structural analysis and interpretation of the surface deformations of the el asnam earthquake of october 10 1980 the el asnam earthquake of october 10 1980 represents the major seismotectonic event of these last decades in the west mediterranean area it has induced a large amount of surface breaks this earthquake reveals the importance of compressional phenomena that characterize nowadays the tectonics of north africa the tectonic analysis of surface rupture shows the complexity of the deformation mechanism the principal mechanism consists of the activation of a nw se trending thrust fault accompanied with a left lateral motion and with an intense deformation of the northwestern overthrusting block an accurate description of these deformations shows that for a large part the breaks geometry depends closely on the substratum structure finally the analysis of the dislocations on irrigation ducts just above the fault traces allowed a quantitative study of the deformation

determination of present day stress tensor and neotectonic interval in the spanish central system and madrid basin central spain a brittle deformation tectonic analysis was performed in central spain spanish central system and madrid basin in order to decipher and understand the deformation processes that take place in a typical intracontinental zone 1174 fault slickensides obtained in materials with ages between late cretaceous and quaternary have been analyzed by means of fault population analysis methods to reconstruct paleostress tensors nine earthquake focal mechanisms have been determined with magnitudes ranging between 3 and 4 1 with regard to regional structural features and sedimentary record data the characteristics of present day and neotectonic stress fields have been figured out which determine the neotectonic period for this region thus we have established that the intraplate zone represented by central spain has been subjected to a stress field from the middle miocene until the present day with a largest horizontal shortening direction shmax located between n130e and n160e finally three paleostress maps with the main active structures are presented for a middle miocene to late miocene the period when the spanish central system was mainly formed b late miocene to quaternary and c the present day stress field deduced from earthquake focal mechanisms

occurrence stratigraphy and geochemistry of late quaternary tephra layers in the aegean sea and the marmara sea abstract several discrete tephra layers occur in 2 5 10 3 m long cores from the aegean sea whereas a single tephra is identified in 3 5 9 7 m long cores from the marmara sea major and trace element data on these tephras delineate eight distinct groups the geochemical data and multivariate statistics allow the correlation of the tephra layers with six previously described marine tephras from the eastern mediterranean sea potential terrestrial sources are suggested for the others the chronostratigraphy of the tephra layers was established using several radiocarbon dates and the oxygen isotope stratigraphy from two long piston cores four widespread tephra layers occur within the upper quaternary sediments of the aegean sea the two youngest widespread tephra layers were derived from the santorini volcano of south central aegean sea z2 the minoan eruption ca 3 6 ka and y2 the cape riva eruption ca 21 7 ka the y2 tephra is also identified in three piston cores from the marmara sea the two older widespread tephra layers originated from the eruptions which emplaced the campanian ignimbrite of the italian volcanic provinces i e the y5 tephra ca 39 3 ka and from the nisyros volcano of the southeastern aegean sea the consistent occurrence of the nisyros tephra below the y5 tephra confirms similar findings in a lake core on the island of lesbos linear extrapolations using the oxygen isotope stratigraphy suggest an age of 42 44 ka for the nisyros eruption three additional tephra layers with a limited regional distribution are identified in the aegean sea cores two of these tephras originated from the yali volcano of the southeastern aegean sea and from the aeolian islands i e x1 tephra a series of six mugearite tephra beds in the south skiros basin is interpreted as a set of redeposited turbidites

evolution of the lithosphere in the area of the rhine rift system the rhine rift system rrs forms part of the european cenozoic rift system ecris and transects the variscan orogen permo carboniferous troughs and late permian to mesozoic thermal sag basins crustal and lithospheric thicknesses range in the rrs area between 24 36 km and 50 120 km respectively we discuss processes controlling the transformation of the orogenically destabilised variscan lithosphere into an end mesozoic stabilised cratonic lithosphere as well as its renewed destabilisation during the cenozoic development of ecris by end westphalian times the major sutures of the variscan orogen were associated with 45 60 km deep crustal roots during the stephanian early permian regional exhumation of the variscides was controlled by their wrench deformation detachment of subducted lithospheric slabs asthenospheric upwelling and thermal thinning of the mantle lithosphere by late early permian times when asthenospheric temperatures returned to ambient levels lithospheric thicknesses ranged between 40 km and 80 km whilst the thickness of the crust was reduced to 28 35 km in response to its regional erosional and local tectonic unroofing and the interaction of mantle derived melts with its basal parts re equilibration of the lithosphere asthenosphere system governed the subsidence of late permian mesozoic thermal sag basins that covered much of the rrs area by end cretaceous times lithospheric thicknesses had increased to 100 120 km paleocene mantle plumes caused renewed thermal weakening of the lithosphere starting in the late eocene ecris evolved in the pyrenean and alpine foreland by passive rifting under a collision related north directed compressional stress field following end oligocene consolidation of the pyrenees west and northwest directed stresses originating in the alps controlled further development of ecris the rrs remained active until the present whilst the southern branch of ecris aborted in the early miocene extensional strain across ecris amounts to some 7 km plume related thermal thinning of the lithosphere underlies uplift of the rhenish massif and massif central lithospheric folding controlled uplift of the vosges black forest arch

stress regime strain release and geothermal implicationsregional stress field and rifting in western europe in situ stress determination is one possibility to determine stress magnitudes in the earth s crust most measurements especially in the northern alpine foreland have been carried out by using the doorstopper technique stress magnitudes are presented as excess stresses a number of sites where stresses have been determined gave sufficiently high values to statistically determine stress directions for the following tectonic blocks 1 1 western alps 2 2 their immediate foreland with the rhinegraben and 3 3 the rhenish shield bordering on the rift segment of the lower rhine embayment in discussing results of the statistical analyses of stress data it is suggested that stresses measured in the western alps have mainly a topographic origin in the alpine foreland to the north of the rhenish shield topographic stresses are superimposed on active tectonic stress considering the structural and lithological differences the foreland blocks show a different response to the same tectonic stress field which trends for 1 at about 146 this active stress field causes shear rifting in the upper rhinegraben but extensional rifting in the lower rhine embayment in the rhenish shield area only local step faults are observed in direction of 1 due to the ductile behaviour of its basement

the application of icp ms methods to tephrochronological problems pearce nicholas westgate j a perkins w t preece s j 2004 the application of icp ms methods to tephrochronological problems applied gechemistry 19 3 pp 289 322 rae2008

microseismicity of the bearn range reactivation of inversion and collision structures at the northern edge of the iberian plate the bearn range located to the north of the axial zone in the western pyrenees is affected by numerous small magnitude seismic events these events overlap an area characterised by specific geological structures which are interpreted to have resulted from multistage extensional and compressional deformation an analysis of surface geology draped over dem together with field investigations allow identification of two main shortening episodes with differing direction of contraction d1 represents the inversion of the north pyrenean basin whose mesozoic infill was detached from highly extended crust and transported southwards over the necking zone and the northern margin of the iberian plate d2 corresponds to the collision stage and is characterised in the study area by backfolding and backthrusting deformation coeval with uplift in the axial part of the chain due to thickening of the iberian plate the microseismicity appears to concentrate along the basal part of the inverted basin units d1 where this initially low angle thrust has been tilted and steepened during collision d2 we propose that local steepening of this ancient inversion structure which should not be named north pyrenean fault provided the suitable dip for extensional solicitation in association with the present uplift of the axial zone whatever the driving mechanism of this uplift could be

continuous gps and broad scale deformation across the rhine graben and the alps in order to study the ongoing tectonic deformation in the rhine graben area we reconstruct the local crustal velocity and the strain rate field from gps array solutions following the aim of this work we compile the velocities of permanent gps stations belonging to various networks euref agnes regal and rgp in central western europe moreover the strain rate field is displayed in terms of principal axes and values while the normal and the shear components of the strain tensor are calculated perpendicular and parallel to the strike of major faults the results are compared with the fault plane solutions of earthquakes which have occurred in this area a broad scale kinematic deformation model across the rhine graben is provided on the basis of tectonics and velocity results of the gps permanent stations the area of study is divided into four rigid blocks between which there might be relative motions the velocity and the strain rate fields are reconstructed along their borders by estimating a uniform rotation for each block the tectonic behaviour is well represented by the four block model in the rhine graben area while a more detailed model will be needed for a better reconstruction of the strain field in the alpine region

the andean subduction zone between 22 and 25 s northern chile precise geometry and state of stress abstract one year of seismicity recorded by a local network is used to obtain more precision about the geometry and the stress regime of the andean subduction between 22 and 25 s in the northern chile seismic gap a sharp image of the wadati benioff zone wbz is obtained down to 270 km in depth a seismically quasi quiescent zone is observed in the wbz below the volcanic arc between 150 and 210 km in depth hypocentres of distant intermediate depth earthquakes located with the local network are compared with worldwide seismic network hypocentres in order to evaluate the accuracy of the wbz image at depth greater than 100 150 km in depth no shallow microearthquakes have been observed in the continental crust but some seismic activity is likely to occur locally at the deep root of the atacama fault the stress field and the characteristics of faulting along the subducted slab are investigated underthrusting and localized reverse faulting earthquakes define the seismically coupled plate interface from 20 to 50 km in depth locked zone downdip intra slab normal faulting prevails tensile zone but some strike slip faulting is observed a transition between normal faulting with variable fault azimuth and normal faulting with nearly homogeneous nnw to nw oriented fault plane is found at about 80 km in depth it is found that the stress axes 1 and 3 in the locked zone are oriented in the convergence direction 75 80 e downdip in the tensile zone 3 has a mean azimuth 60 65 e there the slab is hence submitted to a tensional force slab pull oblique relatively to the convergence the transition between seismic underthrusting and intraplate normal faulting downdip occurs at the depth where the continental moho encounters the wadati benioff zone suggesting that a relationship exists between seismic coupling and the presence of continental crust at the plate interface the pre seismic state of this segment of the andean subduction zone is confirmed by the occurrence of strong earthquakes located by the global network around the presumed rupture area and by the stress regime found along the wadati benioff zone

