contemporaneous extension and compression in the northern apennines from earthquake fault plane solutions summary the northern apenninic arc belongs to the deformation zones surrounding the adriatic plate which behaves as a rigid block it is a ne verging fold and thrust belt which developed since the miocene with the migration of an extensional compressional pair previous seismological data are roughly in agreement with this deformation picture although the outer compressional front was not clearly defined by the few available solutions in this work we confirm the existence of two adjacent zones of contemporaneous extension and compression in the northern apennines defining the extent of these two zones and their interim1 deformation better than was previously done this is accomplished through the analysis of 125 new focal mechanisms of earthquakes 2 6 md 4 8 recorded by the national network of the lstituto nazionale di geofisica in the period 1988 1995 the two deformation zones are clearly separated and lie very close to each other with a partial overlapping in the emilian tuscan apennines strikeslip events are scattered in most of the study area thrust faulting earthquakes are located in the internal part of the most recently active thrust front middle upper pleistocene there is a general trend of the compressional p axes of thrust fault and strike slip solutions to be perpendicular to the apenninic direction in the external zone while the tensional axes of the normal fault and strike slip solutions in the belt do not show a uniform orientation however clearly evident is the ene direction of extension in the peri tyrrhenian region consistent with the direction of shmln in the quaternary volcanoes of this region inferred from borehole breakouts and microearthquake fault plane solutions we determined the orientation of the stress tensor in the two main deformation zones by inversion of the 125 fault plane solutions determined in this study we found that the external belt is characterized by ne sw compression ol horizontal oriented n45 e while a normal faulting regime with o3 e w oriented is characteristic of the umbria tuscany back arc region

moment tensor solutions for small and moderate earthquakes in the ibero maghreb region 1 we applied time domain moment tensor inversion of local and regional waveforms to small and moderate mw 3 5 5 7 shallow earthquakes from the iberian peninsula northern morocco and northern algeria for the 6 years period from november 1995 to march 2002 and the previous network of autonomously recording seismograms nars experiment moment tensor solutions were obtained for 58 events considerably increasing the total number of available solutions in the study area for each event we performed a moment tensor inversion and a double couple grid search for simple faulting events the grid search is valuable as a quality test for its ability to reveal potential ambiguities of the solutions and to assess confidence limits of fault plane parameters or principal axes orientation the computed mechanisms show regional consistency a large part of the iberian peninsula is characterized by normal faulting mechanisms with sw ne oriented t axes thrusting and se nw compression is dominant in algeria in the alboran sea the westernmost part of the mediterranean and the transition between both regimes strike slip mechanisms dominate with approximately n s oriented p axes this pattern suggests a regional anomaly characterized by clockwise rotation of the principal horizontal stress orientations

seismic hazard assessment 2003 2009 for the italian building code this paper describes the probabilistic assessment of seismic hazard psha of italy in view of the building codes from 2003 to 2009 a code was issued in 2003 as a prime minister ordinance requiring that a psha for updating the seismic zoning would be performed in one year in terms of horizontal peak ground acceleration pga with 10 probability of exceedance in 50 years on hard ground for the first time in italy a working group established by the istituto nazionale di geofisica e vulcanologia adopted a logic tree approach to model the epistemic uncertainty in the completeness of the earthquake catalog the assessment of the seismicity rates and m max and the ground motion prediction equations the seismic hazard has been computed over a grid of more than 16 000 points for the median value fiftieth percentile and the eighty fourth and sixteenth percentiles of the 16 branches of the logic tree using the same input model pga values and spectral accelerations for 10 spectral periods were computed for nine different probabilities of exceedance in 50 years this wealth of data made it possible to base the design spectra of a new building code on point hazard data instead of being related to just four zones the 2009 m w 6 3 l aquila earthquake has led many to attempt to test the reliability of this study in this paper we analyze suggestions coming from that event and conclude that significant changes to the design spectra are not to be recommended based just on evidence from the l aquila earthquake

gps constraints on current tectonics of albania abstract current tectonics of albania is documented by neotectonics evidences and by a large number of medium size earthquakes focal mechanisms suggest a current shortening across the external albanides whereas internal albanides are affected by extension with direction varying from e w to n s extension to investigate the kinematics of albanides we integrate continuous and episodic gps velocity measurements with focal mechanisms of the regional centroid moment tensor catalog this study has allowed distinguishing the followings 1 western albania affected by southwestward motions relative to apulia microplate the foreland of albanides illustrating the ongoing collision of external albanides 2 the inner albanides affected by a southward motion with a southward increase relative to both apulia and stable eurasia active thrusts and backthrusts of external albanides are segmented by strike slip faults the fault between the external albanides and the ionian zone appears to be particularly active the fault zone forming the boundary between dinarides and albanides is identified as the northern limit of an area including albania and western greece affected by a clockwise rotation relative to apulia and also the northern limit of the area inner albanides macedonia bulgaria affected by southward motion relative to apulia and stable eurasia the ene wsw transverse fault zone in central albania and western macedonia diber elbasani fault appears to be mainly affected by a moderate extension cgps data confirm that the external inner albanides transition is the western border of the domain inner albania northern greece macedonia bulgaria affected by southward displacements relative to stable eurasia and apulia whereas the fault zone forming the boundary between dinarides and albanides constitutes probably its northern limit

the deep seismicity of the tyrrhenian sea summary l he study reappraises the deep seismicity of the tyrrhenian sea careful examination of the quality of reported hypocentres shows that the earthquakes define a zone dipping nw about 200 km along strike 50 km thick and reaching a depth of about 500 km the zone is slightly concave to the nw at a depth of 300 km but contrary to many previous reports is not tightly concave nor are there significant spatial gaps in the seismicity which is effectively continuous with depth seismicity is however concentrated in the depth interval 250 300 km where the dip of the seismic zone changes from 70 above 250 km to a more gentle dip of 45 at greater depths seven fault plane solutions are available for the largest earthquakes in this depth interval all of them consistent with a p axis down the dip of the seismic zone and all of them requiring movement on faults out of the plane of the subducting slab two deep earthquakes near naples lie well outside the main zone of activity for one of which a fault plane solution is available that has ap axis not aligned with the dip of the seismic zone the tightly concave slabgeometry favoured by other reports is supported mainly by the location of these events near naples which we think may represent deformation in a separate probably shallower dipping piece of subducted lithosphere the lack of shallow seismicity and particularly of thrust faulting earthquakes at the surface projection of the benioff zone suggests that active subduction has ceased estimates of the convergence rate responsible for subduction in the last 10 myr far exceed the present convergence rate of africa and eurasia suggesting that the subduction was related instead to the stretching and thinning of the crust in the tyrrhenian sea

source mechanism of mining induced seismic events resolution of double couple and non double couple models abstract traditional assumption about a seismic source as a double couple dc can represent a serious limitation for describing mechanisms of mining induced seismic events in mining conditions more general process than a shear slip can occur due to stress concentration on mined out areas we assume both non dc components within the dipole description of the source the moment tensor and a single force we processed five seismic events recorded at driefontein gold mine in south africa to demonstrate that waveform modeling is not successful enough due to poor information about the medium inversion of amplitudes of direct p and s waves is more prospective due to their smaller sensitivity to detail of the medium and possibility to correct them for ray bending and shear wave splitting prior to the inversion moreover we are able to estimate the error of the resulting mechanism due to neglect of ray bending all five events processed display non dc mechanisms which are significant at 95 considering the mismodelling of the rock mass by a homogeneous isotropic medium the source mechanisms are in agreement with the underground mining and geological structures one event has a sub vertical pressure single dipole complemented by an implosion which is the body force equivalent of a collapsing horizontal crack or a burst of a pillar supporting the hangingwall of a mined out area two events have mechanisms close to a pressure single couple all three events are located on pillars two out of these three events can be assigned with a downward single force as an alternative mechanism which matches the amplitude data successfully it is the force equivalent of a mined out area collapse when a rock mass falls from the hangingwall to the footwall the events are however rather strong which would require too large rock mass fallen one of the remaining events is a nearly horizontal tensile single couple corresponding to a vertical tensional fault it could be originated by a break of the hangingwall of a mined out area however the hypocenter of this event is deep into the footwall were there is no mining taking place the last event is mostly dc accompanied by a compensated compressive dipole which may be associated to nearly vertical dip slip along a fault in the hangingwall this event is located on the margin of a wide pillar which supports the interpretation

compiling an earthquake catalogue for the arabian plate western asia abstract the arabian plate is surrounded by regions of relatively high seismicity accounting for this seismicity is of great importance for seismic hazard and risk assessments seismic zoning and land use in this study a homogenous earthquake catalogue of moment magnitude mw for the arabian plate is provided the comprehensive and homogenous earthquake catalogue provided in the current study spatially involves the entire arabian peninsula and neighboring areas covering all earthquake sources that can generate substantial hazard for the arabian plate mainland the catalogue extends in time from 19 to 2015 with a total number of 13 156 events of which 497 are historical events four polygons covering the entire arabian plate were delineated and different data sources including special studies local regional and international catalogues were used to prepare the earthquake catalogue moment magnitudes mw that provided by original sources were given the highest magnitude type priority and introduced to the catalogues with their references earthquakes with magnitude differ from mw were converted into this scale applying empirical relationships derived in the current or in previous studies the four polygons catalogues were included in two comprehensive earthquake catalogues constituting the historical and instrumental periods duplicate events were identified and discarded from the current catalogue the present earthquake catalogue was declustered in order to contain only independent events and investigated for the completeness with time of different magnitude spans

mylonites from the towaliga fault zone central georgia products of heterogeneous non coaxial deformation abstract retrograde mylonitic rocks occur in the segment of the towaliga fault southeast of jackson georgia mylonite protoliths are heterogeneous quartz feldspathic gneisses upper amphibolite facies sillimanite zone from the pine mountain and piedmont terranes protoliths contain no distinctive lithological markers that can be used to determine fault displacement shear sense can only be determined using microstructural criteria and type porphyroclast systems shear bands asymmetric microfolded quartz ribbons subgrain fabrics in quartz ribbons the most common porphyroclast system developed in mylonites and ultramylonites is type type systems do not have readily identifiable tails but do produce distinctive asymmetrical pile ups in the matrix such that the angle of intersection between the perturbed zone and the mylonitic foliation points in the shear direction differences in morphology between and type systems can be related to differences in the recrystallization rate deformation rate ratio r reflecting changes in ductility contrast between matrix and porphyroclast that controls the amount of recrystallized material in a porphyroclast mantle that is potentially available to form tails in early stages of mylonitization with low ductility contrasts and large r ratios large mantles occur around porphyroclasts and tailed systems develop in advanced stages of mylonitization with large ductility contrasts and small r ratios either very small or partially or totally missing mantles occur and type systems develop microstructural criteria ubiquitously record a right lateral strike slip motion component to the deformation textural evidence e g unidirectional shear bands consistent vorticity recorded by porphyroclasts and asymmetrical microfolds suggest that the mylonites are the products of non coaxial deformation the local presence of fabrics with coaxial symmetry result from heterogeneity in the deformation the right lateral offset on the towaliga fault most likely occurred during the late paleozoic alleghanian orogeny

