarie line and left lateral strike slip movements along the n s striking faults these faults transferred the strike slip component of the giudicarie line into a wider area of the central southern alps

tectonics of the dolomites southern alps northern italy abstract in post variscan times the dolomites underwent a number of tectonic events which may be summarized as follows permian and triassic rifting phases broke the area into n s trending basins with different degrees of subsidence a middle triassic transpressive event then deformed the region along a n70 e axis generating flower structures within the basement volcano tectonic domal uplift and subsequent caldera formation occurred at the same time as the late ladinian magmatism early jurassic rifting also controlled the subsidence which increased eastward this long period of deformation was followed by a pre neogene late cretaceous palaeogene e w ene wsw compression which generated a w vergent belt possibly equivalent to the folded foreland of the dinaric chain a 70 km e w section of the dolomites indicates shortening of at least 10 km during the neogene the dolomites as far north as the insubric lineament were the innermost part of a s vergent thrust belt the basement of the dolomites was thrust southwards along the valsugana line onto the sedimentary cover of the venetian prealps for at least 10 km this caused a regional uplift of 3 5 km the valsugana line and its backthrusts on the northern side of the central dolomites generated a 60 km wide pop up in the form of a synclinorium within which the sedimentary cover adapted itself mainly by flexural slip often forming triangle zones the shortening linked to this folding is about 5 km with neogene thrusts faulting and folding pre existing thrust planes on the north eastern side of the dolomites neogene deformation is apparently more strictly controlled by the transpressive effects of the insubric lineament and shortening of the sedimentary cover may be greater than in the central dolomites minor deformation linked to the giudicarie belt is present in the western dolomites the present structure of the dolomites is thus the result of a number of tectonic events of different significance and different strike only a 3 dimensional restoration can unravel the true structure of the dolomites

an insightful parametrization for the flatlander s interpretation of time lapsed seismic data an approximation is developed that allows mapped 4d seismic amplitudes and time shifts to be related directly to the weighted linear sum of pore pressure and saturation changes the weights in this relation are identified as key groups of parameters from a petroelastic model and include the reservoir porosity this dependence on groups of parameters explains the inherent non uniqueness of this problem experienced by previous researchers the proposed relation is of use in 4d seismic data feasibility studies and inversion and interpretation of the 4d seismic response in terms of pore pressure and water saturation changes a further result is drawn from analysis of data from the north sea and west africa which reveals that the relative interplay between the effects of pore pressure and saturation changes on the seismic data can be simplified to the control of a single spatially variant parameter cs cp combining these results with those from published literature we find that cs cp 8 appears to be a generality across a range of clastic reservoirs with a similar mean porosity using this cs cp value an in situ seismic scale constraint for the rock stress sensitivity component of the petroelastic model is constructed considering this component carries the largest uncertainty

k ar dating of synkinematic clay gouges from neoalpine faults of the central western and eastern alps abstract with ongoing alpine convergence and deformation during exhumation there is a general progression from ductile to brittle behaviour on the periadriatic fault and kinematically related faults farther north e g the simplon rhone fault and a diffuse discontinuous zone of generally dextral strike slip movement on the southern boundary of the aar massif k ar dating of fine grained illite from clay fault gouges provides a reliable method for establishing the maximum age of this transition to brittle faulting and for short lived faults the approximate time of faulting itself the new results establish that brittle faulting on the northeastern segment of the canavese fault i e the part of the periadriatic fault southwest of lago maggiore occurred around 20 ma with south side up kinematics a k ar age of ca 17 ma for the crosscutting giudicarie fault in the eastern alps is effectively identical with an already published pseudotachylyte age and places a lower limit on major and continuous strike slip movements of the periadriatic fault the age of brittle faulting farther north on the southern border of the aar massif is from 13 6 0 3 to 8 3 1 1 ma consistent with the younger cooling and exhumation in this area the dominantly dextral brittle faulting becoming younger to the north reflects the continued indentation and anticlockwise rotation of adria as alpine units become exhumed and progressively welded to the southern block in contrast to the eastern alps there is no field evidence for westward lateral extrusion of alpine units relative to adria and the european foreland

impact of topography climate and moisture sources on isotopic composition δ 18 o δ d of rivers in the pyrenees implications for topographic reconstructions in small orogens understanding how orogenic topography controls the spatial distribution and isotopic composition of precipitation is critical for paleoaltitudinal reconstructions here we determine the isotopic composition o and d of 82 small rivers and springs from small catchments in the pyrenees calculation of the deuterium excess d excess parameter allows the distinction of four distinct isotopic provinces with d excess values of between 15 and 22 in the northwest between 7 and 14 in the central northern pyrenees and between 3 and 11 in the northeast the southern pyrenees have a homogenous d excess signature ranging from 7 to 14 our results show significant local moisture recycling and or rain amount effect in the northwestern pyrenees and control by evaporation processes during rainfall events in the southern pyrenees and for low elevated samples of the northeast of the range based on the distribution of d excess values we estimate contrasting isotope lapse rates of 2 9 21 4 km o d in the northwest 2 7 21 4 km o d in the north central and 3 7 31 7 km o d in the northeastern pyrenees the southern pyrenees show distinctly higher lapse rates of 9 5 77 5 km o d indicating that in this area the altitudinal effect in not the only parameter driving isotopic composition of rivers despite their relatively low topographic gradient the pyrenees exert a direct control on the isotopic composition of river waters especially on their northern side the variations in isotopic composition elevation relationships documented along the strike of the range are interpreted to reflect an increasing continentality effect driven by wind trajectories parallel to the range and mixing with mediterranean air masses despite these effects the measurable orographic effect on precipitation in the pyrenees proves that the isotopic composition approach for reconstructing past topography is applicable to low elevation orogens

