a common feeding system of the ne and s rifts as revealed by the bilateral 2002 2003 eruptive event at mt etna sicily italy mount etna volcano is often characterized by bilateral eruptive events involving both the south s and the north east ne rifts the last event occurred in 2002 2003 from october 27 to january 28 a detailed stratigraphically time controlled sampling of lavas and tephra of the southern eruptive fissure was performed in order to 1 track the petrological features of products during the eruption and 2 integrate the results with those previously obtained on the ne rift whole rock composition and textural observations were implemented by major and minor element analyses of plagioclases in lavas and tephra from both sides of the volcano fractionation models constrained by mass balance major and trace elements and rayleigh calculations suggest that magmas are linked by the same liquid line of descent by fractionating 9 11 of a mineral assemblage of cpx 52 69 plg 21 41 and ol 7 46 these new data allowed us to identify at least two feeding episodes through the southern fissure and infer that high k2o porphyritic magmas emitted on both the s and ne rifts derives by fractionation from the same parent magma however lavas and tephra from the southern flank were slightly more primitive textural and petrological study of plagioclase moreover indicates that chemical physical conditions in the deep feeding system were similar for magmas erupting from both rifts as suggested by the presence of dissolved rounded cores in both lavas magmas evolved differently on the s and the ne rifts only at shallow levels comparison with published seismotectonic data supports the idea that the main magma feeding the eruption on october 27 ascended along the same pathway at depth and was intercepted by the fracture system of the s and ne rifts at shallow depth between 6 and 3 km b s l

large scale traveling ionospheric disturbances observed by gps total electron content during the magnetic storm of 29 30 october 2003 1 we have investigated the propagation of large scale traveling ionospheric disturbances lstids during the super magnetic storm of 29 30 october 2003 two dimensional total electron content tec perturbation maps over north america were built using tec data provided by the american gps network and the international gnss service three lstid events were observed in the range of 30 degrees n 50 degrees n 60 degrees w 110 degrees w during this period the first two lstids occurred consecutively during 0620 0800 ut on 29 october at the local time of midnight right after the onset of the big substorm the third one was found at noon during the expansion phase of another substorm on 30 october the phase fronts of these lstids passed over the united states and traveled southwestward to the distance of similar to 2000 km with the maximum front width of similar to 4000 km and the duration of less than 2 hours the maximum amplitude of tec perturbations attained 3 total electron content units tecus the results differ from the former observation of afraimovich and voeykov 2004 and afraimovich et al 2006 who reported a solitary lstid propagating southwestward over the united states with the amplitudes of up to 14 tecu on 30 october 2003 we have checked the magnetic h component observed at the geomagnetic observatories in north america and found it is most likely that the auroral westward electrojet was the cause of the lstids on 29 october the source region for these tids was likely to be located several hundred kilometers north of 50 degrees n cross spectral analysis was conducted to obtain the global propagation characteristics of lstids during this superstorm equatorward lstids were found in all the three sectors of north america europe and asia showing high correlation with the occurrence of auroral substorms

peculiar features of the low latitude and midlatitude ionospheric response to the st patrick s day geomagnetic storm of 17 march 2015 the current study aims at investigating and identifying the ionospheric effects of the geomagnetic storm that occurred during 17 19 march 2015 incidentally with sym h hitting a minimum of 232 nt this was the strongest storm of the current solar cycle 24 the study investigates how the storm has affected the equatorial low latitude and midlatitude ionosphere in the american and the european sectors using available ground based ionosonde and gps tec total electron content data the possible effects of prompt electric field penetration is observed in both sectors during the main phase of the storm in the american sector the coexistence of both positive and negative ionospheric storm phases are observed at low latitudes and midlatitudes to high latitudes respectively the positive storm phase is mainly due to the prompt penetration electric fields the negative storm phase in the midlatitude region is a combined effect of disturbance dynamo electric fields the equatorward shift of the midlatitude density trough and the equatorward compression of the plasmapause in combination with chemical compositional changes strong negative ionospheric storm phase is observed in both ionosonde and tec observations during the recovery phase which also shows a strong hemispherical asymmetry additionally the variation of equatorial ionization anomaly as seen through the swarm constellation plasma measurements across different longitudes has been discussed we also take a look at the performance of the iri real time assimilative mapping during this storm as an ionospheric space weather tool

