the 1976 friuli ne italy thrust faulting earthquake a reappraisal 23 years later we revisit the 1976 friuli earthquake sequence by combining hypocenters relocation long period surface wave inversion field geology and strong motion modelling we show that fault related folding is the main active deformation by which the seismic energy was released during the main shock ms 6 5 and that some of the surface effects reported in 1976 correspond to widespread bedding planes displacements induced by flexural slip folding the fault evolved from blind to semi blind along strike showing the control of the inherited structural geology on the fault surface break and rupture arrest our fault model produces waveforms that fit the accelerograms recorded in the area

defining seismogenic sources from historical earthquake felt reports abstract we present a method that uses macroseismic intensity data to assess the location physical dimensions and orientation of the source of large historical earthquakes intensity data contain a great deal of information that can be used to constrain the essential characteristics of the seismic source in particular both the seismological theory and its practice suggest that the orientation of the source of significant earthquakes is reflected in the elongation of the associated damage pattern a plausible and easily manageable way of describing a seismic source is by representing it as an oriented rectangle the length and width of which are obtained from moment magnitude through empirical relationships this rectangle is meant to represent either the actual surface projection of the seismogenic fault or at least the projection of the portion of the earth crust where a given seismic source is likely to be located the systematic application of this method to all the m 5 5 earthquakes that occurred in the central and southern apennines italy in the past four centuries returned encouraging results that compare well with existing instrumental direct geological and geodynamic evidence the method is quite stable for different choices of the algorithm parameters and provides elongation directions that in most cases can be shown to be statistically significant in particular the resulting pattern of source orientations is rather homogeneous showing a consistent appennines parallel trend that agrees well with the ne sw extension style of deformation active in the central and southern portions of the italian peninsula

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

seismogenic sources potentially responsible for earthquakes with m 6 in the eastern southern alps thiene udine sector ne italy summary new geomorphological and structural data permitted to define the active faulting framework of the eastern southern alps ne italy all the active faults detected in the investigated area are thrust segments of the complex thrust system which has been responsible for the latest building of the eastern southalpine chain esc geomorphological investigations were performed to identify the surficial traces of recent fault activity generally represented by gentle scarps connecting uplifted palaeolandscapes of quaternary age with the flat and lower areas of the venetian and friulian plains surficial and subsurficial data the latter from reflection seismic profiles available for the investigated faults indicate that the thrusts have been responsible for the displacement of the entire wedge of quaternary deposits in the western sector of the investigated area the six recognized fault segments represent portions of a 100 km long thrust system at the boundary between the alpine relief and the plain areas in the eastern sector active tectonics is the result of parallel thrust segments located both in the alpine mountainous area and in the friulian plain the 3 d geometry of the active thrust segments has been derived from new structural surficial surveys and the interpretation of reflection seismic profiles for a total length of 1700 km on this basis we defined the geometry of 10 seismogenic sources whose dimensions are consistent with the occurrence of earthquakes with m 6 the comparison between the source geometry and the highest intensity data point distribution of large historical earthquakes has permitted to make hypotheses on the association of past seismic events to specific seismogenic sources this procedure indicated that no large historical events can be attributed to three sources montello conegliano arba ragogna medea this may indicate an elapsed time since the last activation of more than eight centuries based on the completeness of the historical catalogues the available data define therefore sources and related areas for which a high level of seismic hazard may be invoked

hydrologically induced slope deformations detected by gps and clinometric surveys in the cansiglio plateau southern alps abstract changes in groundwater or surface water level may cause observable deformation of the drainage basins in different ways we describe an active slope deformation monitored with gps and tiltmeter stations in a karstic limestone plateau in southeastern alps cansiglio plateau the observed transient gps deformation clearly correlates with the rainfall both gps and tiltmeter equipments react instantly to heavy rains displaying abrupt offsets but with different time constants demonstrating the response to different catchment volumes the gps movement is mostly confined in the horizontal plane ssw direction showing a systematic tendency to rebound in the weeks following the rain four gps stations concur to define a coherent deformation pattern of a wide area 12 5 km 2 concerning the whole southeastern slope of the plateau the plateau expands and rebounds radially after rain by an amount up to a few centimeters and causing only small vertical deformation the effect is largest where karstic features are mostly developed at the margin of the plateau where a thick succession of cretaceous peritidal carbonates faces the venetian lowland a couple of tiltmeters installed in a cave at the top of the plateau detect a much faster deformation that has the tendency to rebound in less than 6 h the correlation to rainfall is less straightforward and shows a more complex behavior during rainy weather the different responses demonstrate a fast hydrologic flow in the more permeable epikarst for the tiltmeters drained by open fractures and fissures in the neighborhood of the cave and a rapid tensile dislocation of the bedrock measured at the gps stations that affect the whole slope of the mountain in the days following the rain both tiltmeter and gps data show a tendency to retrieve the displacement which is consistent with the phreatic discharge curve we propose that hydrologically active fractures recharged by rainfall are the most likely features capable to induce the observed strain variations

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

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

determining the present day kinematics of the idrija fault slovenia from airborne lidar topography abstract located in central europe at the junction of the southern alps and the dinarides the 100 km long idrija fault striking n310 and dipping 80 ne is often considered as the potential source of the historical 1511 earthquake estimated macroseismic magnitude mm 6 8 using 1 25 000 to 1 5000 topographical maps satellite images spot5 12 5 m illuminated dem and airborne lidar data derived 1 m dem we examined in detail the idrija fault trace along a 20 km long swath in the central portion of the fault combining topographic and remote sensing data allows characterizing the recent activity along the idrija fault and estimating its cumulative displacement along strike between tolmin and godovic the fault trace is mostly linear but appears divided into three disconnected segments of 11 20 km long morphological evidences such as offset streams and ridges and major drainage abandonments suggest ongoing movement at three sites field observations and lidar dem analysis allow measuring cumulative dextral offsets comprised between 35 and 65 m we found two larger offsets of 140 m and 360 m at the southeasternmost site the vertical component is significant and revealed by a rake ranging from 0 to 33 the derived n303 n310 striking slip vector is in agreement with the motion along this fault as suggested by the geodesy assuming that the smallest measured offsets have been recorded after the last glacial maximum lgm about 20 ka ago the minimum slip rate for the idrija fault is about 1 5 mm yr over this period of time