imaging lateral heterogeneity in the northern apennines from time reversal of reflected surface waves summary prominent arrivals in the coda of seismograms from the wider alpine area can be associated with lateral reflections of love waves at the northern apennines mountain chain italy where structural heterogeneity causes an abrupt contrast in phase velocity we discuss an approach to image lateral heterogeneity from reflected surface waves using intermediate period threecomponent coda waveforms as sources for an adjoint wavefield that propagates the reflections backward in time we numerically compute three dimensional sensitivity kernels for the dependence of coda waveforms on p velocity s velocity and density based upon correlations between the adjoint and the regular forward wavefields we consider synthetic coda waveforms for a simplified model of the northern apennines as well as real coda observations from five moderate magnitude earthquakes m w 4 6 5 6 in the southern alps wave propagation is simulated using the spectral element method for which a 3 d regional earth model is used in the case of real data single and combined event sensitivity kernels provide clear images of the reflectivity associated with the northern apennines in kernels for density and s wave speed the kernels show that surface wave reflections occur near the axial zone of the mountain chain apart from the apennines the approach is able to image other smaller reflectivity patches from the coda waveforms like the ivrea zone in the southern alps our coda misfit kernels can be integrated in a gradient based waveform tomography where they could enhance the sharpness of the model at lateral discontinuities

active faulting and seismicity along the siculo calabrian rift zone southern italy abstract southern italy is dominated by extensional tectonics that in the calabrian arc and eastern sicily produced the development of the siculo calabrian rift zone scrz this zone is represented by a 370 km long fault belt consisting of 10 to 50 km long distinct fault segments which extend both offshore and on land being also responsible of the crustal seismicity of this region the geological and morphological observations indicate that the active normal faults of the scrz are characterized by throw rates ranging from 0 7 to 3 1 mm a they accommodate an almost uniform horizontal extension rate of about 3 0 mm a along a wnw ese regional extension direction based on our field observations and following empirical relationships between magnitude and surface rupture length connections between large crustal earthquakes and distinct fault segments of the scrz have been also tentatively tested our data indicate moreover that the magnitudes m of the historical and instrumental earthquakes are consistent with the estimated values and that the geometry and kinematics of the fault segments and the related different crustal features of the scrz control the different seismic behaviours of adjacent portions of the active rift zone

active stress from earthquake focal mechanisms along the padan adriatic side of the northern apennines italy with considerations on stress magnitudes and pore fluid pressures abstract the active tectonic regime along the outer northern apennines padan adriatic area is a matter of debate we analyse the active tectonic regime by systematically inverting earthquake focal mechanisms in terms of their driving stress field comparing two different stress inversion methods earthquakes within the area often deviate from andersonian conditions being characterized by reverse or transpressional slip on high angle faults even if the regime is almost purely thrust faulting e g reggio emilia 1996 and faenza 2000 earthquakes we analyse the stress conditions at faulting for the reggio emilia and faenza earthquakes in order to infer the stress magnitudes and the possible role of fluid pressures the stress analysis defines a consistent pattern of sub horizontal active deviatoric compression arranged nearly perpendicular to the eastern front of the padan adriatic fold and thrust system independent of the stress inversion method used the results are consistent with active compression operating within the padan adriatic belt the stress field is thrust faulting sub vertical 3 except for the cesena forli and ancona areas where a strike slip regime sub vertical or steeply plunging 2 operates the strike slip regimes are interpreted as being caused by the superposition of local tensional stresses due to oroclinal bending i e rotations of the belt about vertical axes on the regional compressional stress field kinematic complexities characterize the 1996 reggio emilia seismic sequence the distribution of these complexities is not random suggesting that they are due to local variations of the regional stress field within the unfaulted rocks surrounding the coseismic rupture the stress conditions at faulting for the reggio emilia 1996 and faenza 2000 earthquakes coupled with the observation that seismicity in the padan adriatic area often occurs in swarms suggest that high pore fluid pressures pf 70 of the lithostatic load operate within the compressed crust the estimated stress difference 1 3 is 460 560 mpa at 15 20 km depth

fault plane solutions and seismicity of the italian peninsula abstract a new fault plane solution map of the italian peninsula is presented in this paper the earthquakes analyzed are included in the period 1905 1980 with magnitudes ranging 4 7 75 earthquakes are located in the crust while 31 are related to the deep and intermediate zone of the calabrian arc the large seismic events of the italian peninsula are generally associated with normal faulting while strike slip motion is mostly related to small earthquakes located along lateral segments of the mountain chain the deep and intermediate earthquakes of the tyrrhenian sea indicate predominant down dip compression and strike slip motion at the boundaries of this benioff zone this last is interpreted as a remnant of a subduction zone active since oligocene extending to 500 km depth with a very small lateral size about 300 km the present tectonics of this benioff zone is strongly conditioned by the lateral bending more so than the gravitational sinking process the coexistence of thrust and normal faulting motion associated to the earthquakes within a few tens of kilometers of each other seems to be explained by the strong lateral inhomogeneities of the crustal rocks present in this region more so than to the depth of the seismogenetic zone and the nature of the faulting process

effects of layered crust on the coseismic slip inversion and related cff variations hints from the 2012 emilia romagna earthquake abstract the 2012 emilia romagna italy seismic sequence has been extensively studied given the occurrence of two mainshocks both temporally and spatially close to each other the recent literature accounts for several fault models obtained with different inversion methods and different datasets several authors investigated the possibility that the second event was triggered by the first mainshock with elusive results in this work we consider all the available insar and gps datasets and two planar fault geometries which are based on both seismological and geological constraints we account for a layered elastic half space hosting the dislocation and compare the slip distribution resulting from the inversion and the related changes in coulomb failure function cff obtained with both a homogeneous and layered half space finally we focus on the interaction between the two main events discriminating the contributions of coseismic and early postseismic slip of the mainshock on the generation of the second event and discuss the spatio temporal distribution of the seismic sequence when accounting for both insar and gps geodetic data we are able to reproduce a detailed coseismic slip distribution for the two mainshocks that is in accordance with the overall aftershock seismicity distribution furthermore we see that an elastic medium with depth dependent rigidity better accounts for the lack of the shallow seismicity amplifying with respect to the homogeneous case the mechanical interaction of the two mainshocks

moment tensor inversion for iberia maghreb earthquakes 2005 2008 abstract we present and discuss a set of 77 moment tensor solutions for earthquakes in the iberia maghreb region from mid 2005 to the end of 2008 with moment magnitudes ranging from 3 2 to 6 0 inversion is based upon full three component intermediate period waveforms recorded at regional seismic broadband stations following the recent densification of permanent broadband networks and large scale temporary deployments at present more than 150 stations are recording in spain portugal and morocco this unprecedented station density allows analysis of small events from available short distance recordings and in general leads to more reliable source estimates due to data redundancies that permit elimination of waveforms affected by noise or complicated propagation effects the solutions for 2005 2008 constitute an important upgrade of the iberia maghreb moment tensor inventory to 225 solutions to date enhancing the image of seismotectonics at the compressive n algerian margin in the betic alboran shear zone and at the transpressive sw iberian margin as well as providing valuable constraints on seismic deformation in the western betics and the iberian foreland where little information has been previously available new solutions for the foreland and three recent seismic series in the western betics show strike slip and reverse faulting style contrasting with the dominance of normal faulting in the adjacent areas towards east in these areas as well as at the sw iberian margin faulting orientations are heterogeneous including solutions with opposite kinematics this indicates control by local stress conditions and points to fault interaction along the n algerian margin a counterclockwise rotation of slip vectors of thrust events from east to west becomes apparent several solutions for the area offshore cape st vincent are located at sub moho depths between 40 and 60 km supporting a large brittle layer thickness in the oceanic lithosphere

seismotectonics of the nubia plate compressive margin in the south tyrrhenian region italy clues for subduction inception 1 seismological and structural data are used to constrain the active tectonics of the nubia plate compressive margin in southern italy in this region compressional displacements have resumed at the rear of the maghrebian orogenic wedge since about 700 500 ka and are presently accommodated along a seismic belt in the south tyrrhenian area where a passive margin has developed during late neogene quaternary times earthquake data from the south tyrrhenian belt are analyzed with bayloc a probabilistic nonlinear location method results show that the seismic belt is segmented and involves a series of ne sw and nw se elongated clusters the ne sw clusters are interpreted as high angle reverse fault zones verging toward the southeast whereas the perpendicular clusters are interpreted as possible strike slip fault zones transferring the contractional displacements to advanced segments of the belt in the southeast brittle deformations observed in the quaternary volcanic island of ustica are consistent with the geometry and kinematics of the seismic belt deduced from the seismological data the south tyrrhenian active belt may constitute an early stage of subduction of the tyrrhenian oceanic crust beneath sicily a similar scenario has been hypothesized also for the westward prolongation of the south tyrrhenian belt off the algerian coast by integrating instrumental and historical seismic data with tectonic evidences we infer that the south tyrrhenian belt is probably capable of producing earthquakes with a maximum size close to magnitude 7 the analyzed data suggest a multifault system behavior for the studied compressional belt this inference is important to estimate and mitigate the seismic and tsunamic hazards in such a densely populated region

european mediterranean regional centroid moment tensors 1997 2000 the mediterranean region is seismically very active and undergoing rapid deformation earthquakes as strong as m 6 are present but relatively rare on the other hand moderate magnitude seismicity 4 5 m 5 5 is widespread and often damaging an improved knowedge of moderate magnitude earthquakes can contribute significantly to a better understanding of active tectonics in the region harvard centroid moment tensors cmt today represent the most widely used reference for reliable source mechanisms but modelling seismic sources with the cmt technique for earthquakes with magnitude less than m 5 5 5 is quite difficult since 1997 we are using an extension of the standard cmt algorithm to compute regional centroid moment tensors rcmt for moderate magnitude earthquakes mw as low as 4 0 analyzing intermediate period surface waves from regional and teleseismic seismograms we routinely apply the algorithm to european mediterranean seismicity to produce a catalog of seismic moment tensors for events with magnitude between 4 5 and 5 5 which generally are not included in the harvard cmt catalog in this paper we show the results for earthquakes that occurred between 1997 and 2000 consisting of 252 solutions and we discuss the characteristics of the catalog and the areas where these new data are most relevant

the vallo di diano and auletta extensional basins in the southern apennines italy a simple model for a complex setting this work has been developed within the 2005 2008 firb project research and development of new technologies for protection and defence of territory from natural risks w p c3 crustal imaging in italy coordinated by p montone funded by the italian ministry of uni versity and research

