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

a new approach to the opening of the eastern mediterranean sea and the origin of the hellenic subduction zone part 1 the eastern mediterranean sea we identify long transform faults that frame the eastern mediterranean sea and that were active during jurassic and probably the early cretaceous during the opening of the central atlantic ocean

geodynamic implications of earthquake data in the southern tyrrhenian sea abstract data from short period seismic stations operating in calabria sicily and the aeolian islands have been used to investigate earthquake properties of the southern tyrrhenian lithosphere the results have been analyzed taking into account other geophysical and geological information available in the literature for the same region with the main purpose of contributing to the definition of local geodynamic processes space distribution and focal mechanisms of earthquakes support the hypothesis of southeastward migration of the southern tyrrhenian lithosphere shared by several authors in their tectonic modelling of the area we find that most seismicity appears to be related to two main faults crossing the aeolian island archipelago sisifo and vulcano and propose that these faults are important dislocation structures associated with the lithosphere migration process we also give a detailed picture of the seismic behaviour of the above mentioned fault systems by analyzing the earthquake depth distribution focal mechanisms seismic clustering and strain release some degree of activity was also detected at the eastern boundary of the southern tyrrhenian area calabrian arc in particular our results demonstrate that in this highly stressed zone of contact between different tectonic units tyrrhenian and ionian basins strain is released under seismic form up to depths of the order of 25 km in the crust and not just in the shallowest structures as proposed by other authors

evidence for transform faulting in the ionian sea the cephalonia island earthquake sequence of 1983 accurate locations of aftershocks of the january 17 1983 ms 7 0 main shock in the ionian islands have been determined as well as fault plane solutions for this main shock and its largest aftershock which are interpreted as a right lateral strike slip motion with a thrust component on a fault striking in about a ne sw direction

contemporary stress and strain field in the mediterranean from stress inversion of focal mechanisms and gps data abstract mapping the contemporary stress field of the mediterranean provides fundamental insights on the complexity of plate tectonic forces throughout the region and at different depths despite increased data availability and methodological improvements most recent comprehensive stress field characterization across the entire mediterranean dates back to 1995 to extend the regional stress information we use all earthquake focal mechanisms compiled in the world stress map database release 2016 for a formal stress inversion our main goals are to 1 improve the resolution of the stress field orientation 2 evaluate the performance of the recently refined stress inversion methodology in a tectonically complex region 3 test the hypothesis of a depth dependent stress orientation heterogeneity and 4 compare different types of stress and strain observations from surface using the gps derived information on the strain rate tensor down to the seismogenic crust using summation of normalized seismic potencies the obtained stress orientations generally capture the main seismotectonic features including tectonically complex settings such as the alpine orogeny or the ionian sea the orientation of the maximum horizontal stress shmax tends to be uniform with depth within uncertainties while larger stress heterogeneity quantified by means of the focal mechanism diversity and misfit angles is found between 5 and 14 km both the orientation of the largest horizontal shortening axis of the strain field from potency tensors and horizontal strain rate tensor from gps data are generally sub parallel to shmax orientation indicating a linear stress strain relationship and that the orientations of the co seismic release and interseismic strain accumulation are generally consistent

structure of an island arc wide angle seismic studies in the eastern aleutian islands alaska new seismic wide angle data from the eastern aleutian islands show a mafic composition and a 30 km thick island arc crust traveltimes of p and s refracted arrivals and prominent crustal and mantle reflectors observed to offsets of over 300 km were used to derive velocity models for the eastern aleutian arc between the islands of atka and unimak using a three dimensional finite difference modeling and tomography code we interpret the highest crustal p wave velocities of 7 2 7 4 km s between about 12 and about 22 km depth to the south and north of the main volcanic line as remainders of preexisting oceanic crust into which arc magma is intruded apart from the pieces of oceanic crust the velocities suggest an overall mafic composition for the arc composed mainly of metabasalts diorite and diabase in the upper crust and garnet granulite or amphibolite to hornblendite in the lower crust reflected arrivals from the subducting pacific plate at depths of 45 55 km beneath the fore arc together with pn show a mantle wedge with p wave velocities as low as 7 4 km s increasing with depth to about 8 1 km s with an average of about 7 7 km s a mantle composition that grades from mainly pyroxenite probably ultramafic cumulates near the moho to dunite at greater depths best explains these observed velocities

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

estimates of stress directions by inversion of earthquake fault plane solutions in sicily summary the tectonic stress orientation is estimated in the lithosphere of northern sicily the southern tyrrhenian sea and southern calabria and in the wadati benioff zone below the tyrrhenian by inversion of fault plane solutions of earthquakes covering a magnitude range from 2 5 to 7 1 focal mechanisms of 97 earthquakes are taken from the literature after a critical evaluation of their data quality an average misfit of f 13 indicates that the set of all shallow 50 km earthquakes is generated by a heterogeneous stress field for three subsets based on regional and magnitude separation f was small enough 2 8 lfs5 9 to support the assumption of a homogeneous stress direction for an additional subset with f 7 4 such a condition is close to being fulfilled even though some heterogeneity appears to be present the number of earthquakes in these subsets ranged from nine to 22 and the uncertainties of the principal stress directions were generally of the order of 20 at the 90 per cent confidence level the earthquakes with a425 define a regional stress field with the greatest principal stress ul dipping at a shallow angle to the south in north eastern sicily and south western calabria the stress field estimated by earthquakes is extensional with o3 in a direction of wnw and a near vertical ol in agreement with the graben tectonics mapped geologically in this area in western sicily the c1 direction is oriented wnw but this result is judged less reliable than the others based on the broader confidence limits of the solution and the average misfit of 7 4 the earthquakes in the wadati benioff zone define ol dipping at about 70 to the nw subparallel to the zone with o2 horizontal and striking parallel to the zone

crustal structure and evolution of the mariana intra oceanic island arc a new high resolution velocity model of the mariana arc backarc system obtained from active source seismic profiling demonstrates velocity variations within the arc middle and lower crusts of intermediate to felsic and mafic compositions the characteristics of the oceanic island arc crust are a middle crust with velocity of 6 km s laterally heterogeneous lower crust with velocities of 7 km s and unusually low mantle velocities petrologic modeling suggests that the volume of the lower crust composed of restites and olivine cumulates after the extraction of the middle crust should be significantly larger than is observed suggesting that a part of the lower crust especially the cumulates is seismically a part of the mantle

crustal structure and seismicity of southern tyrrhenian basin abstract in this paper all the travel time data from crustal earthquakes that occurred in the period 1978 1991 along the southern tyrrhenian sea have been re examined in particular 410 local earthquakes recorded at a minimum number of seven seismic stations and 52 shots fired on sea have been utilized to infer a tomographic image of the velocity model beneath a region located in the domain 37 41 39 10 n and 14 10 16 44 e these earthquakes are selected from a database containing about 1000 local earthquakes the results from the inversion of about 9000 travel times confirm the strong lateral variations of the velocity model relative to compressional and shear waves below the volcanic center of the aeolian islands in the upper crust several low velocity bodies are found in agreement with features inferred from seismicity and other geophysical data the 3 d velocity images also show a thickening of the crust from the center of the tyrrhenian sea towards the coasts of sicily and calabria finally hypocenter locations derived from inversion which appear to be significantly less scattered than using 1 d velocity models help to identify with some accuracy two notable fault systems of the southern tyrrhenian basin

horizontal crustal motion in the central and eastern mediterranean inferred from satellite laser ranging measurements four campaigns to acquire satellite laser ranging slr measurements at sites in the mediterranean region have been completed these measurements to the lageos satellite made largely by mobile systems cover a time span beginning in november 1985 and ending in june 1993 the range data from 18 sites in the central and eastern mediterranean have been simultaneously analyzed with data acquired by the remainder of the global laser tracking network estimates of horizontal motion were placed into a regional northern europe fixed kinematic reference frame uncertainties are on the order of 5 mm yr for sites having at least four occupations by mobile systems and approach 1 mm yr for permanently located sites with long histories of tracking the resulting relative motion between sites in the aegean exhibit characteristics of broadly distributed pattern of radial extension but at rates that are about 50 larger than those implied from studies of seismic strain rates based on seismicity of magnitude 6 or greater or across the region the motion estimated for sites in turkey exhibit velocity components associated with the westward motion of the anatolian block relative to eurasia these results provide a present day snapshot of ongoing deformational processes as experienced by the locations occupiedmore by slr systems less

origin and role of major strike slip transfers during plate collision in the central mediterranean variations in the crustal structure along the northern african plate margin have caused different modes of collision with eurasia lateral density variations along the central mediterranean collision zone are expressed in a change of the angle of the downbending african plate and lead to the formation of strike slip transfers in these transition zones that are roughly perpendicular to the trend of the collisional zone in some cases these transfer zones are developed into hinge faults while in others they can be developed into transform faults this process governs the segmentation of the collision zone in the central mediterranean region south of the maghrebian thrust belt in tunisia and sicily through the calabrian arc to the northeastern hellenic arc extending further to the cyprian arc and to the taurus zagros chain