time intervals to assess active and capable faults for engineering practices in italy abstract the time span necessary to define a fault as active and capable can mainly be derived from the framework of the regulations and the literature produced since the 1970s on risk estimation in engineering planning of strategic buildings within this framework two different lines of thought can be determined which have mainly developed in the usa on the one side there is a tendency to produce narrow chronological definitions this is particularly evident in the regulatory acts for the planning of nuclear reactors the much more effective second line of thought anchors the chronological definitions of the terms active and therefore capable to the concept of seismotectonic domain as the domains are different in different regions of the world the chronological definition cannot be univocal i e different criteria are needed to define fault activity which will depend on the characteristics of the local tectonic domain and of the related recurrence times of fault activation current research on active tectonics indicates that methodological aspects can also condition the chronological choice to define fault activity indeed this practice implies the use of earth science methods the applications of which can be inherently limited for example limits and constraints might be related to the availability of datable sediments and landforms that can be used to define the recent fault kinematic history for the italian territory we consider two main tectonic domains a the compressive domain along the southern margin of the alpine chain and the northern and northeastern margins of the apennines which is characterised by the activity of blind thrusts and reverse faults and b the extensional domain of the apennines and the calabria region which is often manifest through the activity of seismogenic normal and normal oblique faults in case a the general geomorphic and subsurficial evidence of recent activity suggests that a reverse blind fault or a blind thrust should be considered active and potentially capable if showing evidence of activity during the quaternary i e over the last 2 6 myr unless information is available that documents its inactivity since at least the last glacial maximum lgm ca 20 ka the choice of the lgm period as the minimum age necessary to define fault inactivity is related to practical aspects the diffusion of the lgm deposits and landforms and to the evidence that ca 20 kyr to assess fault inactivity precautionarily includes a number of seismic cycles in the extensional domains of the apennines and calabria region the general geological setting suggests that the present tectonic regime has been active since the beginning of the middle pleistocene therefore we propose that a normal fault in the italian extensional domain should be considered active and capable if it displays evidence of activation in the last 0 8 myr unless it is sealed by deposits or landforms not younger than the lgm the choice of the lgm as the minimum age to ascertain fault inactivity follows the same criteria described for the compressive tectonic domain

overlapping fault planes of the 1971 san fernando and 1994 northridge california earthquakes aftershocks of the 1971 san fernando and 1994 northridge earthquakes were relocated using a three dimensional velocity model that was derived from inverting p wave travel time data the hypocenters show clear orientations of the dipping fault planes the san fernando aftershocks form a plane extending from a depth of 15 km to the surface dipping toward the northeast at about 40 the northridge aftershocks delineate a fault extending from a depth of 18 km up to about 5 km dipping toward the southwest at about 40 in the region the aftershocks overlap in map view the san fernando plane cuts off the northridge plane at a depth of 5 to 8 km preventing it from reaching the surface the similar but oppositely dipping fault planes suggest a pair of conjugate planes reflecting a horizontal northeast southwest compression

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

the armenian earthquake of 1988 december 7 faulting and folding neotectonics and palaeoseismicity summary the spitak earthquake of 1988 december 7 is the first well documented event directly associated with surface breaks in the transcaucasian regions of the ussr the earthquake was located within the ese wnw oriented pambak sevan thrust and fold zone corresponding to the southern front of the lesser caucasus the mechanism of the earthquake is consistent with the nearly ns compressive tectonics due to the active continental collision between the arabian block and the russian platform the rupture is composed by several branches two of which reach the surface the first branch oriented n140 begins near the village of alavar has a length of 11 km and disappears at about 4 km se of spitak it consists of a right lateral en echelon system of strike slip faults with a maximum offset of 50 cm the second branch is the main one and breaks for about 8 km between spitak and gekhasar with a general orientation n120 showing reverse faulting dipping to the north with a right lateral component surface ruptures between gekhasar and spitak show either a narrow band of pressure ridges in alluvial deposits and soil or a fault scarp in the bed rocks when soil is absent maximum displacements observed between spitak and gekhasar attain 160 cm of vertical motion and 90 cm of horizontal dextral offset the displacement also varies within this branch showing finer segmentation few secondary deformations are observed some normal faults near gekhasar correspond to the collapse of the uplifted block an anticline fold oriented parallel to the fault scarp and situated along its northwestern prolongation emphasizes the regional compressive tectonics landslides were activated on its flanks a 200 m long reverse fault break observed along the hinge of a secondary fold suggests the occurrence of a blind thrust at depth and that the hidden branches which continue the main central segment towards the nw are associated to surface folding therefore the total length of the fault and fold zone is about 40 km in agreement with the rupture length and seismic moment obtained on the basis of surface wave modelling well developed uplifted terraces in the northern block and subsiding valleys in the southern block indicate past quaternary activity in the fault region palaeoseismological evidence of ancient earthquakes has been recognized in trenches across the spitak fault one old event occurred between 17 000 years bp and the beginning of the formation of present day soil

a review on the driving mechanism of the tyrrhenian apennines system implications for the present seismotectonic setting in the central northern apennines abstract the formation of the tyrrhenian apennines system has been characterized by a complex distribution of major tectonic events such as opening of basins migration and distortion of orogenic belts retreat of trench zones stopping of consuming processes and starting of new subductions the various aspects of each event such as timing location dimension and deformation style impose important constraints on the genetic mechanism in this work we argue that the numerous constraints implied by all events together may be plausibly and coherently explained as effects of the convergence of the confining africa arabia and eurasia plates crucial evidence for discriminating among the various geodynamic hypotheses so far advanced is provided by the structural tectonic information recently provided by crop seismic sections in the study area the proposed evolutionary history is illustrated by several paleogeographic maps which provide a more detailed reconstruction than previous attempts particular attention is paid to describing the tectonic setting developed since the middle pleistocene in the apennines belt and its connection with seismic activity

the seismogenic thickness in italy constraints on potential magnitude and seismic hazard the thickness of the seismogenic layer is a key parameter for seismic hazard since it can be used to constrain the maximum depth of faulting and the potential magnitude in this study we compute the seismogenic thickness in the italian region by defining the lower seismicity cutoff using high quality hypocentral locations of earthquakes that occurred in the past decade along the eastern alps the seismogenic thickness is about 12 14 km laterally homogeneous along the entire south verging thrust front in the apennines extensional belt lateral changes in seismogenic thickness are evident and correlate with changes in the seismic energy released by past earthquakes the potential magnitude is larger in the southern apennines where the seismogenic thickness is greater 16 18 km than in the northern apennines where it is less 6 10 km and seismic energy is partially released by the creeping of faults this article is protected by copyright all rights reserved