spectral analysis of the gravity and elevation along the western africa eurasia plate tectonic limit continental versus oceanic lithospheric folding signals large scale folding is a key mechanism of lithospheric deformation and has been described in many parts of the earth both for the continental and oceanic lithospheres some aspects of this process such as the presence of coupling decoupling between the crustal deformation and the mantle lithosphere or between different lithospheres make it necessary to accurately control the periodic characteristics of the elevation and of the gravity signal 1d spectral analysis of gravity and topography profiles is sensitive to a series of factors the location length and orientation of the profiles as well as the number of samples taken we carry out a systematic analysis of the periodicities in the topography and gravity both 1d and 2d along the western border of the africa eurasia plate tectonic boundary we analyze the sensitivity of the 1d and 2d spectral analysis in order to compare the results along a plate boundary where oceanic and continental lithospheres are in contact with different tectonic kinematic and rheological aspects our 1d spectral results indicate that the greater the profile length the longer the wavelength peaks that are found nevertheless there are some periodic signals that appear in almost all the analyzed profiles 100 250 km for the n s profiles across oceanic plate boundary and 150 250 km where the plate boundary is developed over continental lithospheres the 2d spectral analysis avoids the problems found in relation to the particular location of the profile but the resulting wavelengths are slightly higher than those obtained from the 1d spectral analysis the wavelengths estimated for both oceanic and continental lithospheres at the africa eurasia boundary n250 km show low values of mean mantle strength b1013 pa m he presence of lithospheric folds means that the continental and oceanic lithospheres are mechanically oupled this had previously been suggested for iberia but not for the limit between s iberia and the terceira riple junction the orientation of the lithospheric folds is nw se at the contact between continental lithospheres and nne ssw at the contact between oceanic lithospheres this difference is also reflected in the signal anisotropy and must be related to the rotation of the tectonic stresses in the same direction a large periodic signal wavelength n600 km was also detected both in 1d and 2d spectral results after drawing the filtered values the resulting maps indicate that this signal is related to the transition between continental and oceanic lithospheres and to the significant changes in crustal and or lithospheric thickness from the mid atlantic ridge to the continental margins of western eurasia

geomorphological paleontological and 87sr 86sr isotope analyses of early pleistocene paleoshorelines to define the uplift of central apennines italy abstract the eastern border of the middle valley of the tiber river is characterized by several plio pleistocene paleoshorelines which extend for about 100 km along the western margin of the central apennines italy we studied these paleoshorelines by the means of geological and paleontological analyses and new 87 sr 86 sr isotope analyses the youngest and uppermost paleoshorelines have been detected and mapped through detailed geologic and stratigraphic surveys which led to the recognition of nearshore deposits cliff breccias alignments of lithophaga borings fossil abrasion notches and wave cut platforms the altitude of these paleoshorelines decreases almost regularly in the nnw sse direction from 480 to 220 m a s l measurements of the 87 sr 86 sr isotope ratio have been conducted on corals and mollusks collected from sediments outcropping close to the paleoshorelines the isotopic dating results indicate numerical values that range between 0 70907 and 0 70910 all over the 100 km outcrop these results together with biostratigraphic data constrain the age of the youngest paleoshorelines to 1 65 1 50 ma these paleoshorelines are thus considered almost isochronous giving an estimated uplift rate of 0 34 0 17 0 03 mm a moving from nnw to sse shape length and continuity of the 100 km long observed movements indicate that the studied paleoshorelines are an important marker of the quaternary uplift of the central apennines

the structure and formation of mud volcano summit calderas circular depressions bounded by inward dipping faults found at the upper terminations of large mud volcano systems 500 m diameter are termed mud volcano summit calderas from new mapping and comparison with previously identified examples we describe a series of common structural and morphological features found at a number of calderas and propose a mechanism for caldera formation a typical example consists of concentric deformational and volcanic zones including an outermost topographic rim inward dipping circular fault system moat and raised central pedestal of freshly extruded mud volcanic sediment this distinctive moat and pedestal morphology can be explained in terms of the quantity and rheology of extruded mud and appears characteristic of calderas from the south caspian basin and elsewhere the association of fresh mud volcanic deposits with the calderas in combination with extensive literature on caldera modelling leads us to conclude that the most likely causal mechanism is subsidence as a result of evacuation of fluids and sediment from shallow structural levels during eruptions summit calderas mapped in this study characterize dormant periods of mud volcanism in subaerial and submarine settings and appear to be a common structural element in the extrusive domain of mud volcano systems

unusual long period rayleigh wave radiation from a vertical dip slip source the 7 may 2001 north sea earthquake 1 crustal structures with a thick surficial sediment layer with low seismic wave speeds produce a reversal in the polarity of the shear stress eigenfunctions of long period rayleigh waves at shallow depth consequently seismic disturbances with a strong vertical dip slip component that are within or just below the sediment layer should generate rayleigh waves that show a polarity reversal when compared with rayleigh waves from the same source in a more typical crustal structure here the first observation of this unusual behavior is presented by modeling surface waves from the 7 may 2001 north sea earthquake a previous study finds a focal mechanism close to vertical dip slip for this earthquake and suggests that the source is within the 6 km thick sediment layer found in this region an appropriate structural model is used to generate synthetic seismograms and estimate a double couple focal mechanism for the source the orientation of the fault plane determined here is similar to that found by the previous study however the slip direction is opposite demonstrating that the use of an incorrect structural model has a profound effect on focal mechanism determination for this type of seismic source

active stress map of italy we present a new map of the present day stress field in italy obtained from all the available data the map reports 200 horizontal stress directions inferred from 109 borehole breakout data 44 centroid moment tensor solutions 34 other focal mechanisms most of which are from polarity distributions seven stress inversions of microearthquake data two averages of t and p axes of earthquake focal mechanisms in zones of diffuse seismic activity and four fault slip data the integration of breakout data which yield horizontal stress directions with fault plane solutions which reflect the stress regime allows us to obtain an improved map of the present day stress in italy this stress field map can be used for a better comprehension of active tectonic processes for seismic hazard assessment and to foresee the behavior of faults recognized with other methods stress directions obtained from different data although relative to different depth intervals e g 0 7 km for breakouts and 0 20 km for most of the earthquakes and to different tectonic units are consistent since many regions in italy are characterized by an extensional stress regime we report the minimum horizontal stress shmin orientations the map shows that an extensional regime affects most of the apenninic belt conversely a compressional or transpressional regime characterizes the eastern alps the eastern side of the northern apennines and the southern tyrrhenian to northern sicily zone an abrupt change in stress directions marks the transition between northern and southern apennines suggesting that the two arcs are characterized by a different tectonic setting and recent evolution in this paper we report all the data analyzed to date with their geographic coordinates and average stress directions and we describe the main stress provinces in italy in the framework of the tectonic evolution of the region

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

recent and active tectonics of the external zone of the northern apennines italy we present a comprehensive study of the recent and active tectonics of the external part of the northern apennines italy by using morphotectonic geological structural and stratigraphic analysis compared with the current seismicity of the region this analysis suggests that the external part of the northern apennines is characterised by presence of three major systems of quaternary compressive structures corresponding to 1 the apenninic watershed 2 the apennines po plain margin pede apenninic thrust front and 3 the emilia ferrara and adriatic fold systems buried below the po plain geological data and interpreted seismic sections indicate a roughly n s quaternary deformation direction with rates 2 5 mm year the shortening decreased since the pliocene when our data indicate compression in a nnw sse direction and rates up to 7 mm year the trend and kinematics of the structures affecting the apennines po plain margin and the po plain subsoil fit well the pattern of the current seismicity of the area as well as recent gps and geodetic levelling data pointing to a current activity of these thrust systems controlled by an overall compressive stress field close to the apenninic watershed earthquake focal mechanisms indicate that shallow extension is associated to deep compression the extensional events may be related to a secondary extensional stress field developing on the hangingwall of the thrust system affecting the apenninic watershed alternatively this thrust system may have been recently deactivated and overprinted by active normal faulting deeper compressive events are related to the activity of both a major basement thrust that connects at surface with the pede apenninic thrust front and a major moho structure

earthquake scenario based tsunami wave heights in the eastern mediterranean and connected seas we identified a set of tsunami scenario input parameters in a 0 5 0 5 uniformly gridded area in the eastern mediterranean aegean both for shallow and intermediate depth earthquakes and black seas only shallow earthquakes and calculated tsunami scenarios using the swan joint research centre swan jrc code mader 2004 annunziato 2007 with 2 arcmin resolution bathymetry data for the range of 6 5 mwmax with an mw increment of 0 1 at each grid in order to realize a comprehensive analysis of tsunami wave heights from earthquakes originating in the region we defined characteristic earthquake source parameters from a compiled set of sources such as existing moment tensor catalogues and various reference studies together with the mwmax assigned in the literature where possible results from 2 415 scenarios show that in the eastern mediterranean and its connected seas aegean and black sea shallow earthquakes with mw 6 5 may result in coastal wave heights of 0 5 m whereas the same wave height would be expected only from intermediate depth earthquakes with mw 7 0 the distribution of maximum wave heights calculated indicate that tsunami wave heights up to 1 m could be expected in the northern aegean whereas in the black sea cyprus levantine coasts northern libya eastern sicily southern italy and western greece up to 3 m wave height could be possible crete the southern aegean and the area between northeast libya and alexandria egypt is prone to maximum tsunami wave heights of 3 m considering that calculations are performed at a minimum bathymetry depth of 20 m these wave heights may according to green s law be amplified by a factor of 2 at the coastline the study can provide a basis for detailed tsunami hazard studies in the region

contemporary kinematics of the southern aegean and the mediterranean ridge summary this study focuses on the kinematics of the southern aegean and the mediterranean ridge mr a quantification of the deformation of the mr is essential for both evaluating physical models of accretionary wedges in general and for obtaining a self consistent model of the surface deformation over the entire nubia eurasia nu eu plate boundary zone in the eastern mediterranean previous kinematic studies have not properly considered the deformation field south of the hellenic arc although this study focuses on the deformation field of the mr we also discuss the kinematics of the southern aegean because the geometry and movement of the hellenic arc determine to a large extent the kinematic boundary conditions for kinematic studies of the mr we calculate a continuous velocity and strain rate field by interpolating model velocities that are fitted in a least squares sense to published global positioning system gps velocities in the interpolation we use information from a detailed data set of onshore and offshore active faulting to place constraints on the expected style and direction of the model strain rate field in addition we use the orientations of tracks left by seamounts travelling into the wedge to further constrain the offshore deformation pattern our model results highlight the presence of active shear partitioning within the mediterranean ridge high compressional strain rates between the ridge crest and the deformation front accommodate approximately 60 70 per cent of the total motion over the wedge and the outward growth rate of the frontal thrust is 4m m yr 1 strain partitioning within the wedge leads to 19 23 mm yr 1 of dextral motion at the wedge backstop contact of the western mr whereas the pliny and strabo trenches in the eastern mr accommodate 21 23 mm yr 1 of sinistral motion the backstop of the western mr is kinematically part of the southern aegean which moves as a single block the aegean block ae at 33 34 mm yr 1 in the direction of s24 w 1 towards stable nubia nu our model confirms that there is a clear divergence between the western and eastern hellenic arc and we argue for a causal relation between the outward motion of the arc and the gradient in the regional geoid anomaly our results suggest that a significant driving source of the surface velocity field lies south of the hellenic arc and only for the southeastern aegean could there be some effect as a result of gravitational collapse associated with density differences within the overriding plate