comments on structural tectonic controls and geomorphology of the karst corridors in alpine limestone ridges southern carpathians romania by l tirlă and i vijulie geomorphology 197 2013 123 136 abstract in the recently published paper by tirl and vijulie 2013 the authors interpret the abundant trenches affecting the limestone ridge of the v nturari a buila massif southern carpathians romania as bogaz like landforms syn kluftkarren karst corridors karst streets zanjones etc these karst features originated according to the authors through the corrosion of structurally anisotropic limestone bedrock this proposed origin is supported by a comparison of the rose diagrams of the directions of both bogaz and tectonic discontinuities by a morphometric analysis and by observations of the speleothem remnants covering the exposed fault surfaces furthermore the authors described the typically karstic settings of the area such as extremely poor surface drainage subterranean connections between the karst corridors and karst springs in pocket valleys we disagree with their main interpretations and argue that the presumed bogaz are gravitationally induced grabens and trenches created by mass movement activity namely by deep seated slope failures the speleothem remnants are interpreted as flowstones deposited during the subsurface widening of the joints by gravitational activity these speleothem remnants became fossil and even rotated from the original position after sufficient widening of the joints and subsequent exposure of the crevices to the surface due to slope failure progression the morphology of the slope failure along the v nturari a buila massif is similar to numerous other elevated ridges within the carpathian mountains

seismotectonic constraints at the western edge of the pyrenees aftershock series monitoring of the 2002 february 21 4 1 lg earthquake this work was carried out with the support of the marconi ren2001 1734 project from the spanish mcyt mr and cl benefited from a phd grant from the spanish mcyt we would like to thank to the responsible of the ign renass omp and cea databases for sharing the seismological data used in this study

structural tectonic controls and geomorphology of the karst corridors in alpine limestone ridges southern carpathians romania abstract the relationship between surface karst development and the geological frame is widely acknowledged in the study of karst landforms it is of considerable interest especially in alpine environments e g alpine dinaric carpathian orogenic system karst corridors are generally known as kluftkarren or bogaz and form by solution of limestone along a lithoclase network the v nturari a buila massif carpathians romania is a typical alpine karst ridge and a former carbonate platform of upper jurassic age in which geologically controlled karst features have been developing over a geologic timescale field research and mapping were useful in extracting geologic features joint and structure controlled karst corridors are common in the upper section of the mountain between 1600 and 1850 m first a complex system of lithoclases fissures joints and faults occurred then surface runoff or meltwater solutionally enlarged them tension fractures strike in a northeast southwest direction parallel to homoclinal limestone layers the exposed fault walls often preserve draperies and speleothem remnants further statistical analysis of joint fault and bogaz orientations has shown the close relation between the three datasets and morphometric analysis centered only on the karst corridor system results derived from the statistical analysis of orientation data show that there is a strong preferred orientation of the bogaz or bogaz like forms along the directional faults and that they commonly develop in extensional tectonically active environments additional features typical to fluviokarst are also present subterranean connections between the karst corridors and the headwalls of the pocket valleys generating headward recession both by continuous sapping of karst springs at the headwall base followed by collapses an extremely poor surface drainage network developed in the upper pavement facing southeast compared to that on the middle and lower sides

active normal faulting in the upper rhine graben and paleoseismic identification of the 1356 basel earthquake we have identified an active normal fault in the epicentral area of the basel switzerland earthquake of 18 october 1356 the largest historical seismic event in central europe the event of 1356 and two prehistoric events have been characterized on the fault with geomorphological analysis geophysical prospecting and trenching carbon 14 dating indicates that the youngest event occurred in the interval 610 to 1475 a d and may correspond to the 1356 basel earthquake the occurrence of the three earthquakes induced a total of 1 8 meters of vertical displacement in the past 8500 years for a mean uplift rate of 0 21 millimeters per year these successive ruptures on the normal fault indicate the potential for strong ground movements in the basel region and should be taken into account to refine the seismic hazard estimates along the rhine graben

late pleistocene folding above the mail arrouy thrust north western pyrenees france abstract the western pyrenees have experienced several major earthquakes in the last 400 years herein we investigate the ongoing tectonic activity of the arudy area affected by one of the largest earthquakes m 5 1 1980 registered in the instrumental seismicity catalogue in the western pyrenees folding of alluvial terraces younger than 17 3 ky above the mail arrouy thrust mat attest from a late pleistocene tectonic activity this deformation resulted in a shallow fold with a wavelength of 2800 m and amplitude of 7 to 8 m the mat is rooted above a former normal fault of the cretaceous iberian margin which is a potential seismogenic source such observations suggest that the northern flank of the western pyrenees is still subjected to shortening in response to a compressional stress regime this compression is consistent with the african eurasian plate kinematics and the arudy 1980 earthquake nonetheless recent seismological data suggest the presence of an extensional stress regime in the range this extension is indicated by some seismic events mostly observed in the pyrenean high chain our hypothesis is that these extension driven events could be due to a local stress field induced by the elevation of the range on the contrary the compression associated with the regional stress regime could prevail in the outermost domain of the range

strain localization and fluid migration from earthquake relocation and seismicity analysis in the western vosges france summary to understand the mechanisms of intraplate earthquakes well documented seismological and geodynamical studies are needed to provide information for adequate mechanical modelling this paper describes a detailed analysis of the earthquake sequence associated with the rambervillers france m 5 4 earthquake 2003 february 22 which occurred in the western vosges massif france some tens of kilometres to the north of the sites of the epinal 1973 1974 and remiremont 1984 1985 earthquake sequences we computed the location of the mainshock and focal mechanism together with the double difference locations of 419 aftershocks of the subsequent earthquake sequence which included 195 well recorded similar events earthquakes with similar waveforms we combined pp phases recorded by remote dense seismic networks with waveform modelling to accurately determine the mainshock depth 12 5 1 5 km computations of focal mechanisms from regional waveform inversions showed a normal fault plane with a n315 10 strike and a 45 15 dip a detailed space time analysis allowed two earthquake sequences to be identified a classic mainshock aftershock sequence and a secondary sequence that began 250 days after the mainshock more events were recorded during the secondary sequence than during the main sequence very few similar events were recorded during the first 2 days after the mainshock although data were recorded continuously double difference locations from traveltime differences show that these immediate non similar aftershocks occurred in a 4 km 2k m subhorizontal area at a depth of about 12 km similar events were far more numerous during the secondary earthquake sequence double difference relocation of these similar events revealed a n315 striking 65 dipping fault plane that is compatible with the mainshock source mechanism during this later sequence seismicity oscillated over a vertical range of 2 3 km around a mean depth of approximately 12 km this observation strongly suggests fluid migration normal faulting subhorizontal faulting and fluid transfer at about 12 km depth can be interpreted in terms of the crust s response mainshock and post seismic relaxation to flexural stresses induced by the alpine compression this relaxation involves weakening and collapse of the crust and fluid transfer

seismostructural studies in the pyrenees evolution and recent results seismic studies of the last ten years in the pyrenees deep seismic profiles fan profiles at critical distance teleseismic travel time residuals seismicity from temporary networks and their most significant results concerning crustal thickness in the different structural units of the range sharpness of the transition between these units at depth and east west lateral evolution are reviewed in this paper focal mechanisms for three recent earthquakes ofm 4 are given and connections of local seismicity with major tectonic structures such as the north pyrenean fault and its western prolongation at depth are described

new seismotectonic data from an intraplate region focal mechanisms in the armorican massif northwestern france summary focal mechanism solutions are determined for 11 small intraplate earthquakes that occurred between 1990 and 1998 in normandy and the channel islands these mechanisms are obtained from the p wave first motion polarities recorded by stations from local and regional seismic networks the accuracy of each hypocentral location is closely examined and the quality of each fault plane solution is discussed by considering the influence of the velocity structure the predominant feature of the computed focal mechanisms is the relatively widespread near horizontal ne sw t axis orientation horizontal p axes strike roughly nw se mechanism solutions for the earthquakes in the avranches region show left lateral strike slip on a nnw sse fault zone for the overall region it seems that nodal planes of normal faulting solutions trend nw se or wnw ese whereas those of thrust faulting solutions trend ne sw this is in agreement with the general regional stress pattern the ne sw normal fault plane solution of the 1990 jersey event is unique because it is not consistent with the regional style of faulting

intraplate deformation in western europe deduced from an analysis of the international terrestrial reference frame 1997 itrf97 velocity field although tectonic deformation in western europe is essentially concentrated in the appenines and alpine alps pyrenees mountain ranges several large historical and instrumentally recorded earthquakes m 6 are known in the supposedly stable part of europe because of its accuracy and internal consistency at a global scale the international terrestrial reference frame 1997 itrf97 velocity field allows testing of intraplate rigidity in western europe at a millimeter per year level using the full statistical information available on the itrf97 velocities we identify a subset of sites located in central europe that satisfies a rigid cap rotation with residual velocities 1 mm yr and therefore provide a stable europe reference frame serf in this reference frame we find residual velocities at european itrf sites that are consistent with known active tectonic features we identify a northward motion at sites located in italy with internal deformation of the adriatic block rather than rigid plate motion and a westward motion of the westernmost part of europe of the order of 1 2 mm yr relative to central europe the relative motion of the adriatic block and western europe agrees with the current extension known in the tyrrhenian sea and the apennines in central europe we find active deformation 1 mm yr in the eastern alps and western carpathians in the alpine range our results indicate e w extension across the western alps and n s compression across the central and eastern alps in agreement with the strain regime deduced from seismotectonic observations in belgium and the netherlands we find residual velocities of 1 1 5 mm yr to the northwest at all the sites most likely accommodated along the upper and lower rhine graben structures an important outcome of this study is the identification of internal deformation of the order of 1 2 mm yr in an area usually interpreted as stable europe this result should be further checked as new denser and more accurate space geodetic data sets with longer observation time spans become available for europe

