kinematics of the western africa eurasia plate boundary from focal mechanisms and gps data summary the western mediterranean displays a complex pattern of crustal deformation distributed along tectonically active belts developed in the framework of slow oblique plate convergence we used earthquake and global positioning system gps data to study the present day kinematics and tectonics of the africa eurasia plate boundary in this region crustal seismicity and focal mechanisms analysed in terms of seismic moment release and seismic deformation outline the geometry of major seismic belts and characterize their tectonics and kinematics continuous gps data have been analysed to determine euler vectors for the nubian and eurasian plates and to provide the global frame for a new mediterranean gps velocity field obtained by merging continuous and campaign observations collected in the 1991 2005 time span gps velocities and displacements predicted by the nubia eurasia rotation pole provide estimates of the deformation accommodated across the tectonically active belts the rather simple deformation occurring in the atlantic region characterized by extension about perpendicular to the middle atlantic and terceira ridges and right lateral motion along the gloria transform fault turns into a complex pattern of deformation occurring along broader seismic belts where continental lithosphere is involved our analysis reveals a more complex fragmentation of the plate boundary than previously proposed the roughly e w trending mainly compressive segments i e southwestern iberia northern algeria and southern tyrrhenian where plate convergence is largely accomodated across rather localized deformation zones and partially transferred northward to the adjacent domains i e the algero balearic and tyrrhenian basins are interrupted by regions of more distributed deformation i e the rif alboran betics tunisia libya and eastern sicily or limited seismicity i e the strait of sicily which are characterized by less homogeneous tectonics regimes mainly transcurrent to extensional in correspondence of the observed breaks tectonic structures with different orientation interfere and we find belts with only limited deformation i e the high and middle atlas the tunisian atlas and the offshore tunisia libya belt that extends from the plate boundary into the nubian plate along pre existing tectonic lineaments our analysis suggest that the sicilian pelagian domain is moving independently from nubia according to the presence of a right lateral and extensional decoupling zone corresponding to the tunisia libya and strait of sicily deformation zone despite the space variability of active tectonic regimes plate convergence still governs most of the seismotectonic and kinematic setting up to the central aeolian region in general local complexities derive from pre existing structural features inherited from the tectonic evolution of the mediterranean region on the contrary along calabria and the apennines the contribution of the subducted ionian oceanic lithosphere and the occurrence of microplates i e adria appear to substantially modify both tectonics and kinematics finally gps data across the gibraltar arc and the tyrrhenian calabria domain support the hypothesis that slab rollback in these regions is mostly slowed down or stopped

geologic structure and neotectonics of the north african continental margin south of sicily abstract marine geological and geophysical data together with drilling information indicate that the north african passive continental margin has been subjected to extension and wrenching after it collided with the northern part of sicily the area of the tripolitania basin jarrafa trough melita and medina bank and the ragusa malta plateau has formed part of a sinking passive margin since the dispersal of gondwanaland at about 180 my ago as observed from geohistory diagrams a record of rifting in a nw se direction accompanied by dextral shear along the southern troughs is observed in seismic reflection data the rifting started during the neocomian and lasted until the eocene when activity became minor a pre middle miocene period of northward subduction of oceanic crust is inferred from the geology in ne sicily uplift of the northern part of the african margin after collision in the middle miocene is seen in wells in southern sicily after the messinian a rift and dextral shear zone established itself across the african margin from the strait of sicily to the medina ridge in the lonian basin the zone is marked by up to 1 7 km deep grabens narrow active wrench faulted channels volcanic fissures and local uplifted keilhorsts such as malta this zone which varies in width from 100 to 35 km forms the southern boundary of a microplate which includes sicily we speculate that the present motion of this microplate is partly due to the eastward movement of the calabrian arc with the sicilian block over the last remaining oceanic lithosphere in the eastern mediterranean