prediction of elastic wave velocities in sandstones using structural models elastic wave propagation in fluid saturated sandstones depends upon two sets of rock features 1 the volume fractions and elastic constants of the rock constituents quartz clay water etc and 2 microstructural geometry grain contacts pore aspect ratios while the former data are usually obtainable the latter are relatively inaccessible we present a new method for determining microstructural data using idealized but physically representative models of sandstone the key to the method is the simulation of certain depositional and diagenetic processes in a manner that completely specifies the geometry of the resulting models hence the geometric features of the grain space and void space required for various theories of elastic propagation can be calculated directly from the models we find good agreement between predictions and measurements of compressional and shear wave velocities in both clean and clay bearing saturated sandstones in contrast with previous efforts at predicting velocitie

structure of the lithosphere beneath the eastern alps southern sector of the transalp transect abstract the interpretation of the seismic vibroseis and explosive transalp profiles has examined the upper crustal structures according to the near surface geological evidences and reconstructions which were extrapolated to depth only the southern sector of the transalp transect has been discussed in details but its relationship with the whole explored chain has been considered as well the seismic images indicate that pre collision and deep collision structures of the alps are not easily recognizable conversely good records of the neo alpine to present architecture were provided by the seismic sections two general interpretation models crocodile and extrusion have been sketched by the transalp working group 2002 both illustrate the continental collision producing strong mechanical interaction of the facing european and african margins as documented by giant lithosphere wedging processes arguments consistent with the extrusion model and with the indentation of adriatic southalpine lithosphere underneath the tauern window tw are according to the previous dss reconstructions the bouguer anomalies and the receiver functions seismological data the european moho descends regularly attaining a zone south of the periadriatic lineament pl the moho boundary and its geometry appear to be rather convincing from images of the seismic profile the tauern window intense uplift and exhumation is coherent with the strong compression regime which acted at depth thus originating the upward and lateral displacement of the mobile and ductile penninic masses according to the extrusion model the indentation of the penninic mobile masses within the colder and more rigid adriatic crust cannot be easily sustained wedging of the adriatic stiffened lower crust under high stresses and into the weaker penninic domain can be a more suitable hypothesis furthermore the intrusion of the european penninic crustal wedge underneath the dolomites upper crust is not supported by any significant uplifting of the dolomites the total average uplift of the dolomites during the neogene appears to be 6 7 times smaller than that recognized in the tw markedly the northward dip of the pl reaching a depth of approximately 20 km is proposed in our interpretation finally the adriatic upper crustal evolution points to the late post collision change in the tectonic grow up of the eastern alps orogenic chain the tectonic accretion of the northern frontal zone of the eastern and central alps was interrupted from the late miocene serravallian tortonian onward as documented by the molasse basin evolution on the contrary the structural nucleation along the s vergent tectonic belt of the eastern southern alps montello friuli thrust belt severely continued during the messinian and the plio pleistocene this structural evolution can be considered to be consistent with the deep under thrusting and wedge indentation of the adriatic lithosphere underneath the southern side of the eastern alps thrust and fold belt similarly the significance of the magmatic activity for the construction of the southern alps crust and for its mechanical and geological differentiation which qualified the evolution of the thrust and fold belt is highlighted starting with the permian triassic magmatism and progressing with the paleogene occurrences along the periadriatic lineament and in the venetian magmatic province lessini euganei hills

late oligocene neogene evolution of europe adria collision new structural and geochronological evidence from the giudicarie fault system italian eastern alps the giudicarie fault system giudicarie sensu stricto meran mauls passeier thurnstein and jaufen faults represents a sharp break in the generally e w strike direction of the orogen scale periadriatic fault system and is a key element for understanding the late oligocene neogene evolution of the alpine chain the kinematics timing and magnitude of movements on the giudicarie fault system are presented here on the basis of a detailed structural study of the component fault segments combined with zircon and apatite fission track analysis from closely spaced samples two main tectonic phases are established 1 back thrusting of the austroalpine units over the southern alps around 32 ma recorded by basement and limestone mylonites along the giudicarie and meran mauls faults with transport directions toward 100 110 and 2 later sinistral transpressive displacement characterized by structures at the ductile brittle transition which overprinted the top to e ese thrust related mylonites but also partitioned into a major system of transcurrent faults in the southalpine domain it was during this later event that the periadriatic fault attained its present day geometry however the amount of sinistral displacement along the giudicarie system was only 15 20 km the magnitude is established here from the 15 km sinistral offset of the jaufen mylonites across the passeier brittle fault and the 20 km long gap in the otherwise continuous distribution of oligocene tonalitic lamellae along the giudicarie fault a direct structural connection is also established between the brenner and the jaufen faults this constrains the timing of the second phase since it must postdate the main exhumation phase of the tauern window at 20 18 ma the results of this study argue against an originally straight periadriatic fault the giudicarie fault formed a restraining bend in this part of the periadriatic fault system since at least the late miocene and probably since the late oligocene