the late variscan control on the location and asymmetry of the upper rhine graben the nne trending upper rhine graben urg of the european cenozoic rift system developed from c 47 ma onwards in response to changing lithospheric stresses in the northwestern foreland of the alps the composite graben structure consists of three segments each c 100 km long and 30 40 km wide but flares to c 60 km near its southern and to c 80 km near its northern termination normal faulting induced a total extension of 5 8 km of the 1 2 km thick mesozoic sedimentary franconian platform and underlying variscan basement rocks however distribution of an up to 3 5 km thick sedimentary graben fill and cumulative displacements near eastern and western main border fault systems suggest that subsidence of the graben floor and shoulder uplift created strong cross sectional asymmetries cumulative w down displacements 3 km along strongly segmented transfer faults in the east contrast with e down displacements 600 km long zone that delimits the trailing edge of a sw moving lithospheric block in the urg area ne sw oriented seismic anisotropy at sublithospheric depths of c 60 80 km suggest active mantle flow in this direction as a possible driving force for the reactivation of pre graben lithospheric shear zones

recent activity and seismotectonics of the eastern pyrenees results from a recent earthquake in the eastern pyrenees are presented and the seismotectonics of the region is analyzed from the presently available data on 26 september 1984 an earthquake ml 4 4 took place in the area of the historical destructive earthquake of 1428 several portable stations installed in the epicentral area to record aftershocks permitted of defining a precise location at 42 19 2 n 2 10 2 e and 5 km depth a maximum felt intensity of v msk is obtained from macroseismic data the epicentral location lies within a block bounded by e w trending structures and the focal solution shows right lateral shearing with a nw se pressure axis the seismicity in the eastern pyrenees shows a complex pattern which can be associated with both e w fractures and ne sw fault systems focal solutions of another two recent earthquakes of ml 4 with differences in horizontal pressure axis are also discussed

neogene to ongoing normal faulting in the inner western alps a major evolution of the late alpine tectonics 1 widespread brittle extension occurs in the internal zones of the southwestern alps forming a dense fault network which overprints the compressional structures the extension has been followed by transcurrent motions in terms of paleostress this extension is radial to the belt close to the crustal penninic front and multidirectional in the eastern part of the internal zones the paleostress field of the strike slip phase is coherent with the extensional one and compatible with dextral shear along longitudinal faults globally we propose that the internal zones of the southwestern alps underwent a single neogene transtensive tectonic regime to strengthen our structural results the current tectonics has been analyzed using seismotectonic tools this approach allowed the recognition of several active faults moreover the ongoing tectonics is coherent with the observed brittle deformation the fault network controls the present day seismicity the combined seismotectonic and structural approaches give coherency and continuity from the neogene to ongoing extensional tectonics in the southwestern alps in the framework of the whole western alps a synthesis of our results with neotectonic related data allowed us to provide an accurate map of the neogene to present kinematics of the belt extension which appears as a major feature of the internal zones has been coeval with the propagation of thrusts in the outer zones during neogene times the geodynamic processes which rule this major tectonic evolution of the belt remain a matter of debate

trace element composition of single glass shards in distal minoan tephra from sw turkey volcanic glass from the seventeenth century bc c 3600 bp minoan eruption of santorini thera has been recovered from a 4 cm thick tephra deposit at golhisar golu a small lake in sw turkey analysis of single grains of this glass by laser ablation inductively coupled plasma mass spectrometry la icp ms provides for the first time an accurate determination of the trace element composition of the juvenile glass component of this eruption free from contaminants such as phenocrysts or detrital material individual glass shards 150 m show a large degree of variation in their trace element composition indicative of substantial small scale compositional heterogeneity in the magma this is a result of the proximity of crystallizing phases and provides insights into the chemical evolution of the minoan magma the range of elemental compositions displayed by individual glass shards combined with the consistency of many trace element ratios are characteristics of the minoan glass these features provide a trace element signature for the minoan tephra which will be of value in stratigraphic correlation across the eastern mediterranean

stress tensor orientation derived from fault plane solutions in the southwestern alps gephart and forsyth s method has been applied to estimate stress orientations from earthquake fault plane solutions of the southwestern alps a region where the tectonic stress regime is known to be fairly complex fault plane solutions have been either taken from the literature or computed using data from local and regional networks data refer to seismic events of magnitude in the range 2 5 5 3 which occurred in the last decades at depths between 0 and 25 km two zones with a different stress orientation have been identified in the studied area 44 0 45 5 n 6 5 8 5 e the western zone corresponding to the crest of the alpine belt where a high dip maximum compressive stress is found and the eastern zone alps chain to po plain transition characterized by an almost horizontal e w 1 and a nearly vertical 3 hypocenters of earthquakes used for stress inversion lie in the depth ranges 0 15 km and 5 25 km in the western and eastern zones respectively the transition between the two stress domains is very sharp and this is also indicated by space distribution of earthquake individual misfits to the respective stress models the findings of the present study are a good match for tectonic models which assume e w compression derived from the adria europe interaction and producing 1 major thrusting processes in the eastern side of the chain and 2 secondary tensional effects at very shallow depth beneath the alpine belt crest western zone of the area studied in this work

reply to comments on structural tectonic controls and geomorphology of the karst corridors in alpine limestone ridges by l tirlă and i vijulie geomorphology 197 2013 123 136 by j lenart and t panek abstract lenart and panek 2014 disagree with the term bogaz which we have attributed to the main structural discontinuities in the v nturari a buila massif southern carpathians they also insist upon the mass movements as being the defining processes which generate them finally the authors explain the genesis of fossil speleothems found in abundance on the exposed walls of the former crevice type caves we essentially followed within our study two aspects similarities met by the studied tectonic karst corridors and typical bogaz as classically described in literature and their connection with the basic structural and tectonic frame the spatial context of the described landforms was not ignored as we constantly mentioned the role of compressional forces in building a favorable environment for their occurrence tirl and vijulie 2013 neotectonics and structural frame particularly the strike slip fault systems are the major control factors in driving the evolution of the v nturari a buila massif and the formation of the bogaz like forms supplementary evidences for attesting reverse and strike slip faulting were provided slope failures by gravitational collapse prevail and rotational landslides are only isolated the origin of discussed exposed speleothems was correctly explained in the comment except that they were formed on fault walls not on fractures of gravitational origin

geodetic measurements of crustal deformation in the western mediterranean and europe geodetic measurements of crustal deformation over large areas deforming at slow rates 5 mm yr over more than 1000 km such as the western mediterranean and western europe are still a challenge because 1 these rates are close to the current resolution of the geodetic techniques 2 inaccuracies in the reference frame implementation may be on the same order as the tectonic velocities we present a new velocity field for western europe and the western mediterranean derived from a rigorous combination of 1 a selection of sites from the itrf2000 solution 2 a subset of sites from the european permanent gps network solution 3 a solution of the french national geodetic permanent gps network rgp and 4 a solution of a permanent gps network in the western alps regal the resulting velocity field describes horizontal crustal motion at 64 sites in western europe with an accuracy on the order of 1 mm yr or better its analysis shows that central europe behaves rigidly at a 0 4 mm yr level and can therefore be used to define a stable europe reference frame in that reference frame we find that most of europe including areas west of the rhine graben the iberian peninsula the ligurian basin and the corsica sardinian block behaves rigidly at a 0 5 mm yr level in a second step we map recently published geodetic results in the reference frame previously defined geodetic data confirm a counterclockwise rotation of the adriatic microplate with respect to stable europe that appears to control the strain pattern along its boundaries active deformation in the alps apennines and dinarides is probably driven by the independent motion of the adriatic plate rather than by the africa eurasia convergence the analysis of a global gps solution and recently published new estimates for the african plate kinematics indicate that the africa eurasia plate motion may be significantly different from the nuvel1a values in particular geodetic solutions show that the convergence rate between africa and stable europe may be 30 60 slower than the nuvelia prediction and rotated 10 30 counterclockwise in the mediterranean

the structural evolution of the english channel area the structural evolution of the english channel area is controlled by structure and particularly by the pre existing cadomian and variscan crustal discontinuities which have been reactivated repeatedly in post variscan times they controlled the crustal subsidence that produced basin development in the mesozoic prior to the sea floor spreading in the north atlantic region they were then reactivated during the cenozoic compression and basin inversion the english channel development is ascribed to mid tertiary differential uplift oligocene to miocene during late tertiary to quaternary times the channel displays characteristics of a tectonically controlled fluvial basin periodically invaded by the sea at the lithospheric scale the channel can be considered as an active intraplate area influenced by the nw se alpine push the nw se atlantic ridge push and glacial rebound stresses copyright 2003 john wiley sons ltd

an inverse problem in microtectonics for the determination of stress tensors from fault striation analysis abstract a method is proposed to compute some characteristics of a possible stress tensor related to striations measured in a given faulted area if several tectonic phases are responsible for the striations the method separates and determines the successive stress tensors the iterative algorithm consists of alternatively a sorting the data attributed to a tectonic phase and b computing the characteristics of the stress tensor of this phase the method is tested using an application to synthetic and actual data

