structural styles and regional tectonic setting of the gela nappe and frontal part of the maghrebian thrust belt in sicily the gela nappe of south central sicily provides an example of a curved segment of an orogenic front that can be examined both onshore and offshore for deformational style and amount of shortening synorogenic sediments allow the deformation to be dated two distinct structural styles are observed in the gela nappe the central salient part of the nappe caltanissetta basin consists of a single thrust sheet containing a train of continuously tightening folds and the reentrant margins of the nappe sciacca and monte judica consist of a stack of several thrust sheets these different structural styles correspond to the pretectonic mesozoic stratigraphy of the foreland plate carbonate platforms exist on the adventure bank and hyblean plateau ahead of sciacca and monte judica respectively while the caltanissetta basin region appears to have accumulated basinal clay facies where the resistant carbonate stratigraphy provides a buttress to the propagation of the thrust front deformation is taken up by imbrication on steep ramps through the carbonates generating a relatively thick orogenic wedge in the basinal setting where no strong rheology exists the low angle of friction on the clay detachment levels requires the growing thrust wedge to be much thinner with a very low foreland dip hence the thrust front propagates much farther forward into the basin than it does in the adjacent platformal areas producing a nonlinear thrust front in the basinal region accretion of foreland material to the nappe by imbrication was only prominent during the messinian when subaerial exposure prevented low friction transport of the nappe across the highest levels of the stratigraphy a steady thickening of the nappe by internal folding suggests an increase in friction along the basal detachment possibly due to progressive compaction of the clays

late quaternary slip rates on the acireale piedimonte normal faults and tectonic origin of mt etna sicily abstract mt etna is located along the east coast of sicily near the boundary between the continental crust of the hyblean plateau and the mesozoic oceanic crust of the ionian basin the main active faults near mt etna cut the base of its eastern flank forming a 30 km long system of nne and nnw trending ene chelon fault segments the acireale piedimonte system showing dip slip and oblique right lateral motion most segments are associated with shallow depth seismicity and all have late pleistocene to holocene vertical slip rates ranging between 1 and 2 mm yr typical of major active normal faults worldwide eruptive fissures arranged in nne to ne trending zones cut the highest slopes of the volcano on the footwall of the normal fault system structural analysis suggests that current motions along both the active faults and eruptive fissures are kinematically compatible and simply linked with ongoing wnw ese directed regional extension such extension characterizes at a greater scale the active tectonics of southern italy where all large shallow historical earthquakes have remained confined within a narrow normal fault belt or rift zone stretching from the northern calabrian arc to southeastern sicily the southernmost west dipping faults of that rift zone in calabria aspromonte cut across the calabro peloritan thrust belt to join the mostly east dipping acireale piedimonte faults along the western boundary of ionian oceanic lithosphere which continues southwards as the malta escarpment we thus relate magmatism at etna to dilational strain on the footwall of an east facing crustal scale normal fault at the bend where the siculo calabrian rift zone veers 60 eastwards as it begins to cross the calabrian arc leaving the east facing margin of the ionian sea to catch up with the west facing margin of the tyrrhenian sea farther north

very shallow earthquakes and brittle deformation in active volcanic areas the eatnean region as an example abstract some aspects of the stress field acting in active volcanic areas were investigated by studying the relationship between surficial seismicity h 1 2 km and the brittle deformation pattern of the etna volcano the magmatic composition and structural character of mt etna are described together with its geodynamic regional context after a discussion of the problem of the state of stress in active volcanoes and a definition of very shallow seismicity the high level of surficial seismicity the morphology of the sedimentary basement and the kinematic behaviour of the faults suggest that the eastern flank of mt etna is a shallow seismotectonic domain structurally decoupled from the rest of the volcanic body this flank shows a tendency to slide in an eastern direction and is bound to the north by a left lateral oblique slip normal fault trending e w and in the south by an arcuate fault system with right lateral features right lateral oblique slip normal faults

