the puglia uplift se italy an anomaly in the foreland of the apenninic subduction due to buckling of a thick continental lithosphere the apenninic foreland shows two distinct structural signatures comparing the central adriatic sea and the puglia region during the pliocene pleistocene the central adriatic underwent high subsidence rates due to the eastward rollback of the hinge of the west dipping apenninic subduction the puglia region and the bradanic foredeep are located southward along strike in the same foreland but in contrast with the central adriatic after pliocene early pleistocene subsidence they underwent uplift since the middle pleistocene the geometry and the kinematics of the frontal accretionary wedge and related foreland changed from that moment on between the two areas at the front of the central northern apennines off scraping and subsidence continued whereas the foredeep and foreland of the southern apennines were buckled those differences are interpreted as being due to the larger subduction hinge rollback rate since middle pleistocene of the central adriatic lithosphere 70 km thick with respect to the thicker puglia 110 km the different thicknesses of the continental crust and lithosphere were inherited from the mesozoic rifting that disrupted the adriatic plate the different thicknesses appear to have controlled the variable degree of flexure of the lithosphere and its asthenospheric penetration rate the tremiti e w alignment is the right lateral lithospheric transfer zone of those different tectonic regimes the consequent different dip of the subduction in the two sections steeper west of puglia could also explain the lower elevation of the southern apennines compared to their central northern sector

stress field constraints on intraplate seismicity in eastern north america focal mechanisms of 32 north american midplate earthquakes mo 3 8 6 5 were evaluated to determine if slip is compatible with a broad scale regional stress field derived from plate driving forces and if so under what conditions stress regime pore pressure and frictional coefficient using independent information on in situ stress orientations from well bore breakout and hydraulic fracturing data and assuming that the regional principal stresses are in approximately horizontal and vertical planes 10o the constraint that the slip vector represents the direction of maximum resolved shear stress on the fault plane was used to calculate relative stress magnitudes defined by the parameterb s2 s3 s s3 from the fault stress geometry as long as the focal mechanism has a component of oblique slip i e the b axis does not coincide with the intermediate principal stress direction this calculation identifies which of the two nodal planes is a geometrically possible slip plane gephart 1985 slip in a majority of the earthquakes 25 of 32 was found to be geometrically compatible with reactivation of favorably oriented preexisting fault planes in response to the broad scale uniform regional stress field slip in five events was clearly inconsistent with the regional stress field and appears to require a localized stress anomaly to explain the seismicity significantly all five of these events occurred prior to 1970 when many regional networks were installed and their focal mechanisms are inconsistent with more recent solutions of nearby smaller events the frictional likelihood of the geometrically possible slip on the selected fault planes was evaluated in the context of conventional frictional faulting theory the ratio of shear to normal stress on the fault planes at hypocentral depth was calculated relative to an assumed regional stress field regional stress magnitudes were determined from 1 s s3 ratios based on the frictional strength of optimally oriented faults the basis for the linear brittle portion of lithospheric strength profiles 2 the computed relative stress magnitude b values and 3 a vertical principal stress assumed equal to the lithostat two end member possibilities were examined to explain the observed slip in these less than optimally oriented fault planes first the frictional coefficient was held constant on all faults hydrostatic pore pressure was assumed regionally and the fault zone pore pressure was determined since pore pressure is a measurable quantity with real limits in the crust p0 s3 this end member case was used to determine which of the geometrically possible slip planes were frictionally likely slip planes alternately pore pressure was fixed at hydrostatic everywhere and the required relative lowered frictional coefficient of the fault zone was computed slip in 23 of the 25 geometrically compatible earthquakes was determined to also be frictionally likely in response to an approximately horizontal and vertical regional stress field derived from plate driving forces whose magnitudes are constrained by the frictional strength of optimally oriented faults assuming hydrostatic pore pressure regionally the conditions for slip on these 23 relatively well oriented earthquake faults were determined relative to this regional crustal strength model and require only moderate increases in pore pressure between about 0 4 0 8 of lithostatic hydrostatic is about 0 37 of lithostatic or alternately moderate lowering 50 of the frictional coefficient on the faults which slipped superlithostatic pore pressures are not required focal mechanisms for the two other earthquakes with slip vectors geometrically consistent with the regional stress field however did require pore pressures far exceeding the least principal stress or extremely low coefficients of friction these events may reflect either local stress rotations undetected with current sampling or poorly constrained focal mechanisms the analysis also confirmed a roughly north to south contrast in stress regime between the central eastern united states and southeastern canada previously inferred from a contrast in focal mecha nisms between the two areas most central eastern united states earthquakes occur in response to a strike slip stress regime whereas the southeastern canadian events require a thrust faulting stress regime this contrast in stress regime with a constant maximum horizontal stress orientation determined by far field plate driving forces requires a systematic lateral variation in relative stress magnitudes superposition of stresses due to simple flexural models of glacial rebound stresses are of the correct sense to explain the observed lateral variation but maximum computed rebound related stress magnitude changes are quite small about 10 mpa and do not appear large enough to account for the stress regime change if commonly assumed stress magnitudes determined from frictional strength apply to the crust at seismogenic depths

a new view of italian seismicity using 20 years of instrumental recordings in this paper we show the seismicity of the past 20 years that occurred in italy and surrounding regions hypocentral locations have been obtained by using p and s wave arrival times from the ingv national and several regional permanent seismic networks more than 48 000 events selected from an original data set of about 99 780 are used to reconstruct the most complete seismic picture of the italian region so far the seismicity distribution allows inference on seismotectonics of this complex region of subduction versus continental collision our results clearly reveal the geometry of the adria and the ionian subduction and a continuous normal fault belt in the upper crust following the apennines mountain range the depth of the seismogenic layer is computed from the cut off of seismicity at depth and shows large variations along and across the seismic active regions earthquakes are generated by the different velocity of slab retreat and the subsequent asthenospheric upwelling d 2004 elsevier b v all rights reserved

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

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

kinetics of pressure solution at halite silica interfaces and intergranular clay films pressure solution is widely regarded as a potentially important deformation mechanism along crustal faults and during aliagenesis yet the mechanisms and kinetics of this process remain highly controversial to better understand the fundamental factors controwing the rates of pressure solution at the grain to grain scale we conducted experiments in which convex halite lenses were pressed against fiats of fused silica in brine fluid pressures were maintained at 0 1 mpa temperatures and mean contact normal stresses ranged from 8 3 o to 90 2oc and 0 5 to 13 5 mpa respectively the geometry and growth rate of the contact spot between the two lenses and the rate at which the lenses approached one another convergence were monitored using reflected light interferometry and transmitted light photomicrography convergence occurred when halite and silica lenses were pressed together in brine halite silica experiments no undercutting was observed and dry control experiments indicated negligible dislocation creep convergence rates in experiments at 50 2oc ranged from 0 01 to 0 05 m d depending on mean normal stress and contact spot radius the data are consistent with intergranular pressure solution ips rate limited by diffusion through an intergranular film with a very high diffusion coefficient 10 5 10 7 cm2 s the data further suggest that the diffusion coefficient and or thickness of this film increases with decreasing normal stresses at least for normal stresses less than about 4 mpa as no island channel boundary structures were observed we propose that this film consists of a continuous layer of strongly adsorbed i e structured water that is maintained between the halite and silica lenses during deformation convergence rates in similar experiments conducted at a constant load of 0 11 n but at 8 3 o 50 2 o and 90 2oc were approximately constant at a given normal stress and contact spot size the cause of this temperature insensitivity is unknown but might result from changes in interphase boundary structure or thickness with increasing temperature that are sufficient to offset the expected thermal activation an experiment was also conducted in which a halite lens was pressed against a fused silica fiat coated with an 0 8 m thick film of na montmorillonite in brine this clay film produced an approximately fivefold increase in convergence rates over those observed in a halite silica experiment conducted without clay at the same load and temperature the strong sensitivity of ips rates both to contact spot radius and to the presence of second phases along grain boundaries suggests that fine grained clay rich fault gouges and multiphase granular aggregates should be particularly susceptible to pressure solution creep in the middle to upper crust