seismicity wedge beneath the upper rhine graben due to backwards alpine push abstract the distribution of hypocentres in the upper rhine graben area is re examined and discussed with respect to the present day tectonic framework most earthquakes occur within a n60 striking wedge located on top of a moho dome this wedge is limited by the surface and at depth by a plane which in the south of the dome coincides with the se dipping conrad discontinuity in depth the seismicity shows a normal distribution the maximums of which are located on a surface dipping 6 towards se parallel to the south eastward dipping conrad and moho this surface outcrops along the north western edge of the uplifted crystalline vosges and black forest the main shocks in earthquake swarms in the region often occur in the vicinity of this surface and along pre existing n s to ne sw variscan or tertiary faults and show focal mechanisms of strike slip in contrast part of the aftershocks show focal mechanisms of reverse faulting associated with se nw striking compression the seismic wedge and the north westward rising seismic surface suggest initiation of crustal ramp which starts at the south eastern rim of the conrad dome and which may become a thrust plane if se nw compression continues in the south eastern edge of the graben and above the south eastern ridge of the moho dome where evidences for extension have been found we identify clustering of hypocentres along a surface that strikes n150 parallel to the main compression and dipping towards ne dominant normal faulting mechanisms along this surface suggests initiation of a normal probably listric fault at depth the onset of the future fault plane is located on top of the nw se striking ridge of the lower crust and moho which act as a an indenter in addition to thrusting of the whole wedge towards nw increasing of nw se compression would lead to the formation of a half graben at the place of the present sierentz depression

analysis of the mw 4 3 lorient earthquake sequence a multidisciplinary approach to the geodynamics of the armorican massif westernmost france summary a mw 4 3 earthquake occurred on 2002 september 30 in the armorican massif nw france since it was one of the largest events ever recorded in this region this was the opportunity to improve our seismotectonic knowledge of the armorican massif we performed a post seismic survey sisbreizh which allowed us to locate accurately 62 aftershocks within 14 days an analysis of the main shock using broadband records provided a normal fault mechanism with a dextral strike slip component located at 12 km depth the aftershock sequence exhibits 1 a combination of almost pure right lateral strike slip and dominant normal faulting similar to the main shock 2 magnitudes ranging from 0 4 to 1 9 and 3 depths ranging from 11 5 to 13 5 km that is close to the main shock hypocenter the distribution of the aftershocks defines a rupture plane dipping 60 to the south with a fault length of 2 km consistent with the source parameters of the main shock beside the sisbreizh survey a morpho structural analysis has been conducted we found fault plane solutions with southward dipping n120 150 normal fault planes the stress tensor computed after the aftershock focal mechanisms is a strike slip regime with a ne sw extensional direction the lorient earthquake appears to reactivate late hercynian structures and the whole sequence is reflecting the regional scale tectonic stress field expressed by a combination of strike slip and normal faulting

stress tensor determination in france and neighbouring regions abstract the tectonic behaviour of different seismic regions of france is inferred from the properties of the local stress tensor obtained from focal mechanisms of regional earthquakes polarities of p wave arrivals for several earthquakes are used in the inversion of the stress tensor and individual focal mechanisms the principal axes and the shape of the tensor are closely related to the forces which generate seismic ruptures on pre existing faults we analyse 142 earthquakes of magnitude above 3 7 which occurred between 1965 and 1989 good results are obtained for some regions the northern alps and the southern end of the upper rhinegraben show a quasi compressive strike slip tectonic regime with a maximum stress axis oriented nw se the tectonic regime changes to an extensional strike slip type in the rhenish massif and the lower rhinegraben the direction of the minimum stress axis being nne ssw the central and western regions of france central and armorican massifs exhibit an extensional tectonic regime combined with strike slip faulting the minimum stress axis strikes in a ne sw direction a strongly non homogeneous stress field seems to be present in the southwestern alps and no unique stress tensor could be obtained for that region this problem is likely to be related to a rapid variation of the stress field in space which could be expected given the arc like geometry of the mountain range the pyrenean domain is unresolved due to lack of data and moreover existing focal mechanisms are globaly inconsistent nevertheless those mechanisms which are well constrained suggest a nnw sse to nw se direction of maximum stress in the western part of the pyrenees thus the stress field in france is fairly homogeneous at a regional scale for most of the territory except for the highly deformed belts

a preliminary catalog of moment tensors for the pyrenees abstract using waveform data gathered from the different organizations that operate seismological networks in the pyrenees we have obtained a complete moment tensor catalog of pyrenean earthquakes with magnitude larger than 3 covering the time period 2001 2011 our moment tensor solutions are in good agreement with those previously reported by other institutions we find absolutely no evidence for inverse faulting in the pyrenees on the opposite almost all the events have extensional focal mechanisms while only one event has a clear strike slip mechanism the t axes are consistently oriented along a nne ssw direction giving further support for a currently active extensional regime of deformation in the pyrenees the scaling relation between moment magnitude and local magnitude has a slope close to unity in contrast the scaling between our moment magnitudes obtained by waveform inversion and the moment magnitudes determined by inversion of shear wave spectra from drouet et al 2010 has a slope of 1 31 further work is thus required to identify the source of this discrepancy and to define a robust magnitude scale for the quantification of earthquakes in the pyrenees

in situ stress fields and focal mechanism solutions in central france focal mechanisms of 31 central france earthquakes mb 2 9 4 4 were evaluated to determine if slip is compatible with stress field determinations conducted at four nearby sites the coherent picture that results indicates that the regional stress fields can be inferred by linear extrapolation of in situ measurements performed between 400 1000 m depths furthermore the results show that in spite of rather constant principal stress directions from one site to the next 100 km apart principal stress amplitudes vary significantly for the domain investigated 200 200 km the size of the homogeneous stress field regions appears to be fairly small about 100 100 km in addition within these regions important local stress perturbations as identified by extremely inconsistent focal mechanisms are present thus only by integrating different data types is it possible to map properly the regional stress field this mapping provides means to identify the homogeneous regions as well as to highlight zones of local stress perturbations most likely indicative of active faulting

source parameters of the 1926 and 1927 jersey earthquakes from historical instrumental and macroseismic data abstract english channel islands are located off normandy coast of france within an intraplate area not associated with high seismicity rate and active tectonics however in july 1926 a damaging and well documented earthquake occurred there followed by a strongly felt event in february 1927 in this paper we reprocess macroseismic observations analog seismograms and bulletin data in order to re appraise the location and magnitude of these two earthquakes we find that the macroseismic epicentre of the 1926 jersey earthquake is shifted to the east when compared with the location offshore south of jersey given in both the french database sisfrance and the recent french catalog fcat 17 arrival times from published data together with our own onset time readings are processed in order to obtain probabilistic hypocentral locations the maximum likelihood instrumental epicentre of the 1926 event is located about 15 km east of jersey island 49 20 n 1 82 w this epicentre is well constrained within a 10 km radius area the location of the 1927 epicentre is slightly south of jersey at a location similar to that of sisfrance but this latter epicentre is less constrained as fewer observations are available the probability density function for the 1927 epicentre is relatively diluted focal depth remains very poorly determined for both the 1926 and 1927 events analysis of historical seismograms is also performed in order to determine both surface wave and moment magnitudes ms and mw we find ms 5 6 0 2 for the 1926 event and ms 5 0 for the 1927 event waveform fitting of some of the highest quality seismograms of the 1926 event gives us mw in the range 5 0 5 5 depending on the chosen focal depth and focal mechanism the 1927 jersey earthquake is expected with an intensity magnitude mi about 0 6 smaller

evidence for the permutation of stresses σ1 and σ2 in the alpine foreland the example of the rhine graben abstract the orientation of the principal stresses 1 2 and 3 and the ratio r 2 3 1 3 which characterizes the shape of the stress tensor can be calculated using earthquake focal mechanisms in the rhine graben area two types of stress tensor can be determined one of them is an extensional stress state subvertical 1 horizontal 2 n130 in the northern part of the rhine graben the other is a strike slip stress state horizontal 1 n150 in the southern part these results show that the maximum horizontal stress is constant in an approximately n130 150 direction 1 in the south 2 in the north this permutation of the stresses 1 and 2 may be imputed to the interaction between the decrease in alpine pressure and the asthenospheric uprise under the rhenish massif the superficial in situ stresses measured from the alps to the lower rhine embayment showing a decrease in maximum horizontal stress h max support this hypothesis

geomorphology and geochronology of sackung features uphill facing scarps in the central spanish pyrenees abstract the paper analyses uphill facing scarps and associated troughs developed in the oversteepened slopes of two neighbouring glacial valleys in the central spanish pyrenees previous studies of sackung landforms in the pyrenees have argued for deglacial unloading as the genetic mechanism but this causal and temporal relationship has not been proved due to the lack of chronological data the antislope scarps in the two studied locations vallibierna and estos are developed in palaeozoic metasedimentary rocks parallel to the contour lines and the structural grain occur in the intermediate sector of the hillslope and are up to 0 5 km long and several meters high a trench was excavated in a sackung trough fill in each of the valleys in order to gain information about their chronology and genesis charcoal from the lowermost unit in vallibierna provided an age of 5 9 cal ka for the sackung and extrapolation of the three dates obtained in estos indicates that the trough formed ca 7 6 7 8 cal ka deglaciation of the studied sectors of the valleys occurred between 16 and 13 ka the time lag of 5 ka suggests that glacial erosion and the subsequent debutressing of the oversteepened valley walls created slopes predisposed to sackung development but did not initiate the movement seismic shaking is proposed as a probable triggering factor this hypothesis although supported by the sudden deformation event recorded by a failure plane exposed in vallibierna trench and by the seismic and neotectonic activity of the area cannot be proved due to the lack of chronological information about paleoearthquakes

