accumulation variability over a small area in east dronning maud land antarctica as determined from shallow firn cores and snow pits some implications for ice core records we investigate and quantify the variability of snow accumulation rate around a medium depth firn core 1160 m drilled in east dronning maud land antarctica 75 degrees 00 s 15 degrees 00 e 3470 m h a e ellipsoidal height we present accumulation data from five snow pits and five shallow 20 m firn cores distributed within a 3 5 7 km distance retrieved during the 2000 01 nordic epica european project for ice coring in antarctica traverse snow accumulation rates estimated for shorter periods show higher spatial variance than for longer periods accumulation variability as recorded from the firn cores and snow pits cannot explain all the variation in the ion and isotope time series other depositional and post depositional processes need to be accounted for through simple statistical analysis we show that there are differences in sensitivity to these processes between the analyzed species oxygen isotopes and sulphate are more conservative in their post depositional behaviour than the more volatile acids such as nitrate and to some degree chloride and methanesulphonic acid we discuss the possible causes for the accumulation variability and the implications for the interpretation of ice core records

a recent tectonic reorganization in the south central mediterranean abstract new geodetic data combined with seismicity geologic and geochemical information document a major tectonic reorganization in the central mediterranean around 0 8 0 5 ma when rapid trench migration and consequent tyrrhenian back arc extension which dominated the region s evolution since the tortonian 10 8 ma essentially stopped in response the african convergence in sicily was transferred to a back thrust in the southern tyrrhenian characterized by frequent m5 6 earthquakes in the last 20 years a diffuse transform boundary formed across northeastern sicily to connect the sicilian and calabrian plate boundaries causing opening of the messina straits home to large historical earthquakes and unusual volcanism in the aeolian island arc and the intraplate mount etna a divergence of the ionian region from the main part of africa with northeastward motions that reflect the joint influence of african push and hellenic slab pull and are transmitted to calabria and adria could explain motions observed in the sicily channel calabria and apulia as well as the high level of southeastern sicilian seismic activity

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

regional scale morphological pattern of the tyrrhenian sea new insights from emodnet bathymetry abstract a large body of literature exists on the morphology of the tyrrhenian sea the youngest back arc basin of the eastern mediterranean however most of these studies are focused on local areas without considering the broad regional setting in this paper we consider the morphology of the entire tyrrhenian sea at a regional scale based on a dem analysis of middle resolution bathymetry downloaded from the emodnet website based on these data a first morpholineaments map has been created identifying 500 features 10 km in length without considering their tectonic settings and age furthermore a tyrrhenian regional tectonic map has been digitized from literature and the faults divided in pre pliocene pliocene and plio quaternary morpholineaments and tectonic lineaments have been grouped in six tyrrhenian sea areas plotted in rose diagrams in order to obtain the main trends in each region and to detect relationships between morphology and tectonics rose diagrams show that most of the identified morpholineaments have a tectonic origin although they are not coeval as they developed during different phases of the opening of the tyrrhenian back arc basin moreover morpholineaments data suggest that some regions of the tyrrhenian sea may be dominated by a single main trend whereas in other regions the occurrence of more trends testifies a major tectonic complexity

subduction kinematics and dynamic constraints the kinematics of subduction zones shows a variety of settings that can provide clues for dynamic understandings two reference frames are used here to describe the simple 2d kinematics of subduction zones in the first the upper plate is assumed fixed whereas in the second frame upper and lower plates move relative to the mantle relative to a fixed point in the upper plate u the transient subduction hinge h can converge diverge or be stationary similarly the lower plate l can converge diverge or be stationary the subduction rate vs is given by the velocity of the hinge h minus the velocity of the lower plate l vs vh vl the subduction rate 1 increases when h diverges and 2 decreases when h converges combining the different movements at least 14 kinematic settings can be distinguished along the subduction zones variable settings can coexist even along a single subduction zone as shown for the 5 different cases occurring along the apennines subduction zone apart from few exceptions the subduction hinge converges toward the upper plate more frequently along e or ne directed subduction zone whereas it mainly diverges from the upper plate along w directed subduction zones accompanying backarc extension before collision orogen growth occurs mostly at the expenses of the upper plate shortening along e ne directed subduction zones whereas the accretionary prism of w directed subduction zones increases at the expenses of the shallow layers of the lower plate the convergence shortening ratio is 1 along e or ne directed subduction zones whereas it is 1 along accretionary prisms of w directed subduction zones backarc spreading forms in two settings along the w directed subduction zones it is determined by the hinge divergence relative to the upper plate minus the volume of the accretionary prism or in case of scarce or no accretion minus the volume of the asthenospheric intrusion at the subduction hinge since the volume of the accretionary prism is proportional to the depth of the decollement plane the backarc rifting is inversely proportional to the depth of the decollement on the other hand along e or ne directed subduction zones few backarc basins form e g aegean andaman and can be explained by the velocity gradient within the hangingwall lithosphere separated into two plates when referring to the mantle the kinematics of subduction zones can be computed either in the deep or in the shallow hotspot reference frames the subduction hinge is mostly stationary being the slab anchored to the mantle along w directed subduction zones whereas it moves w or sw ward along e or ne directed subduction zones surprisingly along e or ne directed subduction zones the slab moves out of the mantle i e the slab slips relative to the mantle opposite to the subduction direction kinematically this subduction occurs because the upper plate overrides the lower plate pushing it down into the mantle as an example the hellenic slab moves out relative to the mantle i e sw ward opposite to its subduction direction both in the deep and shallow hotspot reference frames in the shallow hotspot reference frame upper and lower plates move westward relative to the mantle along all subduction zones this kinematic observation casts serious doubts on the slab negative buoyancy as the primary driving mechanism of subduction and plate motions w directed subduction zones rather provide about 2 3 times larger volumes of lithosphere re entering into the mantle and the slab is pushed down this opposite behavior is consistent with the down dip extension seismicity along e ne directed subduction zones and the frequent down dip compression along the w directed subduction zones subduction kinematics shows that plate velocity is not dictated by the rate of subduction along the w directed subduction zones the rate of subduction is rather controlled i by the hinge migration due to the slab interaction with the easterly trending horizontal mantle wind along the global tectonic mainstream ii by the far field plate velocities and iii by the value of negative buoyancy of the slab relative to the country mantle alternatively e ne nne directed subduction zones have rates of sinking chiefly determined i by the far field velocity of plates and ii by the value of negative buoyancy of the slab relative to the country mantle along this type of subduction the subduction hinge generally advances e ne ward toward the upper plate decreasing the subduction rate but it moves w sw ward relative to the mantle all this indicates that subduction zones have different origin as a function of their geographic polarity and the subduction process is more a passive feature rather than being the driving mechanism of plate motions a rotational component combined with mantle density and viscosity anisotropies seems more plausible for generating the global tuning in the asymmetry of subduction zones

rheological control of subcrustal seismicity in the apennines subduction italy 1 different rheological behavior of continental vs oceanic lithosphere can account for the shallower and lower subcrustal seismicity below the northern apennines with respect to the deeper and more intense seismicity below the calabrian arc in the south along the same subduction zone we show that for equal temperature distribution oceanic slabs are predicted to display brittle behavior down to depths higher than those predicted for a continental slab this opposite rheology is likely amplified by the higher strain rates and cooler slab temperatures in the south due to the faster subduction rollback and the oceanic composition of the downgoing lithosphere therefore the paucity of seismicity in the central northern apennines might not be related to the absence of the slab but rather to its continental nature and to lower strain rates

trends and patterns in the recent accumulation and oxygen isotopes in coastal dronning maud land antarctica interpretations from shallow ice cores to investigate recent variability in accumulation and d 18 o we synthesize data from five snowcores covering the period1932 96 fromthe sector16 38 w 4 48 e in coastal dronning maudland dml antarctica the d 18 orecords fromthe differentsites areremarkablysimilarand suggestacommon stablemoisturesourceforthis coastal section of dml while the accumulation pattern is local and specific features restricted to the individual sites the overall accumulation pattern is related to the temperature variability as indicated by coastal instrumental records accumulation and d 18 o correlate between 1955 and1985 but deviate thereafter with the proxy temperature record showing a positive trend while accumulation decreased this occurs at the same time as an increase in sea ice extentinthearea whichmayhaveresultedincirculationchangesandmorenortherlystorm paths both stacked accumulation and d 18 o records show that large scale atmospheric sig nals aswellas some pronounced individualevents arerecorded in dmlcoastal ice cores