volcanism and mantle crust evolution the etna case abstract mount etna is located in a particular region of convergence of african and eurasian plates where intense post collisional tectonics caused considerable uplift however we present arguments supporting the hypothesis that volcanism and associated seismic activity would result from a local mantle uprise leading to a horst probably linked to a deep rooted hot spot it ensued deformation and fracturing of the overlying crust with emission of aphyric tholeiitic basalts directly from their mantle source and subsequent development of a deep reservoir or complex of intrusions at the top of a mantle diapir near 30 km depth this is advocated by the appearance of porphyritic alkaline lavas whose mineral equilibria and differentiation processes are consistent with an 8 10 kbar pressure and by the development of central volcanoes the horst itself appears to have begun in the sw sector of the present volcanic area its uplift was greater westward as seen from the trend of the terraces along the simeto river and became later obvious toward the se these differential movements produced fractures and faults which are to day evident in the southern area of mt etna the growth of the horst then proceeded in a ne direction following the regional tectonic lines and with a greater intensity along the side facing se crossed by the regional nnw sse line aeolian maltese escarpment the seismicity and ground deformation registered over the last twenty years support the proposed model earthquakes are unfrequent in the lower southern and western areas of the volcano whereas they are numerous and stronger to the north east in the summit area above 1600 m a s l and in the eastern sector along the nw se faults and fractures finally a digital elevation model recently published reveals the existence of two tectonic domains the first one is associated with the horst and contains prevalently ne sw oriented faults whereas the second is mainly linked to regional tectonics with nnw sse and nw se faults and fractures

understanding etna flank instability through numerical models abstract as many active volcanoes mount etna shows clear evidence of flank instability and different mechanisms were suggested to explain this flank dynamics based on the recorded deformation pattern and character shallow and deep deformations mainly associated with both eruptive and seismic events are concentrated along recognised fracture and fault systems mobilising the eastern and south eastern flank of the volcano several interacting causes were postulated to control the phenomenon including gravity force magma ascent along the feeding system and a very complex local and or regional tectonic activity nevertheless the complexity of such dynamics is still an open subject of research and being the volcano flanks heavily urbanised the comprehension of the gravitative dynamics is a major issue for public safety and civil protection the present research explores the effects of the main geological features in particular the role of the subetnean clays interposed between the apennine maghrebian flysch and the volcanic products and the role of weakness zones identified by fracture and fault systems on the slope instability process the effects of magma intrusions are also investigated the problem is addressed by integrating field data laboratory tests and numerical modelling a bi and tri dimensional stress strain analysis was performed by a finite difference numerical code flac and flac 3d mainly aimed at evaluating the relationship among geological features volcano tectonic structures and magmatic activity in controlling the deformation processes the analyses are well supported by dedicated structural mechanical field surveys which allowed to estimate the rock mass strength and deformability parameters to take into account the uncertainties which inevitably occur in a so complicated model many efforts were done in performing a sensitivity analysis along a wnw ese section crossing the volcano summit and the valle del bove depression this was mainly devoted to evaluate the effect of topography geometry and rheological behaviour of the structural units the 3d numerical model extended 40 60 km was implemented to simulate the volcano deformation pattern first the role of the pleistocene subetnean clays was investigated then two structural weakness zones the pernicana fault system and the ne rift were introduced and their effects on the flank instability evaluated two extreme hydrogeological conditions drained and undrained were analysed the results are expressed in terms of stress strain field displacement pattern plasticity states and shear strain increments two main instability mechanisms were identified one at shallow depth with the sliding surface located inside the subetnean quaternary clay and another deep seated mechanism with a not continuous and less evident sliding surface developed inside the apennine maghrebian chain flysch bordered by active structures both mechanisms contribute to explain the present deformation pattern and some of the main structures of the etna flank the effect of magma pressure exerted on the active dyke walls during eruptions was then simulated and relations between magmatic activity and flank instability were preliminarily investigated