stress field in the northern rhine area central europe from earthquake fault plane solutions abstract fault plane solutions fps from 110 earthquakes in the northern rhine area with local magnitudes ranging from 1 0 to 6 1 and occurring between 1976 and 2002 are determined fps are retrieved from p wave first motions using a grid search approach allowing a detailed exploration of the parameter space the influence of the 1d velocity model on take off angles and resulting fps is examined all events were relocated with a recently developed minimum 1d model of the velocity structure j geophys res 2003 rose diagrams of the orientation of p t and b axes show a clear preference of trends of p and t axes at n292 e and n27 e respectively the majority of b axes trend in northerly directions plunges of p and t axes are mostly around 45 while most b axes are subhorizontal the main direction of the maximum horizontal stress directly inferred from the fault plane solutions is n118 e to calculate the orientations of the principal stress axes and the shape of the stress tensor the inversion method of gephard and forsyth j geophys res 89 1984 9305 was applied to the whole data set and to several subsets of data the subsets were formed by grouping events from various geological and tectonic areas and by grouping events into different depth ranges the subset areas include the lower rhine embayment the rhenish massif the middle rhine area the neuwied basin and the area known as the stavelot venn massif inversion of the entire data set shows some ambiguity between a strike slip and extensional stress regime with a vertical axis for the medium principal stress and a trend of n305 e and n35 e for the 1 and 3 axis respectively as the best fitting tensor earthquakes from the lower rhine embayment and to some degree from the middle rhine area indicate an extensional stress regime in the lower rhine embayment plunge and trend of the 1 axis are 76 and n162 e and for the 3 axis 7 and n42 e the best fitting solution for the area of the stavelot venn massif is a strike slip regime with subhorizontal 1 and 3 axes with a trend of n316 e and n225 e respectively stress orientations found here agree overall with the results from earlier studies based on smaller data sets the directions of the maximum and minimum horizontal stresses inverted from focal mechanisms agree well with the stress field predicted by the european stress map this confirms earlier interpretations that the stress field of the rhine graben system is controlled by plate driving forces acting on the plate boundaries however amplitudes of the stresses change on a local scale and with depth estimates of the absolute magnitude of principal stresses favor a normal faulting regime in the shallow crust above 12 km depth and a strike slip regime in the lower crust

seismicity of the northern upper rhine graben constraints on the present day stress field from focal mechanisms abstract we present new results for the microseismic activity in the northern upper rhine graben by analyzing seismogram recordings from two temporary networks of up to 13 broad band stations in combination with data from permanent stations previous studies have mainly focused on the southern and intermediate sections of the upper rhine graben where the station coverage by regional networks is more dense between october 2010 and september 2013 we recorded 56 earthquakes that occurred within the immediate vicinity of the northern upper rhine graben with local magnitudes ranging from 0 5 to 3 2 the majority of the hypocenters are located beneath the eastern graben shoulder and in the graben itself while activity observed along the western graben shoulder is lower a further active region is located along the southern rim of the taunus mountains to the northwest of the study area the seismicity extends to a depth of 25 km the hypocentral depth distribution exhibits a pronounced peak of seismic energy release in the depth range between 12 and 18 km fault plane solutions for a total of 58 earthquakes including data from previous recordings were derived from p polarities and sv p amplitude ratios this new data set more than quadruples the number of available data for regional stress field analysis the majority of the focal mechanisms show predominantly strike slip movements only a few events are of reverse or normal faulting type t axis trends are oriented ne sw the calculated focal mechanisms presented in this study confirm that the area is in transtension however in contrast to previous studies a stronger strike slip component is identified we also derived the azimuths of the principal stress axes by inverting the fault plane solutions and calculated the direction of the maximum horizontal stress which is mainly oriented n135 e

intraplate seismicity new seismotectonic data in western europe abstract fault plane solutions for 128 earthquakes which occurred in france and neighbouring areas have been determined stress field information given by these data are discussed in relation to previous tectonic knowledge the western alps are characterized by a compressional regime with a fan shaped distribution of p axes which might be related to the interaction mechanism between europe and the adriatic plate the pyrenean region is mainly submitted to a south north compression tectonic activity in this area seems to be determined by the presence of two subduction zones with reverse dips in the south bay of biscay and in the central pyrenees the transition zone between these two active belts is characterized by significant seismicity with a transpression regime

lithospheric anisotropy beneath the pyrenees from shear wave splitting we investigate upper mantle anisotropy beneath the pyrenean range along three n s profiles across the mountain belt the results of a first profile that operated in 1993 in the central part of the belt have been presented elsewhere we present the results of two other profiles that ran in 1995 1996 and 1996 1997 in the eastern and western part of the belt respectively and propose an interpretation of the whole results teleseismic shear waves sks skks and pks are used to determine splitting parameters the fast polarization direction and the delay time t teleseismic shear wave splitting in the eastern pyrenees displays homogeneous values trending n100 e and t values in the range 1 1 to 1 5 s a station located in the southern massif central 100 km north of the range is characterized by different splitting parameters n70 e t 0 7 s in the western part of the belt anisotropy parameters are similar across the whole belt n110 e and t 1 3 to 1 5 s most of the measured delay times including those obtained in the central part of the range are above the global average of the sks splitting around 1 s at the belt scale is generally poorly correlated with recent estimations of the absolute plate motion which predicts a fast direction ranging between n50 e and n80 e instead the orientation of n100 e is parallel to the trend of the pyrenean belt but also to hercynian preexisting structures this parallelism supports an anisotropy primarily related to frozen or active lithospheric structures we show that a signature related to the pyrenean orogeny is likely for the stations located in the internal domains of the belt by contrast the anisotropy measured at the stations located on the external parts of the belt could reflect a pre pyrenean hercynian deformation we suggest that a late hercynian strike slip deformation is responsible for this frozen upper mantle anisotropy and that the pyrenean tectonic fabric developped parallel to this preexisting fabric finally no particularly strong splitting is related to the north pyrenean fault commonly believed to represent the plate boundary between iberia and eurasia

neotectonics and intraplate continental topography of the northern alpine foreland research on neotectonics and related seismicity has hitherto been mostly focused on active plate boundaries that are characterized by generally high levels of earthquake activity current seismic hazard estimates for intraplate domains are mainly based on probabilistic analyses of historical and instrumental earthquake catalogues the accuracy of such hazard estimates is limited by the fact that available catalogues are restricted to a few hundred years which on geological time scales is insignificant and not suitable for the assessment of tectonic processes controlling the observed earthquake activity more reliable hazard prediction requires access to high quality data sets covering a geologically significant time span in order to obtain a better understanding of processes controlling on going intraplate deformation the alpine orogen and the intraplate sedimentary basins and rifts in its northern foreland are associated with a much higher level of neotectonic activity than hitherto assumed seismicity and stress indicator data combined with geodetic and geomorphologic observations demonstrate that deformation of the northern alpine foreland is still on going and will continue in the future this has major implications for the assessment of natural hazards and the environmental degradation potential of this densely populated area we examine relationships between deeper lithospheric processes neotectonics and surface processes in the northern alpine foreland and their implications for tectonically induced topography for the environmental tectonics project entec the upper and lower rhine graben urg and lrg and the vienna basin vb were selected as natural laboratories the vienna basin developed during the middle miocene as a sinistral pull apart structure on top of the east alpine nappe stack whereas the upper and lower rhine grabens are typical intracontinental rifts the upper rhine graben opened during its late eocene and oligocene initial rifting phase by nearly orthogonal crustal extension whereas its neogene evolution was controlled by oblique extension seismic tomography suggests that during extension the mantle lithosphere was partially decoupled from the upper crust at the level of the lower crust however whole lithospheric folding controlled the mid miocene to pliocene uplift of the vosges black forest arch whereas thermal thinning of the mantle lithosphere above a mantle plume contributed substantially to the past and present uplift of the rhenish massif by contrast oblique crustal extension controlling the late oligocene initial subsidence stage of the lower rhine graben gave way to orthogonal extension at the transition to the neogene the entec project integrated geological geophysical geomorphologic geodetic and seismological data and developed dynamic models to quantify the societal impact of neotectonics in areas hosting major urban and industrial activity concentrations the response of europe s intraplate lithosphere to late neogene compressional stresses depends largely on its thermo mechanical structure which in turn controls vertical motions topography evolution and related surface processes

the december 1994 seismic swarm near aoba ambae volcano vanuatu and its relationship with the volcanic processes abstract a seismic swarm which occurred in december 1994 near the aoba volcano vanuatu is investigated in detail by analyzing local and regional broad band seismic records the seismic area is situated in a poorly instrumented region although major seismic and volcanic events are possible the data collected by four permanent short period stations the nearest one being installed in the espiritu santo island located 80 km from the volcano allowed us to locate epicenters with a 2 3 km precision and to document the present local seismicity the quality of available regional broadband data allows us to determine reliable focal parameters though the magnitude of the strongest event is 4 8 data have been selected from the permanent geoscope and iris stations located in the south western pacific region and from two temporary networks one installed in new caledonia and vanuatu by i r d and the e o s t and another one installed in fiji and tonga islands by the washington university st louis usa results obtained either with local epicentral distance d km body waves or regional 500 km surface waves lead us to conclude that the swarm is associated with the volcanic edifice but is not of volcanic type according to the definitions given by minakami phys volcanol 1974 1 and schick bull volcanol 44 1981 491 the observed mechanisms evidence an important local influence of the volcano itself on the stress field and the observed near horizontal p axis argues against a strong increase of phreatic activity in addition seismic and volcanic observations are analyzed in the framework of the interpretation of earthquake swarms occurring in the vicinity of active volcanoes