a new surface accumulation map for western dronning maud land antarctica from interpolation of point measurements as a result of intensive field activities carried out by several nations over the past 15 years a set of accumulation measurements for western dronning maud land antarctica was collected based on firn core drilling and snow pit sampling this new information was supplemented by earlier data taken from the literature resulting in 111 accumulation values using geographical information systems software a first region wide mean annual snow accumulation field was derived in order to define suitable interpolation criteria the accumulation records were analyzed with respect to their spatial autocorrelation and statistical properties the resulting accumulation pattern resembles well known characteristics such as a relatively wet coastal area with a sharp transition to the dry interior but also reveals complex topographic effects furthermore this work identifies new high return shallow drilling sites by uncovering areas of insufficient sampling density

strain and rotation rate from gps in tibet anatolia and the altiplano 1 deformation measured by regional gps networks in continental plateaus reflects the geologic and tectonic variability of the plateaus for two collisional plateaus tibet and anatolia and one noncollisional the altiplano we analyze the regional strain and rotation rate by inverting gps velocities to calculate the full two dimensional velocity gradient tensor to test the method we use gridded velocities determined from an elastic block model for the eastern mediterranean middle east region and show that to a first order the deformation calculated directly from the gps vectors provides an accurate description of regional deformation patterns principal shortening and extension rate axes vertical axis rotation and two dimensional 2 d volume strain dilatation are very consistent with long term geological features over large areas indicating that the gps velocity fields reflect processes responsible for the recent geologic evolution of the plateaus differences between geological and gps descriptions of deformation can be attributed either to gps networks that are too sparse to capture local interseismic deformation or to permanent deformation that accrues during strong earthquakes the altiplano has higher internal shortening magnitudes than the other two plateaus and negative 2 d dilatation everywhere vertical axis rotation changes sign across the topographic symmetry axis and is due to distributed deformation throughout the plateau in contrast the collisional plateaus have large regions of quasi rigid body rotation bounded by strike slip faults with the opposite rotation sense from the rotating blocks tibet and anatolia are the mirror images of each other both have regions of positive dilatation on the outboard sides of the rotating blocks positive dilatation in the aegean correlates with a region of crustal thinning whereas that in eastern tibet and yunnan province in china is associated with an area of vertical uplift rollback of the hellenic trench clearly facilitates the rotation of anatolia rollback of the sumatra burma trench probably also enables rotation about the eastern syntaxis of tibet

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

rifted margin formation in the south tyrrhenian sea a high resolution seismic profile across the north sicily passive continental margin a new 150 km long seismic line across the continental margin of north sicily has been acquired and interpreted the overall structure of the margin is controlled by extension which caused crustal thinning and widespread normal faulting two main thinned zones are observed in the south in correspondence with the cefalu basin and farther to the north at the continent ocean transition zones of thinned crust coincide with zones of intense normal faulting extension began in late tortonian times and caused the opening of the cefalu basin controlled by a northward dipping listric fault messinian stretching affected most of the future margin and provoked a widening of the cefalu basin and normal faulting in the north following a phase of relative quiescence in the early pliocene renewed extension determined further opening of the cefalu basin and subordinate normal faulting in the north here however the record is unclear because of the emplacement of the calc alkaline sisifo volcano with associated volcanoclastic deposits breakup took place in the late pliocene and was followed by the deposition of postrift pleistocene sediments at the lithospheric scale the sites of extension thinning did not migrate during rifting on the smaller scale on the contrary the cefalu basin displays a remarkably systematic pattern of migration toward the foot wall of the listric fault which controlled the opening of the basin the spacing of 4 6 km between faults is also quite systematic elongation experienced by the continental part of the margin presently 97 km has been derived by comparing the present day and the preextensional lengths and is 10 km the corresponding strain rate is 5 10 16 s 1

source of the 1693 catania earthquake and tsunami southern italy new evidence from tsunami modeling of a locked subduction fault plane 1 the 1693 catania earthquake which caused 60000 deaths in eastern sicily and generated a 5 10 m high tsunami is investigated gps data indicate ese wnw convergence in the calabrian arc at 4 5 mm yr new high resolution seismic data image active compression at the toe of the accretionary wedge the lack of instrumentally recorded thrust earthquakes suggests the presence of a locked subduction fault plane thermal modeling is applied to calculate the limits of the seismogenic zone tsunami modeling is performed to test the hypothesis that the 1693 earthquake occurred on the subduction fault plane 160 120 km in size with 2 m of mean co seismic slip this source successfully reproduces historical observations with regard to polarity and predicts 1 3 m high amplitudes it is likely that only the sw segment of the subduction fault plane ruptured in 1693 and 1169 implying a recurrence interval of roughly 500 years for similar events

active tectonics in central italy constraints from surface wave tomography and source moment tensor inversion abstract we investigate the lithosphere asthenosphere structure and active tectonics of central italy with emphasis on the umbria marche area by means of surface wave tomography and seismic moment tensor inversion the data include a large number of short period local and regional group velocity measurements sampling the umbria marche apennines and the adria margin respectively incorporation of published phase velocity measurements sampling italy and surroundings results from deep seismic soundings which go through the umbria marche area the local group velocity maps covering the area reactivated by the 1997 1998 umbria marche earthquake sequence suggest an intimate relationship between the lateral earth structure variations and the distribution of the active fault systems and related sedimentary basins the upper crustal models reveal the importance of inherited compressional tectonics on the recent extensional deformation and associated seismic activity source inversion studies of the main events of the 1997 earthquake sequence show the dominance of normal faulting mechanisms whereas selected aftershocks between the fault segments at the step over reveal that the prevailing deformation is of strike slip faulting type at the regional scale the crust exhibits clear layering and varies in thickness from about 25 km below the tuscan metamorphic complex tmc to about 30 km below the val tiberina extensional thick sedimentary basin and reaches about 35 km below the umbria marche geological domain umd the lithospheric mantle lid is thin about 30 km below tmc while it is about 70 km thick below umd a lithospheric root about 120 km wide between the tmc and umd reaches a depth of at least 130 km a low velocity zone defined mantle wedge vs less than 4 2 km s in the uppermost mantle overlying the high velocity lid is detached this wedge is about 20 km thick and decouples the underlying lid from the crust the retrieved crust and upper mantle structure beneath central italy is in agreement with bouguer anomaly and heat flow data and supports a delamination process the high velocity upper mantle underlying the mantle wedge is inferred to be subcrustal lithospheric material delaminated from the overlying crust

climate variables along a traverse line in dronning maud land east antarctica temperature density and accumulation data were obtained from shallow firn cores drilled during an overland traverse through a previously unknown part of dronning maud land east antarctica the traverse area is characterised by high mountains that obstruct the ice flow resulting in a sudden transition from the polar plateau to the coastal region the spatial variations of potential temperature near surface firn density and accumulation suggest that katabatic winds are active in this region proxy wind data derived from firn density profiles confirm that annual mean wind speed is strongly related to the magnitude of the surface slope the high elevation of the ice sheet south of the mountains makes for a dry cold climate in which mass loss owing to sublimation is small and erosion of snow by the wind has a potentially large impact on the surface mass balance a simple katabatic wind model is used to explain the variations of accumulation along the traverse line in terms of divergence convergence of the local transport of drifting snow the resulting wind and snowdrift patterns are closely connected to the topography of the ice sheet ridges are especially sensitive to erosion while ice streams and other depressions act as collectors of drifting snow