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

crustal and uppermost mantle structure of the bohemian massif based on celebration 2000 data 1 the deep structure of the bohemian massif bm the largest stable outcrop of variscan rocks in central europe was studied using the data of the international seismic refraction experiment central european lithospheric experiment based on refraction celebration 2000 the data were interpreted by seismic tomographic inversion and by two dimensional 2 d trial and error forward modeling of p and s waves additional constraint on crustal structure was given by amplitude modeling using the reflectivity method and gravity modeling though consolidated the bm can be subdivided into several tectonic units separated by faults shear zones or thrusts reflecting varying influence of the cadomian and variscan orogeneses the saxothuringian barrandian moldanubian and moravian velocity models determine three types of crust mantle transition in the bm reflecting variable crustal thickness and delimiting contacts of tectonic units in depth the nw area the saxothuringian has a highly reflective lower crustal layer above moho with a strong velocity contrast at the top of this layer this reflective laminated lower crust reaches depths of 26 35 km and is characteristic for the saxothuringian unit which was subject to eastward subduction the moldanubian in the central part is characterized by the deepest 39 km and the most pronounced moho within the whole bm with a strong velocity contrast 6 9 8 1 km s 1 a thick crust mantle transition zone in the se with velocity increase from 6 8 to 7 8 km s 1 over the depth range of 23 40 km seems to be the characteristic feature of the moravian overthrusted by the moldanubian during variscan collision

a physical model for the origin of volcanism of the tyrrhenian margin the case of neapolitan area abstract the onset of volcanism in the neapolitan area and the tensile tectonics of the tyrrhenian margin of the apennine chain have been related to the opening of the tyrrhenian basin which may have resulted in horizontal asthenosphere flows giving rise in turn to crustal distension local mantle upwellings and ensuing volcanism geological and structural data were taken into consideration the existence of a shallow crust mantle discontinuity in the neapolitan area the onset of volcanism in a graben type structure the distribution of volcanism along three main directions these facts are all consistent with processes of crustal deformation associated with hot masses as well as fracture systems along three branches often separated by a 120 angle such fracture mechanism was therefore analyzed in physical terms on the assumption of an elasto plastic behaviour of the crust and with reference to the limit analysis theorems

the tertiary geodynamical evolution of the aegean arc a paleomagnetic reconstruction abstract the paleomagnetic results obtained in the last 5 6 years from tertiary formations in the aegean domain indicate that the lower miocene arc was almost rectilinear with an e w trend and that its curvature has been acquired tectonically in two major phases during the middle miocene a first phase of deformation is characterized by rotations occurring at the two terminations of the arc clockwise in the west epirus anticlockwise in the east southeastern anatolia a second phase of rotation occurring in the last 5 ma about a pole situated in the southern adriatic sea has affected only the northwestern part the data also indicate that the antalya basin has not been involved in the geodynamical evolution of the arc so that the bey daglari represent its easternmost unit a more complex rotational pattern is observed in the internal zones the large rotations measured in evia 48 and skyros 26 probably occurred in the last 5 ma and result from rotation of fault bounded blocks in a shear zone connecting the north aegean trough to the external arc in the izmir region in the karaburun peninsula of western anatolia and in the island of lesbos significant counterclockwise clockwise or null rotations of coherent blocks have taken place during the neotectonic extensional regime furthermore the values of the inclination obtained from both sedimentary and volcanic oligo miocene formations are systematically shallower than expected on the basis of a geocentered dipole field this suggests that the entire studied area has undergone a northward drift of over 1000 km since the middle miocene

the tyrrhenian apennines system structural setting and seismotectogenesis abstract the available geological geophysical and seismological data of the tyrrhenian apennines system are briefly reviewed and synthesized in a number of sketch maps integrating and comparing these data a large scale simple shear kinematic model is proposed for the tyrrhenian apennines system that is here interpreted as an oblique asymmetric passive continental margin developed during the progressive counterclockwise rotation of the adriatic foreland from the late miocene to the present in the frame of this working hypothesis the thinning and stretching of the tyrrhenian crust were accommodated by progressive eastward motion of extensional allochthonous slices bounded by low angle west dipping oblique shear zones rotating above a common detachment that penetrates into the mantle lithosphere at any given time the most external eastward moving slice is bounded by a transtensional shear zone at the top and by a transpressional one at the bottom the displacement within the hanging wall of the transtensional shear zone is accommodated by high angle normal faults and en echelon grabens the displacement within the hanging wall of the transpressional shear zone is instead accommodated by co axial en echelon sets of folds thrusts and high angle strike slip faults thus the development of the late miocene pliocene pleistocene contractional strain field of the apennines of italy might not be a consequence of complex subduction processes but subordinate to the deformation processes that lead to the progressive opening of the tyrrhenian sea the seismicity of the crustal apennines of italy is analyzed in the frame of the above history of progressive deformation and a seismotectogenetic model is outlined

a contribution in the estimation of tectonic motion in crucial areas the cgs96 slr solution abstract the cgs96 is a global slr solution based on the reduction of the whole available data set for the lageos i and ii satellites starting from 1986 the accurate modelling adopted and the huge quantity of data of continuously growing quality lead to reliable estimates of geodetic and orbital parameters the solution collects a wide variety of parameters daily earth orientation parameters coordinates and site velocities of almost 60 sites plus coordinates for sites with short tracking history orbital parameters and non modelled acceleration for both satellites the core of the paper is the review of the tectonic results and their comparison with the models the pointers of the goodness of the solution are those results regarding sites centrally located on the major plates henceforth comparable to model predictions being a prerequisite for the reliability of the estimates for the crucial sites the tectonic results are particularly interesting in those areas not suitably described by the global models such as the mediterranean periodically occupied by mobile systems

tectonic motion and deformation from satellite laser ranging to lageos satellite laser ranging slr to lageos acquired during the period 1978 1988 has been analyzed to yield estimates of tectonic motion for 22 laser tracking stations situated on seven major plates the analysis is based on the precise modeling of the orbit dynamics of lageos and includes the determination of other geodynamic and nonconservative force model parameters involved in the orbit determination problem at the centimeter level site velocities were recovered from station positions determined each calendar quarter using a network adjustment procedure which maintains the reference frame within the stable interior of tectonic plates the recovered motions indicate good agreement with existing estimates of stress fields particularly across northern europe the eastern pacific and in the basin and range province of north america a comparison of the intersite motions for stations centrally located on separate plates between slr and those implied by the nuvel 1 geologic motion model yield a strong positive correlation of 0 989 and a 3 7 scale difference which may be attributable to recent changes in relative velocities or geologic time scale uncertainties sites located at or within 250 km of convergent plate boundaries have additional components of motion indicating a need for further tectonic modeling beyond that provided by simple rigid plate motions for lines crossing the north atlantic the san andreas fault and within the basin and range province the geodesic rates determined by slr are in good agreement with those determined by very long baseline interferometry an alternative space geodetic technique

karst aquifer evolution in fractured porous rocks the evolution of flow in a fractured porous karst aquifer is studied by means of the finite element method on a two dimensional mesh of irregularly spaced nodal points flow within the karst aquifer is driven by surface recharge from the entire region simulating a precipitation pattern and is directed toward an entrenched river as a base level during the early phase of karstification both the permeable rock matrix modeled as triangular elements and fractures within the rock matrix modeled as linear elements carry the flow as the fractures are enlarged with time by chemical dissolution within the system calcite carbon dioxide water flow becomes more confined to the fractures this selective enlargement of fractures increases the fracture conductivity by several orders of magnitude during the early phase of karstification thus flow characteristics change from more homogeneous pore controlled flow to strongly heterogeneous fracture controlled flow we study several scenarios for pure limestone aquifers mixed sandstone limestone aquifers and various surface recharge conditions as well as the effect of faulting on the aquifer evolution our results are sensitive to initial fracture width faulting of the region and recharge rate

structure and growth of the izu bonin mariana arc crust 1 seismic constraint on crust and mantle structure of the mariana arc back arc system 1 a high resolution seismic velocity model is presented for the crust and upper mantle of the mariana arc back arc system mabs based on active source seismic profiling the major characteristics are 1 slow mantle velocity of 8 km s 1 in the uppermost mantle especially and deep reflectors under the mariana arc ma and the west mariana ridge wmr 2 a deep reflector in the upper mantle beneath the relative thick crust of the mariana trough mt axis 3 distribution of lower velocity lower crusts 6 7 6 9 km s 1 beneath the volcanic front and adjacent to the mt and 4 high velocity lower crust 7 2 7 4 km s 1 beneath the boundary regions between the ma and mt and between the wmr and the parece vela basin pvb adding to structural characteristics of crust and upper mantle beneath the mabs of the characteristics described above characteristic 1 suggests that the origins of the slow mantle velocity and the deep reflectors be explained by transfer of the lower crustal residues to the upper mantle across the moho considering that the wmr is extinct arc currently on the other hand characteristic 2 suggests that the origin of deep reflectors beneath the mt axis might be lower velocity materials due to the diffractive signals with strong amplitudes characteristic 3 suggests that the lower velocity lower crust advanced crustal growth and characteristic 4 suggests that the high velocity lower crust beneath arc back arc transition zone is composed of mafic ultramafic materials created by extensive partial melting of mantle peridotites or last stage of the arc magmatism rather than serpentinized peridotite