changes in strain trajectories in three different types of plate tectonic boundary deduced from earthquake focal mechanisms abstract principal strain orientations minimum horizontal compression ex and maximum horizontal compression ey were established at three different types of plate tectonic boundary two transform faults an oceanic ridge located on the southeast indian ridge and a trench located close to the south sandwich archipelago to establish the strain patterns in each zone 104 earthquake focal mechanisms centroid moment tensor solutions for earthquakes with mb 4 harvard seismology data cmt were examined by fault population analysis despite the existence of only one tectonic process that controlled deformation in these zones divergence convergence or passive displacement and only one main strain tensor several coeval strain ellipsoids were found these differed from the main strain tensor in the location of the principal strains in general permutations were observed between the principal strains i e interchanges between the location of the principal strain axes maintaining the strain ellipsoids in the same 3d orientation only in some cases were changes in the ellipsoid orientation associated with major structures

crustal velocity field of western europe from permanent gps array solutions 1996 2001 we derive a new geodetic velocity field for western europe and the western mediterranean by rigorously combining 1 a selection of 36 itrf2000 sites 2 a solution from a subset of sites of the european permanent gps network euref epn 3 a solution of the french national geodetic permanent gps network rgp and 4 a solution of a permanent gps network in the western alps regal the resulting velocity field describes horizontal crustal motion at 64 sites in western europe with an accuracy of the order of i mm yr 1 or better its analysis shows that central europe defined as east of the rhine graben and north of the alps and the carpathians behaves rigidly at a 0 4 mm yr 1 level and defines a stable europe reference frame in that reference frame we find no significant motion at sites located west of the rhine graben and on the iberian peninsula which sets an upper bound of 0 6 mm yr 1 on horizontal motion across the rhine graben and the pyrenees we find that the current strain pattern in the western alps combines e w extension and right lateral shear we confirm a counterclockwise rotation of the adriatic microplate which appears to control the strain pattern along its boundaries in the friuli area the alps and the apennines our results also suggest that the africa eurasia plate motion in the western mediterranean may be 40 50 per cent slower that the nuvel1a plate motion model and rotated 20 30 counterclockwise

new insight in the tectonics of the southern rhine graben jura region using local earthquake seismology 1 a new seismic data set was acquired using a dense temporary network of mobile seismic stations it is combined with existing seismological data for the southern rhine graben the data yielded some new focal mechanisms and allowed for a detailed local earthquake tomography these methods give new insight in the structure of the crust and stress conditions in the area by combining the tomography with the earthquake hypocenter locations and focal mechanisms some of the structures in the p wave velocity model are interpreted as active faults the eastern boundary fault zone of the graben is found to be activated in a left lateral strike slip sense the southern continuation of these faults is formed by variscan structures in the basement a change in orientation of the graben axis between the main graben and its southern end have played a role during the development of the system this difference in orientation caused the development of the dannemarie and allschwil subbasins during a late stage of the opening of the rhine graben this study shows evidence for active faulting in the basement underneath the detachment of the jura mountains these faults which are interpreted as reactivated permo carboniferous troughs coincide with the frontal thrusts of the jura mountains it might be that these structures in the basement have influence on the detachment tectonics in the region

short scale variations of tectonic regimes in the western european stress province north of the alps and pyrenees the data of the european part of the world stress map wsm are used to study the western european stress province north of the alps and pyrenees the study area is characterised by an almost homogeneous n 145 degrees e orientation of the maximum horizont

neutron activation analysis of mediterranean volcanic rocks an analytical database for archaeological stratigraphy abstract pumice has been used as a serviceable abrasive or religious artifact since antiquity and has therefore been an object of trade by analyzing pumice samples from archaeological excavations and comparing the results to an analytical database it is possible to establish the origin of the sample and thereby get information on the maximum age and the transport route of the pumice sample in addition the deposition of primary tephra deposits can be used as time markers and place constraints on the ages of archaeological materials neutron activation analysis naa was applied to determine the concentrations of 25 elements as ba ce co cr cs eu fe hf k la lu na nd rb sb sc sm ta tb th u yb zn and zr in pumice samples from the mediterranean region milos santorini kos giali and nisyros greece lipari italy and cappadokia turkey it was found that eruption products like pumice or volcanic ash can be correlated in many cases to their volcanic sources by comparison of the typical main and trace elemental concentration patterns chemical fingerprint such a distinction is possible if the volcanic rocks are homogenous enough with respect to the concentrations of geochemically relevant elements using only the pure glass fraction of tephra a sample size of 5 mg is sufficient for identification by naa

present day geodynamics in the bend of the western and central alps as constrained by earthquake analysis summary the contrasted tectonics of the western central alps is examined using a synthesis of 389 reliable focal mechanisms the present day strain regime is mapped and interpolated for the entire alpine belt based on a newly developed method of regionalization the most striking feature is a continuous area of extension which closely follows the large scale topographic crest line of the alpine arc thrusting is observed locally limited to areas near the border of the alpine chain a majority of earthquakes within the alps and its forelands are in strike slip mode stress inversion methods have been applied to homogenous subsets of focal plane mechanisms in order to map regional variations in stress orientation the stress state is confirmed to be orogen perpendicular both for 3 in the inner extensional zones and 1 in the outer transcurrent transpressional zones extensional areas are well correlated with the part of the belt which presents the thickest crust as shown by the comparison with the bouguer anomaly and the average topography of the belt in the northwestern swiss alps extension is also correlated with currently uplifting zones these observations and our strain stress analyses support a geodynamic model for the western alps in which the current activity is mostly a result of gravitational body forces earthquakes do not provide any direct evidence for ongoing convergence in the alpine system but a relationship with ongoing activity of complex block rotations of the apulian microplate cannot be ruled out

tectonic influences on the quaternary drainage evolution on the north western margin of the french central massif the creuse valley example abstract this work examines the links between tectonics and fluvial dynamics on the north western margin of the french central massif geomorphological and sedimentological analyses of detrital deposits were carried out as the basis for correlating the different formations and for reconstructing the palaeodrainage in the creuse basin cross sections of the valleys longitudinal profiles of terraces and glacis indicate post depositional deformation of about 50 m amplitude uplift north and south of gueret and in the eguzon district these deformations are related to the central massif uplift of 50 m above the paris basin since 1 1 ma ois 32 the creuse incision varies from 140 m in the crozant anticline to 60 m in the paris basin an upper pliocene palaeochannel located on the sedelle ardentes issoudun lineament is evidenced by andalusite coming from the fougeres unit the reactivation of the transverse faults between le pin and le menoux has distorted the middle terraces the main knick points are mainly due to tectonics and have been persistent in the landscape since the upper pliocene their recession rate is controlled both by discharge and lithology tributary streams exhibit strong convexities indicating that the erosional response to pliocene uplift has not yet propagated into upland surfaces

the inverse problem in microtectonics and the separation of tectonic phases abstract the algorithm of inverse problems is applied to three cases in microtectonics a collection of striations measured on pre existing faults may be processed automatically and interpreted in terms of tectonic stress a comparison is made between two different methods formerly proposed by the authors both methods are tested with field data the theoretical results agree with independent field criteria for a separation of tectonic phases

seismic activity at the western pyrenean edge abstract the present day seismicity at the westernmost part of the pyrenean domain reported from permanent networks is of low to moderate magnitude however it is poorly constrained due to the scarce station coverage of the area we present new seismic data collected from a temporary network deployed there for 17 months that provides an enhanced image of the seismic activity and its tectonic implications our results delineate the westward continuity of the e w pyrenean band of seismicity through the variscan basque massifs along the leiza fault ending up at the hendaya fault this seismicity belt is distributed on a crustal scale dipping northward to almost 30 km depth other relevant seismic events located in the area can be related to the central segment of the pamplona fault and to different e w thrust structures

three dimensional flexural modelling of the ebro basin ne iberia summary the ebro basin the southern foreland basin of the pyrenees has undergone a complex evolution in which apart from the pyrenees the iberian range and the catalan coastal ranges have played an important role both as sediment sources and as basin confining structures the deflected basement underlying the ebro basin dips north suggesting a lithospheric scale control on the structure of this basin this is compatible with the results of subsidence analyses which show that the study area is not in a local mode of isostatic compensation in order better to understand the mechanisms that led to the present configuration of the ebro basin and particularly the relevance of the various kinds of un loading e g surrounding fold and thrust belts basin topography subsurface loads we carried out a 3 d kinematic modelling study that accounts for the flexural state of the lithosphere subjected to various loads applied at its lateral boundaries and the sedimentary fill of the basin we also included the effect of neogene extensional tectonics along the eastern basin margin which is related to the opening of the valencia trough we show the suitability of the 3 d lithospheric scale flexural modelling approach to the study of ne iberia modelling results point to a relatively strong lithosphere in this area with values of effective elastic thickness ranging from 10 to 35 km in the ebro basin increasing towards the pyrenees we also find that the topographic tectonic load itself is insufficient to explain the observed basement deflection thus an extra subsurface load beneath the pyrenees corresponding to the underthrusted iberian lithosphere is required the effect of lithospheric stretching in the valencia trough on the ebro basin is appreciable only in its eastern part where the lithosphere was uplifted this had considerable repercussions on the sedimentary and erosional regime of the ebro basin we have analysed the link between the stretching related tectonically uplifted areas and the erosional patterns observed onshore northeast iberia

active tectonics of the southeastern upper rhine graben freiburg area germany the upper rhine graben has two plio quaternary depocentres usually interpreted as resulting from tectonic reactivation the southern basin near freiburg im breisgau germany contains up to 250 m of sediments beneath the younger alluvial deposits related to the current drainage system a former river network deeply entrenched in the substratum reveals a very low regional base level of early pleistocene age the offset of channels at faults allows us to infer a pleistocene reactivation of the syn rift fault pattern and the estimation of slip rates maximum vertical movements along the faults have not exceeded 0 1 mm yr since the middle pleistocene current activity is concentrated along the westernmost faults morphologic markers indicate late pleistocene reactivation of the rhine river fault and geophysical prospecting suggests a near surface offset of young sedimentary deposits the size of the fault segments potentially reactivated suggests that earthquakes with magnitude larger than mw 6 3mw 6 3 could be expected in the area with a return interval of about 8000 years extrapolated to the duration of the plio pleistocene the strain rate estimates reveal that the tectonic forcing may account for only one third to one half of the whole thickness of the plio pleistocene sediments of the basin fill thus other processes must be invoked to understand the growth of the plio pleistocene basin especially the piracy of the rhine river to the north during the early pleistocene could explain these effects

modern tectonic stress field in the mediterranean region evidence for variation in stress directions at different scales summary a compilation of more than one thousand stress indicators which include in situ stress measurements focal mechanisms microtectonic and other geological data allowed us to reconstruct the modern stress field in the mediterranean region and the surrounding area average stress directions at different scales have been reconstructed by means of a linear interpolation method this method takes into account the distribution scale and quality of stress data the results of the interpolation at plate scale allow us to recognize slightly deformed regions such as the northwestern european platform where average maximum horizontal stress direction is oriented roughly nnw sse subparallel to absolute and relative plate velocity directions other regions such as the caucasus alps and pyrenees where recent tectonic deformation and seismicity are present display important variations of stress directions the reconstruction of the average stress directions at different scales within the french alps pointed out that the average stress field pattern may vary from one scale to another nevertheless variations of stress directions at a given scale are consistent with the kinematics of faults of the same scale