development of the palaeogeography of pangaea from late carboniferous to early permian abstract old and new well and poorly known lithofacies data of moscovian and artinskian age in the area limited by the arctic sea and central africa the atlantic ocean and the ural mountains have been plotted on present day maps the facies mapped and related environments allow the recognition of a series of different palaeogeographic palaeotectonic units including the late carboniferous to early permian deep sea to palaeo tethyan ocean west siberia kazakhstan continent and uralian kazakhstan tienshan arc uralian foredeep up to the closing arms of the uralian ocean precaspian basin russian platform donets rift basin caucasian moesian dobrogean polish oslo basinal belt syn tectonic hercynian foreland basin intramontane post hercynian basins iran anatolian hellenic dinaric carnic basin branching into the hungarian seaway apennine basin branching into the cantabrian and south portuguese basins oman iraq levantine sicily deep basin and inferred oceanic sea way south peri tethyan platform basins east arabian cratonic basin and north african intracratonic basins the subsidence sedimentation trends of these units were correlated and compared through lithostratigraphic logs bathymetric curves and uncorrected cumulative stratigraphic curves the sets of original and processed data were used to test two different palaeodynamic models a pangaea a model static from late carboniferous to triassic and a mobile pangaea b model with different dextral displacements between laurussia and gondwanaland in the same time interval the best fit for our data requires a strike slip offset of about 800 km from moscovian to artinskian time this model implies a first quasi pangaea or pangaea b assembly at the carboniferous permian transition an ephemeral pangaea b break up driven by an early permian oblique rift across the mediterranean to caribbean areas and a final pangaea a assembly in the mid to late permian the two palinspastic maps describing the model have been cross checked by comparison with an independent set of biogeographic features of late carboniferous and early permian overall floral reptile and marine benthic organism distribution is consistent with the early permian trans pangaea seaway inferred from facies and palaeodynamic analyses

source and qp parameters from pulse width inversion of microearthquake data in southeastern sicily italy 1 source and qp parameters were estimated from the inversion of first arrival p waveform durations of about 300 microearthquakes recorded at a digital seismic network operating in southeastern sicily the average risetime and pulse width at each station do not show large differences allowing us to exclude significant differential attenuation site effects a first qp estimate was obtained by applying the classical risetime method under the assumption of a point like source time function in order to investigate the effect of directivity due to the finiteness of seismic sources new nonlinear relationships based on a circular crack model rupturing at a constant velocity were numerically built these relationships were used to formulate a nonlinear inverse method for retrieving source radius dip and strike of the circular crack and qp parameters from the inversion of risetime and pulse width data the application of the method produced a better fit of the observed data and a qp value higher than that obtained by applying the risetime method the discrepancy between the different q estimates may be due to a trade off among source dimension and qp as we inferred from a test on a subset of low magnitude events ml 2 5 a good agreement with independent estimates of fault plane solutions as inferred from p polarities and s polarizations was found the estimated stress drops are generally very low 0 1 10 bars this suggests that the background seismic activity in southeastern sicily is related to fault segments and or weakened zones where great stress accumulations are hindered

propagation of a lithospheric tear fault step through the western boundary of the calabrian accretionary wedge offshore eastern sicily southern italy the rollback of a segmented slab of oceanic lithosphere is typically accompanied by vertical lithospheric tear fault s along the lateral slab edge s and by strike slip movement in the upper plate defined as a step fault subduction tear edge propagator the neogene evolution of the central mediterranean is dominated by the interaction between the slow africa eurasia convergence and the se ward rollback of the ionian slab that leads to the back arc opening of the tyrrhenian sea here we present post stack time migrated and pre stack depth migrated archimede 1997 multichannel seismic lines that were acquired offshore eastern sicily at the foot of the malta escarpment first we identify the recent deformation along the lateral ramp of the calabrian accretionary wedge towards the east the calabrian wedge is formed by the accretion of the post evaporitic sediments above a decollement at the base of the messinian evaporites at the latitude of syracuse 50 km east of the malta escarpment a major n150 degrees e trending crustal scale and vertical fault slices through the entire accretionary wedge this fault cuts by several kilometers through the pre evaporitic messinian sediments and into the basement the vertical offset along this vertical fault decreases from north to south and the fault is no longer observed on the seismic lines 50 km se of the alfeo seamount a previously published moho depth isocontour map offshore sicily and the recent gps data combined with the presence of strike slip movements ne onshore sicily allow us to identify this 200 km long crustal scale fault as the surface expression of a step fault the presence of syntectonic pleistocene sediments on top this crustal scale fault suggests a recent lithospheric vertical movement of the step fault in response to the rollback of the ionian slab and to the se ward advance of the calabria peloritan block