early development of karst systems 2 turbulent flow a simulation model developed to explore patterns of fracture enlargement within incipient limestone karst aquifers has been extended to turbulent flow in contrast to the highly selective passage enlargement that occurs early in cave network development under laminar flow the transition to turbulent flow results in more general passage enlargement leading to maze networks when initial fractures are large and hydraulic gradients are high these results support previously published hypotheses for the development of maze patterns including formation within structural settings that have created initially large fractures or within flow systems periodically inundated by flooding maze development is also favored under turbulent flow when passages are entirely water filled and where the groundwater flow system is long lived by contrast branched patterns are most common when passages become free surface subterranean streams because depression of the piezometric surface along main passages downcutting along main passages and possible infilling with sediment of side passages limit the sharing of discharge among interconnected fractures or bedding planes that promote maze development

seismotectonics of the calabrian arc abstract relocation of intermediate and deep earthquakes of tyrrhenian sea area through joint hypocenter determination for the period 1962 1979 has allowed a more detailed definition of the geometry of this peculiar benioff zone earthquakes dip along a quasi vertical plane to 250 km depth there is a 50 dip in the 250 340 km depth range and a low dip angle to 480 km depth the structure sketched from the hypocenters is almost continuous but most energy has been released in the 230 340 km depth interval an evaluation of fault plane solutions of intermediate earthquakes in this area indicates predominance of down dip compressions in the central part of the slab at the border strike slip motion occurs independent of depth some earthquakes that occurred at intermediate depth less than 100 km along the ionian margin of calabria show predominance of reverse faulting with the p axis oriented se nw however shallow earthquakes in the calabria sicily region indicate a more complex motion with predominance of normal faulting a possible interpretation of these features according to the available geological history which involves subduction of continental lithosphere is discussed

physical properties and state of the crust and upper mantle of the eastern mediterranean sea deduced from geophysical data abstract by evaluating the geophysical information available for the eastern mediterranean sea ems a crustal thickness map and some conclusions as to the nature of the crustal type were drawn it was found that the ionian abyssal plain is floored by an oceanic type of crust which is 14 km thick and covered by sediments of the order of 8 km thick the herodotus abyssal plain in the levantine sea is floored by a crust 22 km thick and covered by sediments ranging between 10 and 15 km thick the eastern mediterranean rise extending more or less continuously from the apulian plateau to rhodes and the south of the antalya basin is of a thickness ranging between 28 and 34 km the thickness of its sedimentary cover is of the order of 10 km the borders of the eastern mediterranean sea are built up of thick continental crust for example the hellenides of western greece range between 40 and 44 km thick and western turkey has a similar crustal thickness the crust of sicily also exceeds 40 km whereas the southern and eastern borders of the ems are approximately 30 32 km thick tectonically the northern border of the ems is built up of active continental margins defined by the calabrian hellenic and cyprus antalya arcs whereas the southern border represents a passive continental margin controlled mainly by subsidence and stretching to the east the dead sea megashear limits the area the deep basins of the eastern mediterranean sea are tectonically controlled by subsidence and partial stretching the mediterranean ridge or rise is still an area of dispute regarded by some authors as a subsiding continental fragment and separated from the hellenic arc by the hellenic trench whereas others consider it to be a zone of crustal shortening thickened mainly by thrusting both the western and southwestern borders of the mediterranean rise and the hellenides are controlled by compressional processes similar to those deforming the calabrian arc the stravo and pliny trenches to the east southeast border of the hellenic arc are partly affected by strike slip movements various plate tectonic models of the area have been proposed by several authors though the complexity of the deformation hardly permits reliable reconstructions the lack of reliable paleomagnetic information and the absence of linear magnetic anomalies do not favour the application of plate tectonic concepts vertical processes due to the uprising of lithothermal systems below the hellenic and calabrian arcs may also be regarded as the driving force controlling the present day deformation

early development of karst aquifers on percolation networks of fractures in limestone we have modeled flow and dissolution processes within percolation networks representing stochastic primary fracture systems in limestone at the beginning of karstification flow is evenly distributed on all fractures available as the system develops by dissolutional widening of the fractures preferred flow pathways evolve which attract more and more flow until at breakthrough the total flow rate increases dramatically these breakthrough times have been investigated with regard to their dependence on the initial fracture aperture width the dimension of the evolving karst aquifer hydraulic gradients connectivity of the percolation network and the chemical parameters such as higher order rate constants and exponents and equilibrium concentration they exhibit a behavior similar to that of breakthrough times for one dimensional conduits dreybrodt 1996 our results show that the structure of the evolving karst aquifer is determined by the initial geological setting however the final conduits are selected from competing pathways with potential breakthrough times close to each other whereby the details of the distribution of undersaturation with respect to calcite play an important role

seismological evidence for variable growth of crust along the izu intraoceanic arc 1 the processes that create continental crust in an intraoceanic arc setting are a matter of debate to address this issue we conducted an active source wide angle seismic study to examine along arc structural variations of the izu intraoceanic arc the data used were acquired over a 550 km long profile along the volcanic front from sagami bay to tori shima the obtained structural model showed the existence of felsic to intermediate composition middle crust with a p wave velocity vp of 6 0 6 5 km s 1 in its upper part and 6 5 6 8 km s 1 in its lower part the thickness of the middle crust varied markedly from 3 to 13 km the underlying lower crust also consisted of two layers vp of 6 8 7 2 km s 1 in the upper part and vp of 7 2 7 6 km s 1 in the lower part the upper of these layers was interpreted to consist of plutonic gabbro and the lower layer was interpreted to be mafic to ultramafic cumulates average crustal velocities calculated from our model showed remarkable lateral variation which correlated well with arc volcanism low average crustal seismic velocities 6 7 km s 1 due to thick middle crust were obtained beneath basaltic volcanoes e g o shima miyake jima hachijo jima aoga shima while higher average velocities 7 1 km s 1 were obtained beneath rhyolitic volcanoes e g nii jima kurose south hachijo caldera myoji knoll and south sumisu caldera we concluded from these observations that continental crust grows predominantly beneath the basaltic volcanoes of the izu arc and that rhyolitic volcanism may be indicative of a more juvenile stage of crustal evolution or remelting of preexisting continental crust or both

power law distributions of discharge mass and energy in river basins river networks constitute dissipative systems with many spatial degrees of freedom previous work by mandelbrot 1983 and bak et al 1987 1988 1990 suggests that such systems will follow power law distributions in their mass and energy characteristics it is shown that this is the case for river networks where the exponent in the distribution p x x x is approximately equal to 0 45 and 0 90 for discharge and energy respectively in the case of several networks analyzed in north america when these variables are calculated for each individual link throughout the drainage network an explanation of the values of is offered based on the fractal structure of rivers and on principles of energy expenditure in river basins

fractal structures as least energy patterns the case of river networks natural drainage networks like river basins exhibit fractal and multifractal properties this work shows that these properties evolve from arbitrary initial conditions by minimizing the local and global rates of energy expenditure in the system this suggests that many fractal structures may arise as a natural consequence of least energy dissipation requirements