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

stress field in friuli ne italy from fault plane solutions of activity following the 1976 main shock abstract fault plane solutions of 78 earthquakes with magnitude larger than 3 2 which occurred in friuli between may 1976 and august 1979 have been used to estimate the orientations of the principal stress axes by an inversion technique the analysis of the confidence limits and the average angular misfit of the solution found when inverting the entire data set revealed that faulting was not produced by a uniform stress distribution subdivision of the study area into smaller volumes did not lead to significant improvements in terms of stress uniformity whereas temporal subdivision of the sample reduced significantly misfit and confidence areas of the solution for some data sets therefore we conclude that the stress directions changed as a function of time a nearly uniform stress direction compatible with tectonic models proposed for the study area ca n s convergence of the adriatic and south alpine units was found between the main event of 6 may 1976 m l 6 4 and the strong aftershocks of mid september 1976 5 1 m l 6 1 the analysis of the individual misfit cumulative pattern reveals that some degree of stress heterogeneity appeared in july 1976 which is explained here in terms of heterogeneous local responses of the stress field to the seismic activity superimposed to the regional compressive factor the degree of perturbation of the principal stress directions by local effects increased with time and showed in particular a clear variation after the strong earthquakes of mid september 1976 the perturbations appear to be reflected by low magnitude quakes whereas the faulting in strong events is compatible with the regional stress field

seismicity and velocity structures along the south alpine thrust front of the venetian alps ne italy abstract in this paper we show the seismicity and velocity structure of a segment of the alpine retro belt front along the continental collision margin of the venetian alps ne italy our goal is to gain insight on the buried structures and deep fault geometry in a silent area i e an area with poor instrumental seismicity but high potential for future earthquakes as indicated by historical earthquakes 1695 me 6 7 asolo and 1936 ms 5 8 bosco del cansiglio local earthquakes recorded by a dense temporary seismic network are used to compute 3 d vp and vp vs tomographic images yielding well resolved images of the upper crust underneath the south alpine front we show the presence of two main distinct high vp s verging thrust units the innermost coincides with the piedmont hill and the outermost is buried under a thick pile of sediments in the po plain background seismicity and vp vs anomalies interpreted as cracked fluid filled volumes suggest that the ne portion of the outermost blind thrust and its oblique lateral ramps may be a zone of high fluid pressure prone to future earthquakes three dimensional focal mechanisms show compressive and transpressive solutions in agreement with the tectonic setting stress field maps and geodetic observations the bulk of the microseismicity is clustered in two different areas both in correspondence of inherited lateral ramps of the thrust system tomographic images highlight the influence of the paleogeographic setting in the tectonic style and seismic activity of the region

strain accumulation in the southern alps ne italy and deformation at the northeastern boundary of adria observed by cgps measurements 1 we use continuous gps observations to investigate the rate of strain accumulation in the area affected by the 1976 friuli earthquakes comparison between the motion predicted by the rigid rotation of adria and the shortening observed across the study area suggests that the 2 0 0 2 mm yr motion of adria is entirely absorbed in the southern alps through thrusting and crustal thickening with very little or no motion transferred to the north we use elastic dislocation modelling to investigate the rate of interseismic loading and the geometry of the shear zone at depth the best fit solution indicates that a northward dipping creeping dislocation whose edge is located within a 50 km wide area beneath the southern alps accomodates 2 1 0 5 mm yr of the adria motion limited resolution on locking depth acceptable values between 0 and 25 km and trade off between dip and slip do not allow a precise reconstruction of the dislocation geometry the range of acceptable model parameters is consistent with a 20 dipping dislocation locked above 10 km depth and slipping at 2 4 mm yr whose geometry is suggested by seismological informations

new geomorphological and chronological constraints for glacial deposits in the rivoli avigliana end moraine system and the lower susa valley western alps nw italy our new dataset from the rivoli avigliana end moraine system the westernmost amphitheatre of the italian alps provides an important step towards understanding foreland reaching glaciations before and during the last glacial maximum lgm in the western alps 10be data from six boulders in pre lgm deposits gave ages between 26 8 2 1 and 41 2 1 9 ka based on morphological and pedological data we interpret the oldest age as a minimum age for the glacier advance s 10be results suggest that the lgm occurred in two major steps during the first at 24 0 1 5 ka several ridges were constructed demonstrating oscillation of the dora riparia glacier snout at the maximum position our data demonstrate a significantly larger lgm extent in the rivoli avigliana amphitheatre than shown on previous maps the maximum advance was followed by a short re advance of the glacier at 19 6 0 9 ka as recorded by 10be ages from boulders in lateral positions along the lower susa valley the maximum ice surface during the lgm was at 1000 920 m a s l in the final reach of the valley 560 620 m of elevation above the alluvial plain and at 620 340 m a s l at the continuous moraines in the amphitheatre