an active margin across the adriatic sea central mediterranean sea abstract new seismological and structural data from the central adriatic gargano promontory area demonstrate that the current models of an aseismic and slightly deformed adriatic block have to be revised a seismically active deformational belt is mapped along two main fault systems the tremiti islands and mattinata faults moreover geologic and geophysical evidence suggests that a more extensive lithospheric boundary may cut across the central italian peninsula to the tyrrhenian basin

the tectonic regime in italy inferred from borehole breakout data abstract in italy the horizontal stress directions are well constrained in many regions but the tectonic regime is not well known because the stress magnitudes are unknown our intention is to improve the knowledge of crustal stress in italy both at shallow depth and in low seismicity areas therefore we inferred the tectonic regime from the comparison between the depth of breakout occurrence and the physical properties of the rocks in 20 boreholes the critical value of the maximum horizontal stress for which the effective tangential stress at the borehole wall overcomes the rock strength to form breakouts could be computed from rock strength and density comparing the theoretical stress distributions for different tectonic regimes with the depth distribution of breakout occurrence it is possible to infer the tectonic regime that fits best to the breakout depth distribution we investigated boreholes up to 6 km deep located in different tectonic environments over the italian peninsula the po plain the apenninic chain the adriatic foredeep and the tyrrhenian quaternary volcanic region these wells are characterised by breakout data of good quality a b and c according to world stress map quality ranking system the results are in general agreement with the style of faulting derived from earthquake focal mechanisms and other stress indicators our results show a predominance of a normal faulting nf regime in the inner apennines and both normal faulting and strike slip faulting ss style in the surrounding regions possibly also associated with changes in the tectonic regime with depth

seismic anisotropy reveals the long route of the slab through the western central mediterranean mantle abstract in the south eastern corner of the tyrrhenian basin in the central mediterranean sea a tight alignment of earthquakes along a well defined benioff zone marks one of the narrowest active trenches worldwide where one of the last fragment of the former tethys ocean is consumed seismic tomography furnishes snapshot images of the present day position of this slab and seismic anisotropy allows to reconstruct the past kinematics of the subduction process using seismic anisotropy fast directions as a proxy for the present and past mantle flow we look backward for the seismic traces of the slab motion through the western central mediterranean mantle from the starting locus of subduction toward its present day position the result of combining independent data sets provides a coherent pattern of anisotropy that illustrates an example of slab rollback from its initiation point to its present day position

seismicity of the adriatic microplate abstract the adriatic microplate was previously considered to be a unique block tectonically active only along its margins the seismic sequences that took place in the basin from 1986 to 1990 give new information about the geodynamics of this area three subsets of well recorded events were relocated by the joint hypocentre determination technique on the whole this seismic activity was concentrated in a belt crossing the southern adriatic sea around latitude 42 in connection with regional e w fault systems some features of this seismicity similar to those observed in other well known active margins of the adriatic plate support a model of a southern adriatic lithospheric block detached from the northern one other geophysical information provides evidence of a transitional zone at the same latitude

recent tectonic evolution and present stress in the northern apennines italy the present day stress field and its recent tectonic evolution in the northern apennines are reconstructed from borehole breakout analysis and focal mechanisms of crustal earthquakes and through the comparison with paleostress data we have considered 86 wells for breakout analysis with depths down to 6 7 km 125 fault plane solutions of crustal earthquakes with m 5 that occurred between 1988 and 1995 in the northern and central apennines and data of stronger earthquakes m 6 reported in other studies the tyrrhenian coastal region and the apenninic belt are characterized by shmin direction mainly trending ne sw with predominantly normal fault plane solutions along the outer front of the belt and the adriatic offshore shmin is oriented nw se and focal solutions are thrust or strike slip with maximum compression around ne sw conversely south of 43 n breakouts evidence an orthogonal direction of horizontal compression nw se following the southern apennine trend where a widespread ne sw extension was recognized by previous investigations comparing these results to the recent tectonic evolution inferred from structural geology we argue that the extension compression pair characteristic of the post tortonian evolution of the mountain belt has been migrating in time from late miocene to present only in the northern sector of the arc whereas the southern sector underwent a generalized extension at least since middle pleistocene the striking correspondence between the active compression front and the region with evidence of a remnant subducted slab suggests that the migrating extension compression pair has been controlled by progressive retreat of the slab

stratigraphy and tectonics offshore of puglia italy southern adriatic sea abstract the structural and stratigraphic framework of puglia offshore between the gargano promontory and the town of brindisi southern adriatic sea has been analysed based on 1700 km of multichannel seismic profiles and 10 exploratory wells the area includes two different geodynamic settings 1 part of the undeformed apenninic foreland apulian carbonate platform consisting mainly of shallow water mesozoic carbonates and 2 part of the southern adriatic basin which represents the foredeep of the hellenic thrust system a mesozoic slope buried by tertiary clastics and corresponding to the edge of the apulian carbonate platform is observed on seismic data the present physiography of the escarpment is the result of an erosional retreat mainly developed during the tertiary and related to the subsidence of the south adriatic basin at the same time carbonate facies belts as evidenced by well data seem to suggest that in some sectors of the margin the original mesozoic physiography has been preserved and fossilized three seismostratigraphic units separated by regional or local unconformities have been distinguished in the neogene clastic sequence of the south adriatic basin significant deformations in the sedimentary cover are represented by various antiforms one of these antiforms named the gondola ridge is an elongated positive structure deforming the pre tertiary basement the western sector of the gondola ridge belongs to a major e w strike slip lineament extending on land in the gargano promontory in the eastern part of the area in question some tectonic features resembling pop up like and thrust antiforms are arranged along an arcuate pattern named here grifone trend the grifone trend structures indicate a post pliocene tectonism probably related to the late stages of the dinaric hellenic orogenesis the recent westward migration of the hellenic fold and thrust belt can be demonstrated by the south adriatic foredeep shift during the last 5 6 million years