sedimentary and tectonic evolution of the eastern hyblean plateau southeastern sicily during late cretaceous to quaternary time abstract two palaeogeographic domains have been distinguished in the cretaceous quaternary sequences which crop out in the hyblean region of southeastern sicily in the northeast shallow water algal bryozoan calcarenites of oligocene miocene age overlie either cretaceous rudist limestones or volcanics further to the northeast the stratigraphic gap increases as the miocene limestone thins and in the a g i p well catania 10 plio pleistocene sediments and volcanics directly overlie upper jurassic rocks in the southwestern part of the hyblean plateau pelagic sediments occupy the cretaceous miocene interval they were deposited in a shallow basin dipping gently towards the southwest the transition between the two zones is marked by much evidence of synsedimentary tectonic activity such as widespread slumping and the development of megabreccias composed of cretaceous and eocene blocks the palaeogeographic picture is one of carbonate reefs and volcanic seamounts developing in the upper cretaceous they formed platforms fault bounded to the west and southwest from which were derived the detrital sediments found in the basin and occasional spectacular gravity slides in present day terms the structural high probably corresponds to the northeastern margin of the hyblean plateau and in part to the siracusa syracuse malta escarpment the pattern is little changed in the upper miocene with volcanoclastics of phreatomagmatic origin intercalated with coral bioherms overlying algal bryozoan calcarenites upper tortonian lower messinian limestones with a restricted fauna indicate a shallow water environment which grades up into continental conditions in the eastern hyblean plateau the tertiary sequence is capped by pliocene submarine to subaerial mafic lava flows lower pleistocene sediments consist of biocalcarenites and clays which fill deep graben delimited by plio pleistocene faults the inshore continuation of the malta syracuse escarpment system of faults from a tectonic standpoint the hyblean region a gently deformed segment of the african continental margin acted as a foreland during tertiary times a cretaceous eocene tectonic phase was responsible for the palaeogeographic pattern which existed during most of the cenozoic the present pattern is the result of three main tectonic phases following the regional upper miocene uplift of early middle pliocene plio pleistocene and middle pleistocene recent age which influenced the tectonic evolution of the present ionian coast and the malta syracuse escarpment

fault reactivation by stress pattern reorganization in the hyblean foreland domain of se sicily italy and seismotectonic implications abstract between the october 2011 and the july 2012 several seismic swarms occurred in the hyblean foreland domain of se sicily italy along the cavagrande canyon one of the most impressive fluvial incisions of sicily despite the low magnitude of the events main shock with m 3 7 they represent the biggest strain release of the hyblean area over the last 10 years a careful waveform analysis of the earthquakes revealed that most of them form a family of multiplets these findings allow us to reconstruct the attitude of the accountable fault plane by interpolating their high precision 3d location parameters into a gis platform a detailed morpho structural analysis performed at the ideal updip projection of the modeled plane showed that during the middle late pleistocene the epicentral area has been deformed by a belt of extensional faults a segment of which matches well with the computer generated surface despite the field evidence computed focal solutions support contrasting strike slip kinematics on the same fault plane clearly indicating a dextral shearing on this pre existing normal fault the seismic swarms nucleated on a small rupture area along a 10 km long nw se trending fault segment that could be able to generate m 6 earthquakes following our analysis and looking at seismicity distribution in the se portion of hyblean area we assess that a stress pattern reorganization occurred all over the hyblean foreland between the late pleistocene and present day change in the trajectory of the max stress axes from vertical to horizontal seems to have involved a pre existing large scale fault configuration with considerable seismotectonic implications