from rifting to drifting tectonic evolution of the south alpine upper crust from the triassic to the early cretaceous abstract the tectonic evolution of the south alpine rifted margin is discussed on the base of four palinspastic upper crustal profiles extension related to the movements between adria and europe began in the norian after variscan orogeny late carboniferous to middle permian orogenic collapse and continental scale wrenching from the late triassic to the early liassic stretching was mostly limited to the lombardian basin during this time extension was mainly controlled by four major listric faults symmetrically centred around the late carboniferous early permian collio grabens smaller faults which also started in the norian were progressively de activated during the late triassic after the middle liassic faulting in the lombardian basin gradually ceased and the site of extension shifted westwards i e towards the future site of crustal separation extension was then controlled by a set of west dipping normal faults oceanic crust was formed not later than 157 ma the overall extension along the profile which had a final length of 290 km was 52 km which corresponds to a stretching factor of 1 22 for the whole length of the preserved margin the strain rate is ca 1 10 16 s the sedimentation history suggests that the extension of the south alpine margin was a continuous process from the norian to the middle jurassic the changes in tectonic pattern are related to progressive hardening of the lithospheric segment undergoing slow extension

tectonic history of the western tethys since the late triassic the tectonic history of the western tethys since the late triassic is illustrated through a set of computer generated plate reconstructions which are based on a rigorous plate motions model of this region the model is constrained by the atlantic plate kinematics and on land geologic evidence and defines 13 tectonic phases spanning the time interval from the late ladinian 230 ma to the present the kinematics associated with the late triassic western tethyan rifts produced the detachment of a large composite fragment from the northern margin of gondwana it can be considered as the eastern propagation of the central pangea breakup during the early jurassic these rift zones became inactive while new zones of extension formed along the southern margin of eurasia the eastern margin of iberia and within the rifted northern gondwana fragment itself plate motions associated with the first two extensional centers can still be considered as an eastern branch of the central atlantic plate kinematics conversely the kinematic parameters of the latter rift result from the composition of the euler rotation describing the central pangea breakup and the euler pole of closure of the paleo tethys ocean the late triassic early jurassic rifting phases determined the formation of a number of independent microplates at the interface between africa and eurasia starting from the early cretaceous convergence between africa and eurasia triggered further deformation within the dispersed continental fragments and the formation of backarc basins at the active margins ultimately leading to an increase in the number of tectonic elements that were moving independently in the western tethyan region during the late cretaceous and the cenozoic the proposed tectonic evolution of the western tethys area is compatible with both global scale plate kinematics and geological constraints from on land data observed across the present day mosaic of displaced terranes surrounding the mediterranean region

geochronological constraints on the evolution of the periadriatic fault system alps fault rocks from various segments of the periadriatic fault system paf alps have been directly dated using texturally controlled rb sr microsampling dating applied to mylonites and both stepwise heating and laser ablation 40ar 39ar dating applied to pseudotachylytes the new fault ages place better constraints on tectonic models proposed for the paf particularly in its central sector along the north giudicarie fault oligocene e se directed thrusting 29 32 ma is currently best explained as accommodation across a cogenetic restraining bend within the oligocene dextral tonale pustertal fault system in this case the limited jump in metamorphic grade observed across the north giudicarie fault restricts the dextral displacement along the kinematically linked tonale fault to 30 km dextral displacement between the tonale and pustertal faults cannot be transferred via the peio fault because of both late cretaceous fault ages 74 67 ma and sinistral transtensive fault kinematics in combination with other pseudotachylyte ages 62 58 ma widespread late cretaceous paleocene extension is established within the austroalpine unit coeval with sedimentation of gosau group sediments early miocene pseudotachylyte ages 22 16 ma from the tonale pustertal jaufen and passeier faults argue for a period of enhanced fault activity contemporaneous with lateral extrusion of the eastern alps this event coincides with exhumation of the penninic units and contemporaneous sedimentation within fault bound basins

a jurassic tongue of the ocean infilled with oolitic sands the belluno trough venetian alps italy abstract the belluno trough is a narrow and elongate basin on the northwestern corner of the apulian plate continental margin it acquired topographic identity in early liassic time during the breakup of a widespread upper triassic carbonate shelf at the beginning liassic the belluno trough was a starved depression accumulating euxinic mudstone and bounded by two shallow water carbonate banks trento and friuli platforms this typical bahamian physiography lasted until late liassic time when the shallow water trento platform collapsed tectonically and suddenly drowned tilting northward and breaking along an old tectonic line it became therefore a submerged pelagic plateau in the meantime the western edge of the friuli platform now the windward margin of an oceanic platform turned into a prolific super producing oolite factory quite soon the oolite sands of the friuli margin started to flow down the slope reaching the basin through numerous entry points and gradually building a complex of coalescent deep sea fans which prograding westward infilled the belluno trough the fans terminated westward against the faulted edge of the trento plateau on which above a karst like surface locally encrusted with manganese red nodular ammonitic limestone was slowly accumulating northward where the topographic relief decreased the oolite fans could spill over the escarpment onto the edge of the plateau by the end of middle jurassic time the belluno trough was no longer a submarine depression but a gentle slope connecting the friuli platform to the deep pelagic trento plateau in callovian time probably because of a short drop in sea level large parts of the friuli platform were exposed to subaerial diagenesis during the subsequent oxfordian transgression the resulting rocky bottom became the substratum for an extensive growth of reefal organisms hydrozoans corals rudists which fringed the friuli platform for the whole malm and cretaceous times

