estudio sismico de la corteza iberica norte 3 3 a seismic image of the variscan crust in the hinterland of the nw iberian massif an offshore vertical incidence reflection seismic study with simultaneous on land wide angle recording has been conducted as part of the estudio sismico de la corteza iberica norte escin project

major geodynamic processes studied from the ecors deep seismic profiles in france and adjacent areas abstract for more than five years the french ecors project has obtained deep seismic profiles across major structural features that are related to the variscan alpine and pyrenean belts as well as the permo mesozoic subsidence in the celtic sea the english channel and the bay of biscay profiles across the orogenic belts show striking similarities such as the flexure of the down going plate and the geometry of the frontal detachment and related thrusts and nappes whatever the age of the belt however straight dipping reflections cutting through large sections of the crust seem to be common in the variscan belt and are interpreted as late features in its tectonic history the tertiary alpine and pyrenean belts show extensive crustal thickening and crust mantle imbrication while the layered lower crust and its bottom are flat beneath the late palaeozoic variscan belt this is interpreted as a late equilibration of the crust mantle boundary which involved deep metamorphism in the crust and occurred between the permian and the middle jurassic the permo jurassic basins reveal an unattenuated lower crust while both the upper and lower crusts are thinned beneath the cretaceous tertiary ones observation does not support the current models of basin formation and nowhere does extension appear to have played a major role in subsidence the lower crust of the permo jurassic basins may have been reworked and equilibrated after their rifting

the rhinegraben extension subsidence and shoulder uplift abstract we apply a numerical model of the thermal evolution of a continental lithosphere undergoing extensional deformation to the rhinegraben using reasonable parameters the results of computations are in agreement with the present configuration of the rift and of its shoulders as well as with their evolution since the oligocene contrasting evolutions are reconstructed in the northern and southern rhinegraben whereas the northern history is accounted for by a simple model of homogeneous stretching of the lithosphere the history of the southern rhinegraben cannot be explained without introducing two main periods of heterogeneous stretching the results are locally supported by structural analyses of extensional patterns factors of extension average 1 2 in the axial portion of the rhinegraben and 1 15 for the whole rift section suggesting that the total amount of e w extension reaches 6 km

relationship between electrical resistivity and basic geotechnical parameters for marine clays recently considerable efforts have been made in the attempt to map quick clay areas using electrical resistivity measurements however there is a lack of understanding regarding which soil parameters control the measured resistivity values to address this issue inverted resistivity values from 15 marine clay sites in norway have been compared with basic geotechnical index properties it was found that the resistivity value is strongly controlled by the salt content of the pore fluid resistivity decreases rapidly with increasing salt content there is also a relatively clear trend of decreasing resistivity with increasing clay content and plasticity index resistivity values become very low 5 m for high clay content 50 medium to high plasticity ip 20 materials with salt content values greater than about 8 g l or corresponding remoulded shear strength values greater than 4 kpa for the range of values studied there is poor correlation between resistivity and bulk density and between r

a deep reflection seismic line across the northern rhine graben abstract two reflection seismic lines across the tertiary rhine graben in central europe were recorded in 1988 as a joint venture of the french ecors and the german dekorp deep seismic reflection programs in this paper the line across the northern graben is presented the main results are the asymmetry of the graben as documented by the sedimentary fill is accompanied by asymmetric features throughout the entire deep crystalline crust a thin 3 7 s twt reflective lower crust in the east a thick 5 5 s twt relatively transparent lower crust in the west total crustal thicknesses of 8 7 s twt in the east vs 10 5 s twt in the west provided a laterally homogeneous crust existed prior to rifting significant differences in upper and lower crustal thinning must be postulated extension occurred along localized shear zones that are located in the upper crust and at the crust mantle boundary the entire lower crustal layer acts as a decoupling zone

flexural expression of european continental lithosphere under the western outer carpathians we present the results of an analysis of the flexural down bending of the european lithosphere under the western outer carpathians for a grid of five profiles with a lateral spacing of about 100 km crossing the carpathians and its foreland seismic sections including two deep seismic reflection lines and numerous wells allowed us to quantify the flexural curvature of the lithosphere in addition gravity data are used to obtain independent constraints two evolutionary scenarios involving subduction underthrusting of passive margin and a phase change in the lower crust are investigated in a context of relatively flat moho under the area furthermore recent uplift expressing itself in erosional features observed along the distal margin of the foredeep is quantified the generally modest bouguer gravity anomaly points to nonisostatic processes causing this uplift steeply dipping basement under the carpathians to about 10 km depth at the location of the pieniny klippen belt is explained by relatively weak lithosphere which is expressed in the predicted low values of effective elastic thickness of 16 km decreasing locally to 3 km the low strength of the european lithosphere in this region is probably caused by mechanical weakening controlled by partial yielding due to high flexural curvature the weakest parts of the lithosphere along the profiles corresponding to low effective elastic thicknesses are concentrated in the areas of maximum bending predicted flexural bending stresses as a function of bending moment and effective elastic thickness increase dramatically under the outer zone of the carpathian belt explaining reactivations of older basement structures in these regions

characterization of norwegian marine clays with combined shear wave velocity and piezocone cone penetration test cptu data a database of research quality piezocone cone penetration test cptu and shear wave velocity vs information for norwegian marine clays has been assembled to study the small strain stiffness relationships for these materials and to examine the potential use of cptu and vs data in combination for the purposes of characterizing these soils data for sites where high quality block sampling was carried out have mostly been used improvements have been suggested to existing correlations between the small strain shear modulus gmax or vs and index properties for these soils recent research has shown that cptu corrected cone tip resistance qt and especially the pore pressure measured during cptus u2 and vs can be measured reliably and repeatably and are not operator or equipment dependant therefore a new soil classification chart involving the normalized cone resistance qt and normalized shear wave velocity vs1 or vs1 and u v0 where u is the pore water pressure and v0 is the in situ vertical