syndepositional tectonics affecting cenozoic and mesozoic deposition in the malta and se sicily areas central mediterranean and their bearing on mesozoic reservoir development in the n malta offshore region abstract tertiary sedimentation patterns within the maltese islands and se sicily pelagian block of the central mediterranean reflect subtle depositional control by the concurrent evolution of the malta graben lying to the south west and reactivation of regionally important mesozoic fault systems the visible structural style of the maltese islands is the product of malta graben development and commenced some 24 million years ago however north south oriented structures identified from maltese tertiary facies strike patterns can be closely related to reactivated mesozoic faults in se sicily here synsedimentary tectonogenesis is recognized in both mesozoic and cenozoic strata mesozoic synsedimentary faulting was initiated during a former tectonic regime when the pelagian block african plate lay at the southern side of a wide tethys ocean reactivation of these fractures during the tertiary is believed to be related to subsequent african european plate collision the unsuccessful oil search in maltese territorial waters results from the mistaken significance attached to the young malta graben related tectonic pattern of the maltese islands potential traps are more likely to be associated with a cryptic though formerly dominant mesozoic tectonic pattern the hypothesis presented predicts hydrocarbon prospects in horst traps immediately to the north of the malta shelf these can be expected to show many of the characteristics of the gela and ragusa fields

gps velocity and strain fields in sicily and southern calabria italy updated geodetic constraints on tectonic block interaction in the central mediterranean 1 we present an improved rendition of the geodetic velocity and strain fields in sicily and southern calabria obtained through the analysis of 18 years of gps observations from continuous and survey station networks the dense spatial coverage of geodetic data provides precise quantitative estimates of previously established first order active kinematic features including i a narrow east west elongated belt of contraction 1 1 5 mm yr extending offshore northern sicily from ustica to stromboli across the aeolian islands ii a narrow east west trending contractional belt located along the northern rim of the hyblean plateau in southern sicily with shortening at up to 4 4 mm yr iii right motion 3 6 mm yr on the aeolian tindari letojanni fault atlf system a main shear zone extending from the aeolian islands to the ionian coast of sicily with significant transpression and transtension partitioned between discrete sectors of the fault iv transtension 1 mm yr across the sicily channel between sicily and north africa we use geodetic observations coupled to geological constraints to better elucidate the interplay of crustal blocks revealed in the investigated area in particular we focus on the atlf which forms the primary boundary between the sicilian and calabrian blocks the atlf juxtaposes north south contraction between sicily and the tyrrhenian block with northwest southeast extension in northeastern sicily and calabria contraction between sicily and tyrrhenian blocks probably arises from the main europe nubia convergence although sicily has a component of lateral motion away from nubia we found that convergence is not restricted to the northern offshore as commonly believed but is widely accommodated between the frontal belt and the northern rim of the hyblean foreland in southern sicily geodetic data also indicate that active right shear on the atlf occurs to the southeast of the mapped fault array in northern sicily suggesting the fault cuts through till the ionian coast of the island the small geodetic divergence between the hyblean and apulian blocks rimming on both sides the calabria block and subjacent ionian slab coupled with marine geophysical evidences in the ionian sea lends credit to the proposed deep root of the atlf and to a fragmentation of the ionian domain

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

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

lunar gravitational atmospheric tide surface to 50 km in a global gridded data set the lunar gravitational semidiurnal atmospheric tide l2 is detected in the geopotential field in the era interim reanalysis by regressing the data for each of the four daily analysis times onto periodic lunar half synodic cycle time series and differencing the resulting regression maps a robust pattern dominated by zonal wave number 2 emerges which agrees with tidal theory and with previous observational studies based on station data in terms of its amplitude phase and seasonality at the earth s surface above the 100 hpa level the tidal signal amplifies with height and it is downward propagating below that level it is almost barotropic the l2 signal is resolvable even in data for individual months of individual years monthly time series of tidal amplitude and phase exhibit a well defined pattern of seasonality year after year since the era forecast model has no l2 gravitational forcing the source of its l2 signal must be in the observations