rapid techniques for determining annual accumulation applied at summit greenland we have determined accumulation histories by identifying annual layer horizons in records obtained by three independent methods 1 glaciochemical analysis on a core 2 density profiling in the borehole from which the core was taken using the neutron probe np technique and 3 borehole optical stratigraphy bos again in the same borehole we also used three different techniques for determining density to convert annual layer thickness to accumulation 1 gravimetric measurements on core samples 2 measurement of density using np and 3 a simple empirical model based on regional climatology the result is nine different accumulation time series three of which are completely independent the chemical analysis and np derived accumulation time series are correlated and the 70year means are in agreement the bos derived accumulation 70 year mean is slightly lower probably due to a combination of the empirical density model s underestimate of the density profile and the misidentification of sub annual events in the shallow part of the borehole as annual horizons

crustal structure and seismotectonics of central sicily southern italy new constraints from instrumental seismicity summary in this paper we propose a new model of the crustal structure and seismotectonics for central sicily southern italy through the analysis of the depth distribution and kinematics of the instrumental seismicity occurring during the period from 1983 to 2010 and its comparison with individual geological structures that may be active in the area the analysed data set consists of 392 earthquakes with local magnitudes ranging from 1 0 to 4 7 we defined a new detailed 1 d velocity model to relocate the earthquakes that occurred in central sicily and we calculated a moho depth of 37 km and a mean vp vs ratio of 1 73 the relocated seismic events are clustered mainly in the area north of caltanissetta e g mainland sicily and in the northeastern sector madonie mountains of the study area only minor and greatly dispersed seismicity is located in the western sector near belice and along the southern coast between gela and sciacca the relocated hypocentral distribution depicts a bimodal pattern 50 per cent of the events occur within the upper crust at depths less than 16 km 40 per cent of the events occur within the middle and depth crust at depths between 16 and 32 km and the remaining 10 per cent occur at subcrustal depths the energy release pattern shows a similar depth distribution on the basis of the kinematic analysis of 38 newly computed focal plane solutions two major geographically distinct seismotectonic domains are distinguished the madonie mountain domain with prevalent extensional and extensional oblique kinematics associated with upper crust late pliocene quaternary faulting and the mainland sicily domain with prevalent compressional and compressional oblique kinematics associated with thrust faulting at mid to deep crust depth along the north dipping sicilian basal thrust sbt the stress inversion of the mainland sicily focal solutions integrated with neighbouring mechanisms available in the literature highlights a regional homogeneous compressional tensor with a subhorizontal nnw sse striking 1 axis in addition on the basis of geodetic data the mainland sicily domain may be attributed to the sse ward thrusting of the mainland sicily block along the sbt plane seismogenic shearing along the sbt at mid crustal depths was responsible for the unexpected belice 1968 earthquake mw 6 1 with evident implications in terms of hazard assessment

p wave tomography of the mantle under the alpine mediterranean area 1 we study the upper mantle p wave velocity structure below the euro mediterranean area down to 1000 km depth by seismic travel time tomography we invert summary residuals constructed with both regional and teleseismic first arrival data reported by the international seismological centre isc 1964 1995 introducing some alternative strategies in the travel time tomographic approach and a new scheme to correct teleseismic data for global mantle structure our high resolution model pm0 5 is parameterized with three dimensional 3 d linear splines on a grid of nodes with 0 5 spacing in both horizontal directions and 50 km vertical spacing we obtain about 26 root mean square rms reduction of residuals by inversion in addition to roughly 31 reduction after summary rays formation and selection sensitivity analyses are performed through several test inversions to explore the resolution characteristics of the model at different spatial scales the distribution of large scale fast anomalies suggests that two different stages of a convection process presently coexist in very close regions the mantle dynamics of western central europe is dominated by blockage of subducted slabs at the 660 km discontinuity and ponding of seismically fast material in the transition zone contrarily in the eastern mediterranean fast velocity material sinks into the lower mantle suggesting that the flow of the cold downwelling here is not blocked by the 660 km discontinuity on a smaller scale the existence of tears in the subducted slab lithospheric detachment all along both margins of the adriatic plate as proposed by some authors is not supported by our tomographic images

shallow firn cores from neumayer ekstromisen antarctica a comparison of accumulation rates and stable isotope ratios since 1979 80 glaciological studies have been carried out at ekstromisen antarctica including accumulation stake measurements snow pit and shallow firn core studies snow stratigraphy chemical properties and stable isotope ratios 18 o were investigated this study focuses on three cores taken between 1982 and 1998 the 1998 core was dated using dielectric profiling 18 o profiles and stake measurements accumulation rates show high interannual and spatial variability due to the extreme wind influence no significant trend was found for the last 50 years during the first half of the 20th century accumulation decreased the high spatial and interannual variability however means that trends must be interpreted with care in spite of the highly irregular accumulation distribution stable isotope ratios show little spatial variability the mean annual 18 o values of cores b04 and fb0198 agree fairly well for the time period 1955 82 covered by both cores 18 o values have increased during most of the 20th century since the late 1980s a decrease is observed this change is not related to air temperature since mean annual air temperatures at neumayer show no significant trend over the last two decades

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

tectonic history of the submerged maghrebian chain from the southern tyrrhenian sea to the pelagian foreland a description is given here of the structure and tectonic evolution of the submerged nw se trending alpine belt extending from the sardinia channel across the sicily straits to the pelagian sea this mainly results from re interpretation of the existing seismic network in the sicily straits the crust comprises an allocthonous belt composed of tertiary flysch type thrust slices stacked in an imbricate wedge the wedge is composed of mesozoic basin and platform carbonates thrusts derived by deformation of the old sicilian continental margin lower miocene to lower pleistocene foredeep deposits terrigenous and clastic carbonates filled progressively onlapping foreland basins during regional compression in the southern sicily offshore the deformation spanned early miocene to early pleistocene time the structural evolution of the gela foredeep shows the kinematics and timing of emplacement of the gela thrust system that is believed to be the present day thrust front of the sicilian accretionary wedge in the sicily channel the plio pleistocene tectono sedimentary history of the lampedusa linosa sector reveals evidence of middle pliocene extensional tectonics and indicates a rift mechanism for formation of the sicily channel this event was followed by inversion tectonics and strong vertical tectonics in the late pleistocene

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

precise dielectric profiling of ice cores a new device with improved guarding and its theory dielectric profiling dep a capacitive method for measuring an ice core s electrical conductivity and permittivity has been in use for several years we have built an improved dep instrument with a modified guarded electrode geometry whose capacitance can be determined from potential theory the new instrument can measure an ice core s conductivity and permittivity to within a few per cent error a high enough accuracy to infer its density using well known models

depositional and erosional bedforms in late pleistocene holocene pro delta deposits of the gulf of patti southern tyrrhenian margin italy abstract multibeam bathymetry high resolution seismic profiles and seafloor samples have been analyzed to characterize depositional and erosional dynamics recorded pro deltaic deposits and outer shelf sediments along of a sector of the ne sicilian margin southern tyrrhenian sea the deltaic deposits cover an area of ca 15 km 2 in front of the mazzarra river and are morphologically characterized by waveforms trending overall along strike and incised cross strike gullies of variable length the gullies are shallow and characterized by small coaxial erosive scours in the inner middle shelf whereas they become larger and deeper in the outer shelf upper slope in relation to the marked increase of slope gradients at the shelf break here the wider gullies are characterized by a frame of crescent shaped bedforms interpreted as cyclic steps indicating the occurrence of sedimentary gravity flows in supercritical regime prodelta waveforms are widespread between 50 and 120 m with wave lengths of 34 110 m and wave heights of 0 5 3 m morphometric characterization and spatial distribution of the waveforms suggests a main role in their genesis played by hyperpycnal flows although we cannot discard the possible effect of internal waves or slow deformation processes i e creep depositional and erosional features similar to those observed on the seafloor are evident in the subsurface stratigraphy revealing the onset and growth of the mazzarra delta since the last glacial maximum the post glacial sea level rise caused lateral shifts of the mazzarra river mouth controlling migration of depositional lobes and intensity of seafloor incision and sediment reworking ultimately resulting in the observed wavy bedforms extending from the inner shelf to the upper slope