new evidence for the form and extent of the pernicana fault system mt etna from structural and soil gas surveying a multidisciplinary study based on structural and soil gas surveys was carried out in order to investigate the relationship between soil co2 degassing and the tectonic setting of the lower northeastern flank of mt etna volcano the results show that anomalous soil co2 emissions occur mainly along faults trending wnw ese and also where these faults intersect the other main fault set trending ne sw that displaces the study area in particular anomalies in co2 degassing were revealed both along the pernicana fault and along another fault fiumefreddo fault which may represent the prolongation of the former towards the ionian sea coast in the areas where these structures show evident surface faulting they are all characterised by left lateral displacements and aseismic creep behaviour furthermore the geochemical survey revealed that these faults join in an area devoid of geological evidence of surface faulting and continue underneath an apparently unfaulted alluvial cover near the coastline in the light of these findings we suggest that the pernicana and fiumefreddo faults are discrete segments of a near continuous left lateral shear zone affecting the whole north eastern flank of mt etna as far as the ionian coast

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

long term uplift rate of the etna volcano basement southern italy based on biochronological data from pleistocene sediments the eastern flank of mt etna volcano rests on pleistocene marine sediments which unconformably cover the apenninic maghrebian chain units a quantitative biostratigraphic analysis was carried out based on the calcareous nannofossil content of the pleistocene deposits outcropping along the s and ne periphery of the volcano sediments were constrained to the mnn19e and mnn19f biozones deposited from 1 2 to 0 589 ma according to the depth of deposition and the present altitude of the pleistocene succession uplift rates are estimated between 1 1 and 1 7 mm yr 1 for the northeastern sector of the etna edifice and between 0 36 and 0 61 mm yr 1 for the southern one this inhomogeneous long term uplift rate affecting the etna region probably results from a buried thrust below the northern flank of etna which is related to the post tortonian geodynamic evolution of ne sicily

geometric and kinematic variations along the active pernicana fault implication for the dynamics of mount etna ne flank italy abstract geological and structural analyses and ground deformation measurements performed along the eastern portion of the pernicana fault system and its splay segments allow the structural setting and the kinematic behaviour of the fault to be defined in addition the interrelationship between the deformation style of fault segments and the variations of the volcanic pile thickness along the fault strike are investigated using detailed sedimentary basement data brittle deformation dominates the n105 fault segment where the volcanic pile is more than 200 m thick with the development of a well defined fault plane characterised by main left lateral kinematics the transtensive deformation of the n105 fault is partitioned eastward at rocca campana to a main n120 segment here this segment crosses a culmination of the sedimentary basement close to vena village where the deformation pattern of the thin volcanic pile less than 100 m thick is influenced by the more ductile behaviour of the basement generating local short structures with different orientation and kinematics in the southern block of the fault on the northern one short e w trending faults show left lateral displacements with a minor reverse component on south dipping planes this kinematics is related to the oblique orientation of the n120 segment with respect to the seaward motion of the ne flank of etna on the whole the compressive component of the deformation affecting the n120 segment of the pernicana fault system generates a positive flower structure