structural features of the july august 2001 mount etna eruption evidence for a complex magma supply system we describe the evolution of the volcanic activity and deformation patterns observed at mount etna during the july august 2001 eruption seismicity started at 3000 m below sea level on 13 july accompanied by moderate ground swelling ground deformation culminated on 16 july with the development of a ne sw graben c 500 m wide and c 1 m deep in the cisternazza area at 2600 2500 m above sea level on the southern slope of the volcano on 17 july the eruption started at the summit of mount etna from the se crater central lateral eruptive system from which two radial c 30 m wide c 3000 m long fracture zones associated with eruptive fissures propagated both southward 17 july and northeastward 20 july on 18 july a new vent formed at 2100 m elevation at the southern base of the montagnola followed on the next day by the opening of a vent further upslope at 2550 m eccentric eruptive system the eruption lasted for 3 weeks approximately 80 of the total lava volume was erupted from the 2100 m and the 2550 m vents the collected structural data suggest that the cisternazza graben developed as a passive local response of the volcanic edifice to the ascent of a north south eccentric dyke which eventually reached the ground surface in the montagnola area 18 19 july in contrast the two narrow fracture zones radiating from the summit are interpreted as the lateral propagation from the conduit of the se crater of north south and ne sw oriented shallow dykes 2 3 m wide the evolution of the fracture pattern together with other volcanological data magma ascent and effusion rate eruptive style petrochemical characteristics of the erupted products and petrology of xenoliths within magma suggest that the eccentric and central lateral eruptions were fed by two distinct magmatic systems examples of eccentric activity accompanied by central lateral events have never been described before at etna

a single stage megaflood at the termination of the messinian salinity crisis geophysical and modelling evidence from the eastern mediterranean basin abstract the messinian salinity crisis was an extraordinary event that resulted in the deposition of kilometre thick evaporite sequences in the mediterranean sea after the latter became disconnected from the world s oceans the return to fully and stable marine conditions at the end of the crisis is still subject to debate three main hypotheses based on geophysical and borehole data onshore outcrops and climate simulations have been put forward these include a single stage catastrophic flood a two step reflooding scenario and an overspill of paratethyan water followed by atlantic inflow in this study two research questions are addressed i which event marked the termination of the messinian salinity crisis ii what was the sea level in the eastern mediterranean sea during this event geophysical data from the western ionian basin are integrated with numerical simulations to infer that the termination of the crisis consisted of a single stage megaflood following a sea level drawdown of 1900 m this megaflood deposited an extensive sedimentary body with a chaotic to transparent seismic signature at the base of the malta escarpment fine well sorted sediments are predicted to have been deposited within the thicker sections of the flood deposit whereas a more variable distribution of coarser sediments is expected elsewhere the north western ionian basin hosts evidence of episodic post messinian salinity crisis slope instability events in the last 1 8 ma the largest of these emplaced a 200 km3 deposit and is associated with failure of the head of noto canyon offshore se sicily apart from unravelling the final phase of the messinian salinity crisis and the ensuing stratigraphic evolution of the western ionian basin our results are also relevant to better understand megafloods which are some of the most catastrophic geological processes on earth and mars

variations in the styles of erosion along the florida escarpment eastern gulf of mexico abstract gloria sidescan sonographs and seabeam bathymetric data show morphological differences along the florida escarpment which reflect that different erosional styles have been active along different parts of this carbonate platform edge the northern half of the escarpment is cut by numerous small ravines spaced 1 5 km apart its southern half is deeply incised by large box canyons that have flat floors and steep headwalls the northern half of the escarpment is covered by cenozoic aged sediments and erosion appears to be limited to this cenozoic cover an apron of this eroded material is accumulating along the base of this half of the escarpment extending as much as 30 km from its base south of 27 n active erosion of older strata of the escarpment is shown by talus deposits of lower cretaceous limestone that occur at the heads of box canyons the box canyons are not evenly distributed but instead are most abundant where two basins that underlie the florida platform intersect the escarpment pleistocene aged sediments eroded from the slope above the escarpment are funnelled through small valleys into the heads of the box canyons the smooth headwalls of the box canyons suggest that downslope transport of the material from the slope above the escarpment does little to erode the escarpment instead erosion triggered by dissolution of the carbonate rocks by acidic brines that seep out of the escarpment is the proposed mechanism of escarpment retreat the concentration of the erosion at the heads of the box canyons may indicate sites where the platform rocks are more intensely fractured thus enhancing permeability and flow of brines the concentration of box canyons in the escarpment sections adjacent to sedimentary basins beneath the platform may reflect regional differences in the geology and hydrology of the platform