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

rates of active compressional deformation in central italy and sicily evaluation of the seismic budget historical and recent seismicity records and available source mechanisms in eastern central italy marche adriatic region in mainland southern sicily and in the tyrrhenian offshore of northern sicily show comparable deformation patterns seismotectonic considerations indicate that each of the three areas represents a broad seismogenic province of relatively homogeneous deformation on the basis of the historical earthquake catalogue the parameters of the gutenberg richter distribution have been calculated by means of a monte carlo simulation method the average moment tensors have been computed from focal mechanism data and the strain rate and velocity tensors evaluated by means of kostrov s in izv acad sci ussr phys solid earth 1 23 44 1974 relation which also considers the shape and size of the seismogenic volume the uncertainties have been systematically incorporated the results show that the three seismotectonic provinces are all undergoing shortening at seismic rates 0 3 mm year in the wsw ene direction in the eastern marche adriatic region 0 1 mm year in the n s direction in mainland southern sicily and 0 2 mm year in the nw se direction in the southern tyrrhenian zone the motion pattern in the marche adriatic and in the sicilian provinces suggests that these areas undergo active crust scale deformation along reverse shear zones in agreement with recent horizontal gps motion model and other independent evidence

seasonal variations of accumulation and the isotope record in ice cores a study with surface snow samples and firn cores from neumayer station antarctica at the german wintering base neumayer an intensive glacio meteorological program was carried out during the last two decades a complete meteorological data set and data from surface snow samples snow pits firn cores and weekly accumulation measurements from a stake array are available we first investigated the attenuation of the seasonal d18o signal due to water vapour diffusion in the snow pack a comparison of surface snow samples and firn cores of different age shows that only one third of the seasonal d18o signal of the surface snow samples remains in the cores after the first year no further significant change in the amplitude of the seasonal d18o signal is found later changes in the seasonal distribution of accumulation can lead to a bias in ice core properties this is studied on a short time scale using the available high time resolution data of accumulation stable isotope ratios and air temperature mean annual d18o values from firn cores are not well correlated to annual mean air temperatures however the correlation is improved considerably by weighting the annual mean air temperature by accumulation at neumayer mainly the cyclonic activity in late winter early spring determines whether and how the core data are biased

coexisting tectonic settings the example of the southern tyrrhenian sea we performed geodetic strain rate analyses in southern italy using new gps velocities two dimensional strain and rotation rate fields were estimated and results show that most of the shortening is distributed in the northern sicily offshore extension becomes more evident and comparable with shortening on the eastern side of the same margin and greater in the eastern sicily offshore principal shortening and extension rate axes are consistent with long term geological features seismic reflection profiles show both active compressive and extensional faults affecting pleistocene strata we show evidence for contemporaneous extension and transtension in the cefalu basin combining geodetic data and geological features point to the coexistence of independent geodynamic processes i e the active e w backarc spreading in the hangingwall of the apennines subduction zone and shortening along the southern margin of the tyrrhenian backarc basin operated by the nnw motion of africa relative to eurasia

revisiting sites of the south pole queen maud land traverses in east antarctica accumulation data from shallow firn cores 1 ground based accumulation measurements are scarce on the high east antarctic plateau but highly necessary for model validation and the interpretation of satellite data for the determination of antarctic mass balance here we present accumulation results obtained from four shallow firn cores drilled in the antarctic summer season 2007 2008 the cores were drilled along the first leg of the norwegian us ipy traverse through east antarctica visiting sites like plateau station and pole of relative inaccessibility that have been covered by the south pole queen maud land traverses spqmlt in the 1960s accumulation has been determined from volcanic chronology established from the conductivity records measured by dielectric profiling dep the tambora 1815 unknown 1809 double peak is clearly visible in the conductivity data and serves as a reliable time marker accumulation rates averaged over the period 1815 2007 are in the range of 16 to 32 kg m 2 a 1 somewhat lower than expected from the spqmlt data the spatial pattern is mainly influenced by elevation and continentality three of the firn cores show a decrease of more than 20 in accumulation for the time period 1815 2007 in relation to accumulation rates during the period 1641 1815 the spatial representativity of the firn cores is assessed by ground penetrating radar showing a rather smoothly layered pattern around the drill sites validation of the dep results is utilized by comparison with chemistry data proving the validity of the dep method for dating firn cores the results help understanding the status of the east antarctic ice sheet and will be important for e g future model derived estimates of the mass balance of antarctica

temporal variations in gravity at mt etna italy associated with the 1989 and 1991 eruptions results are presented from 11 microgravity surveys on mt etna between 1987 and 1993 a period including the major 1989 and 1991 1993 flank eruptions and subordinate 1990 activity measurements were made with lacoste and romberg d 62 and d 157 gravity meters along a network around the volcano between 1000 and 1900 m a s l and since 1992 a n s summit profile gravity changes of as much as 200 gal were observed at scales from the size of the summit region to that of the volcano none was associated with significant changes in ground elevation the data show an increase in gravity for 2 years before the 1989 eruption the increase is attributed to the accumulation of magma 0 25 1 7 109 m3 in an elongate zone oriented nnw sse between 2 5 and 6 km below sea level part of this magma was injected into the volcanic pile to supply the 1989 and 1990 eruptions it also probably fed the start of the 1991 1993 eruption since this event was not preceded by significant gravity changes a large gravity increase up to 140 gal detected across the volcano between june and september 1992 is consistent with the arrival in the accumulation zone of 0 32 2 2 109 m3 of new magma thus favoring continued flank effusion until 1993 a large gravity decrease 200 gal in the summit region marked the closing stages of the 1991 1993 event and is associated with magma drainage from the upper levels of etna s central feeding system

high frequency wave propagation from mantle earthquakes in the tyrrhenian sea new constraints for the geometry of the south tyrrhenian subduction zone propagation of shear waves produced by 25 mantle earthquakes 80 600 km depth in the subduction zone of the south tyrrhenian sea southern italy has been investigated to infer the geometry and extent of the descending lithosphere from all hypocentral depths high frequency high amplitude shear waves are recorded at most of the stations in southern italy and easternmost sicily this shear wave energy is interpreted to travel as a guided wave within the descending slab in contrast shear waves are either not recorded at all or they are recorded as low frequency low amplitude signals at stations located in the peninsular part of italy north of the calabrian arc in western sicily and in sardinia this systematic s wave attenuation is interpreted in terms of an active and continuous slab correlated with and limited to the calabrian arc

quantifying the pinatubo volcanic signal in south polar snow recent snow and firn core samples from south pole contain increased sulfate so42 concentrations during 1992 1994 as a result of the june 1991 pinatubo eruption and the august 1991 cerro hudson eruption in chile traces of pinatubo tephra volcanic ash were identified in the 1993 and 1994 snow layers supporting the conclusion that increased so42 in 1993 1994 is from the pinatubo eruption although the pinatubo eruption preceded hudson its so42 signal in south polar snow follows and is resolved from that of hudson the deposition of the pinatubo so42 aerosol was delayed due to the long transport to the high southern latitudes and its initial existence at high altitudes in the antarctic atmosphere multi year multi site sampling demonstrates that the volcanic signals are well preserved and spatially consistent measurements on 2 firn cores show that the south pole so so42 flux from pinatubo is 10 9 1 2 kg km 2 over 2 2 years while the hudson flux is 3 2 0 6 kg km 2 in 1 1 years these results when combined with satellite determined pinatubo sulfur dioxide so2 emission make it possible to link quantitatively the atmospheric aerosol mass loading from a low latitude volcanic eruption to its signal in polar ice cores