characterisation and engineering properties of tiller clay abstract a detailed characterisation of the quick clay underlying the ntnu research site at tiller trondheim is presented the objective of the work is to provide guidance on quick clay parameters to engineers and researchers working with similar clays in scandinavia and north america especially on landslide hazard assessment the material is lightly overconsolidated and is characterised by its high degree of structure and very high sensitivity quick clay clay and water contents are both about 40 the plasticity index is low 5 this relates to the low active minerals of the clay and silt fractions illite chlorite and quartz feldspars respectively undrained shear strength is of the order of 30 kpa to 50 kpa medium stiff and increases with depth the deposit is consistent across the site and its properties are similar to other norwegian quick clays significant efforts have been made into examining sample disturbance effects on the material it was found that thin walled steel fixed piston samples can yield results similar to those of block samples provided the work is carried out with extreme care and storage time is minimised the piezocone cptu test proved very useful in characterising the material

review of long seabed samplers and criteria for new sampler design a cost efficient way of investigating shallow sediments and for collecting soils data for many offshore geotechnical problems e g anchoring of floating structures with suction piles or evaluation of submarine slope stability is to carry out seabed sampling to say 25 m below seabed and in addition perform seabed cptus to say 40 m based on a review of data collated from the literature and from in house project experience at the norwegian geotechnical institute it was found that kullenberg type piston core samples give poor recovery and samples which are increasingly disturbed as penetration increase this means that laboratory tests on these samples will give results that are not representative of in situ conditions and will give incorrect parameters for foundation design many different factors control the quality of the samples recovered but the need for an effectively stationary piston a core retainer and improvements to the physical sampler parameters e g diameter wall thickness ratio cutting edge angle inside and outside friction are perhaps the most critical the importance of each of these factors is discussed in detail in addition to the need for instrumentation and the way to penetrate the sampler recommendations are given in terms of criteria for the design of a new sampler which the authors feel will give better results than most samplers used in practice today

towards a mechanical model for the formation of the pannonian basin abstract new maps showing crustal and lithospheric thickness variations in the pannonian basin and the surrounding east alpine carpathian and dinaric mountains have been prepared on the basis of recent seismic seismologic and electromagnetic data a map presenting miocene faults of regional significance has been also constructed for the same region by using a wealth of recently available national and or more local studies it is suggested that observed crustal and lithospheric structural contrasts have been controlled primarily by neogene kinematic history of the region kinematic history is characterized by the following main patterns 1 1 indentation by adria and large scale backthrusting in the southern alps 2 2 eastward escape and extension of the eastern alps 3 3 extensional collapse in the pannonian basin area 4 4 formation of broad wrench fault systems along strike in the dinarides and southern carpathians and the western carpathians with dextral and sinistral shear respectively 5 5 compression and accretion of the external thrust and fold belt in the eastern carpathians these kinematic patterns are thought to be interrelated and all are manifestations of the late stage evolution of an overthickened orogenic wedge in order to arrive at a better understanding of the mechanism of extension which formed the pannonian basin deep crustal seismic profiles hydrocarbon exploration reflection lines and borehole data have been analyzed in the little hungarian plain this plain represents the transition zone between the alps and the pannonian lowlands and the results are illustrated by eight interpreted cross sections one result of regional importance is the clear recognition that the transdanubian central range at the southeastern flank of the little hungarian plain is composed of alpine pre senonian thrust sheets this finding marks the end of a century of debate the allochthony of the substrata of the pannonian basin can be now considered proven another result of more general interest is that these cross sections document the mode of lithospheric extension preexisting compressional detachment planes reactivate as low angle normal faults and lead to tectonic unroofing of deeply buried metamorphic terranes characterized by ductile flow along subhorizontal lineation

tectonics and plate tectonics model for the variscan belt of europe abstract a plate tectonics model is presented to explain the tectonometamorphic characteristics of the european variscides after the closing of two oceanic domains by two sided subduction 500 420 ma and obduction 420 380 ma collision of the european and african continental plates occurred we propose that the subsequent complex intracontinental deformation 380 290 ma is the result of a double subduction of the continental lithosphere accompanied by crust mantle decollement this mechanism explains the progressive crustal thickening and migration of the deformation through time from the sutures toward the external parts of the variscan belt accounting for this model and for the relationships between the european variscides and the other paleozoic peri atlantic belts caledonides appalachian mauritanides and morocco we infer the relative positions of africa america and europe between the silurian and the permian

deep structure of the celtic sea a discussion on the formation of basins the swat south west approaches traverse deep seismic reflection profiles provide complete sections of the crust in the celtic sea area deep mesozoic cenozoic basins are underlain by a non reflective upper crust cut by variscan thrusts and a reflective lower crust one of these thrusts the variscan front has been considered to be a detachment fault which could have initiated the development of the north celtic sea basin during mesozoic times this hypothesis is inconsistent with the obliquity of the front with respect to the basin the migration of the basin depocentres and the existence of normal faults that controlled the subsidence of the basin and intersect the front in the absence of refraction data we used two dimensional gravimetric modelling to determine the depth of the moho this modelling shows that the gravimetric moho is coincident 3 km with the bottom of the reflective lower crust the resulting depth sections show a nearly flat moho and a lower crust with a relatively constant thickness the thinning coefficients of the whole continental crust and the stretching coefficients obtained by comparison of theoretical and computed backstripping method subsidence curves are significantly different we discuss three hypotheses to explain this discrepancy 1 a syn rifting processes not taken into account in the stretching model 2 b previously thickened variscan crust departing from the initial state assumed by the model 3 c post extensional modification of the crustal configuration resulting from rifting each of these hypotheses or a combination of them may correctly account for the data however the flat nature of the moho suggests that at least the third one occurred

epolls model for predicting average displacements on lateral spreads a new empirical method called the epolls model is developed for predicting ground surface displacements due to liquefaction induced lateral spreading lateral spreading is defined as the mostly horizontal deformation of gently sloping ground as a result of soil liquefaction in strong earthquakes lateral spreads often cause considerable damage the epolls empirical prediction of liquefaction induced lateral spreading model can be used to predict the average horizontal surface displacement that can occur on a potential lateral spread the model is presented in three parts designated as the regional epolls site epolls and geotechnical epolls components that allow for progressively better predictions with the addition of more site parameters the model consists of simple algebraic equations with four to nine parameters that represent the seismic input site topography and subsurface conditions the epolls model was developed from a multiple linear regression analysis of data from 71 lateral spread case studies the epolls database regression modeling quality of the fit and limitations on the use of the epolls model are discussed