tertiary to recent oblique convergence and wrenching of the central dinarides constraints from a palaeostress study the late eocene to neogene tectonic evolution of the dinarides is characterised by shortening and orogen parallel wrenching superposed on the late cretaceous and eocene double vergent orogenic system the central dinarides exposes nw trending tectonic units which were transported towards the adria apulian microcontinent during late cretaceous palaeogene times these units were also affected by subsequent processes of late palaeogene to neogene shortening neogene extension and subsidence of intramontane sedimentary basins and pliocene quaternary surface uplift and denudation the intramontane basins likely relate to formation of the pannonian basin major dextral se trending strike slip faults are mostly parallel to boundaries of major tectonic units and suggest dextral orogen parallel wrenching of the whole central dinarides during the neogene indentation of the apulian microplate into the alps and back arc type extension in the pannonian basin these fault systems have been evaluated with the standard palaeostress techniques we report four palaeostress tensor groups which are tentatively ordered in a succession from oldest to youngest 1 palaeostress tensor group 1 d1 of likely late eocene age indicates e w shortening accommodated by reverse and strike slip faults 2 palaeostress tensor group 2 d2 comprises n nw trending dextral and w wsw trending sinistral strike slip faults as well as wnw striking reverse faults these indicate ne sw contraction and subordinate nw se extension related to oligocene to early miocene shortening of the dinaric orogenic wedge 3 palaeostress tensor group 3a d3a comprises mainly nw trending normal faults which indicate early middle miocene ne sw extension related to syn rift extension in the pannonian basin the subsequent palaeostress tensor group 3b d3b includes ne trending se dipping normal faults indicating nw se extension which is likely related to further extension in the pannonian basin 4 palaeostress tensor group 4 d4 i s characterised by mainly nw trending dextral and ne trending sinistral strike slip faults together with some e trending reverse faults they indicate roughly n s shortening and dextral wrenching during late miocene to quaternary this is partly consistent with the present day kinematics with motion of the adriatic microplate constrained by gps data and earthquake focal mechanisms the north north westward motion and counterclockwise rotation of the adriatic microplate significantly contribute the shortening and present day wrenching in the central dinarides d 2005 elsevier b v all rights reserved

construction of a seismotectonic model the case of italy procedures for constructing a seismotectonic model of italy designed to be used as a basis for hazard assessment are described the seismotectonic analysis has essentially been based on a gis aided cross correlation of three data sets concerning the 3 d structural model of italy and surrounding areas the space distribution of historical and present seismicity the kinematic model of the central mediterranean region referred to the last 6 ma and including the available information on the present day plate motion and stress field the seismicity pattern in the study area is controlled by a quite complex geodynamic framework which includes continent continent convergence alps and dinarides with development of a neutral arc bordering the plate margins plate divergence across margins characterized by passive slab sinking northern apennines and calabrian arc with development of backarc basins northern tyrrhenian sea and southern tyrrhenian sea flanked by forelandward migrating thrust belt foredeep systems plate divergence across a margin previously characterized by lithosphere sinking and afterwards discharged from the subducted slab southern apennines with development of quite peculiar rift processes within the inactive thrust belt transpression northern sicily due to the combined effect of plate convergence africa europe and high rate flexure hinge retreat of an intervening plate adria microplate with high angles between the respective slip vectors intraplate strain partition and fault activity mainly combined strike slip and thrust motions possibly in correspondence of inverted structures the results of the seismotectonic analysis are synthesized in a zonation of italy in which every delimited zone corresponds to the surface projection of a kinematically homogeneous segment of a seismogenic fault system in cornell type hazard evaluations every polygon should be considered as a homogeneous source zone seat of randomly distributed earthquakes a homogeneous mechanical behaviour of an entire zone and a random earthquake distribution within a single source zone obviously represent oversimplified assumptions since every zone includes one or more master fault segments responsible for the greatest events in the area and several second order associated faults responsible for the background minor seismicity therefore major faults and background seismicity should be treated separately nevertheless the oversimplified assumption of homogeneous seismic zones was the price the authors consciously paid to produce in a reasonably short time a homogeneous product relative to the entire national territory suitable for earthquake hazard evaluation and for decisions regarding risk mitigatiton

seismotectonics of strike slip earthquakes within the deep crust of southern italy geometry kinematics stress field and crustal rheology of the potenza 1990 1991 seismic sequences mmax 5 7 abstract we present a revision and a seismotectonic interpretation of deep crust strike slip earthquake sequences that occurred in 1990 1991 in the southern apennines potenza area the revision is motivated by i the striking similarity to a seismic sequence that occurred in 2002 140 km nnw in an analogous tectonic context molise area suggesting a common seismotectonic environment of regional importance ii the close proximity of such deep strike slip seismicity with shallow extensional seismicity apennine area and iii the lack of knowledge about the mechanical properties of the crust that might justify the observed crustal seismicity a comparison between the revised 1990 1991 earthquakes and the 2002 earthquakes as well as the integration of seismological data with a rheological analysis offer new constraints on the regional seismotectonic context of crustal seismicity in the southern apennines the seismological revision consists of a relocation of the aftershock sequences based on newly constrained velocity models new focal mechanisms of the aftershocks are computed and the active state of stress is constrained via the use of a stress inversion technique the relationships among the observed seismicity the crustal structure of the southern apennines and the rheological layering are analysed along a crustal section crossing southern italy by computing geotherms and two mechanism brittle frictional vs ductile plastic strength rheological profiles the 1990 1991 seismicity is concentrated in a well defined depth range mostly between 15 and 23 km depths this depth range corresponds to the upper pat of the middle crust underlying the apulian sedimentary cover in the footwall of the easternmost apennine thrust system the 3d distribution of the aftershocks the fault kinematics and the stress inversion indicate the activation of a right lateral strike slip fault striking n100 e under a stress field characterized by a sub horizontal n142 trending 1 and a sub horizontal n232 trending 3 very similar to the known stress field of the gargano seismic zone in the apulian foreland the apparent anomalous depths of the earthquakes 15 km and the confinement within a relatively narrow depth range are explained by the crustal rheology which consists of a strong brittle layer at mid crustal depths sandwiched between two plastic horizons this articulated rheological stratification is typical of the central part of the southern apennine crust where the apulian crust is overthrusted by apennine units both the potenza 1990 1991 and the molise 2002 seismic sequences can be interpreted to be due to crustal e w fault zones within the apulian crust inherited from previous tectonic phases and overthrusted by apennine units during the late pliocene middle pleistocene the present strike slip tectonic regime reactivated these fault zones and caused them to move with an uneven mechanical behaviour brittle seismogenic faulting is confined to the strong brittle part of the middle crust this strong brittle layer might also act as a stress guide able to laterally transmit the deviatoric stresses responsible for the strike slip regime in the apulian crust and may explain the close proximity nearly overlapping of the strike slip and normal faulting regimes in the southern apennines from a methodological point of view it seems that rather simple two mechanism rheological profiles though affected by uncertainties are still a useful tool for estimating the rheological properties and likely seismogenic behaviour of the crust