the kozani grevena greece earthquake of 13 may 1995 revisited from a detailed seismological study the kozani earthquake m s 6 6 of 13 may 1995 is the strongest event of the decade in greece and occurred in a region of low seismic activity using regional data and the strong motion record at the kozani station we relocate the mainshock at 40 183 n and 21 660 e beneath the vourinos massif at a depth of 14 2 km we also compute a focal mechanism by body waveform modeling at te leseismic distance which confirms a normal mechanism the most likely plane strikes 240 1 n and dips 40 1 nwithacentroidd epthof 11 1 km modeling of the strong motion record at kozani confirms that nucleation started at the eastern termination of the bottom of the fault six days after the mainshock we installed a network of 40 portable seismological stations for one week around the epicentral region several thousand aftershocks were recorded among which we locate 622 with a precision better than 1 km we compute 181 focal mechanisms that mostly show normal faulting the aftershock seismicity is restricted between 5 and 15 km depth and defines a plane dipping north at an angle of about 35 consistent with the mainshock mechanism seismic activity with the same pattern of normal fault mechanisms is also seen on an antithetic fault connected to the main one at 12 km depth which cuts the ground surface north of the vourinos ophiolite massif in the siatista valley these results suggest two possibilities for the active fault plane either it is the deskati fault that is flat and dips with a constant angle and therefore the surface breaks are secondary features or more likely it is the paleohori fault that is new of listric shape and located ahead of the deskati fault which was not active during the earthquake

goringe alboran tell tectonic zone a transpression system along the africa eurasia plate boundary neotectonic structures distributed from the goringe bank to the tell atlas mountains show that the africa eurasia plate boundary in the western mediterranean corresponds to an east west trending deforming zone goringe alboran tell main pliocene and quaternary tectonic structures of the northern atlas mountains are northeast southwest striking fault related folds similar to that of el asnam and are related to north south to northwest southeast compressional movements active tectonics in agreement with the main seismicity distribution and focal mechanisms also support an oblique plate convergence and the existence of a 50 100 km wide transpression zone from goringe across alboran to the tell atlas mountains a kinematic model shows the interaction between dextral transcurrent faults and left lateral faults with block rotations and no lateral extension pinned model shortening and lateral movement rates during the quaternary are estimated to be 1 0 2 3 mm yr and block rotation rate is estimated as 2 5 3 9 m y the plate boundary may correspond to a transpression zone active thrust faults being controlled by deep seated dextral transcurrent faults

the southern tyrrhenian subduction zone deep geometry magmatism and plio pleistocene evolution abstract we report on a high resolution vp vp vs and qp model of the southern tyrrhenian subduction zone obtained by the inversion of p and s wave arrival times and t values from intraslab seismicity the arcuate shape of the southern apennines calabrian arc sicilian maghrebides is perfectly mirrored by two rather continuous low and high vp bands lying beneath the belt system at ca 25 and 100 km respectively between 100 and 300 km two independent high vp slabs lie beneath the neapolitan region and the southern tyrrhenian sea separated by unperturbed mantle we suggest that the ca 150 km wide slab window beneath the southern apennines opened after a tear occurring within a composite subduction system formed by the apulian continental lithosphere and the ionian oceanic slab the abrupt slab rupture induced ultrafast southeastward retreat of the ionian slab and the 19 cm yr spreading of the back arc oceanic marsili basin between ca 2 1 and 1 6 ma ago the 25 km low vp zone beneath the arc denotes continental upper crustal rocks below the chain its striking continuity requires a unique orogenic wedge at 25 km depth below the southern apennines the calabrian arc and the sicilian maghrebides the alternative explanation would imply the ubiquitous occurrence of autochthonous lower plate rocks at 25 km depth i e a puzzling autochthonous continental calabria the ionian slab beneath calabria shows high vp high qp and low vp vs anomalies typical of old oceanic lithosphere intermediate depth seismicity is concentrated within its thin oceanic crust suggesting the occurrence of vigorous metamorphism the slab dehydration promotes the melting of the overlying mantle as testified by high vp vs and low qp anomalies between the slab and the aeolian magmatic arc

local and duration magnitude determination for the italian earthquake catalog 1981 2002 this research has been supported in part by project gndt2000 2002 coordinated by a amato and g selvaggi and funded by italian civil protection

mapping the upper mantle three dimensional modeling of earth structure by inversion of seismic waveforms a method is presented for the inversion of waveform data for the three dimensional distribution of seismic wave velocities the method is applied to data from the global digital networks international deployment of accelerometers global digital seismograph network the selected data set consists of some 2000 seismograms corresponding to 53 events and 870 paths the moment tensors of the earthquakes are determined through an iterative procedure which minimizes the corrupting influence of lateral heterogeneity a global model is constructed for shear wave velocity expanded up to degree and order 8 in spherical harmonics and described by a cubic polynomial in depth for the upper 670 km of the earth s mantle although no a priori information is incorporated the model predictions reproduce much of what is known about the dispersion of mantle waves for example high phase velocities for shields low velocities at ridges and a strong degree 2 pattern for rayleigh waves since the method makes use of complete waveforms overtone data are also included it is shown that the model is reproducible in that substantially the same model can be constructed from each half of the total data set considered independently the model shows that shields and ridges are major features in the depth interval 25 250 km the ridges of the southern pacific and the larger shields persist to 350 km but the southeast indian rise is underlain by a high velocity anomaly at this depth as is much of the mid atlantic ridge at 450 650 km the major features are a broad region of high velocities incorporating south america much of the south atlantic and parts of west africa a broad region of low velocities in the central and eastern pacific high velocities in the western pacific and a low velocity anomaly beneath the red sea and the gulf of aden in the absence of a crustal correction degrees 2 and 3 show a high positive correlation with the geoid paradoxically this is largely destroyed when the distribution in crustal thickness is taken into account spherical harmonic degrees 4 7 show a significant negative correlation

seismological geological and geophysical constraints for the gualdo tadino fault umbria marche apennines central italy abstract the april 3 1998 mw 5 1 gualdo tadino earthquake central italy was the last significant event in the 6 month long umbria marche seismic crisis this event and its aftershocks occurred in an area where active faulting produces no striking geological and geomorphological effects in this study we investigated the ruptured fault using detailed seismological data and a re processed and re interpreted seismic reflection profile aftershock location and focal mechanisms were used to constrain the geometry and kinematics of the ruptured fault and a comparison was made with the subsurface image provided by the seismic profile we found that the 1998 gualdo tadino earthquake occurred on a wsw dipping normal fault with a length of about 8 km and a relatively gentle dip 30 40 confined between 3 5 and 7 km in depth kinematics of the mainshock and aftershocks revealed a ne trending extension in agreement with the regional stress field active in the northern apennines belt the mw 5 1 earthquake originated above the top of the basement and ruptured within the sedimentary cover which consists of an evaporites carbonates multilayer we hypothesised that the active fault does not reach the surface blind normal fault

seismicity analysis at the prestige oil tanker wreck area galicia margin nw of iberia an evaluation of the geological hazard related to the sinking of the prestige oil tanker in november 2002 in the galicia margin nw of iberia was supported by the spanish research agency it included a specific seismic study of the local activity and of the regional seismicity in this margin results of which are presented here published global catalogues show that diffuse seismicity of moderate magnitude events up to 5 6 mb can be associated with the northern flank of the galicia margin with a roughly e w distribution however event locations in this area are poorly constrained due to the inappropriate geometry of permanent seismic networks we collected and analyzed new data from a dense deployment of 10 obs around the wreck site and from a network of 12 land stations at the nw corner of iberia during a 7 months operation period the land network permitted location of 120 events with magnitudes ranging from 1 6 to 4 8 more than 30 of which were not reported by the spanish permanent array confirming the existence of a moderate seismicity in this area five new focal solutions have been obtained for events on land providing additional information about the active faults in the region the obs network ran for 1 month and allowed the location of three earthquakes of magnitude 2 5 near the sinking site four more events have been identified with just a rough determination of their epicenters based on polarization of the p wave arrivals besides these earthquakes the obs data recorded numerous seismic events of different types they include i groups of very short and regularly spaced pulses that can be explained as acoustic calls generated by finback whales ii a large number of short duration seismic events 2 3 s long identified only at individual obs iii local intense monochromatic signals lasting for up to 4 h that can be described as harmonic tremors these last two types of seismic events might be related to hydrothermal activity within the uppermost sediments and deserve additional studies to appropriately establish the seismic hazard of this area 2007 elsevier b v all rights reserved

global compilation of interferometric synthetic aperture radar earthquake source models 2 effects of 3 d earth structure 1 we carry out long period surface wave centroid moment tensor cmt inversions using various global tomographic models and two different forward modeling techniques for 32 large earthquakes previously studied using interferometric synthetic aperture radar insar data since insar methods provide an alternative and independent way of locating and characterizing shallow continental earthquakes comparisons of our source parameters with those from insar are a novel way to assess limitations in the insar models as well as the effects of inaccurate wave propagation formulations and or 3 d earth structure on earthquake source determinations we show that comparing insar results with our seismic solutions is valuable to identify inaccuracies in the earthquake slip distribution retrieved using insar moreover we find that using more accurate formulations together with the best fitting earth models substantially reduces biases and differences between moment magnitude and fault strike determined using insar and seismic data as expected for long period surface wave source inversions for shallow earthquakes the fault dip and rake angles are difficult to constrain but we show that when using the best fitting earth models differences to insar estimates are reduced moreover spurious deviations from a pure double couple earthquake mechanism are on average smaller for the best fitting earth models and the more accurate formulation of wave propagation there are large differences between insar epicentral locations and those obtained in this study and on average no clear improvements to the global cmt locations are achieved this suggests that higher resolution earth models are necessary to further refine long period cmt epicentral locations

seismic moment tensor resolution on a local scale simulated rockburst and mine induced seismic events in the kopanang gold mine south africa seismic records contain information about the effect of the source as well as the effect of wave propagation through the rock mass the effect of wave propagation is usually not well known as only simplified models of geological structures are available therefore the information about the source retrieved by inverting seismograms may include errors due to incomplete knowledge of the rock mass along the propagation path which in turn cause a distortion in the calculated moment tensor mt the distortion of the mt on a local scale was observed by inverting records of a simulated rockburst conducted at the kopanang gold mine in south africa a dominant isotropic component of the explosive characteristics was found from the inversion the deviatoric components retrieved from the blast are spurious a test of their stability indicated that they are not significant assuming an uncertainty above 5 for velocities and 10 for attenuation within the homogeneous model available for the mine thus the retrieval of the mt from records of local networks in mines using a homogeneous model of the rock mass seems to be feasible however the homogeneous model of the rock mass can only be applied to close stations within a few kilometers of the source the seismic records from distant stations were too complex to be modelled by a homogeneous rock mass records of six mine induced seismic events recorded at the kopanang gold mine were also inverted a vertical linear dipole along the pressure p axis was found for three of the events suggesting a pillar burst the mechanism of two events contains an isotropic implosion together with a nearly vertical dip slip and seems to indicate a combination of a cavity collapse with a down dip slip along a nearly vertical fault one event corresponds to a dipole along the tensional t axis however it is vertical thus its association with tensile faulting of the hangingwall is uncertain