neogene lateral extension during convergence in the central alps evidence from interrelated faulting and backfolding around the simplonpass switzerland abstract the simplon fault zone occurs at the western end of the lepontine metamorphic dome in the central alps and represents a major low angle 25 dip normal fault associated with wsw ene directed lateral extension movement began in the early miocene and continued until at least 3 ma accumulating a total vertical throw of around 10 km corresponding to 24 km displacement parallel to the fault this displacement is partitioned between a broad zone of ductile mylonites in the footwall and a more discrete cataclastic detachment fault the simplon line in the central region simplon village to zwischbergen some 3 km of the total vertical displacement is accommodated by the discrete cataclastic zone due to the higher exposed structural level the importance of the cataclastic component increases towards the northwest in the northern steep belt around the simplonpass retrograde greenschist facies mylonite formation and younger cataclastic faulting associated with lateral extension occurred contemporaneously with sse vergent large scale backfolding representing nnw sse shortening and crustal thickening the combined effect was an overall shortening across the orogen accommodated by an extension parallel to the orogen allowing lateral escape of continental material normal faulting and the resultant lateral escape was not just superficial it extended to depths of at least 15 km and probably to depths exceeding 25 km the overall geometry and kinematics of the simplon fault zone and in particular the interplay between folding and faulting is very similar to that described from the metamorphic core complexes and detachment faults of the cordillera of the southwestern usa within the central alps extension was associated with rapid exhumation of the lepontine metamorphic dome as evidenced by very rapid cooling rates determined from mineral ages in the footwall similar to the cenozoic tectonics of the himalayas and tibet orogen parallel extension in the mountain belt may have been promoted by an overall reduction in the horizontal compressive stress in this direction more limited extension of the same age and orientation is known from a large area of the european foreland greater extension in the mountain belt compared with the foreland was accommodated by major strike slip transfer fault systems and was linked to coeval overthrusting of the lowlands towards the southwest in the external southwestern alps of haute provence france coeval folding and orogen parallel extension such as at the simplonpass were developed in a dextral transpressive regime due to oblique wnw ese convergence across the alps during the neogene

effects of porosity and clay content on wave velocities in sandstones the ultrasonic compressional vp and shear vs velocities and first arrival peak amplitude ap were measured as functions of differential pressure to 50 mpa and to a state of saturation on 75 different sandstone samples with porosities ranging from 2 to 30 percent and volume clay content c ranging from 0 to 50 percent respectively both vp and vs were found to correlate linearly with porosity and clay content in shaly sandstones at confining pressure of 40 mpa and pore pressure of 1 0 mpa the best least squares fits to the velocity data are vp km s 5 59 6 93 2 18c and vs km s 3 52 4 91 1 89c deviations from these equations are less than 3 percent and 5 percent for vp and vs respectively the velocities of clean sandstones are significantly higher than those predicted by the above linear fits about 7 percent for vp and 11 percent for vs which indicates that a very small amount of clay 1 or a few percent of volume fraction significantly reduces the elastic moduli of sandstones for shaly

the nanogranular acoustic signature of shale a multiscale micromechanics model has been developed for the prediction of anisotropic acoustic properties of shale the model is based on the recently identified nanogranular mechanical response of shale through indentation experiments it recognizes the dominant role of the anisotropic elastic properties of compacted clay in the anisotropic elasticity of shale at different length scales compared to contributions of shape and orientation of particles following a thorough validation at multiple length scales using mineral elasticity data nanoindentation experiment results and ultrasonic pulse velocity tests the model predictions compare adequately with measurements on kerogen free and kerogen rich shales and shaley sandstones the acoustic signature of shale thus is found to be controlled by two volumetric parameters that synthesize the porosity and mineralogy information the clay packing density and the silt inclusion volume fraction through a series of dimensionless isoparametric plots the micromechanics model predicts trends of increasing elastic anisotropy with increasing clay packing density or decreasing porosity which correspond to the intrinsic mechanical response of unfractured shale and quantifies the stiffness reduction induced by the presence of kerogen

earthquake relocations crustal rheology and active deformation in the central eastern alps n italy abstract a revised seismic catalogue 1994 2007 for the central eastern alps n italy is presented 396 earthquake relocations for local magnitudes in the 1 2 5 3 range are performed using a 3d crustal velocity structure and probabilistic locations the location procedure is validated by computing a set of 41 quarry shot solutions and all the results both about shots and seismic events are compared with those obtained using the routine location procedure results are shown for five contiguous seismotectonic domains as supported by geological and geophysical evidence e g fault systems crustal tomography focal mechanisms types earthquake hypocentres are mostly located in the upper crust 0 15 km of depth in good agreement with thermo rheological models about the brittle ductile transitions 8 9 km of depth and total crustal strengths 1 0 2 0 tn m 1 epicentres are clustered and or aligned along present day active geological structures the proposed seismotectonic model shows dominant compression along the giudicarie and belluno bassano montello thrusts with strain partitioning along the dominant right lateral strike slip faults of the schio vicenza domain the present day deformation of the southern alps and the internal alpine chain is compatible with adria indentation and the related crustal stress distribution

subsidence and sedimentation on jurassic passive continental margin southern alps italy the southern alps of italy preserve a tectonically intact array of jurassic facies that record the evolution of a part of the margin of the apulian plate from its ancestral beginnings in a complex of permian and triassic rifted continental basins through the initial stages of breakup and stepwise foundering of a carbonate platform breakup was accompanied first by the rapid accumulation of thick prisms of carbonate turbidites in newly formed fault troughs then as the new ligurian oceanic basin began to open farther west and as subsidence gradually slowed accumulation of a succession of slowly deposited biogenous pelagic sediments recorded not only the increasing depths of the seafloor but also fluctuations in oceanographic conditions of fertility carbonate dissolutio levels and the strength of bottom currents estimates of the history of seafloor depths based on a simple subsidence law of the form subsidence k age 12 provide a basis for the construction of a set of curves showing the changing depths of significant carbonate dissolution surfaces during the jurassic in this region the rapid 1 km deepening of the compensation depth for calcite during the late jurassic may be due to a change in regional oceanic vertical circulation patterns from upwelling fertile silica rich carbonate dissolving to downwelling less fertile silica poor carbonate preserving