an example of river pattern evolution produced during the lateral growth of a central polygenic volcano the case of the alcantara river system mt etna italy abstract analysis of numerous geognostic soundings and geophysical investigation data indicates the presence of a wide depression identifiable as the ancient valley of the alcantara river below the northern flank of mt etna surface and subsurface data were used to reconstruct the complex stratigraphic succession filling the paleo alcantara valley consisting of superimposed lava flows interlayered with thick lentiform clastic bodies the evolution of the alcantara river system was defined with reference to the different phases of growth of mt etna the first correlation between volcanic activity and the drainage system refers to the initial phases of alkaline volcanism 170 100 ka during this period the southern watershed of the paleo alcantara valley acted as a morphological barrier to the products of the various volcanoes which gradually grew in the sector now occupied by the valle del bove the paleo alcantara riverbed was sporadically invaded by lava flows generated by peripheral activity of the central edifice a radical modification of the hydrographic pattern of the region began about 45 40 ka as a consequence of the growth of the ellittico volcano the main eruptive centre of the etnean edifice the gradual expansion of this volcano led over a period between about 30 and 25 ka to the northward deviation of the paleo alcantara riverbed the consequent erosion of a section of the watershed with the adjacent hydrographic basin of the paleo s paolo river resulted in the capture of the latter from then on the hydrographic pattern of the area gradually took on the characteristics it has today a water circulation system developed within the thick volcanic pile filling the paleo alcantara valley with the formation of an aquifer which is today one of the most important hydro structures of the whole volcanic edifice and is in part exploited in the eastern side of sicily

empirical evidence of orthogonal relationship between directional site effects and fracture azimuths in an active fault zone the case of the mt etna lower eastern flank abstract mt etna in eastern sicily is a composite active volcano whose eastern flank is affected by several normal and strike slip active faults in this study geological structural field survey and ambient vibration measurements are performed in the lower eastern flank of mt etna in order to define the role of the tectono stratigraphic setting in the seismic site response the sites of measurements are mainly distributed inside the few hundreds of meters long s caterina graben which is located between two main seismogenic active faults of this volcano sector the acireale and the fiandaca faults our study aims at defining the contribution of the fault related active deformation in determining the local ground motion amplification also providing a subsoil geological model based on the integration of geological and geophysical investigation therefore structural measurements were made in seven sites revealing coseismic and aseismic extensional fractures mainly striking nnw the seismic site response was studied processing the ambient vibration measurements through horizontal to vertical spectral ratio the measured fundamental frequency falls in the range 1 0 4 0 hz that we linked to the presence of a velocity contrast at depth of 80 200 m by calibrating a frequency depth function moreover the seismic site effect is due to the stratigraphic setting and is markedly directional showing maximum amplification along the direction orthogonal to the strike of the observed isooriented extensional fracture field produced by the activity of the s caterina graben it is noteworthy that far from the graben on sites of measurements located near the fiandaca fault we observed directional effects parallel to the direction of maximum extension inferred for this tectonic lineament our results suggest a linkage between directional site effects and local stress tensors and fractures field orientation

a global analysis of mid ocean ridge axial topography summary current views of mid ocean ridges are strongly influenced by extensive mapping of the mid atlantic ridge and east pacific rise the global picture of the mid ocean ridge system particularly in the sparsely surveyed southern oceans is still based primarily on underway bathymetry profiles collected over the past 40 years this study presents a quantitative analysis of global mid ocean ridge morphology based on 156 of these underway bathymetric profiles thereby allowing commonly recognized features such as axial valleys and axial ridges to be compared on a global basis an empirical orthogonal function eof analysis is used to separate deterministic and stochastic components of axial morphology and to quantify the dependence of each on parameters such as spreading rate and axial depth it is found that approximately 50 per cent of the variance in axial morphology may be described as a linear combination of five independent symmetric and anti symmetric modes the remainder is considered stochastic maximum axial valley relief decreases with spreading rate for rates less than 80 mm yr 1 while axial ridge relief remains relatively constant for all rates greater than 50 mm yr 1 the stochastic component of the axial morphology referred to as bathymetric roughness also decreases with spreading rate for rates less than 80 mm yr 1 and remains relatively constant at higher rates although both axial valley relief and bathymetric roughness near the ridge axis show a similar spreading rate dependence they are weakly correlated at slow spreading centres the distinct differences in morphologic variability of fast and slow spreading ridges may result from the episodicity of magmatic heat input which controls the lithospheric rheology at slow spreading ridges these observations support the notion of a critical threshold separating two dynamically distinct modes of lithospheric accretion on mid ocean ridges