geochemical and petrological evidence of the subduction of delaminated adriatic continental lithosphere in the genesis of the neogene quaternary magmatism of central italy abstract serri g innocenti f and manetti p 1993 geochemical and petrological evidence of the subduction of delaminated adriatic continental lithosphere in the genesis of the neogene quaternary magmatism of central italy in m j r wortel u hansen and r sabadini editors relationships between mantle processes and geological processes at or near the earth s surface tectonophysics 223 117 147 the neogene quaternary magmatism of the northern apenninic arc took place in four phases separated in space and time which become progressively younger from west to east phase i 14 ma phase ii 7 3 6 0 ma phase iii 5 1 2 2 ma phase iv 1 3 0 1 ma this magmatism is the result of the activation of three physically separate sources 1 the adriatic continental crust extracted from the mantle in the late proterozoic 2 a strongly refractory recently k enriched harzburgitic mantle located in the mechanical boundary layer mbl of the lithosphere and 3 a recently metasomatized cpx rich mantle compositionally variable from iherzolite to wehrlite clinopyroxenite interpreted as an ephemerally k enriched asthenosphere the adriatic continental crust is the dominant source of the acid plutonic and volcanic rocks of the tuscan region the acid magmatism is mostly found inside an ellipsoidal area about 150 300 km centred on giglio island here defined as the tuscan crustal dome within this area mantle derived magmas unaffected by important crustal contamination processes and mixing with crustal anatectic melts have so far not been found pure crustal magmas are rare but are represented for example by some of the san vincenzo and roccastrada rhyolites virtually all the tuscan acid centres show evidence of mixing with potassic mantle derived magmas major and trace elements as well as 87 sr 86 sr and 143 nd 144 nd data on primitive rocks mg 65 reveal two groups of mantle derived magmas these define two distinct mantle enrichment trends both essentially due to the additions of k rich components which metasomatized separate compositionally diverse upper mantle sectors in both cases the most remarkable mineralogical effect of these enrichment processes is the production of variable amount of phlogopite through reaction between fluids and or melts with the mantle the rocks of group i ol hy and q normative lamproites ultrapotassic high mg latites ultrapotassic shoshonites and shoshonites saturated trend are considered to be derived by partial melting at low pressure 87 sr 86 sr 0 717 ce sr 0 3 and k 2 o na 2 o 6 7 and low ratios of 143 nd 144 nd 0 5121 0 5120 and ba la 87 sr 86 sr 0 712 and k 2 o na 2 o 8 9 values and low 143 nd 144 nd ba la 0 10 ratios these constraints do not allow to exclude a complete identity between the k rich components which metasomatized the mantle sources of the saturated and undersaturated trend magmas the geochemical and isotopic features of the components that metasomatized the mantle sources of the northern apenninic arc magmatism can be explained by a geodynamic process which causes a large amount of crustal materials to be incorporated within the upper mantle we propose that the delamination and subduction of the adriatic continental lithosphere related to the still ongoing northern apennine continental collision provide a viable mechanism to explain the genesis and eastward discontinuous migration of the magmatism in central italy the subduction of delaminated lithospheric mantle with lower crustal slivers would have exposed uppermost mantle adriatic mbl and crustal units previously imbricated in the apennine chain to the heating advected by the upwelling of a recently and ephemerally k enriched asthenospheric mantle wedge and by the underplating of magmas derived from it we consider that the diapiric uprising of a hot crustally contaminated asthenosphere occurs in the wake left above the sinking of the adriatic delaminated subducting continental lithosphere the delamination subduction process of the adriatic lithosphere has probably started in the early middle miocene but earlier than 15 14 ma ago as indicated by the age and petrologic characteristics of the first magmatic episode sisco lamproite of the northern apennine orogenesis

foreshock statistics and their possible relationship to earthquake prediction in the italian region this study focuses on the foreshocks of earthquake sequences recorded by the italian national seismological network between 1975 and 1991 we consider as foreshocks events exceeding a given threshold magnitude that follow a period of quiescence and come before a mainshock occurring within a given time distance range the total number of potential foreshocks identified by the algorithm depends on the size and the duration of the predefined quiescence area whereas the number of mainshocks preceded by foreshocks depends also on the size of the area in which the event is expected and the duration of the alarm period our aim was to optimize the choice of the parameters defining potential foreshocks as precursors of stronger earthquakes in order to improve their validity and reliability a preliminary investigation carried over the whole italian territory allowed the definition of zones where foreshocks mainshocks series are likely to occur one of these zones is an area of about 32 000 km2 in central italy including a total of 2671 events of m 2 5 where there is a significant tendency of moderate shocks to be followed at short distance and in short time by larger shocks our method would lead to issuing 63 alarms with the optimal definition of foreshocks as events of magnitude exceeding 3 0 after at least 80 days of quiescence in an area of 140 km radius the rate of occurrence for mainshocks of magnitude exceeding 4 0 during the following 48 hours in the specified area of 30 km radius is 6 of 23 events the corresponding probability gain is about 150 for comparison another larger zone po valley with 453 events of m 2 5 exhibits only a rate of 1 of 82 precursors in this area most events are single shocks our analysis shows that the foreshock activity can be regarded as a significant earthquake precursor so suggesting that real time observation of seismicity can be used to improve the quality of an earthquake prediction system

continental crust crustal underplating and low q upper mantle beneath an oceanic island arc a detailed structural model of the crust subducting slab and underlying upper mantle across the northern izu ogasawara bonin island arc system is derived from a marine seismic reflection and ocean bottom seismographic refraction survey and subsequent forward modeling combined with tomographic inversion the model indicates that the crust is thickest beneath the presently active rift zone and a granitic crust may have formed in the mid crust a highly attenuative mantle that is one with low quality q seems to be confined mainly beneath the presently active rift zone in contrast high p wave velocity persists in the lower crust between the forearc and eastern margin of the back arc basin suggesting a large scale magma input responsible for the arc formation

modeling three dimensional karst aquifer evolution using different matrix flow contributions summary we have developed the program package karstaquifer which simulates flow and transport in a three dimensional transient karst aquifer consisting of fractures and matrix elements the fractures can be enlarged by chemical dissolution of calcite increasing the secondary permeability of the karst aquifer boundary conditions for our model setup are guided by published benchmark models for karst aquifer evolution in two dimensions length and width with a 100 m high hydraulic head difference across the model domain responsible for relatively fast evolution of the aquifer we are interested in the effect of the third dimension on the evolution of the karst aquifer especially the effect of matrix flow with a matrix defined either as porous medium or as fine fracture system or both we first discuss our model results using a pseudo 3d setup to be able to directly compare results to the 2d benchmark scenarios published we then discuss real 3d models with a prominent fault located in the central part of the aquifer connecting input and output regions finally we replace the prominent fault with a statistical fracture diameter distribution our results compare well with existing 2d scenarios and the additional third dimension offers new insights into the evolution of karst aquifers especially the role of matrix flow under fixed head boundary conditions in their early phases can be studied in more detail

contemporary global horizontal crustal motion summary an analysis of satellite laser ranging slr data to the lageos satellite has yielded improved estimates of the horizontal motion for a subset of 34 tracking sites within the global tracking network the analysis called sl8 3 utilized data acquired between 1980 january and 1993 june by the global network composed of 71 sites the solution design provides for the simultaneous estimation of site positions and their velocities within a pre defined kinematic frame the solution is statistically rigorous and retains the full correlation information content least squares estimates of relative poles of rotation which are used to model the motion of one plate relative to another were made based on the slr estimated velocities for sites known to be well away from deformation zones the resulting slr based relative rotation poles differ slightly from those of nuvel 1 but in general indicate that the magnitude of the slr implied velocities is slower than those implied by nuvel 1 consistent with the 4 5 per cent slowing in relative spherical rates noted in earlier comparisons spherical rates between sites in western north america support models of extension in the basin and range province and the rotation of the sierra nevada microplate an analysis of the spherical rates crossing the north atlantic shows that sl8 3 estimated extension between north america eurasia sites is generally smaller than those implied by nuvel 1 meanwhile sl8 3 rates between north america africa sites are in better agreement with nuvel 1 although they are not so well determined the maintenance and ongoing monitoring of global slr site kinematics provides a well defined global reference which will aid in combination global kinematic solutions where information from other technologies are merged e g very long baseline interferometry and global positioning system and in providing the context for densification studies of regional kinematics derived from terrestrial and global positioning system observations

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

early development of karst systems 1 preferential flow path enlargement under laminar flow modeling of flow and solutional processes within networks of interconnected conduits in limestone aquifers indicates that enlargement occurs very selectively during the early stages of karst aquifer development under laminar flow if initial flow paths are uniform in size almost all enlargement occurs along a single set of connected conduits that lie along a direct path between recharge and discharge locations and are aligned along the hydraulic gradient with a sufficiently large variation in initial aperture widths enlargement occurs along the flow path offering the least resistance to flow but since flow rates in laminar flow are proportional to the fourth power of diameter but only linearly proportional to hydraulic gradient the preferentially enlarged set of fractures may follow an indirect path results disfavor earlier suggestions that nonselective cave patterns result from artesian flows at least under laminar flow conditions and that all passages should be competitive until the onset of turbulent flow

upper crustal structure of the larderello geothermal field as a feature of post collisional extensional tectonics southern tuscany italy abstract reflection seismic profiles crossing the larderello geothermal field permit the distinction of three different seismic facies units in the upper continental crust the upper 3 4 km of the crust is characterized by low reflectivity its base corresponding to a reflector referred to as the k horizon and recognized in many other areas of southern tuscany beneath this reflector a seismic facies of 0 8 1 0 twt thickness is characterized by strong convergent and divergent reflections forming a lozange shaped geometry the lowermost seismic facies is characterized by almost horizontal reflections based on the distribution of the hypocentral microearthquakes temperature data recorded in deep boreholes and the geometry of normal faults the k horizon is explained here as a kinematically active rheological boundary which separates a brittle upper part from a ductile lower part according to this hypothesis the k horizon and the lozange reflections could originate from a mylonite band located at the contact between two geological bodies characterized by different rheological behavior it is inferred that this horizon acts as a decoupling plane in the upper continental crust it developed as a consequence of the extensional tectonics and the high heat flow which characterize southern tuscany