local pattern of stress field and seismogenic sources in the pergola melandro basin and the agri valley southern italy summary our study area is a ca 50 km long section of the central southern apennines tectonic belt that includes the pergola melandro basin pm and the agri valley av this region is located between the areas affected by the 1980 ms 6 9 irpinia and the 1857 m 7 0 val d agri earthquakes and is characterized by rare historical events and very low and sparse background seismicity in this study we provide new seismological and geophysical information to identify the characteristics of the seismotectonics in the area as the prevailing faulting mechanism and the fit of local to regional stress field these data concern focal mechanisms from waveform modelling and p wave polarities analyses of borehole breakouts and detailed investigation of two seismic sequences all the data cover a significantly broad range of magnitudes and depths and suggest that no important local variation in stress orientation seems to affect this area which shows a ne sw direction of extension consistent with that regionally observed in southern italy such local homogeneity in the stress field pattern is peculiar to the study area the variations of orientation and or type of stress observed in the northern apennines or less than only 100 km toward the northwest within the same tectonic belt are absent here furthermore there is a suggestion for a northeastward sense of dip of the seismogenic faults in the region an interesting constraint to the characterization of seismic sources

new gps constraints on the africa eurasia plate boundary zone in southern italy 1 southern italy is a key area for understanding the tectonic processes in the africa eurasia collision zone we analyze new gps measurements carried out between 1994 and 2001 the results are presented in terms of time series trajectories and velocities of crustal motion as well as a geodetic strain rate field while central italy corsica sardinia and the tyrrhenian sea move like the eurasian plate the overall motion of the sicily rift zone region matches african plate motion unexpected are the north northwest directed motions of northeastern sicily and the eolian islands most striking on the deformation field are a north south oriented compression along the northern sicilian coast compression between apulia and northwestern greece as well as extension in the sicily rift zone and the interior of sicily

a crustal model for the eastern alps region and a new moho map in southeastern europe in the last two decades south central europe and the eastern alps have been widely explored by many seismic refraction experiments e g celebration 2000 alp 2002 sudetes 2003 although quite detailed images are available along linear profiles a comprehensive three dimensional crustal model of the region is still missing this limitation makes this region a weak spot in continental wide comprehensive representations of crustal structure to improve on this situation we select and collect 37 published active source seismic lines in this region after geo referencing each line we sample them along vertical profiles every 50 km or less along the line and derive p wave velocities in a stack of homogeneous layers separated by discontinuities depth of crystalline basement top of lower crust and moho we finally merge the information using geostatistical methods and infer s wave velocity and density using empirical scaling relations we present here the resulting crustal model for a region encompassing the eastern alps dinarides pannonian basin western carpathians and bohemian massif covering the region within 45 circ text 51 circ hbox n and 11 circ text 22 circ hbox e with a resolution of 0 2 circ times 0 2 circ we are also able to extend and update the map of moho depth in a wider region within 35 circ text 51 circ hbox n and 12 circ text 45 circ hbox e gathering moho values from the collected seismic lines other published dataset and using the european plate reference epcrust as a background all the digitized profiles and the resulting model are available online

a new active tectonic model for the construction of the northern apennines mountain front near bologna italy 1 we integrate existing and new geologic data retreating trench extension and accretion tectonics retreat project particularly on the origin growth and activity of the mountain front at bologna italy into a new model that explains apennine orogenesis in the context of a slab rollback upper plate retreat process the bologna mountain front is an actively growing structure driving rock uplift 1 mm year cored by a midcrustal flat ramp structure that accommodates ongoing shortening driven by adria subduction at a rate of 2 5 mm year the data we use are assembled from river terraces and associated pleistocene growth strata geodesy including releveling surveys reinterpretation of published reflection lines and a new high resolution reflection line these data constrain a simple trishear model that inverts for blind thrust ramp depth dip and slip apennine extension is recognized both in the foreland as high angle normal faults and modest stretching in the carapace of the growing mountain front and in the hinterland with larger normal faults that accomplish some crustal thinning as the upper plate retreats this coevolution of extension and shortening shares some notable characteristics with other basement involved collisional orogens including the early tertiary laramide orogeny in the american west and the oligocene to miocene evolution of the alps we propose a possible relationship between underplating and the development of the po as a sag basin as a quaternary phenomenon that may also apply to past periods of apennine deformation tortonian continued shortening on the structure beneath the bologna mountain front represents by far the most important and underappreciated seismogenic source in the front of the northern apennines

crustal motion and deformation in greece from a decade of gps measurements 1993 2003 abstract the hellenic plate boundary region located in the collision zone between the nubian arabian and eurasian lithospheric plates is one of the seismo tectonically most active areas of europe during the last 15 years gps measurements have been used to determine the crustal motion in the area of greece with the aim to better understand the geodynamical processes of this region an extended reoccupation network covering whole greece has been measured periodically in numerous gps campaigns since the late eighties and a continuous gps network has been operated in the region of the ionian sea since 1995 in this paper we present a new detailed high quality solution of continuous and campaign type measurements acquired between 1993 and 2003 during the gps processing a special effort was made to obtain consistent results with highest possible accuracies and reliabilities data of 54 mainly european igs and euref sites were included in the gps processing in order to obtain results which are internally consistent with the european kinematic field and order to allow for a regional interpretation after an overview of the results of the igs euref sites the results from more than 80 stations in greece are presented in terms of velocities time series trajectories and strain rates previous geodetic geological and seismological findings are generally confirmed and substantially refined new important results include the observation of deformation zones to the north and to the south of the north aegean trough and in the west hellenic arc region arc parallel extension of about 19 mm yr along the hellenic arc and compression between the ionian islands and the greek mainland due to continuous long term observations of 4 8 years it was possible to extract height changes from the gps time series in greece we observe a differential subsidence of the order of 2 mm yr between the northern and central ionian islands across the kefalonia fault zone the differential subsidence of the central ionian islands with respect to the northwestern greek mainland amounts to 4 mm yr

iranian regional centroid moment tensor catalog solutions for 2012 2017 abstract in 2012 the installation of broadband seismic stations in iran allowed the beginning of the moment tensor project of iranian earthquakes by the iranian seismological center irsc in a period of five years 194 moment tensors with 3 7 mw 7 6 were computed based on analysis of seismograms recorded at local and regional distances included in the catalog are the moment tensors of 83 events not modeled by gcmt a reasonable consistency exists between the mechanisms of common events in the two catalogs the average moment magnitude difference is 0 1 and the kagan angle is below 20 for 61 of the earthquakes the p b and t axes difference is up to 15 the moment tensor catalog of iran shows a decrease of the magnitude of completeness by 0 3 after this study the number of accepted solutions as a fraction of attempts of the project with the average of 55 increased from 40 in 2012 to 68 in 2016 due to the expansions of the seismic networks in iran the dataset includes earthquakes from all seismic zones in iran with the dominance of thrust faulting the calculated depths in this study are consistent with the subregion seismotectonic conditions of iran the information on seven earthquakes with mw 6 0 and 53 events with 5 0 mw

crustal velocity and strain rate fields in italy and surrounding regions new results from the analysis of permanent and non permanent gps networks summary we present a new geodetic velocity solution for italy and the surrounding areas obtained from an analysis of continuous and survey mode global positioning system observations collected between 1991 and 2002 we have combined local regional and global networks into a common reference frame velocity solution providing a new detailed picture of the regional scale deformation field in the central mediterranean our velocity estimates are computed with respect to a new stable eurasian reference frame constraining the kinematics of the greater african eurasian plate boundary system in the study area we provide strain rate values for the main seismotectonic districts which are in good agreement with the seismic deformation inferred from earthquake focal mechanisms the southern tyrrhenian area calabria the apennines the southeastern alps the southern dinarides and the albanides display deformation rates at the order of 20 30 nanostrain yr 1 the corsica sardinia block moves according to eurasian plate motions and there is no indication that the opening of the tyrrhenian is still active the pelagian and sicilian domains are separated by a northwest southeast discontinuity the sicily channel rifted area and marginally significant relative motion between the pelagian plateau and the african plate is also observed the southern tyrrhenian is affected by north south compression and accommodates up to 50 per cent of the africa eurasia relative plate motion whereas the calabrian arc exhibits 2 mm yr 1 northwest southeast extension the observed deformation pattern suggests the presence of a major approximately north south tectonic discontinuity separating the sicilian and calabrian domains an extensional boundary observed along peninsular italy coincides with the distribution of seismogenic faults along the axis of the apennines this boundary separates a tyrrhenian and an adriatic domain with diverging velocities orientated north nnw ward and northeastward respectively the apennines are extending perpendicularly to the chain axis at rates of less than 3 mm yr 1 and only in the outer northern apennines indications of active shortening are observed insignificant deformation is observed in the western po plain and the western alps while the central and eastern alps display north south shortening the eastern adriatic domain is shortening perpendicular to the dinaric front with strain rates increasing from north to south the locus of collision between the aegean balkan system and the adriatic and ionian domains is marked by the kephalonia fault system which accommodates up to 20 1 mm yr 1 of right lateral motion the deformation pattern observed in the peri adriatic domain is well described by a counter clockwise rotation of the adriatic microplate around a pole located in the western alps

late pliocene quaternary evolution of outermost hinterland basins of the northern apennines italy and their relevance to active tectonics abstract we examine the tectonic evolution and structural characteristics of the quaternary intermontane mugello casentino and sansepolcro basins in the northern apennines fold and thrust belt these basins have been classically interpreted to have developed under an extensional regime and to mark the extension compression transition the results of our study have instead allowed framing the formation of these basins into a compressive setting tied to the activity of backthrust faults at their northeastern margin syndepositional activity of these structures is manifested by consistent architecture of sediments and outcrop scale deformation after this phase the mugello and sansepolcro basins experienced a phase of normal faulting extending from the middle pleistocene until present basin evolution can be thus basically framed into a two phase history with extensional tectonics superposed onto compressional structures analysis of morphologic features has revealed the occurrence of fresh fault scarps and interaction of faulting with drainage systems which have been interpreted as evidence for potential ongoing activity of normal faults extensional tectonics is also manifested by recent seismicity and likely caused the strong historical earthquakes affecting the mugello and sansepolcro basins qualitative comparison of surface information with depth converted seismic data suggests the basins to represent discrete subsiding areas within the seismic belt extending along the axial zone of the apennines the inferred chronology of deformation and the timing of activity of normal faults have an obvious impact on the elaboration of seismic hazard models

average strain rate in the italian crust inferred from a permanent gps network ii strain rate versus seismicity and structural geology summary high quality weekly solutions for the coordinates of 45 permanent gps stations spanning 1 6 years and covering the alpine mediterranean area are used to estimate a horizontal velocity field aligned with the itrf2000 velocity datum after subtracting model velocities for the eurasian plate we show that the residual velocity field north of the apennines in the adriatic dinaric region describes a nne trending tectonic flow with a negative velocity gradient from 6 mm yr 1 ne of the apennines to virtually zero ne of the dinarids in the calabria region we observe a divergent pattern with nnw orientation which turns to west as one moves north towards tuscany very small residual velocities are observed for stations in the sardinia corsica block spain southern france and north of the alps this regional pattern of velocities defines areas of intraplate strain on the basis of good station coverage and of a strain rate value above a threshold we define five provinces calabria central apennines both in the extensional regime and north adriatic eastern alps and south adriatic under compression we show that the orientations of the principal strain rate axes agree with the stress pattern that is inferred from local seismicity a comparison of the geodetically determined strain rate with the strain rate associated with the seismic moment of earthquakes in the past 30 yr shows that each province may differ considerably from the others in the amount of seismic moment that is accommodated by surface strain for example the umbria seismic sequence of 1997 seems to have released a seismic moment that was not exceptionally large but concentrated over a short time interval so that the equivalent coseismic strain rate was larger than the value observed geodetically on average depending on the assumptions on the seismogenic volume and time span 70 100 per cent of the surface strain seems to be accommodated by the release of seismic moment in the upper italian crust