morphotectonics and late quaternary seismic stratigraphy of lake garda northern italy abstract lake garda the largest lake in italy at the southern front of the central alps provides a unique opportunity to reconstruct quaternary geological processes related to the interplay between deglaciation driven sedimentation and tectonic activity in fact the topographic depression presently occupied by the lake was site of a major glacial tongue during the lgm and is located close to the epicentral areas of two of the largest magnitude historical earthquakes recorded in the po plain the verona jan 13 1117 and brescia dec 25 1222 seismic events characterized by io ix x mcs respectively despite this peculiarity geophysical surveys of the lake are scant we present results of a waterborne geophysical survey of lake garda leading to the acquisition of a densely spaced grid of high resolution seismic reflection profiles which image the lake floor and uppermost sedimentary sequence these data enabled us to compile thematic maps which provide insights on active geologic processes in different sectors of the basin we focused our work on a prominent seismic reflector h1 correlated over the entire lake surface to estimate the sediment deposition rate at the scale of the last 10 ka and to evaluate the variability of seismic facies and geological processes in different sectors of the basin based on available stratigraphic data we discuss whether h1 could mark the diachronic glacial fluvio glacial transition after the last glacial maximum when the ice tongues south of the alps started to melt and collapse we observed that sediments of the southern lake garda are affected by incipient tectonic deformation and two major seismoturbidite homogenite beds might represent over 50 of the holocene sedimentary record in the lake depocenter making the study of the lake garda stratigraphy an interesting tool for assessing earthquake hazards at the southern front of the alpine chain

variable fault tip propagation rates affected by near surface lithology and implications for fault displacement hazard assessment abstract the fabric of reverse fault zones close to the surface is usually partitioned in between a narrow discrete rupture zone and a more distributed one where folding is predominant this makes quite challenging the adoption of proper setbacks in surface rupture hazard studies for critical facilities or microzoning some of the parameters controlling fault zone fabric are related to mechanics of near surface geology lithology overburden thickness cohesion and water content whose interaction is complex and only partially understood nevertheless these can be seldom measured or derived kinematic models conversely express such an interaction of complex variables as simple synthetic parameters such as the amount of upward propagation of the fault tip for unit of slip usually referred to as the p s ratio propagation on slip here we discuss results on the trishear kinematic inverse modeling of a contractional fault propagation fold at monte netto hill capriano del colle n italy observing a two stage fault and fold growth evolution marked by a significant shift in the p s parameter at this site exceptional sequence of exposures due to ca 10 years of quarry excavations allowed to obtain a series of cross sections across the fault zone we use this detailed high resolution example as a natural analogue for more general large scale surface ruptures involving a thick alluvial cover a very common setting for the siting of critical facilities during the early stage of displacement the fault cut through clast supported fluvial gravels with a high propagation rate p s 7 and a discrete rupture width then during the latest movements of the thrust fault tip propagation slowed down to p s 2 9 as the fault started cutting through several stacked bodies of clays and silty clays pedogenized aeolian silts and overbank deposits causing a pronounced folding of the layers over a wider deformation zone these results strongly suggest that lithological changes in the underlying shallow stratigraphy common in an alluvial plain depositional setting would significantly affect the potential for surface faulting across the same tectonic structure with relevant implications in the fault displacement hazard assessment

tertiary extension in the southern trento platform southern alps italy the southern trento platform southern alps ne italy was the locus of abundant mafic volcanism associated with paleogene extensional tectonics during the pal eocene and throughout the eocene a nnw sse trending graben the alpone agno graben aag developed in the eastern lessini mountains the graben was filled with basaltic volcaniclastics calcarenites and lava flows the aag is a half graben system probably bounded by rotational listric normal faults most faults in the graben dip towards the wsw paleostress analysis within the aag shows that during the eocene the direction of horizontal extension was ene wsw the volcanic activity continued into the oligocene however the relation between oligocene tectonics and volcanism remains unclear gravimetric and magnetic anomalies in conjunction with the crustal thickness variations suggest a locus of lithospheric thinning slightly off axis from the aag this can be explained by an overall asymmetric extensional geometry dominated by a wsw dipping detachment fault the paleogene geodynamic scenario of the trento platform suggests that the aag developed as a foreland extensional response to the active collisional convergence between the european and adriatic plates neogene compressional tectonics reactivated some of the paleogene normal faults as strike sup faults