probabilistic liquefaction induced lateral spread hazard mapping and its application to utah county utah abstract earthquake induced liquefaction may result in the lateral spread displacement of soil down gently sloping ground or towards a free face causing severe and costly damage to various facilities bridges buildings and other critical infrastructure despite the availability of analytical methods most engineers currently use empirical or semi empirical regression models to estimate liquefaction induced lateral spread displacements at specific sites however the application of these regression models for regional mapping over a large geographic areas can be difficult because of challenges associated with the adequate characterization of subsurface soil and groundwater conditions geotechnical properties regional topography and uncertainties associated with the causative seismic loading to address these challenges this paper presents a new and fully probabilistic procedure for regional hazard mapping of liquefaction induced lateral spread displacement the mapping process is demonstrated through an implementation in utah county utah to demonstrate the type of lateral spread displacement hazard maps possible maps corresponding to return periods of 1033 and 2475 years are developed for utah county utah the proposed procedure incorporates topographical data from airborne lidar surveys and geotechnical and geological data from available maps and subsurface explorations it accounts for uncertainties in the soil properties seismic loading and the empirical models for predicting lateral spread displacement using monte carlo simulations

crustal structure of the goban spur continental margin northeast atlantic from deep seismic reflection profiling deep reflection data across the uk continental margin are used to test theories concerning the origin of a pervasive reflective fabric in the lower continental crust seen on many deep reflection profiles worldwide the origin of the reflections is at present little understood but clearly represents an important crustal process the western approaches margin wam line was designed to determine the behaviour of the lower crustal reflections in crust which has undergone significant extension the wam profile across the continental shelf is characterized by bright continuous lower crustal reflections some of which reach 30 km in length and have minimum reflection coefficients of 0 1 deep water multiples in the area of the continental slope partially obscure reflections from the lower crust but detailed analyses show that reflectors are present in the lower crust on the continental slope adjacent to the continent ocean boundary the lower crust on the wam profile is well imaged and free of noise and multiples this very thin crust exhibits the same reflectivity pattern as is observed on the continental shelf i e the upper half of the crust is blank and the lower half contains sub horizontal reflections the lower crustal reflections adjacent to the continent ocean boundary are less continuous than the reflections seen on the shelf and are interpreted as being the remnants after extension of the lower crustal reflectors observed on the continental shelf the lower crustal reflectors are thus interpreted to pre date the extensional episode that led to the opening of the atlantic the preservation of thinned sections of both transparent upper crust and reflective lower crust adjacent to the continent ocean boundary suggests that extension by pure shear was the mechanism by which the crust was thinned in the goban spur area

the evolution of the layered lower crust and the moho through geological time in western europe contribution of deep seismic reflection profiles deep seismic reflection images from a set of profiles shot in western europe have been reviewed and compared and tentative conclusions have been proposed concerning the evolution of the layered lower crust and the moho the disappearance of variscan mountain roots is related to the set up of a new moho at a typical 30 km depth and the creation of seismic layering in the lower crust deep seismic profiles suggest that these processes resulted at least in part from magmatic intrusion partial crustal melting and metamorphism of deep crustal rocks into eclogite on the other hand the layered lower crust is greatly attenuated beneath cretaceous basins and tertiary rifts in relation to prominent moho upwellings the unusual amplitude of the moho reflection and the presence of anomalously high seismic velocities in the lowermost crust beneath the tertiary rifts suggest that the moho and part of the layering are comparatively young features related to interactions between crust and mantle beneath triassic jurassic basins the layered lower crust was not affected by the subsidence of the basement with the whole crustal thinning being entirely concentrated in the upper crust this indicates that the layered lower crust and the moho were formed or restored during or after the main rifting phase seismic data reveal constraints on the processes that affect the crust mantle transition and seem to restore the moho to its typical depth after any mechanical deformation of the lithosphere

the moho depth distribution in fennoscandia and the regional tectonic evolution from archean to permian times abstract from a variety of seismic refraction and reflection profiling results a new detailed moho depth map for the fennoscandian part of the baltic shield has been compiled a complementary crystalline crustal thickness map was compiled for denmark the skagerrak sea offshore western norway and adjacent areas where sedimentary strata reach maximum thicknesses of 10 km and even more these maps are discussed in relation to tectonic evolution and crustal ages of fennoscandia seismic velocities bouguer gravity and seismicity areas deviating from the proposed age thickness relationships are the kola peninsula archean and the oslo rift permian the average crustal thickness in the former area is around 44 km while the latter area is associated with a moho elevation of 3 5 km maximum crustal thicknesses in excess of 50 km have been found in southwestern and central finland and correlate with a crust of proterozoic age the caledonides of western norway do not exhibit as elsewhere a crustal root sub moho p n and s n seismic velocities are relatively small in that area and bouguer gravity values are strongly negative intracrustal p velocity variations do not seem to reflect geological age or specific tectonic features although the seismicity is moderate in fennoscandia most of the earthquake activity and in particular the largest earthquakes are confined to areas where the crustal thinning is most pronounced

fragility functions for liquefaction induced ground failure abstractthe predicted severity of liquefaction manifested at the ground surface is a popular and pragmatic proxy of damage potential for infrastructure toward this end the liquefaction potential

a liquefaction potential integral index based on pore pressure build up abstract the increased attention paid to the effects of liquefaction on the built environment has led over time to the introduction of vulnerability integral parameters that somehow quantify for a given site and a given seismic shaking the severity of the potential liquefaction damage induced at ground level if the vulnerability parameter is properly calibrated and effective it should somehow correlate to the observed damage datasets increasing as the severity of liquefaction effects increase in some cases as for instance for the canterbury earthquakes new zealand 2010 2011 and for the 2012 emilia romagna seismic sequence the existing vulnerability parameters for the assessment of liquefaction potential were not able to capture the observed damages induced by liquefaction highlighting that further progress remains to be made in the current state of practice the potentiality of a new index induced damage parameter iam strictly related to the free field post volumetric consolidation settlement and therefore based on the estimate of liquefaction induced excess pore pressure has been verified for a reference site located in the area struck by the 2012 emilia seismic sequence by means of simplified and 1d effective stress dynamic analyses the results were compared with those obtained by using one of the most convincing parameters existing in literature liquefaction severity number lsn showing the robustness of iam as well as the possibility to calculate it at different levels of complexity via either coupled simplified or super simplified and conservative analyses the outcomes of the analyses allowed to define a simplified procedure for defining liquefaction microzonation maps then representing a step forward towards the definition of a sound but easy to implement procedure to assess the resilience to liquefaction of urban centres