evolution of the southern tyrrhenian slab tear and active tectonics along the western edge of the tyrrhenian subducted slab abstract the evolution of the southern tyrrhenian subduction has been possibly controlled by distinct episodes of slab break off as indicated by a critical review of the geological literature and by the analysis of purposely acquired multichannel seismic profiles within the proposed interpretation the first episode occurred from 8 5 to 4 0 ma and affected the segment of the slab located in the sardinia channel causing the abandonment of the adventure thrust front in western sicily the second episode occurred between 2 5 and 1 6 ma affecting the segment of slab located north of sicily and was preceeded by rifting in the strait of sicily the space and time location of these episodes appear controlled by discontinuities pre existing within the subducted african plate that trend at high angle to the advancing subduction front these discontinuities delimit segment of subducted slab that can be affected by slab break off and can act as wayouts for magma and mantle derived he the major of these discontinuities the malta escarpment has been reactivated in the quaternary as a trench perpendicular tear step faults ultimately the hierarchy in strength of these trench perpendicular features could have affected the timing and amount of trench retreat and backarc opening

kinematic analysis of rock falls in an urban area the case of castelmola hill near taormina sicily italy abstract the village of castelmola in the southern sector of the peloritani mountains sicily sits on the summit of an isolated peak that consists of a limestone and dolomite sequence of white greyish color rocks that occur in thick beds and pass upward into an alternation of lower liassic marly limestones belonging to the taormina unit at the base this passes into sands and red conglomerates of verrucano facies which outcrops along the slopes exposed towards the north and east and which is transgressively superposed upon metamorphic units structurally the succession is affected by deformation which has produced diffuse fracturing of the rock material subdividing it into elements of variable dimensions as a result of the intersection of tectonic discontinuities and stratigraphic planes furthermore in correspondence with the overlapping planes intense cataclastic effects are observed that may lead to the complete disintegration of the rock giving a type of coarse grained detritus in a sandy matrix along the slopes of the castelmola peak widespread weathering occurs mainly related to intensely tectonized zones and there are karstic cavities of various dimensions this leads to an accentuated anisotropy which influences the mechanical properties of the rock material rock masses of huge dimensions have been affected by collapse this causes great risks to the local population since the road through this area constitutes the only access to the village and provides a connection with taormina the most recent collapse 1996 of a significant volume of rock from the nw slope has interrupted the access road and generated a higher hazard due to the lack of support of the rock masses above structural analysis geognostic boreholes and geophysical investigations carried out on the flanks and within the castelmola peak have allowed us to verify in detail the lithostratigraphic and fracturing conditions of the rock mass which strongly control its stability the typologies of possible landslides have been identified permitting the distinction of three zones of geomechanic homogeneity that qualitatively define their stability conditions

fast deformation processes and eruptive activity at mount etna italy the seismic and deformation patterns observed on mount etna before and during the 1991 1993 eruption the third largest since the seventeenth century in terms of lava volume are consistent with the regional tectonic framework of eastern sicily the pattern of the stress field acting on the intermediate and lower crust was defined at the local scale by focal mechanisms of microearthquakes occurring at depths between 10 and 25 km beneath the volcano they provide evidence for a strike slip compressional stress regime with the maximum compressive component acting approximately n s the fault plane solutions and the spatial and temporal distribution of seismicity indicate that usually sinistral shear ruptures occur along approximately ne sw trending fault zones while dip slip ruptures affect approximately nnw sse trending fault zones the latter include the avenues along which magma ascended during the 1991 1993 eruption seismic observations indicate a local inversion of the stress field acting on the upper crust depth 10 km underlying mount etna which was initiated less than 2 months before the eruptive event and disappeared with its end this is consistent with a local tensile regime that favored the magma ascent through the shallow crust the events preceding the eruption and accompanying its onset tilt anomalies and seismic swarms and those occurring shortly after its beginning a mainshock aftershock seismic sequence and associated coseismic tilts provide important evidence for understanding the dynamics of the two main volcano tectonic structures ne sw and nnw sse trending fault zones and associated intrusive mechanisms on etna the shape and location of the eruption feeding dike have been modeled from ground deformation data this approximately nnw sse modeled dike the seismicity and the position of the fractures are consistent with the regional stress field characterized by 1 oriented approximately n s the geophysical data presented and analyzed in the present paper strongly suggest an overall regional tectonic control as well as an active role for the intruding magma in the dynamics of the volcano