centroid moment tensor inversions using high rate gps waveforms displacement time series recorded by global positioning system gps receivers are a new type of near field waveformobservation of the seismic source we have developed an inversion method which enables the recovery of an earthquake s mechanism and centroid coordinates from such data our approach is identical to that of the classical centroid moment tensor cmt algorithm except that we forward model the seismic wavefield using a method that is amenable to the efficient computation of synthetic gps seismograms and their partial derivatives we demonstrate the validity of our approach by calculating cmt solutions using 1 hz gps data for two recent earthquakes in japan these results are in good agreement with independently determined source models of these events with wider availability of data we envisage the cmt algorithm providing a tool for the systematic inversion of gps waveforms as is already the case for teleseismic data furthermore this general inversion method could equally be applied to other near field earthquake observations such as those made using accelerometers

characteristics of well determined non double couple earthquakes in the harvard cmt catalog abstract this paper evaluates earthquakes in the harvard centroid moment tensor cmt catalog which possess well determined deviatoric non double couple mechanisms i e mechanisms with significantly large compensated linear vector dipole clvd components for a cmt m we measure the strength of the non double couple component with the statistic norm 2 6det m m 3 which is 0 0 for a pure double couple and 1 0 for a pure clvd for each cmt we measure whether norm is well determined by allowing individual elements of m to vary within their range of uncertainties as reported in the harvard catalog then determining the range of variation of norm as m varies the most well determined 11 of the catalog has a range for norm of 0 2 or less of these earthquakes about one quarter have predominantly clvd mechanisms with norm of 0 4 or greater these 283 mechanisms make up the principal data for this study these clvd earthquakes occur commonly in almost all tectonic environments along mid ocean ridges and transforms in shallow subduction zones within wadati benioff zones and in the interiors of plates in both oceanic and continental regions along ridge transforms the majority have horizontal t axes in shallow subduction zones the majority have horizontal p axes which are approximately perpendicular to the trench these observations are consistent with a schematic model which explains clvd mechanisms as the sum of two or more elementary double couple subevents with orientation fixed by the type and geometry of the plate boundary within ridge transforms subduction zones and wadati benioff zones where the plate motion lithospheric structure etc is sufficiently uniform about 75 of the clvd mechanisms conform to this model

an improved method for determining the regional stress tensor using earthquake focal mechanism data application to the san fernando earthquake sequence the orientations of fault planes and slip directions indicated by a population of earthquake focal mechanisms can be used to determine best fit regional principal stress directions and r 2 1 3 1 a measure of relative stress magnitudes under the assumption of uniform stress in the source region this analysis allows for the possibility that failure occurs on preexisting zones of weakness of any orientation in the inversion we perform a grid search of stress models to find the one which requires the smallest total rotation of all the fault planes that is needed to match the observed and predicted slip directions the method allows for errors in orientations of both the fault planes and slip directions we have an objective means for identifying the more likely of the two possible fault planes from each focal mechanism relative to a given stress model thus we do not face the problem of ambiguity of nodal planes which plagues other analyses of this kind by using a grid search of stress models rather than a linearization scheme we are able to perform a realistic error analysis and thus establish confidence limits for the preferred regional stresses the method can be used to investigate possible stress inhomogeneities during earthquake sequences by analyzing subsets of the data population the technique has been applied to 76 events from the san fernando earthquake sequence for which we have found best fit stresses plunge and azimuth 1 7 187 2 27 281 3 62 84 and r 0 65 the average misfit between this stress model and all the data is about 8 and all but eight of the aftershocks have misfits of less than 20 these values are considerably less than the uncertainty of the focal mechanism determinations therefore significant stress inhomogeneities are not required by the data our analysis does not support the suggestion of a change in stresses during the aftershock sequence as proposed by others on the basis of an apparent change in focal mechanisms

late holocene tsunamogenic coseismic uplift in kerkira island greece the presence of a coralligenic like bioherm constituted by boulders up to 1 2 m in diameter cemented by bioconcretions of calcareous algae and vermetids spp has been recognized in the southernmost part of kerkira island this biostructure is placed at up to 1 4 m above the present mean sea level a few hundred meters north well developed beach rocks are at about the same elevation the morphological continuity of these landforms allows us to hypothesize that a recent coseismic uplift interested this area ams age determination has been performed on different vermetids sampled in the upper part of the raised bioherm moreover a complete review of the chronological data cited in the bibliography highlights the difficulties in the use of some bioindicators as chronologically precise sea level indicators the entire data set suggests a late holocene tectonic behaviour characterized by sequences of subsidence and coseismic uplift in particular the age of the raised bioherm suggests that a coseismic uplift occurred 3 ka bp due to an earthquake of regional interest capable of generating a strong tsunami that impacted the nearest coast of lefkada island and the plaghia peninsula

seismic strain rates in regions of distributed continental deformation we compare the rates and configurations of seismic deformation determined from moment tensor mechanisms of earthquakes in five continental regions with the rates and configurations expected if the seismicity reflected the relative plate motions in the regions the five regions the aegean iran california western new guinea and central asia are characterized by high levels of seismicity distributed over hundreds to thousands of kilometers from the accepted plate boundaries the earthquake mechanisms are compiled primarily from the catalog of centroid moment tensor solutions which is nearly complete over the interval 1977 1987 for earthquakes greater than ms 5 the thickness of the seismogenic layer in each region is constrained by the results of modeling broadband body wave phases and of previous earthquake studies in the aegean california and western new guinea the observed configurations of deformation agree with a simple model of distributed accommodation of relative plate motion in iran and central asia the moment tensors indicate that there is appreciable strain parallel to the strikes of the belts we augment our 10 year estimates of seismic deformation with the available historical moment and magnitude estimates for the five regions and find that moderate and large earthquakes account for between 25 and 70 of the deformation of the seismogenic layer

automatic regional moment tensor inversion in the european mediterranean region summary we produce fast and automatic moment tensor solutions for all moderate to strong earthquakes in the european mediterranean region the procedure automatically screens near real time earthquake alerts provided by a large number of agencies each event with magnitude m 4 7 triggers an automatic request for near real time data at several national and international data centres moment tensor inversion is performed using complete regional long period 50 100 s waveforms initially the data are inverted for a fixed depth to remove traces with a low signal tonoise ratio the remaining data are then inverted for several trial depths to find the best fitting depth solutions are produced within 90 min of an earthquake we analyse the results for the period 2000 april to 2002 april to evaluate the performance of the procedure for quality assessment we compared the results with the independent swiss regional moment tensor catalogue srmt and divided the 87 moment tensor solutions into three groups 38 a quality solutions with well resolved m w depth and focal mechanism 21 b quality solutions with wellresolved m w and 28 unreliable c quality solutions the non homogeneous station and event distributions varying noise level and inaccurate earthquake locations affected solution quality for larger events m w 5 5 we consistently obtained a quality solutions for m w 4 5 5 5 we obtained a and b quality solutions solutions that pass empirical rules mimicking the a posteriori quality for our data set are automatically disseminated

faulting and effects of earthquakes on minoan archaeological sites in crete greece abstract examination of damages affecting the buildings of the archaeological sites of phaistos and agia triada southern crete suggests that these minoan settlements were probably destroyed by two major seismic events characterized by mks intensities of ix x and occurred at the end of the protopalatial 1700 bc and the neopalatial 1450 bc periods geological and morphological studies carried out in the neighbouring areas show the occurrence of e w trending quaternary normal fault segments spili and agia galini faults that control the present topography and morphology and exhibit steep young scarps mostly holocene in age these fault segments are related to a nw se extension direction which is consistent with that indicated by the available focal mechanisms of the earthquakes occurring in this area in the last 50 years combining structural and seismic data we can infer that the spili and agia galini fault segments could represent good candidates to be considered active faults generating large earthquakes m 6 5 that were responsible for the damages of phaistos and agia triada this hypothesis suggests that the minoan palatial centres were destroyed by several large earthquakes related to ruptures along distinct fault segments rather than by a single catastrophic event that caused the abrupt destruction of the minoan civilisation in the eastern mediterranean

kinematics of the iberia maghreb plate contact from seismic moment tensors and gps observations the iberian peninsula and the maghreb experience moderate earthquake activity and oblique nw se convergence between africa and eurasia at a rate of 5 mm yr coeval extension in the alboran basin and a n35 e trending band of active left lateral shear deformation in the alboran betic region are not straightforward to understand in the context of regional shortening and evidence complexity of deformation at the plate contact we estimate 86 seismic moment tensors mw 3 3 to 6 9 from time domain inversion of near regional waveforms in an intermediate period band those and previous moment tensors are used to describe regional faulting style and calculate average stress tensors the solutions associated to the trans alboran shear zone show predominantly strike slip faulting and indicate a clockwise rotation of the largest principal stress orientation compared to the regional convergence direction 1 at n350 e at the n algerian and sw iberian margins reverse faulting solutions dominate corresponding to n350 e and n310 e compression respectively over most of the betic range and intraplate iberia we observe predominately normal faulting and wsw ene extension 3 at n240 e from gps observations we estimate that more than 3 mm yr of african nubian eurasian plate convergence are currently accommodated at the n algerian margin 2 mm yr in the moroccan atlas and 2 mm yr at the sw iberian margin 2 mm yr is a reasonable estimate for convergence within the alboran region while alboran extension can be quantified as 2 5 mm yr along the stretching direction n240 e superposition of both motions explains the observed left lateral transtensional regime in the trans alboran shear zone two potential driving mechanisms of differential motion of the alboran betic gibraltar domain may coexist in the region a secondary stress source other than plate convergence related to regional scale dynamic processes in the upper mantle of the alboran region as well as drag from the continental scale motion of the nubian plate along the southern limit of the region in the atlantic ocean the 3 5 mm yr westward motion of the gibraltar arc relative to intraplate iberia can be accommodated at the transpressive sw iberian margin while available gps observations do not support an active subduction process in this area

convergence vs retreat in southern tyrrhenian sea insights from kinematics 1 the tyrrhenian sea is an extensional basin opened by trench retreat and back arc extension during subduction of the calabrian slab in the last 10 12 my subduction is still active beneath the semost part of the tyrrhenian sea as testified by seismicity down to 500 km depth by analyzing seismicity and geodetic data together with recent tomographic images we define the present day situation an evident n s compressional regime prevails in the tyrrhenian region west of the aeolian archipelago while east of them a nnw sse extension is documented by focal mechanisms and gps data with a much smaller strain rate with respect to the past the transition between these two domains is accommodated by a n s discontinuity zone which runs from aeolian islands to mt etna with an extensional to strike slip deformation