an ams structural and paleomagnetic study of quaternary deformation in eastern sicily abstract an integrated structural anisotropy of magnetic susceptibility ams and paleomagnetic study was carried out on plio pleistocene sedimentary basins in eastern sicily these basins belong to three main tectonic domains the tyrrhenian hinterland domain the catania foredeep domain and the hyblean foreland domain we sampled 329 oriented samples from 25 sites in selected areas from the different tectonic domains the ams is typical for weakly deformed sediments with a magnetic foliation sub parallel to the bedding plane and a well defined magnetic lineation the orientation of the magnetic lineation is strongly controlled by the main tectonic deformation recorded in the basins structural and ams data define a transition from nw se extension in the tyrrhenian hinterland domain to e w compression in the catania foredeep domain to e w extension in the hyblean foreland domain respectively reliable paleomagnetic results have been obtained in 12 out of 25 sampled sites data show that no significant rotations occurred in any of the studied basins at least since the middle pleistocene these results allow us to define an upper limit to the large rotations about vertical axes that have been previously found in the calabria and sicily regions

tectonic deformation and microseismicity of the saronikos gulf greece we deployed an on offshore seismic network consisting of 36 three component stand alone digital stations in the saronikos gulf and surrounding area and observed the microseismic activity from 17 august to 9 december 2001 the geometry and location of the network were designed to observe the offshore activity to connect known active faults onshore with those offshore an average of 15 events per day were recorded by a minimum of six stations the focal parameters of 739 events could be defined within the network area we located 306 events with an rms travel time residual of about 0 2 sec the epicenters in the saronikos gulf are aligned mainly along an east west trending fault with a length of nearly 30 km this fault is located north of aegina and could produce earthquakes as large as ms 6 5 it is the offshore continuation of a seismic zone located in east corinthia a second active fault was identified east of aegina trending northeast southwest it is probably linked to the northeast southwest striking zone of the salamis fili seismic region activated by the september 1999 event of athens outside the network we mapped an active area at the parnis mountain still active after the ms 5 9 event and a second one further northeast at the western coast of evia this zone is close to chalkis and the recently active psachna area the network also mapped intense activity at the northeastern coast of evia close to the city of kymi and the area of skyros which was seriously damaged by an ms 5 8 earthquake in 2001 the onshore offshore local network identified several regions of very high seismic activity not detectable by regional networks and demonstrated once more the advantage of deploying local seismic networks for mapping active deformation in very short periods of time

the dyke swarm of mount calanna etna italy an example of the uppermost portion of a volcanic plumbing system a new multidisciplinary study combining geology petrography and geochemistry on the rocks of the isolated hill of mount calanna mount etna italy has provided evidence for the existence of a dyke swarm formed by more than 200 dykes distributed over an area of 0 7 km2 with an intensity of intrusion up to 40 all bodies are deeply altered and the geological and mesostructural surveying of 132 dykes revealed that they intruded in e w direction with an average dip of 60 the faults affecting the outcrop have in general an e w strike and dip of 55 these have all normal motion and have been interpreted as coeval with the dykes this interpretation contrasts with the previous hypothesis that considered mount calanna as a thrust resulting from compressive deformation resulting from the gravitational spreading of the volcanic edifice mount calanna is here interpreted as the uppermost portion of a vertically extensive magmatic plexus that fed the eruptive activity of one or more eruptive center s sited in the valle del bove area measurements of the apparent densities on 23 dykes and host rock samples give an average value of 2 420 kg m3 for the entire complex 15 lower than the density expected for hawaiitic magma placing an important constraint on the geophysical identification of similar structures considering that mount etna is not an old eroded edifice but an active and growing volcano the exposure of this subvolcanic structure can be regarded as exceptional its geometry and physical characteristics can be thus regarded as an interesting example of the present day shallow plumbing system of mount etna as well as of other basaltic volcanoes