high frequency attenuation of shear waves in the southeastern alps and northern dinarides summary we investigated the high frequency attenuation of s waves in the southeastern alps and northern external dinarides using waveforms from 331 earthquakes 3 0 mw 6 5 the spectral decay parameter k was computed using 1345 three component high quality records collected by the italian strong motion network ran and by the short period seismometric network of northeastern italy nei in the period 1976 2007 weak motion data from 11 stations of the nei network and strong motion data collected by five accelerometers of the ran were analysed the k parameter was estimated in the 0 250 km distance range in a frequency band extending from the corner frequency of the event up to 25 or 45 hz using the amplitudeaccelerationfourierspectraofs waves theobservedrecord to recordvariabilityof k was modelled by applying a generalized inversion procedure using both parametric and nonparametric approaches our results evidence that k is independent on earthquake size while it shows both site and distance dependence stations of the nei network present the same increase of k with epicentral distance re and show values of the zero distance k parameter k0 s between 0 017 and 0 053 s for the whole region the k increase with distance can be describedthroughalinearmodelwithslopedk dre 1 4 0 1 10 4 skm 1 assumingan average s wave velocity 3 34 km s 1 between 5 and 15 km depth we estimate an average frequency independent quality factor qi 2140 for the corresponding crustal layer the non parametric approach evidences a weak positive concavity of the curve that describes the k increase withre at about 90 km distance this result can be approximated through a piecewise linear function with slopes of 1 0 10 4 and 1 7 10 4 sk m 1 in accordance with a three layers model where moving from the intermediate to the bottom layer both qi and decrease two regional dependences were found data from earthquakes located westward to the nei network evidence weaker attenuation properties probably because of s wave reflections from different parts of the moho discontinuity under the eastern po plain at about 25 30 km depth while earthquakes located eastward in western slovenia where the moho deepens up to 45 50 km evidence a higher attenuation moreover the k estimates obtained with data from earthquakes located in the area of the 1998 mw 5 7 and 2004 mw 5 2 kobarid events are 0 017 s higher than the values predicted for the whole region probably because of the high level of fracturing that characterizes fault zones the comparison between measured and theoretical values of k computed at a few stations with available s wave velocity profiles reveals that the major contribution to the total k0 s is due to the sedimentary column from surface to 800 m depth the hard rock section contribution is limited to 0 005 s in accordance with a maximum contribution of 0 010 s predicted by the non parametric inversion

progressive offset and surface deformation along a seismogenic blind thrust in the po plain foredeep southern alps northern italy here we present for the first time in the po plain foredeep northern italy the middle to late pleistocene growth history of an outcropping secondary fold and related faults whose progressive deformation over an intermediate time window 105 years is driven by an underlying seismogenic blind thrust we trenched and logged an outcropping decametric secondary anticline related to a deeper blind compressional structure which deforms fluvial sediments and an overlying loess paleosol sequence folded units were dated using radiocarbon and optically stimulated luminescence methods to the late pleistocene holocene and tentatively correlated with glacial interglacial phases occurring during the time interval from marine isotope stage 6 to the present a multistep retrodeformation of the fold allowed us to calculate uplift rates for this secondary and shallow anticline varying between 0 02 and 0 1 mm yr since circa 200 kyr trishear forward deformation modeling of the fold indicates that the amplification of the observed fold could be caused by two shallow thrusts formed through a break backward activation this generated a decametric surface fold whose most recent growth was associated with bending moment normal faulting in the crestal and forelimb region our observations demonstrate that near surface compressive tectonics can be caused by blind thrusting via a complex array of fault and folds upward strain propagation and generation of shallow low angle thrust and related folding seem to be mainly due to secondary fold related faulting according to an out of syncline thrusting mechanism

middle eocene nummulites and their offshore re deposition a case study from the middle eocene of the venetian area northeastern italy abstract the middle eocene calcari nummulitici formation from northeastern italy venetian area represents a shallow marine carbonate ramp developed on the northern tethyan margin in the monti berici area its main components are larger foraminifera and coralline red algal communities that constitute thick carbonate sedimentary successions middle ramp and proximal outer ramp environments are recognized using component relationships biofacies and sedimentary features the middle ramp is characterized by larger flattened lenticular nummulites on palaeohighs between which rhodoliths formed larger nummulites palaeohighs containing nummulites millecaput nummulites crassus nummulites discorbinus and nummulites cf gizehensis developed more basin wards the following relatively quiet environments of basin wards of the palaeohighs represent areas of maximum carbonate production the transition between the distal middle and the proximal outer ramp settings is marked in the study area by a large erosional surface which is interpreted to have been formed as a result of an erosive channel body filled in by deposits re sedimented from shallower depths these off shore re sedimented channelized deposits ascribed to the shallow benthic zone sbz 15 lying on hemipelagic marls planktonic foraminiferal zone e9 p11 allow for a biostratigraphic correlation to the late lutetian the studied deposits represented by packstone to rudstones were displaced whilst still unlithified the lutetian bartonian regression along with the local tectonic activity promoted the production of a high amount of biogenic shallow water carbonates mainly produced in the mossano middle ramp settings these prograded towards the basinal areas with high sedimentation rate of carbonate deposits characterized by the larger nummulites rudstones such high amounts of sediment led to sediment instability which potentially could be mobilized either by return currents due to occasional major storms or by earthquakes induced by tectonic activity these will have led to the offshore re deposition of the nummulites sediments into deeper water setting via the observed channels since potential migration pathways are short such distal re sedimented channel filled material surrounded by hemipelagic marls is optimally placed for the formation of potential subsurface oil reservoirs