coincident seismic reflection refraction studies of the continental lithosphere a global review summary vertical incidence reflection profiling has identified several characteristic features of the continental iithosphere including a generally transparent upper crust a reflective lower crust reflections from the crust mantle boundary and a commonly transparent upper mantle the underlying physical causes of these characteristic features remain poorly understood this review summarizes additional information brought to bear on the physical properties of these characteristic crustal structures through the use of coincident wide angle refraction profiling

effect of sample disturbance on triaxial and oedometer behaviour of a stiff and heavily overconsolidated clay the tests in this investigation were performed on a natural soft clay with plasticity index around 32 which was k0 consolidated to a vertical stress of 2942 kpa and then k0 unloaded to a vertical stress of 74 kpa i e to the in situ stress the specimens so created were disturbed in various ways to study the effect of sample disturbance on the stress strain relationships during undrained shearing and during drained k0 loading i e k0 triaxial and oedometer tests the results for two testing alternatives may be summarized as follows alternative 1 allow the specimen to swell at the correct in situ effective stresses but accept an initial water content that is higher than the in situ value this alternative was found to give the best stress strain relationships around the in situ effective stresses for undrained triaxial tests but with undrained shear strength values up to about 20 too low due to the swelling taking place during consolidation to the in situ effective stresses alternative 2

probing into extensional sedimentary basins comparison of recent data and derivation of tentative models abstract more and more deep seismic profiling is revealing the complex evolution of the continental crust which bears the imprints of former plate movements previous subduction zones and mountain belts affected the crust before the formation of intra cratonic sedimentary basins or passive margins therefore the former geological setting must always be taken into account in deep reflection studies of such areas recent deep seismic profiles in europe and other parts of the world have demonstrated the largely heterogeneous nature of the continental crust with dipping reflectors within the crust while bedding heterogeneities or intrusive sill complexes may be invoked these reflectors are most often associated with inherited thrust planes related to crustal shortening during previous orogenies some of these inherited faults have been imaged beneath sedimentary basins with contrasting styles and their reactivation depends on their strike in relation to the regional stress field these pre existing zones of weakness induce a heterogeneity in the upper crust which may control the geometry of future extensional tectonics when the strike of the inherited faults is perpendicular to the extensional stress field they may be reactivated as a detachment surface controlling the sedimentary infill more often the obliquity of these structures induces local changes and segmentation of the rif when they are crossed in such a case they correspond to transfer faults acting as relays between major normal faults or to twist zones where changes occur in the throw of the normal faults sometimes evolving to an inversion of the polarity in the tilting of the major blocks during extension the top of the lower crust may act as a mechanical decoupling boundary separating asymmetrical brittle failure within the upper crust and symmetrical ductile creep within the lower crust extensional modes may explain the great values of crustal thinning observed in both upper and lower crusts beneath rifts and passive margins related to the opening of an oceanic domain it is more difficult to explain the comparatively small amount of horizontal extension generally observed

mechanism of continental crust subsidence in the alpine belt abstract formation of deep basins on continental crust in fold belts is often explained by stretching this mechanism inevitably produces large deformations in the upper crust no deformations typical of significant stretching were revealed in the predominant part of deep basins on continental crust in the alpine belt this means that these basins were not produced by stretching most basins were formed during a short period of time of a few million years the short duration of the subsidences eliminates thermal relaxation as the mechanism the space and time relationships between the subsidence and orogeny and the profile of the basin floor exclude thrust loading as a cause of formation for practically all large basins gabbro to eclogite transformation is suggested as a mechanism of rapid subsidence this occurs under the upwelling of hydrous asthenosphere at moderate temperature to the base of the crust eclogite sinking into the mantle results in a strong attenuation of the crust and lithosphere which permits intense subsequent folding the major part of deep basins in continental crust that formed by rapid subsidence was intensely shortened in the alpine belt significant crustal shortening did not spread over the cratonic lithosphere

evaluation of the liquefaction potential index for assessing liquefaction hazard in christchurch new zealand abstractwhile the liquefaction potential index lpi has been used to characterize liquefaction hazards worldwide calibration of lpi to observed liquefaction severity is limited and the efficacy of the lpi framework and accuracy of derivative liquefaction hazard maps are thus uncertain herein utilizing cone penetration test soundings from nearly 1 200 sites in conjunction with field observations following the darfield and christchurch new zealand earthquakes this study evaluates the performance of lpi in predicting the occurrence and severity of surficial liquefaction manifestations it was found that lpi is generally effective in predicting moderate to severe liquefaction manifestations but its utility diminishes for predicting less severe manifestations additionally it was found that lpi should be used with caution in locations susceptible to lateral spreading because lpi may inconsistently predict its occurrence a relationship between overpredictions of liquefaction severity and profiles h

thrust tectonics deep structure and crustal subduction in the alps and himalayas the structural restoration of collision orogenic belts onto crustal templates provides important insights into the tectonic evolution deep structure and amounts of plate convergence after the initial contact between two continental masses balanced cross sections have been constructed parallel to the local displacement directions across the western alps and western himalayas and demonstrate very large amounts of crustal shortening above intra crustal detachments to achieve a balance substantial volumes of lower crust must have been subducted beneath the two tectonic hinterlands a model of eclogite metamorphism is invoked to facilitate this subduction and to explain the varying isostatic responses of the alpine and himalayan hinterlands patterns of eclogite metamorphism are controlled by the geometry of thrust profiles on a lithospheric scale the development of crust mantle detachments being of crucial importance such a profile is proposed for the himalayas suggesting that relatively small volumes of the footwall crust succumbed to eclogite metamorphism in the alps however a steeper thrust profile apparently developed emplacing mantle onto crust causing wholescale eclogite metamorphism in the underlying franco swiss crust the resultant density increase would provide a mechanism of isostatic collapse and flexural subsidence in the po plain region