magma uprising and flank dynamics on mount etna volcano studied using gps data 1994 1995 1 ground deformation occurring on mount etna from 1994 to 1995 is analyzed in this paper this period was characterized by intense volcanic activity at the four summit craters with frequent strombolian activity fire fountains and emplacement of several new lava flows four gps surveys were carried out during this time two as routinely planned each year and an additional two in 1995 to acquire more data to follow the activity at the ne crater the comparisons between gps surveys are reported in terms of horizontal and vertical displacements of each station and in terms of areal dilatation and principal strain axes during the period considered in this work a trend of increasing areal dilatation of the volcano at a rate of about 5 strain yr was recognized it was briefly interrupted by a small contraction about 2 strain in the autumn of 1995 when volcanic activity at the summit craters began in detail the strain distribution of the network is analyzed it allows the detection of areas showing anomalous behavior such as the summit zone or the pernicana fault inversions of the ground displacement vectors have been performed by appropriately combining numerical and analytical approaches results of the inversions suggest structures defining an eastward and southward sliding of the eastern and southeastern sectors of mount etna

the relationship between late quaternary deformation and volcanism of mt etna eastern sicily new evidence from the sedimentary substratum in the catania region abstract stratigraphical and structural analyses have been carried out on the late quaternary foredeep succession forming the etnean substratum in the catania region eastern sicily in order to investigate in detail the chronology of deformation events that have accompanied a significant period of the eruptive activity of mt etna i e from 240 ka to the present this episode was characterised at about 200 ka by a main change of the petrochemical features of the emitted products from sub alkaline to alkaline this can be related to an evolving mantle diapir located beneath the volcano the new stratigraphical and structural field data presented in this paper constrain the development from 240 to 125 ka of nw se trending dextral faults associated with minor e w to ne sw oriented accommodation thrusts and nnw sse trending normal faults that originated in a dominant transpressive regime strike slip tectonics were active during the earlier emissions of sub alkaline lavas 320 200 ka old and part of the ancient alkaline products 180 100 ka old from scattered eruptive systems which developed in local transtensive zones distributed throughout the whole etnean region a major change in the mode of deformation since 125 ka bp was related to the propagation of a normal fault belt along the ionian coast of the catania region and the eastern sectors of the etnean edifice this process was associated with the growth of open folds that deformed the entire foredeep sequence exposed along the southern boundary of the etnean edifice during this period eruptive activity concentrated along the main extensional features where steady and very efficient feeding systems originated this resulted in a rapid increase in the volume of emitted alkaline products that gave rise to the construction of the modern stratovolcano during the last 80 ka the collected data emphasise some main aspects of the relationship between tectonic deformation at a regional scale and volcanism in the etna area firstly the mode of deformation at the onset of etnean volcanism seems to be inadequate to explain the emplacement at depth of a mantle diapir related to the occurrence of a hotspot almost independent from the local crustal dynamics on the other hand the late quaternary structural assemblages recognised on the surface can be interpreted as direct effects of the europe africa convergence rather than as the products of deformation induced by the emplacement of the mantle diapir in the different stages of etnean evolution a direct relationship exists between the mode of deformation and the distribution as well as the capacity of the feeding systems in particular the amounts of emitted products in the different stages depend on the intensity of crustal stretching associated with deformation rather than the volume of available molten material at depth these conclusions represent a new perspective for the interpretion of the early stages and subsequent evolution of the volcanic activity of mt etna the proposed model also represents an useful tool in deciphering the relationship between the deformation path seismicity and volcanic activity of mt etna