reappraisal of paleomagnetic data from gargano south italy vandenberg j 1983 reappraisal of paleomagnetic data from gargano south italy in e mcclelland brown and j vandenberg editors palaeomagnetism of orogenic belts tectonophysics 98 29 41 the platform limestones of apulia italy outcropping in the gargano peninsula have been restudied paleomagnetic research has been carried out on upper cretaceous lower cretaceous and jurassic rocks despite the low intensities of the nrm 10 100 pa m all samples 268 could be cleaned by stepwise a f and or thermal demagnetization treatments nrm directions could be determined accurately and reproducibly for 85 of the samples using a sct cryogenic magnetometer and double precision measuring procedures nrm of the jurassic limestone is carried by secondary haematite and the results are therefore rejected from further consideration the upper and lower cretaceous limestones have an nrm carried by magnetite minor bedding tilt corrections improve the grouping of the site mean results the upper cretaceous scaglia limestone turonian senonian reveals a characteristic mean direction of decl 327 7 incl 38 2o a ss 4 3 21 sites while the lower cretaceous maiolica limestone neocomian aptian albian reveals a characteristic mean direction of decl 303 1 o incl 35 1 as s 8 7o 8 sites the cretaceous results show a post aptian albian counterclockwise rotation of about 25 which is expressed by the smeared distribution of the late cretaceous site mean results and a post senonian i e tertiary counterclockwise rotation of the same amount with respect to the pole these results are in excellent agreement with contemporaneous paleomagnetic results from other peri adriatic regions a tertiary counterclockwise rotation of all the stable adriatic block is strongly supported by the new results

adriatic flexure and seismotectonics in southern italy abstract the morphological features of the mesozoic platform in the apulo garganic region and beneath the southern apennines have been tentatively interpreted as consequences of the flexure of the adriatic lithosphere to make a rough quantitative check of this hypothesis and to provide a possible interpretation to the main seismotectonic features in this area the flexural pattern of a thin elastic lithospheric plate loaded at one edge by a bending moment has been determined the satisfactory fit between the theoretical results and observations mainly relating to the morphology of the mesozoic platform the distribution of vertical movements and the concentration of strongest earthquakes within a narrow band in the apennines leads us to think that the tectonic premise is feasible

karst aquifer evolution in fractured rocks we study the large scale evolution and flow in a fractured karst aquifer by means of a newly developed numerical method a karst aquifer is discretized into a set of irregularly spaced nodal points which are connected to their set of natural neighbors to simulate a network of interconnected conduits in two dimensions the conduits are allowed to enlarge by solutional widening the geometric flexibility of this method along with a simplified model for the dissolution kinetics within the system water carbon dioxide calcite enables us to study both laminar and turbulent flow in a karst aquifer during its early phase of evolution a sensitivity analysis is conducted for parameters such as conduit diameter hydraulic pressure differences and recharge conditions along the surface of the aquifer and shows that passage evolution depends strongly on the recharge condition and the amount of water available under fixed hydraulic head boundary conditions an early single passage system develops under laminar conditions and is transformed into a maze like passage system after the onset of turbulence fixed recharge boundary conditions are more likely to result in a branchwork like passage system although the addition of distributed recharge may lead to a maze like system of secondary passages

the valencia trough and the origin of the western mediterranean basins abstract evolutionary models for the valencia trough must be necessarily related to the neogene present geodynamics of the western mediterranean basins all these basins occupy new space created in the wake of the westward translation of the alboran block and the counter clockwise rotation of the corso sardinian block this escape tectonics microplate dispersal model can account for the co existence and progressive migration of compressional and extensional strain fields within the africa europe broad zone of convergence in this escape tectonics model the valencia trough has resulted in a complex evolution which includes 1 latest oligocene early miocene rifting along the catalan valencian margin due to the opening of the gulf of lions 2 almost simultaneous early miocene transpressive thrusting in the balearic margin related to the initiation of displacement of the alboran block and 3 late miocene generalized extension as a consequence of the opening of the south balearic basin

regularities in time and space distribution of seismicity in the periadriatic regions tectonic implications abstract the pattern of energy release in the very active seismic belt along the hellenides and southern dinarides which is interpreted as the main collision boundary between the adriatic plate and the balkan regions has been characterized in the last three centuries by a fairly regular succession of active and quiescent phases statistical tests have indicated a very low probability of observing this kind of pattern associated with a random generation of earthquakes the discontinuous release of seismic energy might be connected with a periodic activation of the underthrusting of the adriatic mesozoic platform beneath the dinarides hellenides belts this effect could condition the kinematic behavior of the whole adriatic plate this hypothesis might explain the fact that the italian regions lying on the other side of the adriatic platform also show a seismic energy release pattern characterized by alternating active and quiescent periods which furthermore proves to be well correlated in time with those occurring at the adriatic balkan border

the medina wrench a key to the kinematics of the central and eastern mediterranean over the past 5 ma the medina wrenth in the central mediterranean is a transform fault connecting the plate collision in northwest africa and northern sicily with that occurring at the aegean plate boundary south of greece the more than 800 km long crescent shaped wrench zone is currently seismically quiet but exhibits major deformation since 5 ma within a belt 30 100 km wide it forms the southern boundary of two microplates moving eastward with respect to africa and europe a simple plate rotation model constrained by recent paleomagnetic data indicates that a continental iblean microplate and a hybrid continental oceanic ionian microplate separated along the malta escarpment have rotated anticlockwise by 11 and 12 respectively around poles in southern italy these rotations involved some 100 km of dextral eastward movement relative to africa of the ionian basin north of the medina wrench since 5 ma combining the published 26 clockwise rotation of the peloponnesus and northwest half of the aegean with the 12 anticlockwise rotation of the ionian microplate results in a a 99 agreement between the length of the seismic benioff zone beneath greece and the total convergence of the microplates and b an average rate of convergence across the aegean plate boundary southwest of the peloponnesus of 6 6 1cm a 1 since the miocene relative motion between microplates in a collision zone thus may be as much as 6 times faster than convergence between the major plates which spawned them and they can be considered rigid to the first order over the time span involved

three dimensional q structure beneath the kanto tokai district japan the q structure of the upper mantle beneath the kanto tokai district central japan where the eurasian pacific and philippine sea plates are converging is investigated from seismic p and s wave spectral ratios by means of a three dimensional 3 d inversion method it is found that the subducting philippine sea and pacific plates are characterized by high q zones a high q zone also exists between the philippine sea plate and the pacific plate to the east of the volcanic front on the other hand a low q zone in the uppermost mantle extends westward horizontally from the volcanic front under the philippine sea plate and appears to exist over the wedge mantle beneath the western tokai district a very low q value obtained here is roughly equal to the average qvalue in the low velocity layer derived from surface wave and free oscillation data a low q region that suggests a magma chamber under active volcanoes is not detected in the crust

three dimensional attenuation structure beneath the northeastern japan arc estimated from spectra of small earthquakes abstract a fine scale three dimensional attenuation structure beneath the northeastern japan arc has been obtained using a joint inversion for source parameters site response and q values data used for this study are p wave spectra of microearthquakes occurring in the subducting pacific plate the subducting plate is found to have higher q values than the overlying mantle there is an along arc variation in the distribution of low q zones in the crust and the mantle wedge within the study area for the southern part of the study area low q zones are distributed in the crust beneath the volcanic front they extend into the mantle wedge and become deep toward the west that is toward the backarc region on the other hand the northern part of the study area has low q zones at two depth ranges at shallower depths just beneath the volcanic front and at the deeper part of the mantle wedge beneath the backarc region the region without active volcanoes along the volcanic front has relatively high mantle q values seismic activity in the lower plane of the double planed deep seismic zone is high beneath this relatively high q region of the mantle wedge spatial distribution of low q zones found in the present study is nearly consistent with that of the low velocity zones estimated from studies of travel times tomography partial melting zones in the mantle wedge whose existence has been suggested from the study of seismic velocity structure and laboratory experiments are located in the low q zones obtained in the present study these results suggest that spatial distribution of q values is closely related to heterogeneous distribution of temperature in the mantle wedge

geodynamics of the emile baudot escarpment and the balearic promontory western mediterranean abstract the 348 km long 105 155 km wide and 1000 2000 m high northeast trending balearic promontory separates the valencia trough to the northwest from the south balearic algerian basin to the southeast it consists of three blocks ibiza at the southwest end mallorca in the center and menorca at the northeast end of the promontory the ibiza and mallorca blocks were thrust faulted and folded in the miocene the menorca block appears to be undisturbed but strata within the transform separating the mallorca and menorca blocks are folded and faulted miocene and younger volcanic pinnacles also are extensive along the transform separating the ibiza and mallorca blocks we infer that the tectonic features on the balearic promontory are the creations of the late oligocene miocene southeast migration of the blocks making up the promontory way from the spanish margin leading to the opening of the valencia trough behind them the westward displacement of the alboran microplate along the emile baudot escarpment on the southeast side of the promontory and the opening of the south baleric algeria basin behind it and the clockwise rotation of the ibiza and mallorca blocks produced by the passing alboran microplate