computational tools for relaxing the fault segmentation in probabilistic seismic hazard modelling in complex fault systems use of faults in seismic hazard models allows us to capture the recurrence of large magnitude events and therefore improve the reliability of probabilistic seismic hazard assessment psha in the past decades fault segmentation provided an important framework for quantifying fault based psha recent complex coseismic ruptures e g 2010 mw 7 1 canterbury 2012 mw 8 6 sumatra 2016 mw 7 8 kaik ura 2016 mw 6 5 central italy have shown the need to consider different possible combinations of rupture scenarios in psha here we present two new methodologies that model rates of ruptures along complex fault systems one based on a floating rupture approach fresh and another one based on assumed rupture scenarios sunfish they represent alternatives to a recently proposed approach sherifs and further step to overcome the segmented and un segmented approaches commonly used in psha in europe differences among sherifs sunfish and fresh are related to the way slip rate rupture geometries and magnitude frequency distributions are modelled to quantify the differences between these three methodologies we compared psha results based on geometries and slip rates of a fault system located in northeastern italy assuming a given maximum magnitude and the same seismic moment rate target differences up to 20 30 in the peak ground acceleration at 2 and 10 in 50 years are observed finally we show that the three methodologies are able to solve for the long term rate of ruptures with resulting psha that reflect the fault system geometry and slip rates without any assumption on segment boundaries using fault based approaches in psha requires collecting as much local geological information as possible now that multi fault rupture approaches are available simplifying assumptions often made to model complex fault systems uniform slip rate segmentation hypothesis are no longer necessary on the other hand local data collection should be strongly encouraged to better characterize the actual fault slip rate variability and the complex 3d geometries

three dimensional seismo tectonics in the po valley basin northern italy the po valley northern italy is a composite foreland foredeep basin caught in between the southern alps and northern apennine mountain belts by integrating the 3d structural model of the region with the public earthquake dataset the seismo tectonics of the basin is shown at different scales of observation the three dimensional geo volumeis used to reviewthe seismicity around the region and validate the structure earthquake association for such a complex tectonic framework despite the overall uncertainty due to the original data distribution quality as well as the crustal scale model dimension the direct correlation between structures and seismicity a confirms the po valley region as an active tectonic system and b allows the whole structural architecture to be revised by a unique three dimensional perspective and approach this study also indicates that 3d methodology is a powerful tool for better understanding of highly complex seismo tectonic situations at both regional and local scales

reassessment of the source of the 1976 friuli ne italy earthquake sequence from the joint inversion of high precision levelling and triangulation data summary in this study we revisit the mechanism of the 1976 friuli ne italy earthquake sequence main shocks mw 6 4 5 9 and 6 0 we present a new source model that simultaneously fits all the available geodetic measurements of the observed deformation we integrate triangulation measurements which have never been previously used in the source modelling of this sequence with high precision levelling that covers the epicentral area we adopt a mixed linear non linear optimization scheme in which we iteratively search for the best fitting solution by performing several linear slip inversions while varying fault location using a grid search method our preferred solution consists of a shallow north dipping fault plane with assumed azimuth of 282 and accommodating a reverse dextral slip of about 1 m the estimated geodetic moment is 6 6 1018 nm mw 6 5 in agreement with seismological estimates yet our preferred model shows that the geodetic solution is consistent with the activation of a single fault system during the entire sequence the surface expression of which could be associated with the buia blind thrust supporting the hypothesis that the main activity of the eastern alps occurs close to the relief margin as observed in other mountain belts the retrieved slip pattern consists of a main coseismic patch located 3 5 km depth in good agreement with the distribution of the main shocks additional slip is required in the shallower portions of the fault to reproduce the local uplift observed in the region characterized by quaternary active folding we tentatively interpret this patch as postseismic deformation afterslip occurring at the edge of the main coseismic patch finally our rupture plane spatially correlates with the area of the locked fault determined from interseismic measurements supporting the hypothesis that interseismic slip on the creeping dislocation causes strain to accumulate on the shallow above 10 km depth locked section assuming that all the long term accommodation between adria and eurasia is seismically released a time span of 500 700 years of strain accumulating plate motion would result in a 1976 like earthquake

synsedimentary deformation of pleistocene glaciolacustrine deposits in the albese con cassano area southern alps northern italy and possible implications for paleoseismicity abstract we describe and interpret the well exposed soft sediment deformations preserved in a mid pleistocene proglacial sequence outcropping at albese con cassano near como southern alps n italy the observed deformations affect six distinct stratigraphic intervals within the same depositional sequence the stratigraphy of this sequence the geomorphic setting and the careful geological mapping of the area clearly show that these deformations are not the result of glaciotectonics or cryoturbation but are due to six separate events of synsedimentary liquefaction in particular the 3 basal deformed units include sand and gravel volcanoes that formed at the bottom of a proglacial lake we examined several hypothesis of possible causative mechanism for the formation of these features taking into account all the information available on the local geology and sedimentary environment it is possible to assess that the liquefaction features at albese con cassano had a coseismic origin to our knowledge this would be the first report of similar evidence of paleoseismicity in the lombardia southern alps also there is no record of historical liquefaction triggered by seismic events in an area of ca 70 km of radius near albese con cassano including the town of como the large metropolitan area of milano and most of w lombardia that is one of the largest industrial districts in europe therefore the interpretation of the observed deformations can have critical impact for understanding the current seismicity level in the region and mitigating the associated risk in this paper we show that this interpretation is not a simple process liquefaction features must be treated with caution in order to derive suitable information for seismic hazard characterization even if their coseismic origin has been definitely proved it is necessary to understand the amount of seismic shaking for instance in terms of local macroseismic intensity that can have produced that specific feature at that specific site the location of the causative seismic event epicenter and focal depth and eventually its size in terms of epicentral intensity and or earthquake magnitude in the case of albese con cassano the implications in terms of seismic hazard of the observed possible earthquake paleoliquefactions can only be assessed through the definition of several scenarios taking into account a different thresholds of shaking for triggering the described synsedimentary structures and b different seismotectonic frameworks related to the mid pleistocene to holocene evolution of the s alps including seismicity induced by isostatic glacial rebound we conclude that it is worth checking these scenarios in the field with further paleoseismological research on other possible evidence of past earthquakes there are no unequivocal sedimentological indicators of paleoseismicity however when carefully interpreted within the proper local seismotectonic context and compared with other earthquake induced features soft sediment deformations can offer information of critical value for seismic hazard assessment