surface mass balance and stable oxygen isotope ratios from shallow firn cores on fimbulisen east antarctica the mass balance of antarctica is one of the crucial factors for determining sea level change in a warming climate the marginal zones of the continent namely the ice shelves are most sensitive to climate change during the 2009 10 austral summer an extensive glaciological field campaign was carried out on fimbulisen an ice shelf in east antarctica to investigate its recent surface mass balance shallow 10 18 m firn cores were drilled and accumulation rates and stable isotope ratios determined for firn core dating two different methods were compared 1 seasonal variations of stable oxygen isotope ratios d 18 o and 2 dielectric profiling including using the volcanic eruptions of pinatubo philippines 1991 and el chichon mexico 1982 as time markers the mean annual accumulation for the period 1992 2009 ranges from 298 to 349 mm w e a 1 the interannual variability at the drilling sites is 30 accumulation rates show a weak decreasing trend during the past 20 30 years which is statistically significant only for one of the cores stable isotope ratios were compared to the snowfall temperature of neumayer station neither the temperatures nor the d 18 o values show any trend for the investigated time period

observations beneath pine island glacier in west antarctica and implications for its retreat thinning ice in west antarctica is currently contributing about 10 of the observed rise in global sea level observations obtained from an autonomous underwater vehicle operating beneath pine island glacier west antarctica reveal that the glacier was recently grounded on a transverse ridge in the sea floor but now warm sea water flows through the widening gap above the ridge thinning ice in west antarctica resulting from acceleration in the flow of outlet glaciers is at present contributing about 10 of the observed rise in global sea level1 pine island glacier in particular has shown nearly continuous acceleration2 3 and thinning4 5 throughout the short observational record the floating ice shelf that forms where the glacier reaches the coast has been thinning rapidly6 driven by changes in ocean heat transport beneath it as a result the line that separates grounded and floating ice has retreated inland7 these events have been postulated as the cause for the inland thinning and acceleration8 9 here we report evidence gathered by an autonomous underwater vehicle operating beneath the ice shelf that pine island glacier was recently grounded on a transverse ridge in the sea floor warm sea water now flows through a widening gap above the submarine ridge rapidly melting the thick ice of the newly formed upstream half of the ice shelf the present evolution of pine island glacier is thus part of a longer term trend that has moved the downstream limit of grounded ice inland by 30 km into water that is 300 m deeper than over the ridge crest the pace and ultimate extent of such potentially unstable retreat10 are central to the debate over the possibility of widespread ice sheet collapse triggered by climate change11 12

itrf2005 a new release of the international terrestrial reference frame based on time series of station positions and earth orientation parameters 1 unlike the past international terrestrial reference frame itrf versions where global long term solutions were combined the itrf2005 uses as input data time series weekly from satellite techniques and 24 h session wise from very long baseline interferometry of station positions and daily earth orientation parameters eops the advantage of using time series of station positions is that it allows to monitor station non linear motion and discontinuities and to examine the temporal behavior of the frame physical parameters namely the origin and the scale the itrf2005 origin is defined in such a way that it has zero translations and translation rates with respect to the earth center of mass averaged by the satellite laser ranging slr time series spanning 13 years of observations its scale is defined by nullifying the scale and its rate with respect to the very long baseline interferometry vlbi time series spanning 26 years of observations the itrf2005 orientation at epoch 2000 0 and its rate are aligned to the itrf2000 using 70 stations of high geodetic quality the estimated level of consistency of the itrf2005 origin at epoch 2000 0 and its rate with respect to the itrf2000 is respectively 0 1 0 8 5 8 mm and 0 2 0 1 1 8 mm yr along the x yand z axis we estimate the formal errors on these components to be 0 3 mm and 0 3 mm yr we believe that this low level of agreement between the two frame origins is most probably due to the poor slr network geometry and its degradation over time the itrf2005 combination involving 84 co location sites revealed a scale inconsistency of 1 ppb 6 3 mm at the equator at epoch 2000 0 and 0 08 ppb yr between the slr and vlbi long term solutions as obtained by the stacking of their respective time series possible causes of this inconsistency may include the poor slr and vlbi networks and their co locations local tie uncertainties systematic effects and possible inconsistent model corrections used in the data analysis of both techniques for the first time of the itrf history the itrf2005 rigorous combination provides self consistent series of eops including polar motion from vlbi and satellite techniques and universal time and length of day from vlbi only a velocity field of 152 sites with an error less than 1 5 mm yr is used to estimate absolute rotation poles of 15 tectonic plates that are consistent with the itrf2005 frame this new absolute plate motion model supersedes and significantly improves that of the itrf2000 which involved six major tectonic plates citation altamimi z x collilieux j legrand b garayt and c boucher 2007 itrf2005 a new release of the international terrestrial reference frame based on time series of station positions and earth orientation parameters j geophys res 112 b09401

melt inclusion investigation of the volatile behaviour in historic alkali basaltic magmas of etna crystallization paths of basaltic 1763 eruption and hawaiitic 1865 and 1329 eruptions scoria from etna were deduced from mineralogy and melt inclusion chemistry the volatile behaviour was investigated through the study of melt inclusions trapped in the phenocrysts and those of the whole rocks and the matrix glasses the results from the 1763 eruption point to the early crystallization of olivine fo 81 7 from a water rich alkaline basalt with high cl 1750 2000 ppm and s 2100 2400 ppm concentrations the hawaiitic melt inclusions trapped in olivine fo 74 salite and plagioclase are characterized by a decrease in cl k2o and s k2o ratios in each investigated system there is good correlation between k2o and p2o5 in the whole rocks cl ranges from 980 to 1680 ppm from basaltic to hawaiitic lavas whereas s 110 136 ppm remains low cl and s behaviour in the 1763 magma suggests an early degassing stage of cl and s with co2 and a water rich gaseous phase for a pressure close to 100 mpa consistent with a permanent outgassing at the summit craters of etna during the eruption the sulphur remaining in the hawaiitic liquid is lost and the degassing of chlorine is limited such a degassing model can be extended to the 1865 and 1329a d eruptions

geophysical and petrological modelling of the structure and composition of the crust and upper mantle in complex geodynamic settings the tyrrhenian sea and surroundings abstract information on the physical and chemical properties of the lithosphere asthenosphere system las can be obtained by geophysical investigation and by studies of petrology geochemistry of magmatic rocks and entrained xenoliths integration of petrological and geophysical studies is particularly useful in geodynamically complex areas characterised by abundant and compositionally variable young magmatism such as in the tyrrhenian sea and surroundings a thin crust less than 10 km overlying a soft mantle where partial melting can reach about 10 is observed for magnaghi vavilov and marsili which belong to the central tyrrhenian sea backarc volcanism where subalkaline rocks dominate similar characteristics are seen for the uppermost crust of ischia a crust about 20 km thick is observed for the majority of the continental volcanoes including amiata vulsini roccamonfina phlegraean fields vesuvius vulture stromboli vulcano lipari etna and ustica a thicker crust is present at albani about 25 km and at cimino vico sabatini about 30 km the structure of the upper mantle in contrast shows striking differences among various volcanic provinces volcanoes of the roman region vulsini sabatini alban hills sit over an upper mantle characterised by vs mostly ranging from about 4 2 to 4 4 km s at the alban hills however slightly lower vs values of about 4 1 km s are detected between 60 and 120 km of depth this parallels the similar and rather homogeneous compositional features of the roman volcanoes whereas the lower vs values detected at the alban hills may reflect the occurrence of small amounts of melts within the mantle in agreement with the younger age of this volcano the axial zone of the apennines where ultrapotassic kamafugitic volcanoes are present has a mantle structure with high velocity lid vs 4 5 km s occurring at the base of a 40 km thick crust beneath the campanian volcanoes of vesuvius and phlegraean fields the mantle structure shows a rigid body dipping westward a feature that continues southward up to the eastern aeolian arc in contrast at ischia the upper mantle contains a shallow low velocity layer vs 3 5 4 0 km s just beneath a thin but complex crust the western aeolian arc and ustica sit over an upper mantle with vs 4 2 4 4 km s although a rigid layer vs 4 55 km s from about 80 to 150 km occurs beneath the western aeolian arc in sardinia no significant differences in the las structure are detected from north to south the petrological geochemical signatures of italian volcanoes show strong variations that allow us to distinguish several magmatic provinces these often coincide with mantle sectors identified by vs tomography for instance the roman volcanoes show remarkable similar petrological and geochemical characteristics mirroring similar structure of the las the structure and geochemical isotopic composition of the upper mantle change significantly when we move to the stromboli campanian volcanoes the geochemical signatures of ischia and procida volcanoes are similar to other campanian centres but sr pb isotopic ratios are lower marking a transition to the backarc mantle of the central tyrrhenian sea the structural variations from stromboli to the central vulcano and lipari and western aeolian arc are accompanied by strong variations of geochemical signatures such as a decrease of sr isotope ratios and an increase of nd pb isotope and lile hfse ratios the dominance of mafic subalkaline magmatism in the tyrrhenian sea basin denotes large degrees of partial melting well in agreement with the soft characteristics of the uppermost mantle in this area in contrast striking isotopic differences of plio quaternary volcanic rocks from southern to northern sardinia does not find a match in the las geophysical characteristics the combination of petrological and geophysical constraints allows us to propose a 3d schematic geodynamic model of the tyrrhenian basin and bordering volcanic areas including the subduction of the ionian adria lithosphere in the southern tyrrhenian sea and to place constraints on the geodynamic evolution of the whole region