repeated gps surveys across the ionian sea evidence of crustal deformations summary geodetic evidence of crustal deformation in the ionian area detected by gps surveys is given in this paper a network consisting of nine geodetic sites crossing the ionian sea from calabria southern italy to northwestern greece was repeatedly surveyed starting in 1991 within the framework of the tyrgeonet project the results obtained from processing data from three gps campaigns performed on the same network in 1991 1994 and recently in 1995 show significant changes in the positions of five sites the deformations in terms of displacements coordinate differences are obtained by applying a rigorous statistical approach that analyses their significance by an original iterative procedure based on the classical f fisher test although more substantial geophysical conclusions require more observations the estimated relative displacement pattern is generally coherent with the features of the main tectonic structures identified for this area the detected deformations for the greek sites confirm the activity of the kephalonia right lateral transform fault and a rightlateral motion of the mattinata fault northern apulia seems to have been detected by the italian sites moreover within the time span analysed the site of matera shows a different behaviour from the three adriatic sites tremiti m s angelo and specchia cristi since relative displacements among matera and these sites were detected this fact may indicate the weakness of the assumption reported in some papers that matera could be a representative site of the motion of the whole adriatic plate furthermore the site of specchia cristi shows the maximum relative displacement in the network with a vector magnitude of about 5 cm with a 3 cm confidence interval at the 95 per cent level therefore even if some additional gps observations are needed to achieve a clearer picture of the tectonic behaviour of the ionian sea area the detected relative displacement pattern of the italian sites agrees with a possible rotational behaviour of the apulian platform with respect to the adriatic plate as already hypothesized by finetti 1982

mesozoic and cenozoic rocks from malta escarpment central mediterranean sedimentary rocks of triassic neogene age are present on the malta escarpment of the eastern mediterranean upper triassic dolomitic limestones of shallow water origin at depths between 2 5 and 3 5 km are similar in lithofacies to coeval platform carbonates of the siracusa syracuse belt of southern sicily jurassic rocks include lower middle liassic shallow water limestones followed by condensed hemipelagic lime deposits indicative of sinking and starving of the former platform cretaceous materials are represented by both red marls rich in planktonic faunas and reworked volcaniclastic breccias including shallow water skeletal material paleogene rocks are both shallow water limestones with corals algae and bivalves and redeposited calcarenites of lithofacies similar to those from surface and subsurface of the ragusa zone oligocene lower miocene rocks from the escarpment are also similar in lithology to the coeval ragusa deposits tortonian is represented by hemipelagic marls indicating open marine environment pervasive dolomitization on lime crusts and on initial stage fissure fillings with strongly positive isotopic oxygen ratio is thought to be a product of messinian evaporitic drawdown pliocene sediments belong to the trubi facies and consist of pelagic foraminiferal chalk an impressive vertical relief existed by miocene times as attested by messinian crusts and veins on or in rocks as old as late triassic our data do not provide evidence that this morphologic feature necessarily coincides with a continent ocean transition the present escarpment was produced by faulting erosion and defacement

the strain field in northwestern greece and the ionian islands results inferred from gps measurements abstract recent crustal movements detected by the analysis of repeated satellite geodetic measurements reflect the ongoing geodynamic processes in the alpine mediterranean area superimposed on the large scale counterclockwise rotation of the african plate complex dynamic processes are affecting the lithospheric fragments between the african and eurasian plates key features to better understand the driving forces and associated seismic activity in the africa eurasia collision zone are the calabrian and hellenic arcs in this paper geodynamic investigations along the west hellenic arc are discussed they are based on two epochs 1989 and 1993 of satellite geodetic measurements carried out using the us global positioning system gps the results are presented in terms of relative displacements and strain rates within the time span of 4 years southwestern greece has moved to the southwest relative to southeastern italy by an average of 120 mm increasing from 80 mm at lefkada in the center of the ionian islands to 160 mm at the peloponnesus the maximum strain rate is 0 18 strain a located in the vicinity of lefkada where anomalously high earthquake activity is observed the data provide strong evidence for dextral strike slip motion on the order of 25 mm a along the kephalonia fault zone kfz the deformation field of the kfz is interpreted as a transition zone between the kinematics of the apulian platform and the west hellenic fold and thrust belts

amplitude modeling of the seismic reflectors in the crust mantle transition layer beneath the volcanic front along the northern izu bonin island arc the izu bonin island arc is a typical oceanic island arc formed by subduction of the pacific plate beneath the philippine sea plate although some crustal structures of this island arc have been identified detailed information about the region between the deeper crust and uppermost mantle especially the crust mantle transition layer has been inadequate to elucidate a crustal growth model comparison of the observed and synthetic waveforms of wide angle seismic data yielded velocity contrast values of the top and bottom of this transition layer beneath the volcanic front along the northern izu bonin island arc using those data we clarify the nature of the crust mantle transition layer the top of the crust mantle transition layer has a velocity contrast value of about 0 4 km s in the southern area extending from kurose hall to tori shima along the northern izu bonin island arc except for the northern area extending from nii jima to kurose hall 0 25 km s the velocity contrast value at the bottom of this transition layer is large 0 4 km s between nii jima and kurose hall and small 0 2 km s from kurose hall southward these results and the average p wave velocity in the crust mantle transition layer indicate that this transition layer beneath the volcanic front along the northern izu bonin island arc is a mixture of mafic residues and olivine cumulates formed during crustal growth furthermore the variation of the velocity contrast at the top and bottom of this transition layer and the average p wave velocity in this layer along this arc imply that this layer in the southern area extending from kurose hall southward has a larger ratio of mantle materials olivine cumulates to mafic residues than that in the northern area extending from nii jima to kurose hall the moho along the volcanic front in the oceanic island arc probably has a complex signature as suggested by the crust mantle transition layer comprising a mixture of mafic residues and olivine cumulates

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

seismic imaging of a convergent continental margin and plateau in the central andes andean continental research project 1996 ancorp 96 1 a 400 km long seismic reflection profile andean continental research project 1996 ancorp 96 and integrated geophysical experiments wide angle seismology passive seismology gravity and magnetotelluric depth sounding across the central andes 21 s observed subduction of the nazca plate under the south american continent an east dipping reflector nazca reflector is linked to the down going oceanic crust and shows increasing downdip intensity before gradual breakdown below 80 km we interpret parts of the nazca reflector as a fluid trap located at the front of recent hydration and shearing of the mantle the fluids being supplied by dehydration of the oceanic plate patches of bright quebrada blanca bright spot to more diffuse reflectivity underlie the plateau domain at 15 30 km depth this reflectivity is associated with a low velocity zone p to s wave conversions the upper limits of high conductivity and high vp vs ratios and to the occurrence of neogene volcanic rocks at surface we interpret this feature as evidence of widespread partial melting of the plateau crust causing decoupling of the upper and lower crust during neogene shortening and plateau growth the imaging properties of the continental moho beneath the andes indicate a broad transitional character of the crust mantle boundary owing to active processes like hydration of mantle rocks in the cooler parts of the plate margin system magmatic underplating and intraplating under and into the lowermost crust mechanical instability at moho etc hence all first order features appear to be related to fluid assisted processes in a subduction setting

spreading of tracer plumes through confined telogenetic karst aquifers a model summary to calculate spreading of a tracer or contaminant through an aquifer all details of the aquifer e g distribution of hydraulic parameters must be known this is not possible in nature to study the spreading of plumes through karst we have used a digital model of a confined karst aquifer at different stages of early karstification in these models all details such as fracture aperture widths their lengths and widths and the hydraulic boundary conditions are known therefore the flow velocity of water can be calculated in each fracture using this information a particle tracking method is employed to calculate the propagation and spreading of a plume caused by an instantaneous input pulse into selected regions of the aquifer from this information the time dependence of the outflow of particles from any selected region is obtained this function represents the transfer response function for an instantaneous dirac function input two digital karst models are designed in the first homogeneous one the aperture widths of the fractures are statistically distributed but of similar width in the second a coarse percolating net of prominent fractures with larger constant aperture width is embedded into the dense net of narrow fissures propagation of the plumes and the transfer response function are presented at the onset of karstification and at different times of karst evolution if particles are injected at the entrance of evolving karst channels propagating towards the output boundary tracer breakthrough times increase with increasing time of karst evolution until shortly before breakthrough of the karst conduit they drop to half of their maximal value with increasing evolution of the karst aquifer the hydraulic heads are redistributed and regions of low hydraulic gradients in the upstream side of the aquifer are created particles injected into fractures which have stopped dissolutional widening of their aperture widths and are located in regions of low gradient are kept in these regions for long times in the order of 100 years until they have propagated towards regions of high hydraulic heads where a fan like plume develops along the pathway of steepest gradient