tectonic stresses and volcanism in situ stress measurements and neotectonic investigations in the etna area italy abstract mt etna has been building up for about 500 000 years on the eastern margin of sicily at the external border of the apenninic maghrebian mountain chain and at the crossing of several important regional fault systems the tholeiitic and alkaline magmatism of mt etna represents the northernmost manifestation of present day volcanism which was continuous in space and time from the upper miocene to the lower pleistocene in central eastern sicily in situ stress measurements and neotectonic investigations have been carried out on mt etna on its periphery and on the hyblean mountains to obtain a better understanding of the stress field which is connected to the present day activity of the volcano and a clearer picture of the regional geodynamical evolution the investigations allow a comparison of the present stress field with that acting during the quaternary the neotectonic analysis has given evidence of strong compressional stresses exerted on the pleistocene sediments overlying the substratum of the volcano and its immediate surroundings in addition to evidencing the already known extensional deformation the compressional forces were oriented approximately n s at the beginning of the volcanic activity the in situ stress measurements show now that this n s compression is today active only in the northernmost part of the etna area whereas in the remaining area extensional stresses oriented approximately wnw ese prevail it is concluded that the compressional stresses near the surface today limited to the northernmost part of the etna area had a much more widespread distribution at the beginning of the volcanic activity this conclusion is important for understanding the deep seated magmatic process focal mechanisms of earthquakes indicate a complex tectonic situation with normal faulting down to a depth of 5 km and reverse faulting at deeper levels

new insights into the local crust structure of mt etna volcano from seismological and morphotectonic data abstract the reconstruction of the extensional active tectonic structures on the eastern flank of mt etna and of the related earthquakes allowed the analysis of fault parameters for more than 50 episodes of coseismic ground rupture for the last 250 years the calculation of statistical relationships among earthquake magnitude surface rupture length surface fault displacement and their combination was performed moreover we found out that the minimum earthquake magnitude to have ground rupture effect is ca 2 5 we were therefore able to hypothesize a reduced seismogenic layer 5 6 km under the lower eastern flank of the volcano we also analysed structural and marine geology data to find further surface evidences of the volcano dynamics we recognized for the first time a local component of uplift affecting the volcanic domain at least in the last 20 ka with a rate up to 3 5 mm yr that is likely related to a volcanic dome effect coupling the two aspects the seismological one and the morphostructural one of our research we propose a local thinning of the brittle crust in this sector of mt etna the thermal effects of the uprising magma on the rheology of the crust rocks well explain all our observations

geodetic techniques applied to the study of the etna volcano area italy volcanic behaviour of mt etna is due to the complex interaction between both the local and the regional stress field involving the eastern sicily eruptions could trigger be triggered during crust extension and or compression which are strictly linked with the dynamics of the lower mantle in this study very long baseline interferometry vlbi space geodesy technique has been used in order to study etna volcano s activity by means of the crustal deformations between noto and matera located on the african and the eurasian plates respectively by analysing vlbi data we obtained the behaviour of the baseline which crosses the etnean area from 1990 december to 2003 march representing the time variations of the distance between the two geodetic stations the linear trend of the baseline shows a general increasing pointing out an extension of the crust between them a detailed analysis of the noto matera baseline allows the identification of three parts of the vlbi curve in the considered period in the first part of the curve from 20 12 90 to 09 02 94 vlbi data are rather poor and therefore no reliable consideration about correlation between crust movements and volcanic and seismicity activity has been made in the second part of the curve from 09 02 94 to 04 09 00 vlbi data are more frequent and show slightly fluctuations in the distance increasing in the extension and compression were observed in the central and in the final part of this period in the third period from 04 09 00 to 25 03 03 vlbi data are very sparse even if the time series was quite long therefore to fill gaps in the information we analysed global positioning system gps data gps technique performs continuous observations and we were able to highlight both extensions and compressions in detail comparisons between the trend of noto matera baseline length variations volcanic activity and seismicity in the etna area show the complexity of the development over time and space of the phenomenology determined by a deep cause which can be traced in our opinion to the interaction between the asthenospheric mantle deep crust and surface crust therefore we state that crustal distension and compression are determined by the lower pulsating mantle