accumulation variability derived from an ice core from coastal dronning maud land antarctica a 100 m long ice core was retrieved from the coastal area of dronning maud land dml antarctica in the 2000 01 austral summer the core was dated to ad 1737 by identification of volcanic horizons in dielectrical profiling and electrical conductivity measurement records in combination with seasonal layer counting from high resolution oxygen isotope d 18 o data a mean long term accumulation rate of 0 29 m a 1 w e was derived from the high resolution d 18 o record as well as accumulation rates during periods in between the identified volcanic horizons a statistically significant decrease in accumulation was found from about 1920 to the present a comparison with other coastal ice cores from dml suggests that this is a regional pattern

tropical pacific high latitude south atlantic teleconnections as seen in δ18o variability in antarctic coastal ice cores 1 we use a network of eight ice cores from coastal dronning maud land dml antarctica to examine the role of the tropical enso el nino southern oscillation in the temporal variability of 18o in annual accumulation the longest record from the s100 ice core covering the period 1737 1999 is used to analyze the teleconnections between the tropical pacific and coastal dml on decadal scales and longer a shorter stacked coastal dml 18o series spanning 1955 1999 is constructed to assess the variability of enso teleconnection on interannual scales results suggest that on typical enso timescales of 2 6 years the strength of the teleconnection varies in time being stronger for years with generally negative phase of the southern annular mode sam on the timescales of approximately two decades bidecadal positive isotope anomalies are associated with oceanic warming and a westward sea surface temperature sst gradient in the equatorial pacific bidecadal variability in sam forced by the tropical pacific is proposed as a critical element in the teleconnection our analysis suggests that a multidecadal positive trend in the annual mean 18o values from the analyzed cores can be indicative of the atmospheric warming that begun in this part of the dml already in the 1910s the trend in 18o quantified in terms of long term surface air temperature sat changes is consistent with the instrumental data yet we speculate that the accurate estimation of sat trends requires an assessment of the potential role of secular sam and sea ice extent changes in shaping the isotopic signal

new gps constraints on the kinematics of the apennines subduction abstract we present the velocity field of the italian area derived from continuous gps observations from 2003 to 2007 the gps sites were installed by different institutions and for different purposes they cover the whole country with a mean inter site distance of about 60 km and provide a valuable source of data to map the present day kinematics of the region the absolute itrf2005 rotation poles and rates of eurasia africa and adriatic plates are estimated to study the kinematics along their boundaries in the apennines belt the corsica sardinia block coherently moving as the eurasia plate is used as reference of the upper plate for the apennines subduction zone we apply a simple kinematic model to estimate the rates and spatial pattern of the subduction along the apennines we identify at least four different independently moving lower plates i e the adriatic diverging and internally segmented ionian sicily and africa converging plates with different subduction rates the conservative estimates of the subduction rate are 5 mm yr in the calabrian arc 1 5 mm yr in sicily and 0 9 mm yr in the northern apennines this variegate mixture of behaviors seems to reflect the variable lithospheric thickness and composition of the lower plates inherited from the mesozoic rifting an unexpected along strike contraction is observed along the western side of the central northern apennines velocities are estimated both relative to eurasia and relative to the deep and shallow hotspot reference frames hsrf the hotspot representation seems more coherent with the geophysical and geological constraints along the subduction system in which the adriatic and ionian plates move sw ward and their deeper slab portions provide an obstacle to the opposite relative mantle flow all these patterns better reconcile if the subduction process is conceived as a passive feature controlled by the far field plate velocities and the relative eastward mantle flow acting on a disrupted slab

sicily s fold thrust belt and slab roll back the si ri pro seismic crustal transect sicily is a thick orogenic wedge formed by 1 the foreland african and its sicilian orogen and 2 the thick skinned calabrian peloritani wedge the crust under central sicily from the tyrrhenian margin to the coastline of the sicily channel has been investigated by the multidisciplinary si ri pro research project the project dealt with the nature and thickness of the crust and depth and geometry of the moho which is essential in formulating subduction models and improving the knowledge of african and tyrrhenian european lithospheres the results resolve features such as 1 the main orogenic wedge 2 the very steep nw se trending regional monocline suggesting inflection of the foreland crust 3 the deep caltanissetta synform imaged for the first time to about 25 km and 4 the top of the crystalline basement and the inferred crust mantle boundary the si ri pro transect confirmed that the nnw dipping autochthonous iblean platform of se sicily and its basement extends all the way into central sicily further nw towards the nnw end of the transect a large uplift involves the iblean platform and its underlying basement the associated gravity anomaly is interpreted as the southern wedge edge of the tyrrhenian mantle that splits the subducting iblean pelagian african continental slab from an overlying synformal stack of allochthonous thrust sheets supplementary materials additional data are available at www geolsoc org uk sup18594

dielectric stratigraphy of ice a new technique for determining total ionic concentrations in polar ice cores a 133 m deep antarctic ice core from dolleman island antarctic peninsula has been profiled by dielectric measurements in the af lf 20 hz 100 khz frequency range this has revealed large variations in dielectric relaxation and conductivity down the core a comparison with the chemical stratigraphy along 45 m of the core demonstrates for the first time the decisive role played by acids and salts in determining the electrical behaviour of natural ice the total ionic concentration along the ice core can be deduced from the dielectric response this technique may be applied rapidly in the field and as it requires no contact between ice core and electrodes the core is maintained in pristine condition for later chemical analysis

current strain regime in the western alps from continuous global positioning system measurements 1996 2001 four to six years of continuous measurements at 10 permanent global positioning system sites in the western alps show horizontal residual velocities of 2 mm yr with respect to stable europe uncertainties range from 0 3 to 1 4 mm yr these velocities and the associated strain rate field indicate that the central part of the range is currently dominated by east west extension whereas the southern part shows north south to northwest southeast compression the geodetic and seismotectonic data are consistent with a model where strain is essentially controlled by the counterclockwise rotation of the adriatic microplate with respect to eurasia this rotation together with the arcuate shape of the contact between the adriatic microplate and the alps induces dextral shear kinematic boundary conditions across the western alps with an additional divergence component in their central part and in switzerland and a convergence component in their southern part

coexistent pre existing extensional and subsequent compressional tectonic deformation in the kashmir basin nw himalaya abstract this paper presents a new interpretation of overlapping differential deformations and likely causes of the structural heterogeneity within the kashmir basin representing a prominent and distinctive strain feature in nw himalaya the broad geomorphic expression of the kashmir as an elongated nw se trending sedimentary trough is inconsistent with general compression governing structural trend and deformation pattern of 2500 km long himalayan frontal thrust zone in addition to the general extensional geometry there are prominent anomalous deformation features at varied spatial scales in the basins that imply dominance of extensional tectonics we infer that contrary to the overall compression dominant mechanism of the himalaya the apparent extensional geometry of the basin connotes orogen parallel extensional deformation pull apart triggered by oblique convergence in the nw himalaya moreover we construe that the comparatively younger contractile positive features in form of the geomorphic convexity push up accompanied by out of sequence reverse faulting balapur fault hereafter called as bf within the basin which is generally believed to be associated with the uplift along ne dipping southern thrust complex mbt mct possibly resulted due to the tectonic reversal positive inversion the presence of the compressional features within the locally predominant extensional setting is suggestive of the basin s hybrid character where variable tectonic regimes earlier extension and subsequent compression seem to be coexistent