influence of early diagenesis on geotechnical properties of clay sediments romania black sea abstract the geotechnical properties of clay sediments were investigated using laboratory and in situ measurements as part of the geohazard assessment in the romanian sector of the black sea affected by landslides and seafloor deformation features the sediments were characterized as predominantly high plastic silty clay of high compressibility low undrained shear strength low cohesion and moderate sensitivity a shallow increase in shear strength exceeding the general trend could have been reconciled with evidence for the precipitation of iron sulfides and calcium carbonates related to early diagenetic reactions of sulfate reduction e g cryptic sulfur cycle and anaerobic oxidation of methane comparison of the compression behaviour of natural and reconstituted samples indicated that precipitation of these materials at particle contacts produced cementation the analysis of deeper sediments sharing similar geochemical properties illustrated that the early precipitation of even low quantity of sulfur and carbonate cements allowed clays to develop sufficient strength to preserve an abnormal high water content even under tens of meters burial depth because this cementation process was observed to be associated with an enhanced sensitivity and a strain softening response to undrained shearing it was concluded that such early diagenesis should be considered as a key environmental factor leading to weak layer formation that may influence the susceptibility of seafloor to failure

lithospheric wedging in the western alps inferred from the ecors crop traverse the ecors crop traverse integrates vertical and wide angle seismic reflection gravity and magnetic studies along a 190 km profile across the western alps the combination of geophysical and geologic data constrains the deep structure along the traverse although alternative models are not excluded the model that best fits the data of crustal accretion implies that after the consumption of the piemontese ocean continental collision proceeded by lithospheric wedging of the subducting european continental foreland in the internal zones further shortening may have been achieved by an unknown amount of penetrative deformation and by back thrusting

application of revised ray tracing migration to imagine lateral variations of seismic fabric corresponding to different tectonic styles in the northern apennines abstract migration of zero offset seismic sections of deep crust can be done with methods based on ray tracing we modify the classical ray tracing migration method rtm introducing a consistency check to control whether back propagated rays satisfy the condition of strict normal incidence at the migrated reflector a synthetic test shows the effectiveness of the method in particular the control of normal incidence allows elimination of physically inconsistent reflectors from the migrated section then rtm is applied to a crustal seismic profile acquired in central italy using a velocity model obtained from wide angle data that reproduces the gross structures of the apenninic crust the lateral variation of the seismic fabric shown from the migrated section reveals the presence of coexisting extensional and compressional tectonic regimes kinematic diffraction modelling gives additional information about both the distribution of seismic velocities and major active geodynamic processes in the upper lithosphere the migrated section supports the subdivision of northern apennines in two tectonic regions a stretched upper plate tuscany and northern thyrrenian supported by a rise of the asthenosphere and a downwarped lower plate adria subducted below the mountain belt

a study on the identification of liquefaction induced failures on ground surface based on the data from the 1999 kocaeli and chi chi earthquakes one of the major causes of earthquake damage is liquefaction however it doesn t result in severe harm unless it leads to ground surface damage or ground failure therefore prediction of potential for ground surface damage due to liquefaction is one of the important issues in microzonation studies for liquefaction induced damage in areas with high seismicity in 1985 based on a database compiled from chinese and japanese earthquakes ishihara considered the influence of the non liquefied cap soil on the occurrence or non occurrence of ground failure mainly sand boiling and proposed an empirical approach to predict the potential for ground surface damage at sites susceptible to liquefaction however some investigators indicated that this approach is not generally valid for sites susceptible to lateral spread or ground oscillation in this study a contribution to improve the approach by ishihara is made for the purpose an index called liquefaction severity index lsi and data from two devastating earthquakes which occurred in turkey and taiwan in 1999 were employed the data from liquefied and non liquefied sites were grouped and then analysed based on the observations reported by reconnaissance teams who visited both earthquake sites and the results of the liquefaction potential analyses using the filed performance data a chart to assess the potential for ground surface disruption at liquefaction prone areas was produced the analyses suggest that the procedure proposed by ishihara is quite effective particularly for the occurrence of sand boils while the bounds suggested in this method generally may not be valid for the prediction of liquefaction induced ground surface disruption at sites susceptible to lateral spreading the chart proposed in this study shows an improvement over the ishihara s approach for predicting the liquefaction induced ground surface damage the microzonation maps comparing the liquefaction sites observed along the southern shore of izmit bay and in yuanlin and the surface damage and non damage zones predicted from the proposed chart can identify accurately the liquefaction sand boiling and lateral spreading and no liquefaction sites

crustal reflection seismics the contributions of oblique low frequency and shear wave illuminations summary continuous vertical seismic reflection profiling the use of which has been extended by cocorp birps ecors dekorp and other programmes barazangi brown 1986 from stratified sedimentary basins to the entire crust provides a high resolution cross section of reflectivity a similar extension of oblique or variable offset sounding would be expected only to provide complementary velocity information however combined use of the two methods at crustal scale is new and we show that refractions and wide angle reflections do contribute original and relevant information but generally in areas other than velocities the reason being that interfaces and layers may have a different nature in the crystalline crust from that in sediments

the granulite eclogite facies transition a comparison of experimental work and a natural occurrence in the bergen arcs western norway a unique segment of the deeper parts of the caledonian continent continent collision zone is exposed in one of the thrust sheets in the bergen arcs of western norway it demonstrates that precambrian granulite facies rocks underwent fluid controlled eclogitization on a regional scale the transition from granulite to eclogite facies is sharp it occurs over distances of centimetres to metres and follows shear zones and infiltration fronts major anastomosing shear zones typically 50 to 100 m thick with well banded eclogite facies rocks crosscut the lithological boundaries they can be followed continuously for several kilometres breccias where metre size blocks of granulite float in an eclogite matrix outcrop over areas of 0 5 km2 areas comprising more than 80 eclogite occupy several square kilometres this mixture of metamorphic facies indicates the metastable occurrence of granulite facies rocks in the lower crust of modern and ancient orogenic belts in contrast to earlier experimental work such field relations imply that the granulite eclogite facies boundary in nature can be sharp and independent of lithological boundaries a partly eclogitized lower crust of the kind exposed in the bergen arcs can explain the 7 2 7 8 km s vp layer present in many crust mantle transition zones anastomosing shear zones and areas of almost complete eclogitization represent potential lower crustal reflectors