neogene quaternary tectonic stratigraphy of the eastern southern alps ne italy abstract in order to reconstruct the neogene quaternary tectonic stratigraphy of the eastern southern alps the late tortonian lower pleistocene foredeep clastic sequences cropping out in the veneto and friuli piedmont areas have been extensively investigated focusing on the contractional features observed in the frequent conglomerate layers pitted pebbles the eastern southern alps is the result of a typical polyphase tectonic activity initiated in late oligocene characterised by the occurrence of several non coaxial stress regimes based on careful analyses of the pebbles surfaces shape and orientation of the indented features and following a systematic and statistical approach the mean orientation of the maximum compressive stress axis 1 has been obtained for more than 30 sites of measurements along the ca 120 km long investigated piedmont area the affected lithostratigraphic units and the orientation pre versus post tilting of the stereonets density peaks make it possible to recognize four distinct deformational events and characterize them in terms of mean 1 direction and timing late tortonian 1 313 00 late messinian early pliocene 338 04 late pliocene 314 03 and early middle pleistocene 160 03 the tectonic stratigraphy of the eastern southern alps during the last ca 10 ma shows the occurrence of several variations of the stress field characterized by a repeated oscillation of the 1 axis between an nnw sse and nw se directions twist tectonics taking also into account literature data about older deformational events chattian burdigalian and serravallian tortonian we analyse the neogene quaternary tectonic evolution in the frame of the central mediterranean realm and compare it with the convergence direction between the adria africa and europe lithospheric plates we show that compressional directions within the eastern southern alps are basically governed by the remote plate convergence though since late messinian the approaching northern apennines started to play a crucial role within the investigated area alternating short lived phases 1 2 ma of coupling and decoupling along the basal detachment of the apennines accretionary wedge probably caused temporary perturbations of the local stress field and complex accommodation structures in this region of ongoing crustal collision

large scale thin skinned thrusting in the southern alps kinematic models the tectonics of the southern alps are dominated by thrusting on extensive ramp flat systems and by folding some of which is ramp folding basement slivers are involved that frontally are not thicker than 5 km the most unequivocal section is that of the grigna mountains east of lake como for which kinematic modeling based on material balance considerations results in a shortening of 40 km it is separated from the grona section in the west and the valtorta section in the east by probably pre existing transverse zones that cut through the important decollement horizons and define blocks of different depths to basement local tectonics across these transverse zones change abruptly while over all shortening remains constant in particular both east and west of the grigna section basement ramp folds were wedged into the very incompetent raibl beds provoking back thrusting of the thick hauptdolomit and higher sediments with the substitution of the original cover of the frontal limb of the basement fold this new kinematic interpretation is compatible with the information facilitates the construction of balanced sections and is required for lateral constancy of shortening

evidence for east west crustal extension in the eastern alps implications for the unroofing history of the tauern window the contact between the western border of the tauern window and the overlying austroalpine nappes austria and italy is marked by a structural petrologic and geochronologic discontinuity that developed in the early stages of unroofing of the window within the window pressure temperature time paths j selverstone 1985 indicate that significant ductile thinning occurred shortly after the cessation of thrusting paleocene eocene sense of shear indicators rotated porphyroblasts asymmetric augen and pressure shadows s c fabrics associated with a west plunging stretching lineation indicate that this thinning occurred in response to top to the west low angle normal shear during metamorphism the same sense of normal shear is present in the mesozoic members of the austroalpine sequence west of the window in these rocks however west directed shear occurred at low temperatures 300 c after the thermal peak of metamorphism structural data and the regional geometry imply that the western end of the tauern window is a low angle normal fault brenner line that juxtaposed brittlely deformed rocks of the austroalpine nappes against more ductilely deformed rocks from the window biotite k ar and rb sr data suggest a miocene age for final movement on the brenner line these data indicate a prolonged history of east west extension in the eastern alps that affected all crustal levels early ductile thinning of lower crust followed by mid to upper crustal low angle normal faulting a model is presented that relates the young east west extension to displacement transfer from dextral movement on the periadriatic lineament in this model the brenner line and by analogy the simplon line can be thought of as detachment faults that tectonically unroofed the tauern window and lepontine thermal highs respectively

the stress sensitivity of shaley sandstones the link between the stress sensitivity of shaley sandstones and their porosity and clay content is investigated this is achieved by firstly fitting a compliance based stress sensitivity law to laboratory measurements of ultrasonic velocity taken from four sets of reservoir sandstones extracted from a variety of depositional settings correlations are then sought between the independent parameters of this law and the porosity or clay fraction of the rocks which are then subsequently interpreted in terms of framework or pore space related microstructural clay models the general conclusion drawn from the results is that both of the parameters defining the stress sensitivity law the asymptotic modulus and the stress dependent excess compliance clearly vary with porosity however only the asymptotic modulus shows a convincing trend with clay and there is little observed variation of the stress dependent compliance with clay there is therefore a resultant variation of stress sensitivity with clay but it is controlled only by the asymptotic modulus the analysis also concludes that all four data sets fall into a framework related category of clay model

transalp cross line recording during the seismic reflection transect in the eastern alps abstract cross line recording formed a companion experiment of the transalp seismic reflection transect through the eastern alps conducted by partner institutions from austria germany and italy in three field campaigns in the period fall 1998 to fall 1999 besides of the originally expected three dimensional control for the north south running main transect additional information on seismic anisotropy and alternative images of crucial parts of the main transect could be gained conventionally processed sections along n s running common midpoint cmp binning lines confirm and strengthen the predominance of midcrustal reflective structures of the sub tauern ramp beneath and south of the tauern window velocity analysis of the first arrivals exhibit about 10 higher velocities in east west propagating p waves compatible with texture dominated rock anisotropy recorded on cross lines at the tauern window pre stack depth migration of cross line recordings shows dominant south dip of the sub tauern ramp with easterly dip components and a sub horizontal root zone of the sub dolomites ramp

structure and properties of the adriatic crust in the central eastern southern alps italy from local earthquake tomography structure and properties of the adriatic crust were determined from local earthquake tomography around the giudicarie fault zone central eastern southern alps italy tomographic results based on well suited 436 revised earthquakes period 1994 2007 have a resolution comparable to the scale of regional geological domains and tectonic structures the observed strong velocity anomalies correlate well with lithological variations corresponding to different geological domains particularly magmatic complexes at depth and with high fracturing and or presence of fluids along active fault systems south giudicarie and valsugana bassano del grappa montello thrusts