earthquake induced rockfall hazard zoning abstract a methodology for quantitative probabilistic hazard zonation for earthquake induced rockfalls is presented and demonstrated in the area of friuli eastern italian alps affected by the 1976 mw 6 5 earthquake four rockfall datasets have been prepared both from historical data analysis and field surveys the methodology relies on a three dimensional hazard vector whose components include the rockfall kinetic energy the fly height and the annual frequency the values of the first two components are calculated for each location along the slope using the 3d rockfall runout simulator hy stone the rockfall annual frequency is assessed by multiplying the annual onset frequency by the simulated transit frequency the annual onset frequency is calculated through a procedure that combines the extent of unstable areas calculated for 10 different seismic hazard scenarios with different annual frequencies of occurrence and the magnitude relative frequency relationship of blocks as derived from the collected field data for each annual frequency of occurrence the unstable area is calculated as a function of morphometric and earthquake characteristics a series of discriminant analysis models using the rockfall datasets and dems of different resolution 1 and 10 m identified the controlling variables and verified the model robustness in contrast with previously published relationships we show that the slope curvature plays a relevant role in the computation of the unstable area

crustal structure and active tectonics in the eastern alps 1 during the last decade a series of controlled source seismic experiments brought new insight into the crustal and lithospheric structure of the eastern alps and their adjacent tectonic provinces a fragmentation of the lithosphere into three blocks europe eu adria ad and the new pannonian fragment pa was interpreted and a triple junction was inferred the goal of this study has been to relate these deep crustal structures to active tectonics we used elastic plate modeling to reconsider the moho fragmentation we interpret subduction of eu below ad and pa from north to south and underthusting of ad mantle below pa from southwest to northeast the moho fragmentation correlates well with major upper crustal structures and is supported by gravity seismic and geodetic data an analysis of crustal thickening suggests that active convergence is associated with continued thrusting and lateral extrusion in the central eastern alps and thickening of the adriatic indenter under the southern alps according to the velocity relations at the triple junction pa moves relative to eu and ad along ene and se striking faults mainly by strike slip an eastward directed extensional component is compensated by the lateral extrusion of the central eastern alps the periadriatic insubric line east of the triple junction and the mid hungarian fault zone have relatively recently lost their role as first order active structures we favor the idea that the pannonian fragment and the tisza block merged to a soft microplate surrounded by the eastern and southern alpine carpathian and dinaric orogens

a decade of passive seismic monitoring experiments with local networks in four italian regions we report on four seismic monitoring experiments that in the past ten years we carried out with dense local networks in seismically active italian areas where for at least a year tens of three component seismic stations were set up to record microseismicity the areas observed are alpago cansiglio located in the venetian alps citta di castello in the northern apennines marsica in the central apennines and val d agri located in the southern apennines we produced homogeneous catalogues regarding earthquake locations and local magnitudes to investigate seismicity patterns during an inter seismic period the four regions are characterised by different kinematics strain rates and historical recent seismicity we investigate earthquake distribution in space time and size obtaining reference seismic rates and parameters of the gutenberg and richter law we declustered the catalogues to look for coherent signs in the background seismic activity despite a difference in the catalogues magnitudes of completeness due both to the diverse detection threshold of the local networks and different seismic release we detect and observe two common main behaviours a the alpago cansiglio and marsica regions are characterised by a relatively lower rate of seismic release associated to the episodic occurrence of seismic sequences with the largest event being 3 ml 4 in these areas the seismicity is not localised around the main faults b the citta di castello and val d agri regions have a relatively high rate of seismicity release almost continuously with time and the increase in earthquake production is not clearly related to seismic sequences in these areas the seismicity nucleates around defined fault systems and is usually lower than ml 3 we suggest that the presence of over pressured fluids in the citta di castello and val d agri uppermost crustal volume may favour and mould the higher rate of microseismic release

post messinian drainage changes triggered by tectonic and climatic events eastern southern alps italy abstract the messinian quaternary history of tectonic and climatic control on sedimentation in the eastern southern alps northern italy was reconstructed using an integrated petrographic and sedimentological analysis of five sedimentary successions these units mainly consist of fluvial conglomerates of the tagliamento sequence deposited within the eastern southern alps since the upper miocene messinian salinity crisis at that time the closure of marine gateways between the atlantic ocean and the mediterranean sea caused a drop in sea level causing exchanged fluvial erosion and widening of the alpine catchments sediment composition in the upper miocene to lower pliocene units shows an abrupt change in the source areas from sediments characterized by carbonate rock fragments to detritus rich in low grade metamorphic grains in spite of tectonic activity within the eastern southern alps no major modifications in sediment supply took place during the pliocene early pleistocene time span in the middle pleistocene the first major expansion of the alpine glaciers triggered a change in drainage patterns and a marked increase in erosion rates predominantly climatic control on sedimentation in the tagliamento basin and the erosion of the carnic alps produced sediments rich in quartz siltstone and metamorphic rock fragments deposited in the upper pleistocene unit and in modern river sediments