redistribution of recent collision push and ridge push in central europe insights from fem modelling summary 2 d elastic finite element models of the recent stress field of central europe are built to evaluate the loads exerted on the continental boundary and the magnitude of tectonic stresses within the continental part of the plate the models comprise 24 tectonic blocks their stiffness is either constant throughout the model or varies from block to block 16 fault zones and 12 geologically significant boundary segments we have obtained a relatively unique balance of external tectonic forces by 1 careful adjustment of calculated stress directions and regimes to complex pattern of stress from data and 2 by calibration with gravitational potential energy a high level of compression ca 9 10 12 nm 1 exerted to the short ionian side of the adriatic indenter is crucial for the stress field pattern in central europe the adria microplate rotates due to eccentricity between the africa push from the south and the alpine buttress to the north a free boundary of the apennines does not contribute significantly to this motion kinematics of this indenter is controlled by friction on the dinaric suture which in turn is decisive for strain energy distribution between the alpine and the pannonian domains the predicted pronounced extension in the greece aegean segment 2 5 10 12 nm 1 implies active pull transferred from the hellenic subduction zone this extension releases stress in the balkan pannonian region and enables the eastward escape of tectonic blocks in front of advancing adria significant changes of tectonic push trends are found along the black sea caucasus boundary segment and at the european passive margin from the north sea to the arctic ocean differential stresses in central europe are estimated in the range of 10 60 mpa when averaged over the 30 80 km thick mechanically heterogeneous lithosphere the maximum stiffness contrast across the model is predicted to be of one order of magnitude apparent friction coefficients of fault zones differ between the north european part of the plate 0 4 0 7 the pannonian region 0 15 0 25 and the dinaric suture 0 55

local regional and plate scale sources for the stress field in the adriatic and periadriatic region abstract the stress field at a specific location is the sum of regional stress controlled by plate scale tectonic processes with local sources here we evaluate and discuss the different sources from geodynamic to local scale and the controlling factors including the jurassic paleogeography of the adriatic passive margin of present day stress in the adriatic sea and periadriatic regions of italy using two kinds of numerical models 3d mantle scale viscoelastic models and 2 5d lithosphere scale thin shell models the subcrustal stress field of the slabs in the dinarides hellenic and apennines calabrian subduction zones are characterized by downdip extension and compression respectively this difference is explained by the velocity of the adriatic slab with respect to the upper mantle in the hotspot reference frame the slab in the calabrian subduction zone is encroached and down pushed whereas the slab in the hellenic subduction zone is sustained by the mantle flow at the plate scale the upper crustal stress field at the apennines front is governed by the different nature of the lithosphere probably oceanic in the ionian sea and continental elsewhere which in turn determines first order rotations of the stress axes second order rotations of the stress axes depend on the jurassic paleogeography and consequent differential advancement of the thrust fronts with recesses and salient occurring in correspondence with jurassic structural highs and lows respectively the eastward relative motion of the mantle with respect of the lithosphere enhances the onset of nw se oriented compression within the adriatic plate consistent with observations finally 2 5d thin shell models demonstrate that present day stress does not simply follow the long wavelength pattern 500 1000 km due to plate tectonics and mantle interaction but is greatly affected by the presence of second and third order sources like crustal structure faults and topography most importantly these factors give an observable effect in data

new seismological constraints on growth of continental crust in the izu bonin intra oceanic arc the process by which continental crust has formed is not well understood though such crust mostly forms at convergent plate margins today it is thus imperative to study modern intra oceanic arcs such as those common in the western pacific ocean new seismic studies along the representative izu bonin intra oceanic arc provide unique along strike images of arc crust and uppermost mantle to complement earlier cross arc lithospheric profiles these reveal two scales 1000 10 km scale of variations one at the scale of the izu versus bonin thick versus thin arc crust the other at the intervolcano 50 km scale these images show that 1 the bulk composition of the izu bonin arc crust is more mafic than typical continental crust 2 the middle crust with seismic velocities similar to continental crust is predominantly beneath basaltic arc volcanoes 3 the bulk composition beneath basaltic volcanoes changes little at thick and thin arc segments and 4 a process to return lower crustal components to the mantle such as delamination is required for an arc crust to evolve into continental crust continued thickening of the izu bonin crust accompanied by delamination of lowermost crust can yield velocity structure of typical continental crust

tonga ridge and lau basin crustal structure from seismic refraction data 1 the crustal structure across the tonga lau arc back arc system from the lau ridge to the pacific plate 178 170 w 18 19 s is modeled using data from an 840 km long air gun refraction line over 19 ocean bottom seismometers and one land station the data reveal that the pacific plate crust is 5 5 km thick with a velocity structure similar to that found at the present day east pacific rise epr beneath tonga ridge an intermediate velocity layer 6 7 km s is up to 7 5 km thick and has a velocity depth distribution similar to andesitic rocks found in continental crust the crust is abnormally thin 4 km at the boundary between the tonga ridge and the lau basin at the east end of lau basin the crust is 5 5 6 5 km thick and resembles crust formed at the epr except for a thicker sheeted dike section 2 3 km and thinner lower crust 2 km the lau basin crust thickens to 7 8 km near the central lau spreading center clsc mostly through thickening of the lower crust the crust thickens again to 8 5 9 5 km at 50 km west of the clsc mostly through thickening of the midcrust in the thick westernmost section the crustal structure is uniform even though one part of this section formed through extension of arc type crust while the rest was created at an oceanic spreading center the relative homogeneity of these rocks suggests that their petrology may be dominated by postemplacement magmatic infilling from a mantle source west of the spreading center

structure and deformation processes in the strait of sicily rift zone abstract the strait of sicily rift zone ssrz is a young tectonic feature early pliocenerecent cutting across the pelagian sea it is characterized by a thin continental type crust which progressively thickens towards the african continental margin and beneath the sicilian chain geophysical data available for the whole area show that extensional faulting is active in many places along structures trending roughly nnw sse but that the dominant mode of deformation at a regional scale can be best described in terms of strike slip tectonics strike slip faults trending nw se are seismically documented west of the island of pantelleria in the eastern sector of the malta graben and along the southern border of the medina graben similar features have also been mapped on land in malta and pantelleria kinematic analysis of these structures suggest that the ssrz cannot be considered as a classical intracontinental rift because the deformation does not appear to be dominated by a generalized thermal instability but rather by compressive stresses in a transcurrent tectonic regime therefore an alternative model which accounts for the activation of large scale right lateral strike slip faults seems to be more suitable within this main dextral shear zone the progressive development of pull apart basins could be responsible for the incipient separation of the sicilian microplate from the african continent and for the thinning of the crust and the associated volcanic activity of the northwestern sector of the ssrz

configuration of subducting philippine sea plate and crustal structure in the central japan region abstract a seismic experiment with six explosive sources and 391 seismic stations was conducted in august 2001 in the central japan region the crustal velocity structure for the central part of japan and configuration of the subducting philippine sea plate were revealed a large lateral variation of the thickness of the sedimentary layer was observed and the p wave velocity values below the sedimentary layer obtained were 5 3 5 8 km s p wave velocity values for the lower part of upper crust and lower crust were estimated to be 6 0 6 4 and 6 6 6 8 km s respectively the reflected wave from the upper boundary of the subducting philippine sea plate was observed on the record sections of several shots the configuration of the subducting philippine sea slab was revealed for depths of 20 35 km the dip angle of the philippine sea plate was estimated to be 26 for a depth range of about 20 26 km below this depth the upper boundary of the subducting philippine sea plate is distorted over a depth range of 26 33 km a large variation of the reflected wave amplitude with depth along the subducting plate was observed at a depth of about 20 26 km the amplitude of the reflected wave is not large and is explained by the reflected wave at the upper boundary of the subducting oceanic crust however the reflected wave from reflection points deeper than 26 km showed a large amplitude that cannot be explained by several reliable velocity models some unique seismic structures have to be considered to explain the observed data such unique structures will provide important information to know the mechanism of inter plate earthquakes

paleomagnetic implications on the evolution of the tethys belt from the atlantic ocean to the pamirs since the triassic abstract we first re examined the apparent polar wander curves for stable eurasia and africa since the triassic these curves were then combined together with curves of north and south america according to the kinematics of the atlantic ocean and a synthetic polar wander curve was given then most of the paleomagnetic results from the tethys mobile belt from the atlantic to the pamirs were analysed several groups of plates microplates and blocks can be seen first relatively stable regions like maghreb and sicily which have not moved much then we have a group formed by iberia sardinia italy and to a lesser extent corsica and the western and central alps for these blocks movements are anticlockwise rotations chiefly driven by the anticlockwise rotation of africa but they are sometimes stronger to the east a major change takes place the north of the aegean sea and the ionian zone are clockwise rotated and these rotations are recent oligocene miocene for the first part pliocene to the present for the second part a major problem arises in turkey caucasus and iran paleomagnetic results indicate a position far to the south of eurasia and at the same time geological evidence is in favour of a position close to eurasia we discuss these discrepancies