in situ shear wave velocity from multichannel analysis of surface waves masw tests at eight norwegian research sites the multichannel analysis of surface waves masw technique which is used to determine shear wave velocity vs and hence small strain stiffness gmax has recently generated considerable interest in the geophysics community this is because of the ease of carrying out the test and analysis of the data the objective of this work was to assess the repeatability accuracy and reliability of masw surface wave measurements for use in engineering studies tests were carried out at eight well characterized norwegian clay silt and sand research sites where vs had already been assessed using independent means as well as being easy and quick to use the masw technique gave consistent and repeatable results and the masw vs profiles for the clay sites were similar to those obtained from other techniques reasonable results were also obtained for the silt and sand sites with the best result being obtained for the finer silt this work also confirms that masw vs clay profiles are comparable to those obtained

effects of sample disturbance and consolidation procedures on measured shear strength of soft marine norwegian clays after many decades of research the issue of sample disturbance is still important as regards to determining reliable and representative soil parameters for foundation design in soft clays parallel laboratory tests have been carried out on high quality block samples and ordinary piston tube samples from 12 deposits of soft norwegian marine clays undrained triaxial and direct simple shear dss tests on samples reconsolidated to the in situ effective stresses show that sample disturbance has a significant effect on the measured stress strain strength behaviour the more disturbed the sample the lower the shear stress at small strains and the higher the shear stress at large strains breakdown of the clay structure including cementation bonds is the assumed cause of lower shear resistance at small strains whereas at large strains the shear resistance is governed mainly by the water content which for soft clay samples reconsolidated to the in situ effective stresses will be lower and the strength t

basalts water or shear zones in the lower continental crust abstract bright sub horizontal laterally extensive multi cyclic layered reflections have now been recorded in the lower continental crust from many areas in contrast this reflection signature is rare in the continental upper crystalline crust and upper mantle and in the oceanic lithosphere with the present state of knowledge it is sensible to seek a single quantitative explanation for all such layering qualitative explanations for lower crustal layering abound and include igneous metamorphic structural and fluid related models measurements of reflection coefficients from the lower crust place strong quantitative constraints on possible models structurally induced anisotropy metamorphic layering or free fluids cannot realistically produce sufficiently bright reflections igneous layering or the juxtaposition of pre existing heterogeneities by shear zones can produce strong reflections results from crustal xenoliths helium isotope ratios palaeo geothermal gradients and chemistry of flood basalts together with numerical modelling of lithospheric extension and asthenospheric melting suggest that underplating and intrusion of the lower crust with mantle derived mafic igneous rocks is common the apparent spatial relationship between lower crustal layering and continental extension and the strength and continuity of the reflections suggest that underplating related to extension and or elevated mantle temperatures is a good explanation for lower crustal layering

crustal thinning on the aquitaine shelf bay of biscay from deep seismic data in recent years an increasing amount of new scientific data on the structure and nature of the whole continental crust has been acquired from deep seismic profiling the bay of biscay profile was recorded in 1984 at sea along the aquitaine platform for the french ecors group in association with hispanoil it collected a unique set of two ship multi channel seismic data with constant offset and expanded spread profiles in a complex geological area the data are of very good quality and contain clear moho and lower crust reflections as seen under most parts of western europe where similar experiments have been conducted1 4 this profile provided for the first time the most convincing evidence for an anomalously thin crust below a rifted basin the parentis basin which is directly connected to the oceanic area of the bay of biscay it gives new constraints for understanding the formation of extensional sedimentary basins

probabilistic assessment of liquefaction induced lateral spreads using cpt focusing on the 2010 2011 canterbury earthquake sequence abstract strong earthquake events often result in liquefaction induced ground movements such as settlements and lateral spreads that are a major cause of damage to buildings bridges and lifelines this paper focuses on the subject of liquefaction induced lateral spreads case histories with detailed cone penetration test cpt data are derived from the 2010 2011 canterbury new zealand earthquake sequence and used to examine an existing empirical model for liquefaction induced lateral spreads the results confirmed the existence of a substantial discrepancy between the predicted and observed lateral spreads indicating a need for improved models that consider uncertainties in the input parameters using a maximum likelihood analysis of the derived case histories a new empirical probabilistic model was developed for the estimation of lateral spreads in the christchurch new zealand area emphasis is placed on assessing the probability of exceedance of limiting displacements for design against the threat of lateral spreads the new cpt based probabilistic model with detailed formulations is presented along with an illustrative example the limitations of the model are discussed

results of dekorp 2 s and other reflection profiles through the variscides summary the first dekorp profile dekorp 2 s a 250 km long line perpendicular to the variscan strike direction has provided evidence of major crustal shortening during the variscan orogeny sporadic dipping events in a generally transparent upper crust are interpreted as thrust faults while the highly reflective lower crust fits into the general picture of palaeozoic provinces correlations are established between certain reflectivity patterns and rheology moho depths and reflecting lamellae are considered to be post variscan

deep structure of the aquitaine shelf constraints from expanding spread profiles on the ecors bay of biscay transect abstract this paper describes the analysis and interpretation of six expanding spread profiles esp which were shot approximately perpendicular to a 300 km long vertical reflection profile along the eastern continental margin of the bay of biscay aquitaine shelf by the french ecors program in association with hispanoil this transect crosses various tectonic features of different ages the armorican shelf the parentis basin and the cantabria shelf velocity depth models have been derived from the esps by the combination of two complementary methods using time distance and intercept slowness domains they provide important constraints for the analysis of the vertical reflection data the velocities allow definition of crustal layering with a 5 8 6 2 km s 1 upper crust and a 6 5 7 1 km s 1 lower crust this layering matches the change of reflectivity observed on cdp data with a relatively transparent upper crust and upper mantle in opposition to a highly layered lower crust important variations of the thickness of these two layers are revealed by this study the most important one occurs beneath the parentis basin with a 15 km shallowing of the upper mantle the velocity distribution suggesting that major crustal thinning has taken place at the cost of a large part of the lower crust