multiseismic cycle deformation rates from holocene normal fault scarps on crete greece morphotectonic features reveal recent seismic activity on normal faults on crete allowing slip rates palaeoearthquake magnitudes and earthquake recurrence intervals to be inferred the studied faults show major escarpments 100s m high 10s km long separating uplifted mesozoic rocks from quaternary deposits during the holocene slip rates outpaced erosion sedimentation rates and 5 15 m high fresh scarps formed at the base of the major escarpments based on our field observations and following empirical relationships between magnitude surface rupture length and maximum co seismic vertical displacement it is possible to infer some important seismotectonic parameter relative to the investigated faults taking into account the possible sources of error and the corresponding uncertainties our preferred long term slip rates range between 0 5 and 1 3 mm yr 1 the maximum expected magnitudes between 6 3 and 6 6 or 6 5 and 6 8 considering worst case scenarios while the mean recurrence intervals range between 260 and c 840 years these estimates are in good agreement with the shallow seismicity thus allowing to improve our knowledge on the seismic potential in crete horizontal extension rates could be also inferred from our geological data and compared with the few available gps data

active faulting on the island of crete greece in order to characterize and quantify the middle late quaternary and ongoing deformation within the southern aegean forearc we analyse the major tectonic structures affecting the island of crete and its offshore the normal faults typically consist of 4 30 km long dipslip segments locally organised in more complex fault zones they separate carbonate and or metamorphic massifs in the footwall block from loose to poorly consolidated alluvial and colluvial materials within the hangingwall all these faults show clear evidences of recent re activations and trend parallel to two principal directions wnw ese and nne ssw based on all available data for both onland and offshore structures morphological and structural mapping satellite imagery and airphotographs remote sensing as well as the analysis of seismic profiles and the investigation of marine terraces and holocene raised notches along the island coasts for each fault we estimate and constrain some of the principal seismotectonic parameters and particularly the fault kinematics the cumulative amount of slip and the slip rate following simple assumptions and empirical relationships maximum expected magnitudes and mean recurrence periods are also suggested summing up the contribution to crustal extension provided by the two major fault sets we calculate both arc normal and arcparallel long term strain rates the occurrence of slightly deeper and more external low angle thrust planes associated with the incipient continental collision occurring in western crete is also analysed although these contractional structures can generate stronger seismic events m 7 5 they are probably much rarer and thus providing a minor contribution to the overall morphotectonic evolution of the island and the forearc a comparison of our geologicallybased results with those obtained from gps measurements show a good agreement therefore suggesting that the present day crustal deformation is probably active since middle quaternary and mainly related to the seismic activity of upper crustal normal faults characterized by frequent shallow 20 km moderate to strong seismic events seldom alternating with stronger earthquakes occurring along blind low angle thrust planes probably ramping from a deeper aseismic detachment ca 25 km this apparently contradicting co existence of juxtaposed upper tensional and lower compressional tectonic regimes is in agreement with the geodynamics of the region characterised by continental collision with nubia and the aegean mantle wedging

seismic deformation in the mediterranean area estimated by moment tensor summation summary theoretical relationships allow the distributed deformation due to seismic activity to be quantified on the basis of the analysis of moment tensors we apply this method to a data set consisting of seismic events that have occurred in the past 85 yr 1908 1992 along the most important seismogenic zones of the mediterranean region we use the centroid moment tensor cmt catalog prepared at harvard university covering the last 16yr and older data from jackson mckenzie 1988 we determine the seismic deformation and compare it to estimates of the overall deformation as obtained from global plate motion and geological studies we generally find that the geometry of seismic deformation is similar to tectonic predictions even though spanning a shorter time interval the cmt catalog often gives a better estimate of deformation geometry than the whole data set 85yr seismic deformation generally ranges from less than 10 per cent to more than 90 per cent of the total deformation uncertainties arise because data sets may not be representative of the long term seismic behaviour of each zone more reliable estimates for comparison with geodynamic processes should result from analysis of a longer time period for which no instrumental data are available the similarity of the deformation geometry using cmt data with tectonic expectations suggests for several zones the possibility of using historical data to infer longer term deformation rates based on current deformation geometry

an experiment in systematic study of global seismicity centroid moment tensor solutions for 201 moderate and large earthquakes of 1981 data from the global digital seismograph network were used to obtain centroid moment tensor solutions using the method of dziewonski et al 1981 results were obtained for 201 earthquakes ranging in seismic moment from 7 1023 to 3 1027 dyne cm the wide dynamic range of the sro asro stations allows us to investigate using the same algorithm series of events among which the smallest and the largest may differ in moment by a factor as large as 1000 among the events studied is a particularly interesting series in january 1981 off the island of honshu the main shock was preceded by three foreshocks and followed by four aftershocks all falling within the range of our analysis there is an indication that the source mechanism changes with the size of the event statistical analysis of the results for all earthquakes reveals that the half duration of shallow and intermediate events is approximated by 1 6 10 8 m01 3 the shifts in origin time for deep focus earthquakes are indicative of the general complexity of these events which depends only weakly on the seismic moment the extreme departures from a double couple mechanism seem to depend both on the moment and on the focal depth while for shallow earthquakes these departures decrease from a maximum at about 1025 dyne cm with increasing moment the reverse appears to be true with respect to deep focus earthquakes shallow earthquakes north of new guinea and along the solomon islands show systematic and substantial departures from the double couple mechanism

moment tensor analysis of the central italy earthquake sequence of september october 1997 the larger earthquakes in the umbria marche central italy seismic sequence of september october 1997 are analyzed using long period seismograms from the mediterranean seismographic network mednet and additional data from the global seismographic network gsn we modify the harvard centroid moment tensor cmt algorithm to allow moment tensor inversion of long period waveforms primarily rayleigh and love waves for small earthquakes at local to regional distances 5 5 in the sequence moment tensors have previously been determined using teleseismic waveforms and standard methods of analysis our results agree well with those of earlier studies we determine additional moment tensors for the largest foreshock and 10 aftershocks with mw 4 2 the earthquakes are characterized by normal faulting mechanisms with a ne sw tension axis and the presumed fault plane dips towards the sw only one of the fourteen events studied has a different faulting geometry indicating instead right lateral strike slip faulting on a plane oriented approximately e w or left lateral faulting on a plane oriented n s the september 26 mainshock 09 40 ut accounts for only approximately 50 of the total moment release in the sequence

pattern of deformation around the central aeolian islands evidence from multichannel seismics and gps data the tectonics of the central aeolian islands which are located within the tyrrhenian backarc basin has been investigated through a marine seismic reflection survey we find that compressional structures dominate around the islands whereas extensional faults occur only to the north of salina and filicudi towards the marsili basin this pattern of deformation although different from previously reported is in agreement with the strain field and stress regime obtained from gps measurements and seismological data age constraints suggest that contractional deformation was active since middle pleistocene being coeval with the building of the volcanic edifices of the aeolian islands and is superimposed on pre existing extensional deformation compressional and extensional regimes therefore can coexist within a backarc setting seismic profiles show that the tindari letojanni fault considered as a major tectonic element does not extend to the north towards the island of vulcano as a throughgoing fault rather deformation is accommodated in a broader belt displaying greater structural complexity

fault segmentation as constraint to the occurrence of the main shocks of the 2016 central italy seismic sequence we perform the finite extent fault inversion of the three main events of the 2016 central italy seismic sequence using near source strong motion records we demonstrate that both earthquakes nucleation and rupture propagation were controlled by segmentation of the n nw s se trending quaternary normal faults the first shock of the sequence august 24th mw 6 0 ruptured at the relay zone between the laga mts lf and the cordone del vettore cvf normal faults the second shock october 26th mw 5 9 nucleated at a minor relay zone within the mt vettore mt bove fault vbf while the third and largest one october 30th mw 6 5 initiated at the relay zone between the vbf and cvf triggering the multiple rupture of the vbf cvf and probably lf we show that this latter relay zone corresponds to the deeper high angle fault zone of the sibillini mts cross structure a thrust ramp inherited from the miocene pliocene contractional phase of the apennines this structure acted as a barrier to rupture propagation of the first two events thus defining an area of large stress concentration until it acted as the initiator of the rupture originating the largest mw 6 5 event that crossed the barrier itself we suggest that the young cvf have started to cut through the barrier acting as a soft linkage between the two long lived lf and vbf the evidence that coseismic cumulative slip shows a maximum at the cvf provided by both slip inversion and original surface rupture data suggests that the cvf is growing faster than the adjacent faults

the northwestern maghreb boundary of the nubia africa plate abstract a study of the present compressional deformation of the northwestern maghreb nubia africa margin is derived from the analysis of more than 20 000 km of seismic profiles in the western part the compression is distributed in a large zone with on land compression in algeria mainly strike slip deformation on the algerian margin and folds and strike slip faulting in eastern spain in the middle of the algerian margin around algiers the evidences of compression become more obvious in this area a ridge trending n s that is interpreted as a middle to late miocene spreading center interacted with the transpressional margin that trends e w north of the location of the boumerdes zemmouri earthquake the oceanic crust is deformed by blind thrusts up to 60 km from the coast these thrusts are south dipping and with the northward dipping thrusts located onshore form a wedge that maybe a positive flower structure at a crustal scale related to the right lateral transpression of the margin in the eastern part of the northwestern maghreb nubia africa deformed belt off eastern algeria and tunisia the deformation is more intense but limited to the north by the continental slope large late miocene tortonian folds are cut by the messinian erosional surface but the present deformation is also evident it is suggested that the deformation with a double vergence may be followed up to the north of sicily after the docking 18 ma of the kabylies to the africa plate the crust has been thinned and the algerian basin opened during the middle late miocene with an e w direction from the late miocene to the present the margin has been rethickened by transpression and uplifted

the migration of plate boundaries in se sicily influence on the large scale kinematic model of the african promontory in southern italy abstract a detailed field mapping coupled with structural analyses and morphological investigation has been carried out along the northern and western borders of the hyblean plateau se sicily in order to define the nature and the kinematics of a major quaternary fault belt this here designed as the scicli line fault belt is composed of two n50 oriented extensional basins that linked by a regional n10 trending transfer zone originated during the early pleistocene and experienced since the late quaternary a positive tectonic inversion in both the two stages of deformation the scicli line fault belt has been characterised by displacement rate comparable with the relative velocities measured between the distinct plates composing the central mediterranean region in the period going from 1 5 1 2 to 0 85 ma the fault belt accommodated the entire divergence between adria and nubia at present the scicli line fault belt absorbs most of the nubia eurasia convergence while the western divergent margin of the adria microplate has jumped to the eastern and the southern margins of the hyblean plateau along the late quaternary siculo calabrian rift zone the off shore prolongation of the two tectonic boundaries of the hyblean plateau has been recognised in the sicily channel where they are both interrupted by a wnw ese oriented dextral fault according to our reconstruction the hyblean plateau represents an isolated lithospheric block whose evolution can be related to the propagation of the western divergent margin of the adria microplate accompanied with the southward migration of the triple junction between eurasia nubia and adria in this new large scale kinematic picture the gps velocity measured in the hyblean region at the permanent site of noto is actually representative of the local kinematics rather than of the entire african promontory of southern italy this implies a correction of previous regional kinematic models based on combination of gps vectors in particular our data constrain a new interpretation both for the kinematics along the e w oriented nubia eurasia margin dominated by prevalent dextral deformation rather than reverse motions and for the intraplate deformation in the sicily channel within the africa promontory which would be dominated by a roughly n110 oriented extension this conclusion has implication also on the mechanism and the origin of the pantelleria linosa malta rift that is here interpreted as a transtensive feature developed along a major transform fault rather than the result of passive rifting induced by the nubia eurasia collision as it is currently interpreted