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

geological constraints on the alpine evolution of the mediterranean tethys abstract the geological data on the mediterranean chains and basins are used to point out the constraints that they put on the location through time of oceanic versus continental lithosphere and on the successive relations between them emphasis is put on the rules and conventions which enable us to interpret the geological data in terms of plate tectonics and on the major disputed points for which a solution must be chosen in the first part the location of oceanic versus continental lithosphere is dealt with using the data on the present day basins the ophiolites and the subduction processes a neogene age is retained for the western mediterranean and the surrounding continental blocks are considered to have been previously a part of iberia a cretaceous age is retained for the eastern mediterranean apulia is considered as a part of the african plate except for this period the black sea is considered as a back arc basin formed mostly during the upper cretaceous the ophiolites are used to locate the mesozoic oceans for the double ophiolitic belts of the dinaro hellenides and the taurides the tectonic interpretations which minimise the number of oceanic basins have been retained for the kirsehir block of turkey the chosen solution locates a jurassic ocean to the north and makes it disappear when a cretaceous ocean opens to the south data on the subduction processes added to the information on these basins and led us to consider as oceanic the unknown basements of the carpathian flysch and the maghrebian flysch basins the second part deals with the organisation of basins and platforms emphasising the chronology of their formation and subsequent crushing it furnished step by step constraints on the tectonic history of the system which is related to plate displacement the general pattern derived from these data shows a wedge shaped tethyan ocean which disappeared mostly through repeated subduction below the eastern part of its northern margin the jurassic stage shows westward extension of the ocean between the eurasian and african plates and ends with the dinaro hellenic obduction the cretaceous stage shows a complete reorganisation including individual displacement of the iberian apulian and kirsehir sub plates the tertiary stage shows the general collision between the renewed eurasian and african plates and neogene subduction of the basins which avoided collision

thrust front segmentation induced by differential slab retreat in the apennines italy new seismic reflection data reveal that the south eastward prolongation of the apennine thrust front in the central adriatic sea is most likely located in a more external position with respect to the traditional interpretation in this new interpretation the apennine thrust front shows a segmented geometry in correspondence to the tremiti lithospheric transfer zone the available data suggest that the north eastward flexural retreat of the subducting adriatic lithosphere and the related frontal accretion of the apennine accretionary prism have acted during the last 5 ma and may be considered still lively in both the po plain and in the central adriatic domain north of the tremiti lineament by analysing the tectonic evolution of the apulo adriatic areas it may be argued that the differential slab retreat between the central and southern sectors of the subducting adriatic plate has been able to induce the segmentation of the apennine thrust front

strike slip fault propagation cleavage in carbonate rocks the mattinata fault zone southern apennines italy disjunctive spaced solution cleavage in carbonate rocks is genetically associated with the propagation of the left lateral strike slip mattinata fault in the gargano promontory italy typical cleavage development is restricted within the 200 300 mwide fault zone which is bounded by virtually unfractured wall rocks the cleavage consists of sub parallel solution surfaces which are often reactivated as sheared solution planes geometrical and kinematic relationships exist between the fault and the associated cleavage planes thus 1 cleavage fault intersection lines lie parallel to the fault and the sheared cleavage rotational axes and 2 the cleavage fault angle is almost constantly equal to 408 a model for the development of the mattinata fault is proposed in which the cleavage surfaces are interpreted as fault propagation deformations cleavage nucleates as solution planes at the front of the advancing fault as the result of stress concentration in this region two distinct time sequential processes are shown to operate during the fault propagation 1 typical millimetre to centimetre spaced solution surfaces form in the distal tip zone of the advancing fault plane 2 as the tip advances the fault plane breaks through the cleavage as minor shear displacements reactivate some of these nascent surfaces these observations may prove useful in understanding mechanisms for fault controlled enhanced reduced permeability and fluid pathways 1999 elsevier science ltd all rights reserved

geodynamic evolution of the central dinarides abstract the central part of the dinarides unlike the northwestern and southeastern dinarides shows a consistent pattern in the distribution of the large tectonostratigraphic units from southwest apulia to northeast the following five main units originating in different parts of the mesozoic tethys can be distinguished 1 adriatic dinaridic carbonate platform formations 2 carbonate clastic units flysch bosniaque of the passive continental margin 3 ophiolite bearing formations of the dinaridic ophiolite zone also containing radiolarites greywackes and shales including melange formations and overstepped late jurassic to cretaceous cover sequences 4 active continental margin units represented by upper cretaceous palaeogene trench sediments with blueschists tectonized ophiolite melange alpine medium pressure metamorphic rocks originated from upper cretaceous palaeogene sediments and alpine synkinematic granitoids 5 a nappe consisting of allochthonous palaeozoic triassic formations which is thrust onto the ophiolites and genetically related sedimentary formations the frontal parts of this nappe directly overlie the northeastern margin of the adriatic dinaridic carbonate platform i e the external dinarides the evolution of the central dinarides was controlled by a sequence of tectonic events which took place within the alpine cycle 1 rifting processes lasting some 40 50 ma which started in the late permian and ended in the norian 2 opening of the oceanic dinaridic tethys commenced in the late triassic and persisted for some 70 80 ma until the end of the jurassic 3 subduction processes and emplacement of ophiolites started in late jurassic early cretaceous times during the closing phase of the dinaridic ocean or dinaridic tethys the palaeozoic triassic nappe was emplaced on the ophiolites the thrusting was accompanied by alpine metamorphism 120 100 ma 4 the main alpine deformational event and medium pressure metamorphism with synkinematic granite plutonism took place in late eocene early oligocene times when the ophiolite and palaeozoic triassic nappes were emplaced on the adriatic dinaridic carbonate platform which at the same time was deformed resulting in the development of the external dinarides fold and thrust belt

the italian cmt dataset from 1977 to the present abstract the ingv harvard european mediterranean regional centroid moment tensor rcmt catalog collects solutions routinely computed since 1997 for earthquakes with moderate magnitude 4 5 m 5 5 in the mediterranean region the database represents an extension to smaller magnitudes of the harvard global cmt catalog based on analysis of seismograms recorded at regional distance and modeling of intermediate period surface waves the catalog includes about 600 events 200 of which in the italian region this study extends the catalog back in time for the italian region as long as made possible by available digital data i e since 1977 with the same analysis and inversion method used for current seismicity as a result we present here 65 new moment tensors for years between 1977 and 1997 these solutions represent 45 of the total number of events analyzed the existing seismograms being often too scarce to allow a stable solution the new dataset includes events in many seismic zones where moderate seismicity had previously been scarcely documented e g the po plain the central to southern apennines and the adriatic sea the complete dataset including previously determined rcmts and cmts represents the seismic deformation in the italian area during the last 25 years

frontal part of the northern apennines fold and thrust belt in the romagna marche area italy shallow and deep structural styles in this study surface geological data resulting from a detailed field survey including structural and biostratigraphic analysis have been integrated with subsurface seismic lines and well logs data in order to reconstruct the tectonic evolution of the external zones of the northern italian apennines in the romagna marche foothills and adriatic sea areas this integrated analysis shows 1 a late messinian to lower pleistocene progression of structural development from the hinterland to the foreland of the studied sector of the thrust belt 2 relatively limited 20 southward increasing amounts of shortening obtained by the construction of line length balanced and restored geological cross sections 3 a regional deformation style characterized by the presence of backthrusts associated with most foreland vergent thrust ramps leading to quasi symmetric uplift and a low critical taper for the wedge typical of foreland fold and thrust belts with a weak basal decollement triassic anhydrites in the present case 4 an important influence of basement faulting which despite a general basement cover decoupling appears to control stress localization in the latter producing linkage of basement and cover stuctures in a combination of thin and thick skinned tectonic styles and 5 contrasting structural styles characterizing deep features as imaged by seismic reflection profiles and shallow ones deep stuctures consist of growth anticlines bounded by major thrust ramps and back limb back thrusts separated by broader open synclines both involving a mesozoic paleogene mainly carbonate passive margin succession in the crestal zones of major anticlines shallow structures affecting neogene terrigenous foredeep sediments show a complex pattern of upright to recumbent folds of tens to hundreds of meters wavelength related to minor thrusts and backthrusts deformation of the mesozoic paleogene multilayer appears to be dominated by thrust propagation in the cores of early formed anticlines developed by buckling instabilities the overlying neogene deposits are detached from the carbonate substratum along the base of the foredeep succession bedding parallel slip occurring along this detachment level appears to be accommodated by the complex structures in the crests of major anticlines where the thrusts lramp to the surface cutting up section complex shallow structures interpreted to accommodate at shallow structural levels the deep deformation would therefore represent a geometrical requirement for maintaining strain compatibility across the shallow detachment level located at the base of the foredeep succession