modification of the liquefaction potential index to consider the topography in christchurch new zealand abstract in recent years many have mapped the liquefaction potential index lpi to describe the liquefaction hazard at regional scale several investigators have calibrated the lpi to field observations of liquefaction induced ground failure after a number of major earthquakes the significance of lpi values and their correlation with the severity of liquefaction induced ground failure can vary greatly depending on the calibration in this study the lpi was computed at more than 1200 cone penetration test soundings across the christchurch area new zealand using peak ground accelerations from the 2011 christchurch earthquake based on detailed field observations of liquefaction induced ground failure after the earthquake it was shown that the lpi has potential for discriminating between areas with no liquefaction induced ground failure hazard and areas that may experience liquefaction induced ground oscillations and settlement however the lpi performed poorly at sites where severe ground failures occurred especially at sites that experienced lateral spreading as many researchers have found a positive correlation between lateral spreading and the proximity and depth of a nearby free face i e a steep topographic depression river channel etc a new lpi framework was proposed that includes a parameter named the free face ratio ffr ffr was shown to have a significant correlation with field observations of lateral spreading in christchurch it was shown that by incorporating ffr into the lpi framework modified lpi values are positively correlated with the severity of field observations of liquefaction induced ground failure in christchurch it was also shown that maps can be produced based on lpi and ffr and such maps rarely underpredict the liquefaction induced ground failure hazard unlike maps based on the unmodified lpi

moho and lower crustal reflectivity beneath a young rift basin results from a two ship wide aperture seismic reflection experiment in the valencia trough western mediterranean summary we present new images of the lower crust and moho beneath the valencia trough a young rift basin in the western mediterranean these images were obtained from a two ship wide aperture reflection experiment and show several features not distinguishable on previously available conventional single ship reflection profiles the moho which was previously only seen intermittently can now be confidently traced throughout the basin we have constructed a present day depth to moho map and estimated the degree of crustal thinning for the whole basin crustal thinning is at a maximum in the centre of the basin where values reach 3 15 0 25 at the margins of the basin the value decreases to 1 5 0 1 the reflective character of the lower crust and moho is different beneath different parts of the basin we have been able to correlate these differences with the amount of stretching we therefore interpret the variations of the observed lower crustal reflectivity as having been caused by the most recent neogene stretching event that opened the valencia trough along the iberian margin there is well developed lower crustal reflectivity consisting of 1 2s two way time twt of 1 4 km long near horizontal reflectors underlain by a more continuous although not significantly stronger reflector interpreted to be the reflection moho offshore this lower crustal reflective unit thins rapidly such that it is undetectable 40 50 km from the coastline where the crust has been stretched by a factor of 1 7 0 1 as the lower crustal reflectivity becomes undetectable the reflection moho becomes a robust continuous event where exceeds 2 4 0 2 however the moho is a weak event and difficult to trace we infer that either the extension itself or associated melting significantly weakened or even destroyed the lower crustal reflectivity in the centre of the basin and enhanced the moho where extension was moderate the balearic margin is somewhat anomalous in that there appears to have been flexural loading of the crust due to thrusting and folding that occurred at the same time as extension in the valencia trough the lower crust shows evidence of weak but locally variable lower crustal reflectivity it is possible that the lower crustal reflectivity was preserved simply because the moho was flexed downward and so decompression and hence melting of the upper mantle was restricted this suggests that the melting itself rather than the extension is the primary mechanism of lower crustal modification

a new zealand specific pseudospectral acceleration ground motion prediction equation for active shallow crustal earthquakes based on foreign models abstract the applicability of foreign ground motion prediction equations gmpes for predicting geometric mean pseudospectral acceleration amplitudes from active shallow crustal earthquakes in new zealand nz is examined four different foreign gmpes were considered as well as the nz based mcverry et al 2006 mcv06 model it was found that the mcv06 model exhibited the lowest applicability with a database of 2437 recorded ground motions and that the chiou et al 2010 c10 modification of the chiou and youngs 2008b cy08 model was the most applicable discrepancies between the c10 model and the nz database which were empirically identified and theoretically justified were used to modify the c10 model for 1 small magnitude scaling 2 scaling of short period ground motion from normal faulting events in volcanic crust 3 scaling of ground motions on very hard rock sites 4 anelastic attenuation in the nz crust and 5 consideration of the increased anelastic attenuation in the taupo volcanic zone the developed nz specific model therefore contains features as evident from recorded ground motions in nz and consistent scaling for parameters not well constrained by nz data comparisons with ground motions from the 4 september 2010 darfield and 22 february 2011 christchurch earthquakes which occurred following completion of the nz specific model illustrate that it provides an empirical prediction with sufficient accuracy and precision

potential improvements of design parameters by taking block samples of soft marine norwegian clays undrained triaxial and direct simple shear tests on samples reconsolidated to the in situ effective stresses and oedometer tests have been carried out on standard piston tube and on high quality bl

liquefaction potential index field assessment cone penetration test cpt soundings at historic liquefaction sites in california were used to evaluate the predictive capability of the liquefaction potential index lpi which was defined by iwasaki et al in 1978 lpi combines depth thickness and factor of safety of liquefiable material inferred from a cpt sounding into a single parameter lpi data from the monterey bay region indicate that the probability of surface manifestations of liquefaction is 58 and 93 respectively when lpi equals or exceeds 5 and 15 lpi values also generally correlate with surface effects of liquefaction decreasing from a median of 12 for soundings in lateral spreads to 0 for soundings where no surface effects were reported the index is particularly promising for probabilistic liquefaction hazard mapping where it may be a useful parameter for characterizing the liquefaction potential of geologic units