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

simultaneous magma and gas eruptions at three volcanoes in southern italy an earthquake trigger this study was partly funded by the deutsche forschungsgemeinschaft wa 1642 1 4 and protezione civile project ingv dpc v2

active thrust faulting offshore boumerdes algeria and its relations to the 2003 mw 6 9 earthquake 1 we investigate the active seismogenic fault system in the area of the 2003 mw 6 9 boumerdes earthquake algeria from a high resolution swath bathymetry and seismic survey a series of 5 main fault propagation folds 20 35 km long leave prominent cumulative escarpments on the steep slope and in the deep basin fault activity creates plio quaternary growth strata within uplifted areas such as a rollover basin on the slope and piggyback basins in the deep ocean most thrusts turn to fault propagation folds at the sub surface and depict ramp flat trajectories we find that the two main slip patches of the 2003 mw 6 9 boumerdes earthquake are spatially correlated to two segmented cumulative scarps recognized on the slope and at the foot of the margin the overall geometry indicates the predominance of back thrusts implying underthrusting of the neogene oceanic crust

late cenozoic subduction complex of sicily abstract besides remnants of hercynian deformations in the peloritani nappe and of pre oligocene alpine structures in the troiani nappe most compressive structures observed in the sicilian accretionary wedge result from the late cenozoic tortonian to present continental subduction of the apulia iblei block and are thus synchronous with distensive structures related to the opening of the tyrrhenian sea syntectonic deposits fill southward migrating foredeeps in a sequential fashion and the dating of these deposits helps to constrain the timing of deformation similarly plio quaternary sediments eroded from the accreted units rest on top of the allochthon in either compressive piggy back depressions or extensional basins the age and configuration of these overlap deposits constrain our reconstructions of the subsurface geometry of the underlying peri tyrrhenian detachment faults or s verging thrust faults post depositional erosion normal faulting and syntectonic filling of basins contribute to maintaining the critical taper of the prism whose geometry is continuously altered owing to frontal accretion underplating and isostatic uplift

high resolution morpho bathymetric imaging of the messina strait southern italy new insights on the 1908 earthquake and tsunami the 28 december 1908 reggio calabria and messina earthquake named after the two most damaged cities on the coasts of messina strait was one of the strongest mw 7 1 ever to occur in italy and was also followed by a tsunami that severely impacted the coasts of the strait although there is general agreement that its epicentre is located offshore in the messina strait the source fault has never been detected a century long question is therefore pending on the source of both the 1908 earthquake and tsunami within the ongoing debate on this subject little attention has been given so far to morphological insights from high resolution bathymetric multibeam data particularly as regarding the evidence of faults affecting the seafloor and the question of whether a submarine landslide may had been the cause of the tsunami we aim to address this issue by presenting the results of a morpho bathymetric study in the messina strait and surroundings investigated by means of high resolution swath bathymetry the primary morpho structural feature in this area is the axial channel of the messina canyon towards which flow several tributary canyons that incise the steep continental slope on the calabrian and sicilian margins these canyons carve deeply into a very narrow almost lacking continental shelf and merge laterally forming a continuous erosional margin rimming the messina strait this giant composite canyon environment is the locus of intense erosional and depositional processes that superimpose on active tectonic deformation resulting in a complex geomorphology that hinders the distinction between tectonic and sedimentary features seafloor ruptures that may be linked to fault systems compatible with the source of the 1908 earthquake and tsunami could not be identified based from our morpho bathymetric analysis however we provide evidence of several geomorphic features indicative of tectonic deformation in the messina strait define the presence and distribution of submarine landslides and evaluate their possible role as tsunami sources

seismic potential of southern italy abstract to improve estimates of the long term average seismic potential of the slowly straining south central mediterranean plate boundary zone we integrate constraints on tectonic style and deformation rates from geodetic and geologic data with the traditional constraints from seismicity catalogs we express seismic potential long term average earthquake recurrence rates as a function of magnitude in the form of truncated gutenberg richter distributions for seven seismotectonic source zones seismic coupling seems to be large or even complete in most zones an exception is the southern tyrrhenian thrust zone where most of the african european convergence is accommodated here aseismic deformation is estimated to range from at least 25 along the western part to almost 100 aseismic slip around the aeolian islands even so seismic potential of this zone has previously been significantly underestimated due to the low levels of recorded past seismicity by contrast the series of 19 m6 7 earthquakes that hit calabria in the 18th and 19th century released tectonic strain rates accumulated over time spans up to several times the catalog duration and seismic potential is revised downward the southern tyrrhenian thrust zone and the extensional calabrian faults as well as the northeastern sicilian transtensional zone between them which includes the messina straits where a destructive m7 event occurred in 1908 all have a similar seismic potential with minimum recurrence times of m 6 5 of 150 220 years this potential is lower than that of the southern apennines m 6 5 recurring every 60 to 140 years but higher than that of southeastern sicily minimum m 6 5 recurrence times of 400 years the high seismicity levels recorded in southeastern sicily indicate some clustering and are most compatible with a tectonic scenario where the ionian deforms internally and motions at the calabrian trench are small the estimated seismic potential for the calabrian trench and central and western sicily are the lowest minimum m 6 5 recurrence times of 550 800 years most zones are probably capable of generating earthquakes up to magnitudes 7 7 5 with the exception of central and western sicily where maximum events sizes most likely do not exceed 7

effects of seasonal variability of accumulation on yearly mean δ18o values in antarctic snow the annual mean oxygen isotope content of antarctic snow is strongly influenced by the seasonal variability ofaccumulation since the annual mean 18 o value is frequently used to derive mean annual temperatures from ice cores changes in atmospheric circulation pattern can lead to large errors in the deduced temperature record at the german antarctic wintering base neumayer accumulation measurements have been carried out continuously over the last 16 years weekly readings of accumulation stakes combined with snow pits and shallow firn cores are used to investigate the influence of the seasonal variability of accumulation on the annual mean 18 o values and to estimate the possible error in the determination ofannual mean temperatures from ice cores by using the oxygen isotope record

paleogeography and structure of the central mediterranean sicily and its offshore area abstract the geology of the mainland and offshore of sicily is illustrated by a few geologic sections and seismic profiles across the late cenozoic orogenic belt of central and western sicily and across the sardinia channel and sicily straits this belt is the result of several tectonic events deformation involved mainly the sedimentary cover of the old african continental margin characterized by a broad basinal domain flanked along its external southern margin by a shallow water carbonate platform attached to africa in the triassic compressional deformation started in the more internal basinal rock assemblages overlying a thinned crust the most important structural characteristic of the early phase of thrusting is the duplex pile forming the bulk of the chain in central western sicily the structure consists of a basal allochthon made up of permian to middle triassic layers an intermediate duplex wedge composed of competent mesozoic carbonates and a roof complex including upper mesozoic lower tertiary less competent rocks large scale clockwise rotation of the thrusts accompanied transpressional movements in the hinterland during the pliocene right oblique reverse faults modified the previous tectonic contacts between the allochthons in the hinterland zones contemporaneous south directed imbrications affected the southern external areas progressively incorporating foreland and piggyback basins development of the gela thrust system appears to be linked to the transpressional event its accretion is also related to contemporaneous underthrusting at deeper levels of mesozoic carbonate substratum the older buried thrust sheets were pushed up to the surface breaching the deformed tertiary cover of the gela ts northwards in the belt post messinian normal growth faults opened half graben whose sedimentary fill underwent structural inversion alternation of extension and compression tectonics characterizes the sicilian continental margin in the last million years