reactivation of deep faults beneath southern apennines evidence from the 1990 1991 potenza seismic sequences we relocate the 1990 1991 potenza southern apennines belt italy sequences and calculate focal mechanisms this seismicity clusters along an e w dextral strike slip structure second order clusters are also present and reflect the activation of minor shears the depth distribution of earthquakes evidences a peak between 14 and 20 km within the basement of the subducting apulian plate the analysed seismicity does not mirror that of southern apennines which include nw se striking normal faults and earthquakes concentrated within the first 15 km of the crust we suggest that the e w faults affecting the foreland region of apennine propagate up to 25 km of depth the potenza earthquakes reflect the reactivation of a deep preexisting fault system we conclude that the seismotectonic setting of apennines is characterized by nw se normal faults affecting the upper 15 km of the crust and by e w deeper strike slip faults cutting the crystalline basement of the chain

global cmt analysis of moderate earthquakes mw 4 5 using intermediate period surface waves a new method for calculating centroid moment tensor cmt solutions for moderate sized earthquakes is presented and tested in the new algorithm which is a modification to the standard harvard cmt method intermediate period surface waves are included in the inversion for source parameters the dispersion of teleseismic surface waves in the period range 40 to 150 sec is predicted by interpolation of recent global phase velocity maps the method is tested on a set of 20 moderate and large 5 2 mw 7 2 earthquakes with known mechanisms the retrieved mechanisms are similar to the previous results even when noise is added to the seismograms to simulate earthquakes of a smaller magnitude mw 4 5 the inversion algorithm is applied to the 1993 klamath falls mainshock and aftershock sequence and the results compare well with earlier results a catalog of mw 4 5 focal mechanisms for greece and surrounding areas for the first six months of 1995 is derived using the new method of analysis

moment tensor solutions for the iberian maghreb region during the iberarray deployment 2009 2013 abstract we perform regional moment tensor inversion for 84 earthquakes that occurred in the iberian maghreb region during the second and third leg of iberarray deployment 2009 2013 during this period around 300 seismic broadband stations were operating in the area reducing the interstation spacing to 50 km over extended areas we use the established processing sequence of the iag moment tensor catalogue increasing to 309 solutions with this update new moment tensor solutions present magnitudes ranging from mw 3 2 to 6 3 and source depths from 2 to 620 km most solutions correspond to northern algeria where a compressive deformation pattern is consolidated the betic rif sector shows a progression of faulting styles from mainly shear faulting in the east via predominantly extension in the central sector to reverse and strike slip faulting in the west at the sw iberia margin the predominance of strike slip and reverse faulting agrees with the expected transpressive character of the eurasian nubia plate boundary new strike slip and oblique reverse solutions in the trans alboran shear zone reflect its left lateral regime the most significant improvement corresponds to the atlas mountains and the surroundings of the gibraltar arc with scarce previous solutions reverse and strike slip faulting solutions in the atlas system display the accommodation of plate convergence by shortening in the belt at the gibraltar arc several new solutions were obtained at lower crustal and subcrustal depths these mechanisms show substantial heterogeneity covering the full range of faulting styles with highly variable orientations of principal stress axes including opposite strike slip faulting solutions at short distance the observations are not straightforward to explain by a simple geodynamic scenario and suggest the interplay of different processes among them plate convergence in old oceanic lithospheric with large brittle thickness at the sw iberia margin as well as delamination of thickened continental lithosphere beneath the betic rif arc

a reappraisal of seismicity and eruptions of pantelleria island and the sicily channel italy three main tectonic depressions the pantelleria linosa and malta troughs the expression of a continental rift characterize the sicily channel a region with recent volcanic activity attested by the pantelleria and linosa volcanic islands as well as numerous seamounts to understand the seismic and eruptive behaviour of this area we compare historical and instrumental seismicity retrieved from catalogues with recordings from both a mobile seismic network and a permanent station deployed at pantelleria a review of historical eruptions affecting the sicily channel is also presented recent instrumental seismicity shows that the sicily channel is characterized by a low level of seismicity with earthquakes mainly occurring as isolated events rather than swarms as observed during the few documented eruptive periods the results of a seismic survey in 2006 2007 as well as the signals recorded by a permanent station in 2010 2014 enable stating that also pantelleria is characterized by a very low rate of seismicity the available though scant historical information suggests a recurrence time of about a century for the volcanic activity and that eruptions are usually preceded by seismic swarms in the only historical known eruption of pantelleria in addition to shocks uplifting and increasing fumarole activity were observed notwithstanding the lack of eruptions over the past century and despite the low recent seismic rate we believe that the geophysical monitoring of the sicily channel needs improving since it is an area of potentially high seismic and volcanic hazard given the presence of several active submarine eruptive centres

a 3 d density velocity model between the cretan sea and libya abstract a 3 d density model for the cretan and libyan seas and crete was developed by gravity modelling constrained by five 2 d seismic lines velocity values of these cross sections were used to obtain the initial densities using the nafe drake and birch empirical functions for the sediments the crust and the upper mantle the crust outside the cretan arc is 18 to 24 km thick including 10 to 14 km thick sediments the crust below central crete at its thickest section has values between 32 and 34 km consisting of continental crust of the aegean microplate which is thickened by the subducted oceanic plate below the cretan arc the oceanic lithosphere is decoupled from the continental along a nw se striking front between eastern crete and the island of kythera south of peloponnese it plunges steeply below the southern aegean sea and is probably associated with the present volcanic activity of the southern aegean sea in agreement with published seismological observations of intermediate seismicity low density and velocity upper mantle below the cretan sea with 3 25 103 kg m3 and vp velocity of compressional waves around 7 7 km s which are also in agreement with observed high heat flow density values point out at the mobilization of the upper mantle material here outside the hellenic arc the upper mantle density and velocity are 3 32 103 kg m3 and vp 8 0 km s respectively the crust below the cretan sea is thin continental of 15 to 20 km thickness including 3 to 4 km of sediments thick accumulations of sediments located to the ssw and sse of crete are separated by a block of continental crust extended for more than 100 km south of central crete these deep sedimentary basins are located on the oceanic crust backstopped by the continental crust of the aegean microplate the stretched continental margin of africa north of cyrenaica and the abruptly terminated continental aegean microplate south of crete are separated by oceanic lithosphere of only 60 to 80 km width at their closest proximity to the east and west the areas are floored by oceanic lithosphere which rapidly widens towards the herodotus abyssal plain and the deep ionian basin of the central mediterranean sea crustal shortening between the continental margins of the aegean microplate and cyrenaica of north africa influence the deformation of the sediments of the mediterranean ridge that has been divided in an internal and external zone the continental margin of cyrenaica extends for more than 80 km to the north of the african coast in form of a huge ramp while that of the aegean microplate is abruptly truncated by very steep fractures towards the mediterranean ridge changes in the deformation style of the sediments express differences of the tectonic processes that control them that is subduction to the northeast and crustal subsidence to the south of crete strike slip movement between crete and libya is required by seismological observations

travel time tomography of the european mediterranean mantle down to 1400 km abstract the 3 d p wave velocity structure of the mantle below europe the mediterranean region and a part of asia minor is investigated this study is a considerable extension of an earlier tomographic experiment that was limited to imaging upper mantle structure only here the earth s volume under study encompasses the mantle to a depth of 1400 km and we increase the number of international seismological centre isc data for inversion by a factor of four by taking more years of observation and by including data from teleseismic events the most important departure from the earlier study is that we do not use the jeffreys bullen model as a reference model but an improved radially symmetric velocity model the pm2 model which is appropriate for the european mediterranean mantle our inversion procedure consists of two steps first the radial model pm2 is determined from the isc delay times by a nonlinear trial and error inversion of the data as opposed to the jeffreys bullen model the new reference model has a high velocity lithosphere a low velocity zone and seismic discontinuities at depths of 400 and 670 km next the isc data are corrected for effects related to the change in reference model and inverted for 3 d heterogeneity relative to the pm2 model we follow this two step approach to attain a better linearizable tomographic problem in which ray paths computed in the pm2 model provide a better approximation of the actual ray paths than those computed from the jeffreys bullen model hence the two step scheme leads to a more credible application of fermat s principle in linearizing the tomographic equations inversion results for the 3 d heterogeneity are computed for both the uncorrected isc data and for the pm2 data the data fit obtained in the two step approach is slightly better than in the inversion of isc data using the jeffreys bullen reference model a comparison of the tomographic results demonstrates that the pm2 data inversion is to be preferred to assess the spatial resolution an analysis is given of hit count patterns sampling of the mantle by ray paths and results of sensitivity tests with 3 d synthetic velocity models the spatial resolution obtained varies with position in the mantle and is studied both in map view and in cross section in the well sampled regions of the mantle the spatial resolution for larger scale structure can qualitatively be denoted as reasonable to good and at least sufficient to allow interpretation of larger scale anomalies a comparison is made of the results of this study with independent models of s velocity heterogeneity obtained in a number of investigations and with a prediction of the seismic velocity structure of the mantle computed from tectonic reconstructions of the mediterranean region in the context of this comparison interpretations of large scale positive anomalies found in the mediterranean upper mantle in terms of subducted lithosphere are given specifically addressed are subduction below southern spain below the western mediterranean and italy and below the aegean in the last region a slab anomaly is mapped down to depths of 800 km

holocene activity of the scilla fault southern calabria insights from coastal morphological and structural investigations abstract integration of on land and offshore geomorphological and structural investigations coupled to extensive radiometric dating of co seismically uplifted holocene beaches allows characterization of the geometry kinematics and seismotectonics of the scilla fault which borders the eastern side of the messina strait in calabria southern italy this region has been struck by destructive historical earthquakes but knowledge of geologically based source parameters for active faults is relatively poor particularly for those running mostly offshore as the scilla fault does the 30 km long normal fault may be divided into three segments of 10 km individual length with the central and southern segments split in at least two strands the central and northern segments are submerged and in this area marine geophysical data indicate a youthful morphology and locally evidence for active faulting the on land strand of the western segment displaces marine terraces of the last interglacial 124 to 83 ka but seismic reflection profiles suggest a full quaternary activity structural data collected on bedrock faults exposed along the on land segment provide evidence for normal slip and nw se extension which is consistent with focal mechanisms of large earthquakes and gps velocity fields in the region detailed mapping of raised holocene marine deposits exposed at the coastline straddling of the northern and central segments supplies evidence for two co seismic displacements at 1 9 and 3 5 ka and a possible previous event at 5 ka co seismic displacements show a consistent site value and pattern of along strike variation suggestive of characteristic type behaviour for the fault the 1 5 2 0 m average co seismic slips during these events document me 6 9 7 0 earthquakes with 1 6 1 7 ka recurrence time because hanging wall subsidence cannot be included into slip magnitude computation these slips reflect footwall uplift and represent minimum average estimates the palaeoseismological record based on the palaeo shorelines suggests that the last rupture on the scilla fault during the february 6 1783 mw 5 9 6 3 earthquake was at the expected time but it may have not entirely released the loaded stress since the last great event at 1 9 ka comparison of the estimated co seismic extension rate based on the holocene shoreline record with available gps velocities indicates that the scilla fault accounts for at least 15 20 of the contemporary geodetic extension across the messina strait