dynamic processes controlling evolution of rifted basins abstract the extension of the lithosphere controlling the development of rifted basins is driven by a combination of plate boundary forces frictional forces exerted on the base of the lithosphere by the convecting asthenosphere and deviatoric tensional stresses developing over upwelling branches of the asthenospheric convection system although mantle plumes are not a primary driving force of rifting they play an important secondary role by weakening the lithosphere and by controlling the level of rift related volcanic activity a distinction between active and passive rifting is only conditionally justified the extension of the lithosphere depending on its rate and magnitude and the potential temperature of the asthenosphere can cause by adiabatic decompression partial melting of the lower lithosphere and upper asthenosphere in rift systems the level and timing of volcanic activity is highly variable the lack of volcanic activity implies passive rifting an initial passive rifting stage can be followed by a more active one during which magmatism plays an increasingly important role magmatic destabilization of the moho may account for the frequently observed discrepancy between upper and lower crustal extension factors combined with evidence for thermal thinning of the mantle lithosphere this suggest that the volume of the lithosphere is not necessarily preserved during rifting as advocated by conventional stretching models the structural style of rifts is controlled by the rheological structure of the lithosphere the availability of crustal discontinuities that can be tensionally reactivated the mode orthogonal or oblique and amount of extension and the lithological composition of pre and syn rift sediments simple shear extension prevails in rifts that subparallel the structural grain of the basement pure shear extension is typical for rifts cross cutting the basement grain pre existing crustal and mantle lithospheric discontinuities contribute to the localization of rift systems the duration of the rifting stage of extensional basins is highly variable stress field changes can cause abrupt termination of rifting in major rift systems progressive strain concentration on the zone of future crustal separation entails abandonment of lateral rifts depending on constraints on lateral block movements crustal separation can be achieved after as little as 9 my and as much as 280 my of rifting activity syn rift basin subsidence is controlled by isostatic adjustment of the crust to mechanical stretching of the lithosphere its magmatic inflation and thermal attenuation of the mantle lithosphere post rift basin subsidence is governed by thermal reequilibration of the lithosphere asthenosphere system deep seated thermal anomalies related to syn rift pull up of the asthenosphere lithosphere boundary have decayed after 60 my by about 65 and after 180 my by about 95 the magnitude of post rift subsidence is a function of the rift induced thermal anomaly and crustal density changes the potential temperature of the asthenosphere and initial water depths intraplate stresses can have an overprinting effect on post rift subsidence stretching factors derived from post rift subsidence analyses must be corrected for such effects

the 2003 lefkada earthquake field observations and preliminary microzonation map based on liquefaction potential index for the town of lefkada abstract a strong earthquake mw 6 2 occurred offshore the island of lefkada or lefkas on august 14 2003 the maximum intensity has been evaluated io viii ems at lefkada municipality while vi to vii intensities were evaluated at many other villages of the island the offshore nne ssw oriented strike slip right lateral fault was activated by the main shock this fault is the northern termination of the cephalonia transform fault the most characteristic macroseismic effects were extensive typical ground failures like rock falls soil liquefactions subsidence densification ground cracks and landslides these macroseismic effects are remarkably similar to those reported from some historical lefkada shocks e g 1704 1914 ms 6 3 and 1948 ms 6 5 sand boils and ground fissures with ejection of mud were observed at the seaside of the town of lefkada and in the villages of nydri and vassiliki in situ soil profiles are obtained based mainly on borings after the earthquake boreholes records with spt values standard penetration test are obtained and the simplified procedure originally developed by seed and idriss was employed to evaluate the liquefaction resistance of soils the results indicated that the silty sandy layer which lies beneath the artificial fill in the coastal zone in lefkada town had liquefied during the 14 august earthquake an attempt was also made to establish a preliminary microzonation map for lefkada town using the data from liquefaction potential index analyses our map was validated by the occurrence of liquefaction phenomena inside the town

nontypical birps on the margin of the northern north sea the shet survey summary striking similarities in the reflectivity of the crust and upper mantle on birps profiles has led to the development of the typical birp a model seismic section for the british continental lithosphere the shet survey collected in the region of the shetland islands and the northern north sea fits the general pattern to a certain extent caledonian structures and devonian or younger basins are imaged in the otherwise acoustically transparent upper crust an unexpected and exciting feature imaged on shet is a short wavelength structure on the moho or abrupt moho offset beneath the strike slip walls boundary fault shet differs markedly from the swat typical birp however by showing a poorly reflective lower crust only a narrow zone 1 s at the base of the crust contains high amplitude reflections the shet survey therefore highlights the wide variation in lower crustal reflectivity within the total birps data set rather than the similarities

crustal structure from p and s seismic waves and petrological models of the ukrainian shield presented are the results of reinterpretation of data from deep seismic sounding profiles viii and xxiv located in the central part of the ukrainian shield seismic models of the crustal structure were determined by 1 d and 2 d modelling using refracted and reflected p and s waves velocities of the uppermost crystalline basement vary between 5 8 6 0 km s at the surface and 6 3 6 4 km s at a depth of 5 8 km underlain by a 4 9 km thick low velocity layer the boundary below the low velocity layer is situated at a depth of 10 16 km and characterized by a velocity of 6 25 6 4 km s which increase towards the lower crust reaching up to 6 8 7 3 km s with a gradient of 0 015 0 025 s 1 the moho depth varies greatly from 30 to 56 km and the velocity below moho is 8 1 8 35 km s these results show that the crustal structure is heterogeneous and differentiated apart from a distinct division into the upper and lower crust crustal blocks are observed the deep fracture zones correlate on the surface with faults which are well known from geology a large range in the velocity ratio k p s is observed in the upper crust k is usually from 1 65 to 1 71 the lower crust is characterized by a low gradient and a relatively low value of the s wave velocity with k reaching 1 8 petrologically we interpret the uppermost part of the crust as represented by rocks cropping out at the surface migmatites granitoids gneisses and granites the middle and lower parts of the crust consist of enderbites and metamorphic rocks of granulite facies charnockites the rocks of the lower crust with velocities of 7 2 km s and higher are interpreted as a subfacies of eclogitelike rocks

estimating liquefaction induced lateral displacements using the standard penetration test or cone penetration test a semiempirical approach to estimate liquefaction induced lateral displacements using standard penetration test spt or cone penetration test cpt data is presented the approach combines available spt and cpt based methods to evaluate liquefaction potential with laboratory test results for clean sands to estimate the potential maximum cyclic shear strains for saturated sandy soils under seismic loading a lateral displacement index is then introduced which is obtained by integrating the maximum cyclic shear strains with depth empirical correlations from case history data are proposed between actual lateral displacement the lateral displacement index and geometric parameters characterizing ground geometry for gently sloping ground without a free face level ground with a free face and gently sloping ground with a free face the proposed approach can be applied to obtain preliminary estimates of the magnitude of lateral displacements associated with a liquefaction induced lateral spread