plio quaternary reactivation of the neogene margin off nw algiers algeria the khayr al din bank the algiers region northern algeria is known to be seismically active with recurrent large m 6 earthquakes because of the lack of high resolution bathymetry the offshore structures remained for a long time poorly known thanks to a new marine data base maradja 2003 cruise the offshore part of the margin is accurately mapped and new active and recent structures are described west of the bay of algiers the margin enlarges forming the khayr al din bank interpreted as a tilted block of the passive margin born during the opening of the algero provencal basin at the slope break a 80 km long fault tip quaternary fold namely the khayr al din fault extends at the foot of the margin off nw algiers and represents the largest active structure of the coastal area together with the sahel anticline we also map for the first time a set of overlapping en echelon active folds in the upper part of the khayr al din bank located off previously known active structures on land most of these faults represent actually a threat for the algiers region in terms of seismic hazard but also geological hazards such as tsunamis as most of them depicts significant dimensions and slip rates the highest long term horizontal shortening rate is found on the khayr al din fault and is estimated at 0 5 0 1 mm yr with a maximal magnitude of 7 3 which provides one of the highest seismogenic potential in the region a new tectonic framework for the algiers region is proposed in which the main south dipping offshore structure of opposite vergence relative to most thrusts on land appears to be nowadays the main driving fault system as also found further east in the boumerdes m 6 8 2003 rupture zone the overall apparent pop up structure of the recent and active faults may result from a progressive migration of the plate limit from the late miocene north dipping suture zone on land to the quaternary south dipping main khayr al din fault at sea suggesting a process of subduction inception

crustal structure of central sicily abstract we processed crustal seismic profile siripro acquired across central sicily to improve the seismic image we utilized the wave equation datuming technique a process of upward or downward continuation of the wave field between two arbitrarily shaped surfaces wave equation datuming was applied to move shots and receivers to a given datum plane removing time shifts related to topography and to near surface velocity variations the datuming procedure largely contributed to attenuate ground roll enhance higher frequencies increase resolution and improve the signal noise ratio processed data allow recognizing geometries of crust structures differentiating seismic facies and offering a direct image of ongoing tectonic setting within variable lithologies characterizing the crust of central sicily migrated sections underline distinctive features of hyblean plateau foreland and above all a crustal thinning towards the caltanissetta trough to the contact with a likely deep permo triassic rifted basin or rather a zone of a continent to oceanic transition inhomogeneity and fragmentation of sicily crust with a distinct separation of central sicily basin from western and eastern blocks appear to have guided the tectonic transport inside the caltanissetta crustal scale syncline and the accumulation of allochthonous terrains with south and north verging thrusts major tectonic stack operated on the construction of a wide anticline of the maghrebian chain in northern sicily sequential south verging imbrications of deep elements forming the anticline core denote a crust wedge indenting foreland structures deformation processes involved multiple detachment planes down to decoupling levels located near crust mantle transition supporting a presence of high density lenses beneath the chain interrelated to a southwards push of tyrrhenian mantle and asthenosphere

tectonics and seismicity of the tindari fault system southern italy crustal deformations at the transition between ongoing contractional and extensional domains located above the edge of a subducting slab 1 the tindari fault system southern tyrrhenian sea italy is a regional zone of brittle deformation located at the transition between ongoing contractional and extensional crustal compartments and lying above the western edge of a narrow subducting slab onshore structural data an offshore seismic reflection profile and earthquake data are analyzed to constrain the present geometry of the tindari fault system and its tectonic evolution since neogene including the present seismicity results show that this zone of deformation consists of a broad nnw trending system of faults including sets of right lateral left lateral and extensional faults as well as early strike slip faults reworked under late extension earthquakes and other neotectonic data provide evidence that the tindari fault system is still active in the central and northern sectors and mostly accommodates extensional or right lateral transtensional displacements on a diffuse array of faults from these data a multiphase tectonic history is inferred including an early phase as a right lateral strike slip fault and a late extensional reworking under the influence of the subduction related processes which have led to the formation of the tyrrhenian back arc basin within the present regional geodynamic context the tindari fault system is interpreted as an ongoing accommodation zone between the adjacent contractional and extensional crustal compartments these tectonic compartments relating to the complex processes of plate convergence occurring in the region the tindari fault system might also be included in an incipient oblique extensional transfer zone linking the ongoing contractional belts in the calabrian ionian and southern tyrrhenian compartments

implications for the interpretation of ice core isotope data from analysis of modelled antarctic precipitation by consideration of model generated atmospheric data dominant anomalies in the synoptic circulation patterns are observed under conditions of high ant arctic precipitation this is associated with strong moisture advection of marine origin examining precipitation at individual locations reveals a strong relationship between local surface temperature and precipitation amount days with 5 mm of precipitation which on average corresponds to about 8 of days over antarctica have surface tem peratures that are around 10 c warmer than the mean this bias suggest that abnormal conditions are captured in the ice core record and that interpretation or reconstruction of palaeotemperatur es will succeed only under the possibly flawed assumption that similar abnormal conditions existed at the time of deposition although isotopic analysis of ant arctic ice cores has been used successfully in palaeoclimate studies a complete under standing of the underlying processes affecting the deposition of the core remains to be found it is reasoned that by obtaining such an understanding it may be possible to recon struct the synoptic conditions under which accumulation occurred

active upper crust deformation pattern along the southern edge of the tyrrhenian subduction zone ne sicily insights from a multidisciplinary approach abstract using a multidisciplinary dataset based on gravimetric seismic geodetic and geological observations we provide an improved picture of the shallow structure and dynamics of the southern edge of the tyrrhenian subduction zone with a local earthquake tomography we clearly identify two main crustal domains in the upper 15 km characterized by different p wave velocity values a high velocity domain comprising southeasternmost tyrrhenian sea ne sicily and messina straits and a low velocity domain comprising mt etna and eastern sicily the transition between the two domains shows a good spatial correspondence with a wider set of faults including the taormina fault system tfs and the aeolian tindari letojanni fault system atlfs two nearly se striking fault systems crossing northeastern sicily and ending on the ionian shoreline of sicily according to many investigators within this set of faults most of the deformation seismicity occurs along the northern and central segments of atlfs compared to low activity along tfs a lack of seismicity both recent and historical is observed in the southern sector of atlfs where however geodetic data reveal significant deformation our multidisciplinary dataset including offshore observations suggests the southeastward continuation of the atlfs into the ionian sea until joining with the faults cutting the ionian accretionary wedge described in the recent literature our findings imply the existence of a highly segmented crustal shear zone extending from the aeolian islands to the ionian abyssal plain that we believe plays the role of accommodating differential motion between the southern tyrrhenian unit and the western compressional domain of sicily the atlfs which is a main part of the inferred shear zone behaves similarly to what often observed at the edges of retreating subduction slabs where the overriding plate drifts with a highly non uniform transform motion along the lateral borders

crustal deformation across and beyond the los angeles basin from geodetic measurements we combine 6 years of global positioning system gps data with 20 years of trilateration data and a century of triangulation taped distance and astronomic azimuth measurements to derive 66 interseismic station velocities in the greater los angeles region we interpolate the velocities to construct a regional strain rate map beyond the los angeles basin our results generally agree with the model proposed by the working group on california earthquake probabilities in 1995 important regional findings of this study are as follows 1 there is a significant n s convergence and e w extension about 0 22 and 0 17 0 05 strain yr respectively for the two components along the southern frontal fault system of the san gabriel mountains 2 the crustal deformation around the big bend of the san andreas fault saf cannot be explained solely by wrench style motion across the saf remaining motion could be part of a nw se extension which is the response to nfsw compression in the central transverse ranges region alternatively it could be caused by left lateral faulting on an oblique blind thrust beneath the san gabriel mountains 3 low strain rates axe found along the elsinore fault and newport inglewood 4 north south compression decreases from the raymond hill fault westward to the santa monica fault there is little east west extension along this fault system