distributed fracturing affecting isolated carbonate platforms the latemar platform natural laboratory dolomites north italy abstract isolated carbonate platforms are highly heterogeneous bodies and are typically composed of laterally juxtaposed first order domains with different sedimentological composition and organization i e a well stratified platform interior a massive margin and a slope with steeply dipping and poorly organized layers once subjected to overburden and tectonics forces directions and magnitudes of principal stresses inside such heterogeneous bodies are expected to deviate significantly from the regional trends potentially resulting in non obvious fracture patterns in addition characteristics such as fracture height and spacing distances are likely to change moving from one domain to the other as well as through time the middle triassic latemar platform dolomites n italy is affected by ubiquitous fractures typically joints orientation and height of more than 1500 fractures from 33 outcrops have been measured and their spatial characteristics were assessed with dedicated software fractures are organized in two directional sets nnw sse and ene wsw the orientation of each set is constant throughout the platform showing that the trajectories of causative stresses were not influenced by the platform architecture fracture spacings and heights of each set change moving from one domain to the other in the well bedded platform interior fractures are generally there are also significant differences in the characteristics of fractures of the two sets in all platform domains fractures of nnw sse set are less tall and more narrowly spaced than those of the ene wsw set in the platform interior fractures of the first set have a higher tendency to be confined to fracture units than those of the second set these differences are associated with diagenesis driven changes in bulk mechanical properties of the platform during its subsidence to maximum burial depth

balancing cross sections with kinematic constraints the dolomites northern italy balancing of structural cross sections is often hindered by a limited database or tectonic complications in such cases kinematic constraints may help to better constrain the construction of a cross section and its extrapolation to depth the kinematic implications of a known structure generally at the surface have to be considered for the unknown structure and for the internal consistency of a cross section a key point is the quantification of shortening of the known structure the extrapolation of this parameter allows balancing in an approximate way emphasizing major structures while minor structures are either neglected or treated in a simplified way with this approach a quick overview can be achieved on how much leeway for interpretation exists critical points for testing various working hypotheses become more evident and the trial and error effort during the construction of a balanced section is considerably shortened still the implications the observed structures have on the deeper crustal levels can be assessed this concept is applied to a section across the italian dolomites a brittle fold and thrust belt lacking reflection seismic data so far and thus with a poorly known deep structure still active south vergent alpine thrusting is oriented approximately perpendicular to previous dinaric thrusting the ramp flat style is dominant due to rheological constrasts within the stratigraphic sequence thanks to kinematic balancing based on surface data three alpine thrust systems could be identified each defining a thrust sheet with its particular basement unit and its sedimentary part superposition of the two more external basement units led to the presently observed high elevation of the triassic sequence in the dolomites shortening since late miocene times amounts to more than 50 km retrodeformation of alpine thrusting is a key for better understanding the previous dinaric structures and kinematics

compressional velocity and porosity in sand clay mixtures laboratory measurements of porosity and compressional velocity were conducted on unconsolidated brine saturated clean ottawa sand pure kaolinite and their mixtures at various confining pressures a peak in p velocity versus clay content in unconsolidated sand clay mixtures at 40 percent clay by weight was found the peak in velocity is 20 30 percent higher than for either pure clay or clean sand a minimum in porosity versus clay content at 20 40 percent clay by weight is also observed such behavior is explained using a micro geometrical model for mixtures of sand and clay in which two classes of sediments are considered 1 sands and shaley sands in which clay is dispersed in the pore space of load bearing sand and thus reduces porosity and increases the elastic moduli of the pore filling material and 2 shales and sandy shales in which sand grains are dispersed in a clay matrix for these sediments the model reproduces the extrema in velocity and porosity and accounts for much of the scatter in

a sedimentary record of holocene surface runoff events and earthquake activity from lake iseo southern alps italy this study presents a record of holocene surface runoff events and several large earthquakes preserved in the sediments of pre alpine lake iseo northern italy a combination of high resolution seismic surveying detailed sediment microfacies analysis non destructive core scanning techniques and ams 14c dating of terrestrial macrofossils was used to detect and date these events based on this approach our data shed light on past seismic activity in the vicinity of lake iseo and the influence of climate variability and human impact on allochthonous detrital matter flux into the lake the 19 m long investigated sediment sequence of faintly layered lake marl contains frequent centimetre to decimetre scale sandy silty detrital layers during the early to mid holocene these small scale detrital layers reflecting sediment supply by extreme surface runoff events reveal a distinct centennial scale recurrence pattern this is in accordance with regional lake level highstands and minima in solar activity and thus apparently mainly climate controlled after c 4200 cal yr bp intervals of high detrital flux occasionally also correlate with periods of enhanced human settlement activity in consequence deposition of small scale detrital layers during the late holocene apparently reflects a rather complex interplay between climatic and anthropogenic influences on catchment erosion processes besides the small scale detrital layers five up to 2 40 m thick large scale detrital event layers composed of basal mass wasting deposits overlain by large scale turbidites were identified which are supposed to be triggered by strong earthquakes the uppermost large scale event layer can be correlated to a documented mw 6 0 earthquake in ad 1222 in brescia the four other large scale event layers are supposed to correspond to previously undocumented local earthquakes these occurred around 350 bc 570 bc 2540 bc and 6210 bc and most probably also reached magnitudes in the order of mw 5 0 6 5