is the adriatic an african promontory seismicity patterns and fault plane solutions for the largest recent earthquakes in the adriatic region are used to test the hypothesis that the adriatic is a promontory of the african continental mass the horizontal projections of the slip vectors for the 24 best constrained focal mechanisms trend at a high angle to those predicted for the africa eurasia collision and so the adriatic cannot be thought of as a promontory of africa the slip vectors define an instantaneous pole of rotation that describes anticlockwise rotation of the adriatic relative to eurasia the adriatic is a stable continental block moving within the broad zone of deformation between africa and eurasia

magnetic anisotropy of plio pleistocene sediments from the adriatic margin of the northern apennines italy implications for the time space evolution of the stress field abstract the anisotropy of magnetic susceptibility ams of the marine fine grained plio pleistocene sediments that crop out at the eastern adriatic front of the central northern apennines italy indicates a prevalent sedimentary compactional magnetic fabric with variable overprint of the tectonic strain the degree of anisotropy and the geometry of the ams ellipsoids suggest a subdivision of the studied sediments in two distinct ages early middle pliocene and late pliocene early pleistocene the early middle pliocene sediments show a weak but well defined magnetic lineation parallel to the main fold and thrust axes throughout the region analogously to the messinian sediments located in a more internal western position of the apenninic chain since the late pliocene the ams data are not regionally coherent and indicate a reduced and locally variable tectonic influence on the magnetic fabrics the ams data have been integrated with the available geophysical information of the present day stress in the region with the aim to reconstruct the time spatial evolution of the stress field in the adriatic margin of the central northern apennines during the past 5 ma the present day stress field was evaluated using borehole breakout in deep wells about 50 wells focal mechanisms of crustal earthquakes 2 5 m d

the influence of water on the stress supported by experimentally faulted westerly granite summary fault zones in wet westerly granite deformed at temperatures of 300 and 400 c require markedly lower shear stresses for sliding than when dry even when the effective confining pressure is held constant between the wet and dry tests provided that the strain rate is lower than lo s l the rate of strength reduction is enhanced by increasing the pore water pressure the deformation rate is a power function of the applied stress where the stress exponent is approximately 7 for pore water pressure of l00mpa and 21 for pore water pressure of 20 mpa the experimental results are extrapolated to conditions believed to occur at depths of 10 km along the san andreas fault zone it is suggested that for slow tectonic deformation at strain rates of lo and 10 14s the shear stress for sliding on faults in granite would be approximately 60 and 20mpa respectively at pore water pressures equal to the hydrostatic head fluid overpressures of c 0 8 lithostatic pressure are required to lower the shear stress for sliding into the 10mpa range at the slower strain rate

tertiary geodynamic evolution of the southern adria microplate the southern adria microplate is the common foreland for the hellenide and southern apennine thrust belts the apulian platform dominates the microplate outcrop well and seismic data allow us to trace the carbonate platform edge whilst structural analysis geophysical and palaeomagnetic data provide important clues to the geodynamic evolution of the region the present structural fabric of apulia is dominated by several e w lineaments that divide the region into different blocks rospo plateau gargano promontory murge ridge salento peninsula apulian plateau one such lineament the pescara dubrovnik line a prominent feature traversing the adriatic sea between central italy and southern croatia has been active since the early mesozoic when it acted as a major transform fault controlling sedimentation along the northern margin of southern adria during the cenozoic the pescara dubrovnik underwent predominantly vertical and oblique movement due to a differential flexural response of the platform and the adjacent pelagic sequences to the thrust belt loading in tertiary time the southern adria microplate was partly involved in heilenide collision the apulian platform can be considered as an area of thicker crust more resistant to underthrusting than the surrounding basins during the orogenic events it acted as a passive rigid indentor causing local distortion of the most external hellenide structures the dextral transpressive activity recorded along the south east margin of this indentor kephallinia line can be interpreted as the result of the oblique collision between the margin of the thick apulian platform in this zone nne ssw striking and the nw se striking hellenic thrust belt horizontal stress generated during the collision was partly transmitted to the rigid foreland re activating palaeo e w faults within the south adria microplate in a dextral strike slip sense the clockwise rotation recorded in the salento peninsula can be explained by the rotation of several nw se striking faulted blocks the rotation was accompanied by the opening of small transtensional basins between blocks this block rotation was caused by the dextral shear that is expressed along the north and the south salento fault zones

constraints on the location and mechanism of the 1511 western slovenia earthquake from active tectonics and modeling of macroseismic data abstract the 1511 western slovenia earthquake m 6 9 is the largest event occurred so far in the region of the alps dinarides junction though it strongly influences the regional seismic hazard assessment the epicenter and mechanism are still under debate the complexity of the active tectonics of the alps dinarides junction is reflected by the presence of both compressional and transpressional deformations this complexity is witnessed by the recent occurrence of three main earthquake sequences the 1976 friuli thrust faulting events the 1998 bovec krn mountain and the 2004 kobarid strike slip events the epicenters of the 1998 and 2004 strike slip earthquakes ms 5 7 and ms 4 9 respectively lie only 50 km far from the 1976 thrust earthquake ms 6 5 we use the available macroseismic data and recent active tectonics studies to assess a possible epicenter and mechanism for the 1511 earthquake and causative fault according with previous works reported in the literature we analyze both a two and a single event case defining several input fault models we compute synthetic seismograms up to 1 hz in an extended source approximation testing different rupture propagations and applying a uniform seismic moment distribution on the fault segments we extract the maximum horizontal velocities from the synthetics and we convert them into intensities by means of an empirical relation a rounded to integer misfit between observed and computed intensities is performed considering both a minimized and a maximized databases built to avoid the use of half degree macroseismic intensity data points our results are consistent with a 6 9 magnitude single event rupturing 50 km of the idrija right lateral strike slip fault with bilateral rupture propagation

solution slip and separations on strike slip fault zones theory and application to the mattinata fault italy we present a set of relationships to determine the component of slip and separations generated by the cleavage controlled volume contraction in strike slip fault zones the fault walls can translate toward each other along the cleavage normal axis of maximum shortening as rock is dissolved by pressure solution along patterned cleavage surfaces within strike slip fault zones the fault zone shortening produces an apparent slip and possible separations of reference stratigraphic surfaces across the fault zone solution related slip and separations can differ in magnitude and have either the same or the opposite sense these discrepancies depend upon the amount of fault zone shortening and upon the angles between the fault and the shortening axis and between the fault and the reference stratigraphic surface separations can be considerable at any scales even for very low amounts of fault zone thinning apparent slip can be appreciable for large amounts of fault zone thinning and or high fault to cleavage incidence angles with the proper geometrical conversions the relationships here presented can apply to any fault type the application of this technique to the left lateral mattinata fault italy demonstrated that both left and right lateral strike separations can occur along the fault even for low amounts of fault zone contraction by rock dissolution q 2002 elsevier science ltd all rights reserved