siliciclastic sequence stratigraphic patterns in foreland ramp type basins stratal patterns within shelf depositional sequences are dependent on tectonically controlled subsidence rates and their regional patterns in active tectonic basin settings regional subsidence patterns can be very different from passive continental margin settings resulting in substantial modifications of the basic sequence stratigraphic model in ramp type foreland basins on the tectonically active side subsidence rates decrease seaward in contrast with passive continental margins where the opposite subsidence pattern exists analysis of the interplay between eustasy and subsidence suggests the existence of two tectono stratigraphic zones occurring proximally and distally with respect to the basin margin zone a is defined as the region within which the rate of subsidence always exceeds the rate of eustatic fall consequently relative sea level rises continuously during a eustatic cycle albeit at varying rates zone b is defined as the region within which the rate of eustatic fall periodically exceeds the rate of subsidence resulting in an interval of relative sea level fall during a eustatic cycle on the tectonically active sides of foreland basins zone a lies on the landward side of the basin margin proximal to the orogenic belt and zone b lies seaward off zone a away from the orogenic belt where subsidence rates are lower on passive continental margins because of the opposite subsidence patterns zone a lies seaward of zone b where subsidence rates are greater the location of the shoreline relative to these zones determines the stacking patterns and stratal discontinuities within a depositional sequence if the shoreline remains in zone a then only type 2 sequence boundaries will occur if sufficient sediment flux is available allowing the shoreline to prograde into zone b then type 1 sequence boundaries can occur in foreland basins these type 1 sequence boundaries would become type 2 sequence boundaries updip in zone a the pattern of seaward decreasing subsidence on the tectonically active sides of foreland basins results in characteristic longitudinal facies and stratal patterns when the two zones occur the updip region of the basin proximal to the orogenic belt is characterized by nearly continuous nonmarine deposition albeit at varying rates the downdip region is characterized by forced regressions and deposition primarily of lowstand and transgressive systems tracts a transitional region containing deposits of all three systems tracts commonly occurs between the updip and downdip areas

delineation of the geometry of nodes in the alps dinarides hinge zone and recognition of seismogenic nodes m 6 we introduce a new method based on the analysis of the topographical alignments and used to delineate the structural boundaries of the nodes which permits the definition of relatively narrow earthquake prone areas by the pattern recognition approach the structurally bounded nodes capable of earthquakes with m 6 0 identified with pattern recognition in fact cover a significantly smaller area of the study region as compared with that defined by gorshkov et al 2004 who used conventional circles the proposed method thus improves the precision in the location of potential large earthquakes

active deformation and seismicity in the southern alps italy the montello hill as a case study abstract the montello anticline is a morphotectonic feature of the east pede mountain of the south alpine chain in northern italy which lies ca 40 km northwest of venice italy the purpose of this study is to characterize the present day crustal deformation and seismotectonics of the montello area through multi parametric geophysical observations we used new data obtained from the installation of a temporary network of 12 seismic stations and 6 gps sites the gps observations indicate that there is 1 mm yr shortening across the montello thrust sites located north of the montello thrust front deviate from the nnw ward adria eurasia convergence direction as they are constrained by a relative rotation pole in northwestern italy that has a nne ward motion trend over 18 months seismographic recordings allowed us to locate 142 local seismic events with ml 0 5 3 5 with good reliability rms 0 80 the source focal solutions indicate that i there is thrusting seismic activity on the basal sub horizontal portion of the montello structure and ii strike slip source kinematics prevail on the western edge of the montello hill our observations on the source mechanisms and the measured crustal deformation confirm that the montello thrust is tectonically active

life at cold seeps a synthesis of biogeochemical and ecological data from kazan mud volcano eastern mediterranean sea recent field observations have identified the widespread occurrence of fluid seepage through the eastern mediterranean sea floor in association with mud volcanism or along deep faults gas hydrates and methane seeps are frequently found in cold seep areas and were anticipated targets of the medinaut medineth initiatives the study presented herein has utilized a multi disciplinary approach incorporating observations and sampling of visually selected sites by the manned submersible nautile and by ship based sediment coring and geophysical surveys the study focuses on the biogeochemical and ecological processes and conditions related to methane seepage especially the anaerobic oxidation of methane aom associated with ascending fluids on kazan mud volcano in the eastern mediterranean sampling of adjacent box cores for studies on the microbiology biomarkers pore water and solid phase geochemistry allowed us to integrate different biogeochemical data within a spatially highly heterogeneous system geophysical results clearly indicate the spatial heterogeneity of mud volcano environments results from pore water geochemistry and modeling efforts indicate that the rate of aom is similar to 6 mol m 2 year 1 which is lower than at active seep sites associated with conditions of focused flow but greater than diffusion dominated sites furthermore under the non focused flow conditions at kazan mud volcano advective flow velocities are of the order of a few centimeters per year and gas hydrate formation is predicted to occur at a sediment depth of about 2 m and below the methane flux through these sediments supports a large and diverse community of micro and macrobiota as demonstrated by carbon isotopic measurements on bulk organic matter authigenic carbonates specific biomarker compounds and macrofaunal tissues because the aom community appears to be able to completely oxidize methane at the rate it is seeping through the sediments ultimate sinks for methane in this environment are authigenic carbonates and biomass significant differences in organic geochemical data between this site and those of other cold seep environments even within the eastern mediterranean mud volcanoes indicate that the microbiological communities carrying out aom varies depending on specific conditions such as methane flux and salinity c 2004 elsevier b v all rights reserved

fault behavior and characteristic earthquakes examples from the wasatch and san andreas fault zones paleoseismological data for the wasatch and san andreas fault zones have led to the formulation of the characteristic earthquake model which postulates that individual faults and fault segments tend to generate essentially same size or characteristic earthquakes having a relatively narrow range of magnitudes near the maximum analysis of scarp derived colluvium in trench exposures across the wasatch fault provides estimates of the timing and displacement associated with individual surface faulting earthquakes at all of the sites studied the displacement per event has been consistently large measured values range from 1 6 to 2 6 m and the average is about 2 m on the basis of variability in the timing of individual events as well as changes in scarp morphology and fault geometry six major segments are recognized along the wasatch fault on the basis of the most likely number of surface faulting events 18 that have occurred on segments of the wasatch fault zone during the past 8000 years an average recurrence interval of 400 666 years with a preferred average of 444 years is calculated for the entire zone geologic data on the distribution of slip associated with prehistoric earthquakes and slip rates along the south central segment of the san andreas fault suggest that the m 8 1857 earthquake is a characteristic earthquake for this segment comparisons of earthquake recurrence relationships on both the wasatch and san andreas faults based on historical seismicity data and geologic data show that a linear constant b value extrapolation of the cumulative recurrence curve from the smaller magnitudes leads to gross underestimates of the frequency of occurrence of the large or characteristic earthquakes only by assuming a low b value in the moderate magnitude range can the seismicity data on small earthquakes be reconciled with geologic data on large earthquakes the characteristic earthquake appears to be a fundamental aspect of the behavior of the wasatch and san andreas faults and may apply to many other faults as well