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

simulation of the development of karst aquifers using a coupled continuum pipe flow model 1 this paper is intended to provide insight into the controlling mechanisms of karst genesis based on an advanced modeling approach covering the characteristic hydraulics in karst systems the dissolution kinetics and the associated temporal decrease in flow resistance karst water hydraulics is strongly governed by the interaction between a highly conductive low storage conduit network and a low conductive high storage rock matrix under variable boundary conditions only if this coupling of flow mechanisms is considered can an appropriate representation of other relevant processes be achieved e g carbonate dissolution transport of dissolved solids and limited groundwater recharge here a parameter study performed with the numerical model carbonate aquifer void evolution cave is presented which allows the simulation of the genesis of karst aquifers during geologic time periods cave integrates several important features relevant for different scenarios of karst evolution 1 the complex hydraulic interplay between flow in the karst conduits and in the small fissures of the rock matrix 2 laminar as well as turbulent flow conditions 3 time dependent and nonuniform recharge to both flow systems 4 the widening of the conduits accounting for appropriate physicochemical relationships governing calcite dissolution kinetics this is achieved by predefining an initial network of karst conduits protoconduits which are allowed to grow according to the amount of aggressive water available due to hydraulic boundary conditions the increase in conduit transmissivity is associated with an increase in conduit diameters while the conductivity of the fissured system is assumed to be constant in time the importance of various parameters controlling karst genesis is demonstrated in a parameter study covering the recharge distribution the upgradient boundary conditions for the conduit system and the hydraulic coupling between the conduit network and the rock matrix in particular it is shown that conduit diameters increase in downgradient or upgradient direction depending on the spatial distribution local versus uniform of the recharge component which directly enters the conduit system

palaeotectonic reconstruction of the central alpine mediterranean belt for the neogene abstract the structural patterns of the central alpine mediterranean belt ranging from the eastern balearic sea to the western aegean sea have been reconstructed for 10 and 20 ma b p they have been obtained in the frame of the africa europe convergence through a step by step rigid plastic reconstruction using available geological and palaeomagnetic data all domains outlined in the present situation are shown in the palaeotectonic reconstructions while the structural pattern at 10 ma b p is similar to that of the present except for the tyrrhenian region that at 20 ma b p differs from it in most areas the well known adriatic promontory of the african plate is recognizable in both pictures and at 20 ma its original boundaries are revealed as strongly deformed flysch belts the adriatic promontory was broken up in the early or middle miocene into two microplates of comparable sizes the norther one is the adriatic microplate s s which suffered counter clockwise rotation by 20 relative to africa around the alpine apenninic whirl centre the southern one is the apulian microplate first outlined in the present work including the south apenninic and the apulian s s south of the gargano peninsula platforms which suffered no rotations relative to africa but which moved towards the northeast of it the primary reason for the break up of the adriatic promontory was most probably the opening of the balearic ligurian sea since 10 ma the adriatic and apulian microplates were again integral with africa or perhaps they moved towards the west relative to africa pushed by the turkish microplate the orogeny in the area discussed is mostly linked with collisional processes on the boundaries of the adriatic apulian unit

kinematic evolution of the tethys belt from the atlantic ocean to the pamirs since the triassic abstract we present an updated series of kinematic reconstructions of the major plates around the tethys from the atlantic ocean to the pamirs between the early jurassic and the present this set is used elsewhere as a basis for paleogeographic maps of the entire region the problems related to the positions of the continents in the lower triassic are also discussed no direct analyses of magnetic anomalies and fracture zones in the atlantic have been made rather all available poles and rotations have been tested in order to eliminate or minimize possible kinematic errors the reconstructions are shown for nine key geological periods which correspond to well recognized magnetic anomalies except for the jurassic cretaceous boundary and the cretaceous tertiary boundary which correspond to interpolated positions paleolatitudes have been drawn using the study of westphal et al 1986 an attempt has been made to take into account the displacements caused by formation of the continental margins and basins by stretching the resulting relative vector of motions along the northern boundary of the tethys shows a significant change 80 m y ago left lateral motion with compression dominates before whereas right lateral motion with compression dominates after to the east rates of motion vary by a factor of three with time and four maxima can be clearly related to tectonic events in the late jurassic late cretaceous eocene and post middle miocene to the west north of apulia on the contrary the motion rate has not changed significantly since the early cretaceous and is close to 1 cm yr as an average these rather complex adjustments in rates and directions of relative motion are produced in great part through a complex migration of the africa eurasia pole of rotation and seem to be mostly governed by the tectonics of the tethys plate boundary

deformation pattern in the central mediterranean and behavior of the african adriatic promontory abstract the adriatic platform has been described in the literature both as an africa promontory moving in close connection with the main continent and as an independent microplate this evident incongruity is mainly due to the wide spectrum of kinematic hypotheses proposed on the basis of paleomagnetic data and to the fact that the adriatic africa transition is not marked by any clear decoupling fracture or by any interruption of lithological facies along the marginal belts apennines maghrebides and dinarides hellenides in this work it is argued that the counterclockwise rotation of the adriatic plate driven by africa pushing beneath the calabrian arc and southern tyrrhenian may coherently account for all major plio quatemary events in the central mediterranean

sources of recent tectonic stress in the pannonian region inferences from finite element modelling summary we present the results of finite element modelling of the recent stress field in the pannonian basin and surrounding alpine orogenic belt our results show that the recent predominantly compressive stress regime in the alpine pannonian carpathian dinaric system is governed by distinct tectonic factors of great importance is the deformation of crustal blocks with diverent geometries and rigidities in an overall convergent setting associated with the africa europe collision the most important stress source appears to be the counterclockwise rotation of the adriatic microplate at the southwest boundary of the pannonian basin this plate tectonic unit has been interpreted as moving independently of both the european plate and the african plate additional boundary conditions active shortening and compression in the vrancea zone and the bohemian massif and the evect of the immobile moesian platform also significantly influence the modelling results the incorporation of additional stress sources such as crustal thickness variation and the presence of two main fault zones separating the primary tectonic units in the study area have only locally important evects but improve the fit between the calculated results and the observed stress pattern

ground deformation of the southern sector of the aeolian islands volcanic arc from geodetic data abstract the deformation pattern and the dynamics of the southern sector of the aeolian archipelago are investigated a study on the ground deformation measured over the last 20 years in the trilateration geodetic network between the islands of vulcano and lipari has been conducted analysis of the relative displacements and the uniform strain tensor parameters as well as the comparison between areal dilatation and the vertical variations deduced by precise levelling allow distinguishing different phases associated both with the regional dynamics and the local volcanic context of the area these phases however appear to be closely interrelated the analysis of the deformation pattern allows to constrain the predominance of a roughly e w trending extension and a n s contraction at a regional scale this regime is consistent with right lateral movements along a nw se striking fault system

character of the stress field in the calabrian arc and southern apennines italy as deduced by geological seismological and volcanological information abstract three crustal sections located in key zones of the calabrian arc and southern apennines have been drawn on the basis of the available geological geophysical seismological and volcanological data the purpose is to gather information on the state of stress at different crustal levels and to test to which extent data sampled at different time intervals may be consistently compared the analysis allows for the individualization of the following sectors 1 1 peri tyrrhenian belt marked by a tensional state of stress down to the moho depth 2 2 apenninic chain subjected to tension only in its shallow portions and to a compressive regime at depth 3 3 external chain internal foretrough characterized by a deep compressive regime which is expressed at the surface in its outermost zone only 4 4 external foretrough foreland with tensional processes in the whole crust compressional processes are linked to the activity of a deep shear zone which causes the thrusting of the tyrrhenian crust over the adriatic crust and which seems to control the present distortion of the calabrian arc the analysis suggests a change in the stress field and deformation mechanisms from the uppermost to the lowermost levels of the crust and an eastward migration with time of the compressional events these facts would explain the contrasting evidence sometimes given by stress constraints derived from geological seismological and volcanological data

three dimensional attenuation qs structure beneath the kanto district japan as inferred from strong motion records 1 the three dimensional 3d s wave attenuation qs structure beneath the kanto plain where the pacific and philippine sea plates subduct was estimated using strong motion records of the k net and kik net in addition to several low qs zones corresponding to the volcanic front a large nw se trending low qs zone is estimated under the non volcanic kanto area at depths of 20 60 km this zone corresponds to a previously identified low velocity both vp and vs zone with a high poisson s ratio at 40 km depth it further indicates a wedge immediately above the subducting philippine sea plate predicted seismic ground motions using the estimated 3d attenuation structure is very similar to the actually recorded by recent earthquake on july 2005 m 6