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

a kinematic model for the plio quaternary evolution of the tyrrhenian apenninic system implications for rifting processes and volcanism abstract during the frontal accretion due to the late miocene quaternary thrusting the interior of the apenninic chain underwent large scale extension which produced the opening of the tyrrhenian oceanic basin a back arc basin in respect to the late cenozoic apenninic chain and the onset of the quaternary volcanic activity in the campanian plain and more generally in the tyrrhenian area to outline the space time distribution and the geotectonic setting of the tyrrhenian volcanics we approached the problem from a kinematic point of view a synthesis of the available geological and geophysical data leads us to suggest that the progressive migration of the apenninic arcs is responsible for the extension phenomena which took place during the last 5 ma at first the extension resulted from the kinematic interaction between the northern apenninic arc and the southern apenninic arc during the late pliocene then from the early pleistocene the extension was controlled by the se migration of the southern arc only and therefore it can be regarded as part of the general southern tyrrhenian extension phenomenon due to the intense thinning the isotherms migrated upward very rapidly within the toscana latium and campania lithosphere where the melting point was reached giving rise to the onset of volcanic activity at the end of the early pleistocene

tectonic implications of the gps velocity field in the northern adriatic region 1 continuous and episodic gps observations between 1991 and 2004 show that adria moves independently of both stable eurasia and nubia adria moves nne at 3 4 5 mm yr increasing from n to s relative to eurasia and may be fragmenting along the gargano dubrovnik seismic zone the observed 2 3 mm yr of n s adria eurasia convergence is taken up by contraction across a narrow 70 km zone in the eastern alps and concomitant extrusion of the alpine north pannonian unit the adria central dinarides boundary is a broader collisional zone with intense 1 1 5 mm yr shortening near shore and 2 mm yr spread across the dinarides the remaining 1 2 mm yr motion e of the alps and ne of the dinarides is absorbed by the inverted contracting pannonian basin leaving no significant deformation above 0 5 mm yr in the western and northern carpathians and european platform

different foreland basins in italy examples from the central and southern adriatic sea abstract the central adriatic basin cab and the southern adriatic basin sab are foreland or foredeep basins relative to the non coeval apenninic and dinaric hellenic orogenic systems and currently characterized by different physiographies these are separated by a major forebulge of the adriatic lithosphere running throughout the adriatic region from istria to the gargano promontory the clastic basin filling of the cab is mostly plio pleistocene whereas it is upper oligocene pleistocene in the sab stratigraphy reveals that the cab has experienced an overfilling regime throughout the plio pleistocene whereas the sab has been probably continuously underfilled during the same time span in the cab the foreland plate dips westward at an average angle of 5 6 whereas in the sab the basement dips to the east at an angle of 1 2 this discrepancy is congruent with the already noticed distinction between east and west dipping subduction systems and possibly has geodynamical implications in the cab the non homogeneous distribution of thrust sheets suggests strike slip tectonic movements along roughly ne trending lineaments that occurred up to the middle late pliocene on the western part of the sab the overall structural assemblage recalls the fabric typical to strike slip regimes and includesboth extensional and contractional structures it is proposed that the messinian salinity crisis and relative eustatic lowstand affected the subsequent tectono sedimentary evolution of the cab in terms of subsidence rate and depositional style one still tentative hypothesis is that water and sediment removal in the basin lasted for a sufficient time span to promote viscoelastic relaxation temporary migration of the forebulge towards the thrust belt and downwarping of the foreland plate

effects of dissolution precipitation processes on the strength and mechanical behavior of quartz gouge at high temperature hydrothermal conditions laboratory experiments on simulated quartz gouges at a temperature of 927 c a confining pressure of 300 mpa and a pore water pressure of 200 mpa demonstrate the interactions between cataclastic and dissolution precipitation processes and their effects on the strength and mechanical behavior significant porosity reduction and microstructures including grain interlocking grain interpenetration and widespread growth of euhedral shaped grains indicate the operation of dissolution precipitation processes under conditions which favor the activity of dissolution precipitation processes i e for small grain size or at slow displacement rates deformation is distributed across the whole gouge layer and strength increases continuously with increasing displacement so that coefficients of friction reach to 0 7 in contrast for specimens with large grain size sheared at fast displacement rates deformation is localized along a gouge forcing block interface after a small amount of displacement and results in slip softening and subsequent quasi stable sliding with coefficients of friction as low as 0 45 analysis of our results indicates that where the kinetics of dissolution precipitation is sufficiently fast to partly accommodate shear strain the mechanical behavior and strength of quartz gouge can be characterized by slip hardening and high strength with velocity strengthening in contrast where cataclastic processes predominantly accommodate shear strain the mechanical behavior and strength can be characterized by slip softening and subsequent localized sliding with low strength and velocity strengthening

a critical revision of the seismicity of northern apulia adriatic microplate southern italy and implicationsfor the identification of seismogenic structures abstract northern apulia is an emerged portion of the adriatic microplate representing the foreland foredeep area of a stretch of the apennine chain in southern italy the interaction between the relatively rigid microplate and the contiguous more deformable domains is responsible for the intense seismicity affecting the chain area however strong sometimes even disastrous earthquakes have also hit northern apulia on several occasions the identification of the causative faults of such events is still unclear and different hypotheses have been reported in literature in order to provide guidelines and constraints in the search for these structures a comprehensive re examination and reprocessing of all the available seismic data has been carried out taking into consideration 1 the characteristics of historical events 2 the accurate relocation of events instrumentally recorded in the last 20 years 3 the determination of focal mechanisms and of the regional stress tensor the results obtained bring to light a distinction between the foreland and foredeep areas in the first region there is evidence of a regional stress combining nw compression and ne extension thus structures responsible for major earthquakes should be searched for among strike slip faults possibly with a slight transpressive character these structures could be either approximately n s oriented sinistral or e w dextral faults in the foredeep region there is a transition toward transtensive mechanisms with strikes similar to those of the previous zone or maybe also towards nw oriented normal faults more similar to those prevailing in the southern apennine chain in relation to a dominant ne extension this appears to be the effect of a reduction of the nw compression probably due to a decrease in efficiency of stress transmission along the more tectonised border of the adriatic microplate