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

evidence for short scale stress field variations within intraplate central western france summary refinement of the seismicity distribution 4574 events in western and central france has been done by synthesis of seismological bulletins earthquakes have then been relocated by joint hypocentre and velocity structure inversion the new hypocentre distribution indicates that the seismicity of those regions is much less diffuse than previously thought mainly with regard to the depth distribution the hypocentre improvement allows us to compute 44 new focal mechanisms and to revise bibliographic focal mechanism solutions then the regional stress field was determined from 119 available focal mechanisms it is characterized by a regionally significant strike slip regime with nw trending 1 however the refinement in location and increasing available focal mechanism solutions allow us to show that this strike slip regime is overprinted by local extensional perturbations in three distinct areas in the massif central the sillon houiller a ancient vertical shear zone appears to be acting as a passive boundary between a western unit and an eastern unit that is uplifted by the ascension of a hot mantle plume at the base of the lithosphere extension is unexpectedly observed in the southern armorican massif sam as well as in northwestern massif central one can observe a good relation between the observed perturbed zones and lateral variation of pn anisotropy in the mantle this correlation and the scale of these areas are arguments in favour of a lithospheric process as the origin for the stress characteristics we believe these extensional perturbations could be related to the anticlockwise rotation of the iberian microplate and or incipient subduction in the bay of biscay

stress tensor and fault plane solutions for a population of earthquakes an algorithm for the simultaneous estimation of the orientation and shape of the stress tensor and the individual fault plane solutions for a population of earthquakes is studied it corresponds to a synthesis of the methods used by brillinger et al 1980 to obtain focal mechanisms and by armijo and cisternas 1978 for stress tensor analysis in microtectonics the input data are the polarities of the p arrival and take off angles for the set of source station pairs the method distinguishes in general which one of the nodal planes corresponds to the fault and gives the direction of the slip the application to the aftershock sequence of the 1980 arudy earthquake western pyrenees shows that the observations may be explained by a single stress tensor producing a n32 e extension with a likelihood of 95 per cent

stress pattern and strain release in the alpine foreland abstract illies j h baumann h and hoffers b 1981 stress pattern and strain release in the alpine foreland in p vyskocil r green and h malzer editors recent crustal movements 1979 tectonophysics 71 157 172 the tectonism of central europe is governed by a generally se nw 140 directed compressive stress flux from the alps towards their northern foreland since alpine folding had relaxed in the late miocene to early pliocene times only to be replaced by high rates of post orogenic uplift these stresses are understood to be of mainly topographic origin the strain release in the foreland is predominantly restricted to pre existing block boundaries shear or extensional movements could come about along those boundaries under the active regional stress regime the rhinegraben which was an extensional rift valley during the eocene to lower miocene has been subjected to a sinistral strike slip motion with shear controlled en echelon faulting on the present surface hydrothermal convection is observed along deep seated fissure systems held open by continuous shear strain since the central segment of the rift caused by its deviatory trend is under compressive shear strike slip motion will be slowed down in the near geological future a parallel shear belt about 100 km e of the rhinegraben became active by changing its function of primary normal faulting this belt characterized locally by high rates of pleistocene movements and some dense clusters of seismic epicenters swings around the impediment to shear which is situated in the central segment of the rhinegraben the shear motion of both belts converging towards the northernmost segment of the rhinegraben is blocked by the rhenish shield which interrupts the extension of the rift system transversally from here on a belt of seismic activity and slight pleistocene normal faulting traverses the shield in the northwesterly direction of maximum horizontal compression crustal rifting is lacking at this segment due to the tectonic incompetency of the prevailing slaty rocks of the hercynian basement to the north of this lithological unit the seismic belt extends to the rift segment of the lower rhine embayment which shows active crustal spreading along discrete dip slip faults

detection of active crustal structures in the upper rhine graben using local earthquake tomography gravimetry and reflection seismics abstract this paper presents a case study in which three different geophysical methods are combined to link the large scale seismically active deformation of the basement to the deformation of the sedimentary cover in the seismically active southern end of the upper rhine graben local earthquake tomography shows velocity contrasts related to large scale faulting in the basement the observed faults coincide with the discontinuities in the bouguer anomaly map for the upper part of the basement and the sedimentary cover reflection seismic profiles show distinct faulting in the sedimentary cover at the position of the structures observed in the local earthquake tomography and the bouguer anomaly maps they provide the link of the seismogenic structures at depth and the near surface geology it is shown that the structure of the southern end of the rhine graben is dominated by faults that have a nne ssw trend slightly oblique to the graben axis the presence of earthquake hypocenters nearby the faults indicate their present day activity

analyses of the stress field in southeastern france from earthquake focal mechanisms summary owing to the apparent deformation field heterogeneity the stress regimes around the provence block from the fronts of the massif central and alpine range up to the ligurian sea have not been well defined to improve the understanding of the se france stress field we determine new earthquake focal mechanisms and compute the presentday stress states by inversion of the 89 available focal mechanisms around the provence domain including 17 new ones calculated in the current study this study provides evidence of six distinct deformation domains around the provence block with different tectonic regimes on a regional scale we identify three zones characterized by significantly different stress regimes a western one affected by an extensional stress normal faulting regime a southeastern one characterized by a compressional stress reverse to strike slip faulting regime with nnw to wnw trending s1 and a northeastern one namely the digne nappe front marked by a ne trending compression note that the digne nappe back domain is controlled by an extensional regime that is deforming the western alpine core this extensional regime could be a response to buoyancy forces related to the alpine high topography the stress regimes in the southeast of the argentera massif and around the durance fault are consistent with a coherent nnw trending s1 implying a left lateral component of the active reverse oblique slip of the moyenne durance fault in the rhone valley an e trending extension characterizes the tectonic regime implying a normal component of the present day no mes fault displacement this study provides evidence for short scale variation of the stress states which arises from abrupt changes in the boundary force influences on upper crustal fragments blocks these spatial stress changes around the provence block result from the coeval influence of forces applied at both its extremities namely in the northeast the alpine front push and in the southeast the northward african plate drift in addition to these boundary forces the mantle plume under the massif central influences the western block boundary

patterns of reservoir triggered seismicity in a low seismicity region of france we analyzed the impact of the 26 largest impounded reservoirs on reservoir triggered seismicity rts patterns in the low seismicity region of continental france we treat reservoir triggered earthquakes as tectonic earthquakes and apply similar concepts in our analysis generally the spatial extent of an aftershock zone is controlled by the mainshock rupture length in a similar manner we use reservoir length as an equivalent length to the rupture length to assess the spatial extent of reservoir triggering earthquakes and one to three reservoir lengths as a proxy for the near field distance where the stress change induced by reservoir impoundment may trigger seismicity accordingly we define the 1lr distance as the near field reservoir effect on seismicity and the 10lr distance as the far field null effect of reservoir stress change on background seismicity we find that 1 about a quarter of the reservoirs trigger mmax 2 5 4 7 within the 1lr distance in a 15 yr space time window and 2 as tested against a randomized series superposed epoch analysis demonstrates a robust increase in the average seismicity rate within 2 yrs for the 1 3lr distance from reservoirs the reservoirs that trigger in the 1lr near field distance are significantly larger than the nontriggering ones while considering the distance of triggering of earthquakes from the reservoir it is more appropriate to consider the normalized distance the distance normalized by the reservoir length to identify earthquake triggering reservoirs at a 1lr distance while considering reservoir dimensions the reservoir length appears to be a more important parameter than the reservoir depth as the length is proportional to the area of significant stress change our results suggest that the rts mimics the aftershock sequence of a slow reservoir impoundment loading with a corresponding m reservoir m lr mainshock magnitude further when considering mainshock aftershock interactions our analysis and observations support that the mmax for rts for a given reservoir remains on average smaller than the reservoir magnitude equivalent

the recent upper miocene to quaternary and present tectonic stress distributions in the iberian peninsula a general synthesis of the recent and present stress situation and evolution in the iberian peninsula was obtained from microstructural and seismological analysis the stress evolution was deduced from 1 fault population analysis fpa from 409 sites distributed throughout the iberian peninsula 2 paleostress indicators given by 324 stations taken from the bibliography and 3 seismic data corresponding to 161 focal mechanisms evenly spread in the studied region the application of fpa together with the determination of stress tensors and focal mechanisms for the whole iberian microplate has provided two main results 1 the iberian peninsula is undergoing a nw se oriented compression except for the northeastern part pyrenees ebro basin and iberian chain where it is n s to ne sw and the gulf of cadiz where it seems to be e w and 2 the main trends of the stress field have remained almost constant since the upper miocene the analysis performed by zones suggests the presence of local heterogeneities in the stress field