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

the 1998 bovec krn mountain slovenia earthquake sequence we study the 1998 bovec krn mountain slovenia earthquake sequence by combining hypocenters relocation strong motion inversion digital elevation modelling and field geology the main shock ms 5 7 a 12 km right lateral strike slip event on the dinaric fault system occurred on a sub vertical fault plane the rupture confined between 3 and 9 km depth with no evidence of surface faulting propagated bilaterally within two structural barriers the northwestern barrier is at the junction between dinaric and alpine structures where there is a sharp change in the geometry of faulting the southeastern barrier is within the dinaric system and its surface expression corresponds to the tolminka spring perched basin a 1 km restraining step over at this site the bovec krn earthquake fault overlaps with a 30 km strike slip fault segment that is free of aftershocks and could be undergoing an increase of stress this fault system represents the northern branch of the idrija right lateral fault

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

earthquake hazards of active blind thrust faults under the central los angeles basin california we document several blind thrust faults under the los angeles basin that if active and seismogenic are capable of generating large earthquakes m 6 3 to 7 3 pliocene to quaternary growth folds imaged in seismic reflection profiles record the existence size and slip rates of these blind faults the growth structures have shapes characteristic of fault bend folds above blind thrusts as demonstrated by balanced kinematic models geologic cross sections and axial surface maps we interpret the compton los alamitos trend as a growth fold above the compton ramp which extends along strike from west los angeles to at least the santa ana river the compton thrust is part of a larger fault system including a decollement and ramps beneath the elysian park and palos verdes trends the cienegas and coyote hills growth folds overlie additional blind thrusts in the elysian park trend that are not closely linked to the compton ramp analysis of folded pliocene to quaternary strata yields slip rates of 1 4 0 4 mm yr on the compton thrust and 1 7 0 4 mm yr on a ramp beneath the elysian park trend assuming that slip is released in large earthquakes we estimate magnitudes of 6 3 to 6 8 for earthquakes on individual ramp segments based on geometric segment sizes derived from axial surface maps multiple segment ruptures could yield larger earthquakes m 6 9 to 7 3 relations among magnitude coseismic displacement and slip rate yield an average recurrence interval of 380 years for single segment earthquakes and a range of 400 to 1300 years for multiple segment events if these newly documented blind thrust faults are active they will contribute substantially to the seismic hazards in los angeles because of their locations directly beneath the metropolitan area

present state of tectonic stress of the friuli area eastern southern alps stress orientations are determined for the friuli area from focal mechanisms using the inversion technique of gephart and forsyth 1984 the data consist of 244 fault plane solutions selected for the period 1988 1995 where the data coverage was poor this period was extended to 1978 1996 local magnitude ranges from 2 0 to 4 3 and the depths extend from 4 to 16 km the friuli area is subdivided into five seismotectonic zones on the basis of tectonic characteristics seismic activity and focal mechanisms and for each zone a stress tensor is determined the results show that the active tectonic stress in the friuli area is heterogeneous and conditioned by the complex structural pattern which is characterized by two indented tectonic wedges the western and central parts of the area are mainly affected by a compressional state of stress while in the eastern part a strike slip state of stress prevails the orientation of the principal stresses varies from the western to the eastern part of the area and differences are also noticeable with depth in the central part of the friuli area the maximum compressional stress is n s trending at shallow depths 10 km changing to nw se at deeper levels the maximum compressional stress is nw se oriented in the western part while in the eastern part it is n s oriented

influence of inherited taper on structural variability and conglomerate distribution cordilleran fold and thrust belt western united states north south changes in thickness of the prethrust stratigraphy of the north american cordillera within the united states controlled kinematic development of the late mesozoic sevier fold and thrust belt variation in stratigraphic thickness determined the initial slope o of the basal decollement beneath the thrust wedge as predicted by critical wedge theory segments of the sevier thrust belt with initially thick precambrian and paleozoic stratigraphic sections are structurally simple and are composed of few thrust sheets segments with thin prethrust stratigraphy and comparably low values of o are intensely imbricated the difference in structural style resulted because wedge segments with higher values of o required less internal deformation to build and maintain the critical taper required for thrust wedge advance transverse structural zones across which kinematic style differed formed at the terminations of thrust belt segments and controlled the locations of long lived antecedent drainage systems that transported gravel to the foreland therefore along strike changes in prethrust stratigraphic thickness resulted in an observed disjunct distribution of conglomerate in synorogenic deposits of the thrust wedge and foreland basin

the seismotectonic characteristics of slovenia slovenia with its neighbouring areas lies at the junction of the alps the dinarides and the pannonian basin these belong to the three plates europe adria and tisza on the slovenian territory itself converge the external dinarides nw se oriented right lateral strike slip faults the transdanubian range ne sw oriented left lateral strike slip faults and the southern alps e w oriented thrusts the direction of the principal stress 1 azimuth 6 dip 8 is determined under the assumption of uniform stress throughout the region dip of the least principal stress 3 of 5 is consistent with the regional strike slip regime listed structures form a pure shear structural mechanism on a regional scale

fault slip analysis and late exhumation of the tauern window eastern alps exhumation of the eastern alps from the early tertiary to the late miocene was localized mainly in the tauern window a thermal and structural dome located in front of the dolomites indenter stress inversions based on new structural investigations over the entire tauern window indicate a regional zoning of the paleostress field with a predominance of strike slip states of stress in the core of the investigated area and dominant extensional regimes in the eastern and western borders of the dome few inverse fault structures have been highlighted we propose a two stage deformation history in order to explain the different types of structures that characterise the ductile and the brittle domains during the first stage of exhumation of the tauern window corresponding to the folding event the brittle crust was probably dominated by n s shortening and compression the second stage of exhumation was marked by normal faulting at the borders of the dome and strike slip faulting in the core during the second stage the brittle part of the crust that was previously affected by compressive structures belonging to the first stage was eroded normal faulting associated to e w extension along the eastern and western borders of the tauern window was accommodated by strike slip faulting located in the core of the tauern window yielding e w extension and n s shortening the orientation of the extensional axes and the nature of the stress tensors are similar to the ones inferred for the late stage brittle overprint of the internal basement massifs of the central alps pointing to a possible common large scale state of stress acting well beyond the area of the eastern alps