structural inheritance in mountain belts an alpine apennine perspective abstract the geological structure of continental lithosphere shows complex variety that is inherited into orogenic belts and influences the localization and amplification of contractional structures during mountain building in the alpine apennine sector together with other sectors of the tethyan orogenic system the pre orogenic crustal template can include arrays of extensional faults other faults can form adjacent to the evolving mountain belt and subsequently become incorporated as the thrust belts migrate into their forelands while in some areas these inherited features may simply reactivate under inversion more commonly faults show complex partial reactivation structures in volumes of distributed strain faults may serve to nucleate large scale buckle folds for example along basement cover interfaces these different patterns of basement reactivation may reflect spatially varying strength depth profiles in continental lithosphere that are themselves inherited from spatially distinct geological histories even when not themselves reactivating basement faults can control deformation in the overlying sedimentary cover by offsetting otherwise regionally extensive detachment horizons the 3d form of thrust systems can be strongly compartmentalized by pre existing cross faults such as the oblique lineaments of the apennines on a large scale the distribution of pre existing faults and other weaknesses may affect the propensity for orogenic contraction in basement and therefore directly control larger scale tectonic processes in the central mediterranean the evolution of slab roll back and the related growth of overlying extensional basins e g tyrrhenian sea may be strongly modulated by the distribution of rift related weak zones in the adjacent continental crust the subduction of continental crust will strongly depend on the inherited structure of this crust specifically the distribution of deep crust of basic composition this develops relatively higher densities associated with eclogite metamorphism which act in turn to reduce the buoyancy of thickened continental crust that otherwise serves to inhibit further shortening investigating all these aspects from the scale of bulk crustal compositions to the geometry timing and strength of earlier fault zones preserved in orogenic belts requires the integration of substantial multidisciplinary geological data sets the extent to which continental orogenic belts represent the amplification of inherited geological heterogeneities as opposed to self ordered phenomena modulated by the syntectonic environment remains unclear

the adriatic region an independent microplate within the africa eurasia collision zone 1 we use gps measurements and block modeling to investigate the present day deformation of the adriatic region whose kinematics within the nubia eurasia plate boundary zone is not well constrained and remains controversial block modeling allows us to compute rigid plate angular velocities while accounting for elastic strain accumulation along block bounding faults results suggest that the adriatic is a microplate adria and that the southern boundary with the nubia plate and the aegean domain may be located along the apulia escarpment and the kefallinia fault geodetic data alone cannot discriminate between a single block ap or a two blocks gdap description of adria but the gdap model predicts boundary slip rates that are in better agreement with observations from previous studies

structural architecture of the central apennines interpretation of the crop 11 seismic profile from the adriatic coast to the orographic divide 1 we present an interpretation of the eastern half portion of the crop 11 line a deep reflection seismic profile 265 km long that cuts across the central apennines from the tyrrhenian coast to the adriatic coast in the study area the line cuts across a pile of thrust sheets that underwent tectonic transport between the messinian and the pleistocene in its easternmost part the line runs through the plio pleistocene deposits of the adriatic foredeep in the foreland region the crop 11 line integrates previous information on the crustal structure derived from petroleum exploration and from deep seismic sounding refraction experiments in particular the crop 11 line confirms the existence of a very thick sedimentary sequence underlying the mesozoic tertiary carbonates of the apulia platform interpreted as the paleozoic triassic sedimentary cover of a pre cambrian crystalline basement in the mountain chain where the base thrust of the orogenic wedge reaches a depth of about 25 km this sedimentary sequence appears to be the deepest geological unit incorporated in the thrust system this interpretation of the crop 11 profile suggests an unusual thin skin tectonic style implying the detachment from the original basement and the incorporation in the post tortonian tectonic wedge of a very thick paleozoic triassic sedimentary sequence possibly affected by low grade metamorphism in the lower part other new suggestions from the crop 11 seismic data concern the origin of the fucino basin one of the most remarkable plio pleistocene intramontane basins the normal faults bordering this structural depression as other important normal faults present in the central apennines e g the caramanico fault system in the majella region seem to have been controlled by gravitational collapse processes driven by uplift during crustal shortening rather than by a generalized extension subsequent to the apennine compression as usually reported in the geological literature if this interpretation is correct the strong seismic activity in correspondence to the apennine watershed may be related to the very recent increase in the structural relief caused by an out of sequence propagation of the active thrusts

the brittle deformation regime of water saturated siliceous sandstones summary we present here new experimental data on the mechanical behaviour of water saturated bentheim and fontainebleau sandstones deformed in the brittle failure regime bentheim sandstone samples were stressed at room temperature and subjected to confining pressures pc ranging from 12 to 120 mpa and pore pressures pp ranging from 1 to 70 mpa for all samples the evolution of the volumetric strain first shows compaction eventually reversing to dilation of the pore volume when approaching the peak stress all samples failed localized on a single shear zone critical stresses that is onset of dilatancy and peak stress can be uniquely defined as a function of the effective pressure peff pc pp the failure curve parameters when fitted with the hoek brown criterion or a parabolic envelope are consistent with previous values obtained on similar material when compared to data obtained on dry samples of the same rock the present data show no notable effect of the presence of water on the critical stress levels the same conclusion holds for the stress strain curves when dry and water saturated experiments under equivalent effective confining pressures are compared when compared to previously published data obtained on various quartzose rocks which show a quite variable water weakening effect our results lead to the conclusion that the quasi exclusive presence of quartz grains bonded together by a quartzose cement combined with the absence of clayey minerals may explain the absence of this effect in bentheim sandstone moreover this conclusion is supported by complementary results obtained by fontainebleau sandstone with similar microstructural and compositional characteristics a previously developed micromechanical model based on the interaction of pore cracks has been used and modified to take into account the presence of water when compared to the experimental data the results of the model show good agreement for low to intermediate effective confining pressures critical stresses as well as deformation curves are well reproduced as was the case for the dry rock provided that effective pressure is introduced at higher effective pressures a mix of mechanisms including shear enhanced compaction may explain the progressive discrepancy between the modelled and the experimental curves when approaching the apex of the failure envelope

crustal image of the ionian basin and its calabrian margins abstract previous seismic investigation of the crustal structure in the ionian basin has been limited to shallow penetration seismics of the 1970 s characterized by inadequate source power and low fold earlier obs and esp seismic refraction experiments have not been able to firmly resolve one of the principal scientific problems for this region which is whether the ionian basin is floored by oceanic crust or by highly attenuated continental crust a second elusive problem is the nature of the transition of the boundaries between the ionian basin and its margins in this paper we describe and interpret new deep seismic reflection and wide angle data collected in the western ionian sea and the calabria region of italy one of the principal features of our multichannel reflection data beneath the ionian basin is a band of layered high amplitude reflections near the base of the crust this band shows a quasi monochromatic ca 8 to 10 hz frequency and a traveltime thickness of 1 to 1 5 s these images contrast with the well known reflection patterns of mesozoic oceanic crust investigated in the atlantic ocean there is evidence that the low frequency band dips down towards the edge of the malta escarpment me where landward dipping reflectors separate continental and intermediate type crust in the central tract of the me the increased traveltimes of the lower crustal reflectors and moho from the basin towards the southern and eastern margins of southern calabria could be partially due to the velocity pull down effect of the sedimentary pile of the arc although a true dip of 15 to 18 over 60 km distance can be substantiated moreover the reflecting band maintains its reflectivity and thickness until its abrupt termination beneath the ionian continuation of the calabrian compressional crustal structures the coincident acquisition of wide angle seismic data and marine reflection seismic data provided a landward extension of the survey which will complement existing geologic information on the deep framework of the ionian basin and its calabrian margin