structural control of geothermal reservoirs in extensional tectonic settings an example from the upper rhine graben abstract in extensional tectonic settings major structural elements such as graben boundary faults are typically oriented subparallel to the maximum horizontal stress component shmax they are often structurally accompanied by transfer zones that trend subparallel to the extension direction in the upper rhine graben such transfer faults are typically characterized by strike slip or oblique slip kinematics a major re orientation of the regional stress field by up to 90 of the upper rhine graben in the early miocene led to the present day normal and strike slip faulting regimes in the north and south of the upper rhine graben respectively and a transition zone in between consequently conditions for fault frictional failure changed significantly moreover it has been observed during tracer and stimulation experiments that such transfer faults may be of major importance for the hydraulic field of geothermal reservoirs under the present stress condition especially when located between production and injection well in this context we have investigated slip and dilation tendencies ts and td of major structural elements at reservoir scale for two representative geothermal sites bruchsal germany and riehen switzerland located close to the eastern main boundary fault of the upper rhine graben we have evaluated the quality and uncertainty range of both tendencies with respect to potential variation in shmax orientation despite significant differences in orientation of the structures and the stress regimes the resulting variation of ts and td reveal major similarities concerning the reactivation potential of both the graben parallel structures and the transfer faults the conditions of criticality for tensile failure and non criticality for shear failure suggest that transfer faults are most likely naturally permeable structures with low stimulation potential this is in agreement with the absence of both immediate tracer recovery and seismicity in the studied geothermal sites

present day and future tectonic underplating in the western swiss alps reconciliation of basement wrench faulting and decollement folding of the jura and molasse basin in the alpine foreland abstract the western alps form a geodynamically active mountain belt showing the typical features of an evolving orogenic wedge with its pro wedge geometry to the nnw and its retro wedge structures to the sse renewed tectonic underplating of european continental crust occurred after the orogenic wedge underwent major dynamic disequilibrium following the break off of the southward subducting slab of the european passive margin the most important of these basement imbricates are the mont blanc aiguilles rouges and gastern aar crystalline massifs also forming the alps highest mountains the upper plate present day orogenic wedge of the western alps includes the molasse basin and the jura fold and thrust belt both decoupled from the basement over a basal decollement surface the overall geometry of this wedge appears to be strongly unstable according to simple wedge models in its attempt to regain stability out of sequence thrusts form in the existing basement nappes but also new basement nappes should develop beneath the southern portion of the molasse basin new out of sequence thrusts in the cover trigger higher than average uplift rates concentrated around the newly forming structures and are accompanied by a concentration of earthquakes tectonic underplating is further corroborated by neotectonics and the tectonic structures observed in the prealpes molasse basin and jura similarly uplift rates and earthquakes along the southern edge of the jura mountains seem to witness the development of a new incipient basement nappe at depth partial inversion of former permo carboniferous grabens in the basement a possible spatial coincidence of areas with strong earthquake activity and zones with uplift rates above surrounding values suggest a common mechanism for their origin in the western swiss alpine foreland combined with information from basement geometry and wedge dynamics it is proposed that the common mechanism is the development of basement imbricates by tectonic underplating the proposed model for ongoing and possible future tectonic underplating beneath an active alpine orogenic wedge also allows to reconcile the models of basement wrench faulting in the molasse basin and jura with the distant push theory where the molasse basin and jura develop over a basal decollement horizon

regional patterns of tectonic stress in europe nearly 1500 stress orientation determinations are now available for europe the data come from earthquake focal mechanisms overcoring measurements well bore breakouts hydraulic fracturing measurements and young fault slip studies and sample the stress field from the surface to seismogenic depths three distinct regional patterns of maximum compressive horizontal stress shmax orientation can be defined from these data a consistent nw to nnw shmax stress orientation in western europe a wnw ese shmax orientation in scandinavia similar to western europe but with a larger variability of shmax orientations and a consistent e w shmax orientation and n s extension in the aegean sea and western anatolia the different stress fields can be attributed to plate driving forces acting on the boundaries of the eurasian plate locally modified by lithospheric properties in different regions on average the orientation of maximum stress in western europe is subparallel to the direction of relative plate motion between africa and europe and is rotated 17 clockwise from the direction of absolute plate motion the uniformly oriented stress field in western europe coincides with thin to medium lithospheric thickness approximately 50 90 km and high heat flow values 80 m w m2 in western europe a predominance of strike slip focal mechanisms implies that the intermediate principal stress is vertical the more irregular horizontal stress orientations in scandinavia coincide with thick continental lithosphere 110 170 km and low heat flow 50 m w m2 the cold thick lithosphere in this region may result in lower mean stresses associated with far field tectonic forces and allow the stress field to be more easily perturbed by local effects such as deglaciation flexure and topography the stress field of the aegean sea and western anatolia is consistent with n s extension in a back arc setting behind the hellenic trench subduction zone the stress field is influenced in places by regional geologic structures e g in the western alps where shmax directions show a slight tendency toward a radial stress pattern not all major geologic structures however appear to affect the shmax orientation e g in the vicinity of the rhine rift system horizontal stress orientations are continuous

stress inversion and basement cover stress transmission across weak layers in the paris basin france we investigate the source of non purely gravitational horizontal stresses in the paris basin a nowadays tectonically quiet intracratonic basin in its eastern border of which outstandingly dense stress measurements are available based on a synthesis of published data the stress state in the basin is first shown to be very close to the one that may be extrapolated for the underlying basement in terms of principal stress orientations and horizontal to vertical stress ratios this is in favour of a mechanical coupling between the basement and its sedimentary cover which may seem contradictory to the presence of several weak rock layers in the basin fill e g an argillite layer that was shown to bear low deviatoric stresses and salt layers that are implicated in a major decollement elsewhere to unravel this apparent contradiction a 3d numerical modelling is performed following a rigorous inverse problem approach to determine the long term elastic properties of both the basement and the basin rocks the objective is to find the set of elastic constants that provides the best fit between the calculated stress state in the basin and the in situ data by assuming that the stress state in the basement is known this methodology provides a realistic set of mechanical parameters in agreement with previous studies which leads to the conclusion that the horizontal stresses in the basin constitute its mechanical response to the stresses that developed in the underlying basement during and since the last tectonic event alpine phase the fact that horizontal stresses could be transmitted across the weak horizons contrary to what may be expected at first glance is explained both by the geometry of the basin and the fact that over the long term the stiffnesses of the various sedimentary rocks are only slightly different from each other

more than just a convoluted table discussion of mediterranean tephra stratigraphy revisited results from a long terrestrial sequence on lesvos island greece by margari et al j volcanol geotherm res 163 2007 34 54 bichler m pearce n j g steinhauser g sterba j h 2009 more than just a convoluted table discussion of mediterranean tephra stratigraphy revisited results from a long terrestrial sequence on lesvos island greece by margari et al j volcanol geotherm res 163 2007 34 54 journal of volcanology and geothermal research 181 3 4 247 250

regional stress field and rifting in western europe abstract baumann h 1981 regional stress field and rifting in western europe in j h illies editor mechanism of graben formation tectonophysics 73 105 111 in situ stress determination is one possibility to determine stress magnitudes in the earth s crust most measurements especially in the northern alpine foreland have been carried out by using the doorstopper technique stress magnitudes are presented as excess stresses a number of sites where stresses have been determined gave sufficiently high values to statistically determine stress directions for the following tectonic blocks 1 western alps 2 their immediate foreland with the rhinegraben and 3 the rhenish shield bordering on the rift segment of the lower rhine embayment in discussing results of the statistical analyses of stress data it is suggested that stresses measured in the western alps have mainly a topographic origin in the alpine foreland to the north of the rhenish shield topographic stresses are superimposed on active tectonic stress considering the structural and lithological differences the foreland blocks show a different response to the same tectonic stress field which trends for 1 at about 146 this active stress field causes shear rifting in the upper rhinegraben but extensional rifting in the lower rhine embayment in the rhenish shield area only local step faults are observed in direction of 1 due to the ductile behaviour of its basement

the beni ilmane algeria seismic sequence of may 2010 seismic sources and stress tensor calculations a moderate earthquake with a moment magnitude of mw 5 5 struck the sub bibanique region of eastern algeria on 14 may 2010 killing three people injuring hundreds of others and causing moderate damages in the epicentral area mainly in the villages of beni ilmane and samma the focal mechanism of the seismic source for the first shock obtained by near field waveform modelling exhibits left lateral strike slip faulting with the first nodal plane oriented at n345 and right lateral strike slip faulting with the second nodal plane oriented at n254 a second earthquake that struck the region on 16 may 2010 with a moment magnitude of mw 5 1 was located 9 km sw of the first earthquake the focal mechanism obtained by waveform modelling showed reverse faulting with nodal planes oriented ne sw n25 and n250 a third earthquake that struck the region on 23 may 2010 with a moment magnitude of mw 5 2 was located 7 km s of the first shock the obtained focal mechanism showed a left lateral strike slip plane oriented at n12 and a right lateral strike slip plane oriented at n257 field investigations combined with geological and seismotectonic analyses indicate that the three earthquake shocks were generated by activity on three distinct faults the second and third shocks were generated on faults oriented wsw ene and nne ssw respectively the regional stress tensor calculated in the region gives an orientation of n340 for the maximum compressive stress direction 1 which is close to the horizontal with a stress shape factor indicating either a compressional or a strike slip regime