coastal elevation changes in eastern sicily implications for volcano instability at mount etna the eastern flank of mount etna sicily has been recognised as being unstable and three contrasting models have been proposed to account for this phenomenon these being deep seated spreading shallow sliding and tectonic block movements these models are examined by making reference to the rates and patterns of crustal movement along the eastern coastline of sicily as determined from palaeoshoreline data the south eastern coastline of sicily portopalo to catania provides no evidence of holocene emergence in contrast the volcanic coastline catania to capo schiso and the northeastern shoreline taormina to milazzo display widespread evidence of coastal emergence radiocarbon dated remains indicate that both the volcano and northeastern sicily have been uplifted at a rate exceeding 1 5mm yr during holocene times although more recent rates of uplift may have been greater the pattern of uplift suggests that the northeastern coastline of sicily including the volcanic ediface is apparently uplifting as a coherent unit with superficial flank movements being superimposed on a regionally uplifting sub volcanic basement

early deformations at a submarine compressive front the quaternary catania foredeep south of mt etna sicily italy abstract in the catania foredeep south of mt etna oil drilling has revealed the existence at depth of an allochthonous complex emplaced during the middle quaternary at the surface outcropping middle quaternary marine marly clays and sands display complex deformations which are partly synsedimentary and which can be correlated with the emplacement of this allochthonous complex most of these deformations are thought to result from gravitational gliding of slope sediment apron this process probably facilitated by high pore pressure would be in particular the cause of a semi penetrative shear deformation with an eastward vergence in the clays thus our study rules out the classical view of a shallow pre etnean gulf that was steadily filled in before emerging some 400 000 to 300 000 years ago this particular example of neotectonics shows the precocity and complexity of deformations occurring in sediments deposited along the compressive margin of a foreland basin or similarly at an accretionary prism front

control of rock rheology on deformation style and slip rate along the active pernicana fault mt etna italy abstract the already known part of the active left lateral strike slip pernicana fault on the eastern flank of mt etna volcano has a holocene high slip rate of 1 5 2 7 cm yr but its surface trace abruptly disappears eastward approaching the lower slope of the volcano using geological geomorphological and structural surveys we found that the pernicana deformation zone extends 8 km further to the east beyond this point through a different mechanism as the thickness of the volcanic pile decreases the single e w to ese striking main fault plane gives way to a set of faults arranged in a splay structure which partitions the fault motion here slip rates are 0 4 to 1 4 cm yr on each fault further east where the lava succession is very thin and unfaulted we suggest that lavas are decoupled from plastic deforming sub etnean clay deposits which absorb the strain or that lavas have a too low mass to slide on the very lowest slope of the volcano i e further east lavas are once again thicker and the pernicana deformation zone behaves at the surface once again in a brittle manner locally known as the fiumefreddo fault with a low slip rate of

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

the interaction of volcanic activity in quaternary times upon the evolution of the alcantara and simeto rivers mount etna sicily summary the interaction between volcanic and alluvial sequences is described for the alcantara and simeto valleys mount etna sicily this study provides valuable information on the stratigraphy for prehistoric lavas exposed on the lower western flanks of the volcano eight orders of terrace are recognised in the simeto valley the basal tholeiitic volcanics the oldest exposed lavas of etna are associated with terrace 7 of the simeto which is correlated with either the pre rianian nomentanan erosive phase or the early rianian stage of the pleistocene the earliest evidence of trachybasaltic volcanism in the simeto catchment occurs in terrace 4 which is considered to be of late maspinian age the oldest known volcanics in the north western part of the volcano are related to terrace 3 which is dated at around 20000 bp the alluvial deposits of these terraces provide a valuable sequence of italian quaternary sediments dating back over the last 300000 years the nature of these deposits is described and the probable conditions of their deposition considered the terraces in the upper part of the alcantara are quite different in their mode of formation from the lava capped cut and fill terraces of the simeto valley the current upper course of the alcantara river is considered to be quite youthful versilian in age and the terraces are bench features formed as the river cut down through the lava sequence