how multiple foliations may control large gravitational phenomena a case study from the cismon valley eastern alps italy abstract the right slope of the high cismon valley trento province italy carved into the poly deformed phyllites of the south alpine basement shows evidence of differential quaternary slope evolution which highly depends on how the slope intersects the inherited structures in the study area the regional schistosity outlines a kilometer scale nnw sse trending fold with close flanks and an axial plane dipping to the ne the structure obliquely intersects the nne ssw trending slope so that the northern part of the slope follows the upper limb of the fold and the southern sector coincides with the lower limb and the hinge the secondary axial plane foliation is typically incipient at the fold flanks and much more pervasive and fan shaped near the hinge zone this foliation as well as the asymmetric polyharmonic secondary folds has significant consequences on rock mass mechanical properties and on mechanisms and timing of the gravitational phenomena developed along the slope in particular the joint compressive strength jcs and the geological strength index gsi obtained on stable outcrops outside the deforming area display a decrease from north to south this points to a progressive deterioration of the rock mass strength which directly reflects the influence of the pre existing fabric the results obtained by the analysis of lidar derived digital elevation model show evidence of two different gravitational movements located in the northern and southern sectors of the slope respectively the northern side is characterized by an ongoing deep seated gravitational slope deformation dsgsd likely triggered by post glacial unloading derived from the retreat of the ice tongue that filled the cismon valley during the last glacial maximum lgm conversely the southern part of the slope is the expression of a fully evolved pre lgm gravitational collapse this heterogeneous behavior of the slope is most likely controlled by the secondary foliation and asymmetric polyharmonic folds the former being of paramount importance for the release of the mobilized mass at the crown area and the latter easing or impeding the downslope movement although it is widely accepted that the regional foliation is the dominant controlling factor of dsgsds on poly deformed and highly foliated metamorphic basement our work suggests that the secondary foliation as well as parasitic folds may also have remarkable effects on slope evolution if favorably oriented and sufficiently pervasive

karstic and alluvial aquifers a conceptual model for the plain prealps system northeastern italy summary a 3d geostructural model extending north south from the valsugana line to the southern border of the high plain trough the pre alpine thrust and east west from the adige valley to the brenta valley trough the schio vicenza line has been constructed a detailed reconstructions of the regional aquiclude pre permian basement werfen formation integrated with information on the position of the main karstic springs allowed the geometric definition of the karstic saturated zone plain groundwater hydrochemical data suggests i a hydraulic connection between the carbonate units of the pre alpine plateau and the same formations buried under the plain and ii the important role of the faults to connect the carbonate aquifer to the alluvial porous system cutting the entire thickness of the tertiary unit such relation implies an effect of the pre alpine aquifer on pressure and flow contributions of the intensely exploited phreatic system of the venetian plain

fragmentation of the adriatic promontory new chronological constraints from neogene shortening rates across the southern alps ne italy key points folded alluvial surfaces and balanced cross section constrain post lgm and neogene shortening rates decrease in shortening rate and change in compression direction are inferred at 1 2 ma kinematic reorganization is best explained by a shift from nubia driven to adria driven convergence abstract the eastern southern alps are located at the northern tip of the adria microplate which imposes 2 0 2 5 mm yr of n s convergence relative to stable eurasia we map surface evidence of recent folding faulting in this area from a 5 m dem in the eastern part of the belt observations reveal a 30 km wide zone of active folding composed of at least five growing anticlines the most recent ones warped the post glacial alluvial surface by 10m combining these findings with published geological and geophysical data allows us to infer that active thrusting occurs along a single deeply rooted thrust which accommodates the indentation of the adriatic crust resolving the observed pattern of uplift on the inferred fault geometry indicates that nne ssw shortening across the eastern southern alps has occurred at a rate of about 1 5 mm yr over the post glacial period on the other hand a balanced cross section for the eastern southern alps at the scale of the upper crust constrains a minimum of 43 km of finite shortening over the last 14ma yielding a shortening rate of about 3 mm yr which is two times higher than the post glacial shortening rate this decrease in the shortening rate is associated to the pleistocene activation of new thrusts that is compatible with a change in the direction of compression the inferred local change in the kinematics of thrusting during the pleistocene is consistent with a change from nubia imposed to adria imposed convergence indicating that the fragmentation of the adriatic promontory could have occurred 1 2 ma ago

modeling surface gps velocities in the southern and eastern alps by finite dislocations at crustal depths abstract the indentation of the adria plate into the southern and eastern alps is an ongoing collisional process accompanied by seismicity surface and rock uplift and lateral escape we present a 3d quantitative description of the process by combining gps and structural data with an elastic dislocation model horizontal velocities of 70 austrian and italian permanent gps stations in the eastern and southern alps serve as boundary condition on the free surface of an elastic half space containing six rectangular faults each with a uniform slip rate the geometry of the rectangular faults and the slip rate vector are constrained by least squares taking into account the structural setting of the area and the geographic distribution of the velocity data we find that the surface velocities of the order of some mm yr require reverse north side of the tauern window transpressional giudicarie north alpine wrench corridor pustertal dinarides and normal brenner fault slips ranging from 10 to 30 mm yr at crustal depths the regional stress pattern computed from fault plane solutions agrees with the principal directions of our rectangular fault planes the model although constrained by horizontal velocities only predicts a pattern of vertical motion which qualitatively agrees with known phenomena such as the surface uplift in the tauern window area of the order of up to few mm yr if the heat on the shearing fault planes is removed mostly by upwards diffusion the absence of large heat anomalies on the earth s surface suggests for nominal geotherms shear stresses and concentration of subcrustal radiogenic elements that the time of initiation of the slip dates to pliocene hence more recent than late oligocene miocene time of collision of the adria indenter