the morphostructural setting of mount etna sedimentary basement italy implications for the geometry and volume of the volcano and its flank instability abstract the reinterpretation of more than 2500 subsurface data consisting of geoelectric and borehole prospecting undertaken at mount etna allows reconstructing the contour map of the sedimentary basement this reconstruction highlights a complex asymmetric topography due to the inhomogeneous long term updoming of the region and the interrelationship between the development of the drainage network and flank instability these different processes have produced a major morphological difference between the eastern sector characterised by a 17 km wide horseshoe shaped depression and the other flanks formed by palaeovalleys the origin of the wide horseshoe shaped depression can be attributed to the large scale flank instability processes involving the entire continental margin in the etna offshore this depression of the etna basement was generated by a series of coalescent landslides before the beginning of the eruptive activity of the timpe phase more than 220 ka ago this wide depression is the main cause of the flank instability that produced the gravitational slope failures of the valle del bove about 10 ka ago regarding mt etna s geometry we have estimated a total volume of about 532 km 3 that was emplaced during the past 330 ka resulting in an average rate of volcanic output of 0 0016 km 3 a the reconstruction of the temporal variation of the average eruptive rate highlights a drastic increase of volcanism during the last 100 ka in response to the gradual stabilization of the plumbing system in the etna region that led to the build up of the composite stratovolcano structure the data presented in this paper represent the state of knowledge of the sedimentary basement of etna which can be used for future studies aimed at developing a detailed understanding of the deep structure of the volcano s unstable flanks

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

geological and geodetic constraints on the active deformation along the northern margin of the hyblean plateau se sicily abstract a geologic and geodetic integrated analysis of the northern margin of the hyblean plateau se sicily has been carried out in order to test the relationship between the active deformation recorded by gps data and the long term tectonic evolution reconstructed by the interpretation of structural and morphological data our study revealed the active growth of a large antiform as a consequence of the positive tectonic inversion of the previous flexure bordering the hyblean foreland the deformation of middle late pleistocene marine terraces and the evolution of the drainage system are consistent with a progressive regional tilting of the entire eastern sector of the hyblean plateau siracusa domain representing the southern limb of the active antiform the geometry of the late quaternary marine strandlines compared with the results of analogue models is compatible with the effects of the nw ward propagation of a detachment fault at depth the active deformation of the hyblean region coherent with the nubia eurasia plate convergence suggests to candidate the inverted tectonics at the northern border of the hyblean plateau as potential seismogenic sources of the area

parameterized thermal convection in a layered region and the thermal history of the earth parameterized convective schemes for constant viscosity fluids are used to investigate the influence of layering on the relationship between the rate of heat loss from and heat supply to a number of convecting layers of different viscosity and thicknesses simple analytic expressions are obtained which accurately predict the behavior to a step decrease in the heat supply and show that layering considerably increases the response time the same arguments are applied to a planet consisting of spherical shells they show that the response of the earth s heat loss to the decay of radioactive elements depends strongly on whether or not mantle convection extends from the core to the surface if it does so the surface heat flux is only about 50 greater than the heat generation rate however if upper and lower mantle convection occurs in two separate shells as seismological and geochemical arguments suggest the response time is increased the present surface heat flux is then principally controlled by the thermal structure of the earth at the time it was formed the best estimate of the present ratio of the heat loss to heat generation is about two and this value is consistent with the behavior of an earth model consisting of a two layered mantle overlying a core