crustal extension in the northern apennines the transition from compression to extension in the alpi apuane core complex an interpretation of northern apennine geology is presented which relates the temporal and spatial occurrence of both compressional and extensional deformation features in terms of the changing dynamic evolution within an accretionary wedge after a model proposed by platt 1986 followed by the initiation and development of continental rifting during cretaceous to eocene time an accretionary wedge formed as remnant tethyan oceanic crust subducted beneath the rotating corsica sardinia microplate microplate collision during the oligocene was characterized by the rapid imbrication of buoyant continental crust of the italian continental margin the record of which is preserved within the duplex structure geometry of the alpi apuane region the overthickened wedge geometry returned to a more stable configuration by developing extensional features during the miocene both listric normal faults at upper crustal levels and shear zones indicating evidence of distributed ductile extensional strain at mid crustal levels are recorded it is proposed that large scale regional extension with associated volcanism beginning in the messinian was represented by the intrusion of asthenospheric material from the subducted plate into the already attenuated accretionary complex further rifting perhaps aided by subduction and back arc processes in the southern apennines led to the formation of the tyrrhenian sea as an oceanic basin both the apennines and north american core complexes record evidence of crustal thickening followed by crustal thinning and finally of continental rifting this suggests that the similar histories of these regions with vastly different plate tectonic settings may both be explained by processes linked to the changing internal dynamics of accretionary wedges

revel a model for recent plate velocities from space geodesy 1 we present a new global model for recent plate velocities revel describing the relative velocities of 19 plates and continental blocks the model is derived from publicly available space geodetic primarily gps data for the period 1993 2000 we include an independent and rigorous estimate for gps velocity uncertainties to assess plate rigidity and propagate these uncertainties to the velocity estimates the velocity fields for north america eurasia and antarctica clearly show the effects of glacial isostatic adjustment and australia appears to depart from rigid plate behavior in a manner consistent with the mapped intraplate stress field two thirds of tested plate pairs agree with the nuvel 1a geologic 3 myr average velocities within uncertainties three plate pairs caribbean north america caribbean south america and north america pacific exhibit significant differences between the geodetic and geologic model that may reflect systematic errors in nuvel 1a due to the use of seafloor magnetic rate data that do not reflect the full plate rate because of tectonic complexities most other differences probably reflect real velocity changes over the last few million years several plate pairs arabia eurasia arabia nubia eurasia india move more slowly than the 3 myr nuvel 1a average perhaps reflecting long term deceleration associated with continental collision several other plate pairs including nazca pacific nazca south america and nubia south america are experiencing slowing that began 25 ma the beginning of the current phase of andean crustal shortening

shear wave attenuation in the lithosphere beneath italy and surrounding regions tectonic implications more than 700 waveforms produced by 51 shallow earthquakes and recorded at regional distances 250 1400 km by the italian seismic network have been analyzed to characterize the amplitude and frequency contents of the crustal and uppermost mantle shear waves lg and sn respectively the crustal phase lg efficiently propagates through the relatively stable adriatic continental crust while it is not observed along propagation paths crossing major physiographic features like the apennine chain and the basinal domain of the tyrrhenian and ionian seas similar to lg efficient sn propagation is observed in the uppermost mantle beneath the po plain and the adriatic sea efficient sn transmission is also observed across the northern ionian sea and sicily and in the area between sardinia and the northern coasts of africa sn are efficiently transmitted across the sicily channel and rather efficient sn propagate beneath the ligurian sea on the contrary inefficient sn transmission characterizes the uppermost mantle beneath the apennines the western margin of the italian peninsula and the southern tyrrhenian sea shear wave attenuation suggests the presence of asthenospheric material in the uppermost mantle probably related to the present day extension along the apennine chain and in the tyrrhenian basin this interpretation is consistent with the presence of extensive neogene and quaternary volcanic activity in these areas and related high heat flow proposed lithospheric delaminatioh processes beneath the apennines and subduction beneath the tyrrhenian sea can reasonably explain the observed high attenuation zones in the uppermost mantle in contrast a high strength mantle lid is inferred to underlay the po plain the adriatic sea and the northern ionian sea the available waveforms also indicate that a continuous mantle lid is present beneath sicily and the extensional domain of the sicily channel as well as in the marine area south of sardinia

neogene to quaternary sedimentary basins in the south adriatic central mediterranean foredeeps and lithospheric buckling up to several kilometers deep sedimentary basins of neogene to quaternary age are found in the south adriatic between the apennines and the dinarides albanides they are the apennines foredeep the central adriatic basin and the south adriatic basin two regional seismic lines 260 and 170 km long across the entire system provide hitherto unavailable constraints on the kinematics and dynamics of basin development the apennine foredeep imaged along the lines formed in middle to late pliocene times through a rapid westward tilting of the basin floor a paleobathymetry of few kilometers was created in which allochthonous bodies were emplaced and sediments deposited unaffected by deformation and farther rotations the central and south adriatic basins formed in neogene to quaternary times and are both characterized by strong subsidence in their central parts gradually diminishing toward the edges in the sw and ne depocenters did not shift laterally through time subsidence rates increase through time and subsidence continued also following the end of main shortening episodes in the dinarides albanides the central and south adriatic basins form two crustal scale synclines with subsidence concentrated in their central parts basins geometries and subsidence patterns indicate that the adriatic crust has undergone episodes of buckling since miocene times wavelengths and amplitudes of such folds change along strike corresponding to mechanical changes of the folded medium

flexure of lithosphere beneath apennine and carpathian foredeep basins evidence for an insufficient topographic load the pliocene foredeep basin external to the apennine thrust belt and the late miocene foredeep basin external to the outer east carpathians are considered typical molassic foredeeps that formed contemporaneously with thrusting in the adjacent mountain belts a simple mechanical model in which the response of the lithosphere to loading was approximately by a semi infinite broken elastic plate overlying a weak fluid was used to analyze the deflection of the foreland lithosphere beneath the apennine and outer east carpathian foredeep basins along three transects perpendicular to the thrust belts comparison between the calculated and observed depth to basement suggests that the emplacement of thrust sheets onto the foreland lithosphere during mountain building failed to pr duce a sufficient load to create the observed foredeep basins and observed topography regardless of the position of the slab end or the flexural rigidity assumed for the foreland lithosphere we infer that an additional subsurface load must be present and that its magnitude must be roughly equal to the load created by that part of the thrust belt that is above sea level for the two apennine transects an acceptable fit to the shape and size of the observed foredeep basin was generated by assuming effective elastic plate thicknesses of 8 and 15 km 4 9 and 9 3 mi and applied vertical forces of 2 1015 dynes cm and 1 3 1015 dynes cm at the slab end for the carpathian transect an effective plate thickness of 30 km 18 6 mi and an applied force of 1 5 215 1015 dynes cm generated an acceptable fit this study suggests a method whereby an estimate of the depth to autochthonous basement rocks beneath overthrust belts can be made in some areas where this information is not available from seismic or drilling data such an approach may enable exploration geologists to determine if crystalline rocks encountered in drilling overthrust terranes are a part of the autochthonous basement or if they are part of an overthrust sheet in the latter situation oil bearing sequences of sedimentary rocks might lie below crystalline rocks contained in the allochthonous sheet