spatial variation in stresses in peninsular italy and sicily from background seismicity abstract we have retrieved the stress tensor orientation in the italian region applying the fmsi technique gephart j 1990b fmsi a fortran program for inverting fault slickenside and earthquake focal mechanism data to obtain the regional stress tensor comput geosci 16 953 989 to fault plane solutions of 298 small earthquakes 2 5 m d istituto nazionale di geofisica in the period 1988 1995 first we verified that the stress inversion procedure generally applied to a large number of focal mechanisms of earthquakes recorded in a local seismic network could be successfully used in italy using background seismicity recorded over large 100 200 km regions then comparing the stress inversion results with other stress indicators we find that they are geologically sound for many regions in italy even if the misfit values are relatively large we also find that the largest misfit values are determined by a few earthquakes only 10 20 of the total number excluding these earthquakes from inversion the average misfit becomes much lower by 30 40 the results obtained in this study confirm the large variations of the stress field over a relatively short distance in italy but also confirm the existence of regions extending for a few hundred kilometres within which the stress is homogeneous among these most of the apennines are dominated by extension perpendicular to the trend of the mountain belt only in the northern apennines is there any clear distinction between an area of extension in the inner portion of the belt and an area under horizontal compression along the adriatic margin of the belt more rapid variations occur around calabria and sicily as expected because of the complexities linked with the tyrrhenian subduction and with active volcanism in the ionian calabrian coastal region there are hints of active nw se compression although constrained by a few data whereas in the messina strait we observe e w extension and a vertical 1 in northern and western sicily our results indicate n s to nw se compression roughly consistent with the general convergence between the european and the african plates

recent dyke induced large scale block movement at mount etna and potential slope failure here we report the results of a geodetic survey undertaken on mount etna between 1981 and 1988 observed horizontal ground movements in the vicinity of the valle del bove caldera demonstrate that dyke emplacement during 1983 and 1985 resulted in the 2 8 m eastward displacement of a block of western caldera rim a history of past instability and collapse along the rim is indicated by the presence of large back rotated blocks of prehistoric volcanics1 furthermore the unusually linear form of the present western rim indicates past slope failure along north south aligned surfaces and therefore that dyke induced collapse may have been an important agent in caldera enlargement we suggest a self sustaining mechanism whereby the stress regime generated as a consequence of the caldera s existence results in the repeated injection of north south orientated dykes adjacent to the western rim2 3 dilation associated with magma intrusion leads in turn to periodic phases of slope instability and failure of the cliff wall causing a progressive westward migration of the western rim

intrusive mechanisms at mt etna forerunning the july august 2001 eruption from seismic and ground deformation data in this work we present seismological and ground deformation evidence for the phase preparing the july 18 to august 9 2001 flank eruption at etna the analysis performed through data from the permanent seismic and ground deformation networks highlighted a strong relationship between seismic strain release at depth and surface deformation this joint analysis provided strong constraints on the magma rising mechanisms we show that in the last ten years after the 1991 1993 eruption an overall accumulation of tension has affected the volcano then we investigate the months preceding the 2001 eruption in particular we analyse the strong seismic swarm on april 20 24 2001 comprising more than 200 events mmax 3 6 with prevalent dextral shear fault mechanisms in the western flank the swarm showed a ca ne sw earthquake alignment which in agreement with previous cases can be interpreted as the response of the medium to an intrusive process along the approximately nnw sse volcano genetic trend these mechanisms leading to the july 18 to august 9 2001 flank eruption are analogous to ones observed some months before the 1991 1993 flank eruption and more recently in january 1998 before the february november 1999 summit eruption

medium scale traveling ionospheric disturbances detected with dense and wide tec maps over north america 1 nighttime and daytime medium scale traveling ionospheric disturbances mstids are detected with dense and wide detrended total electron content tec maps over north america using multiple gps receiver networks the tec maps cover a wide region of 60 130 w and 24 54 n 30 65 n in geomagnetic latitude and have a spatial resolution of 1 05 1 05 in latitude and longitude 0 15 0 15 with 7 7 pixel smoothing and a temporal resolution of 30 seconds the tec maps reveal for the first time that the nighttime mstids propagate southwestward with 200 500 km wavelengths over north america and have wavefronts longer than 2 000 km we also observe that daytime mstids with 300 1 000 km wavelengths propagate southeastward until mid afternoon and southwestward in the late afternoon in the mid to late afternoon these mstids propagating in the different directions are superimposed the tec maps can be a new powerful tool to investigate the mstids

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

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

tracing the thermohaline circulation in the western north atlantic using chlorofluorocarbons abstract measurement of chlorofluorocarbons cfcs f 11 and f 12 were obtained from vertical sections extending across the deep western boundary current dwbc along the western margin of the north atlantic ocean between 32 45 n in 1983 and 1986 these sections revealed an upper and a deep cfc maximun with highest concentrations along the continental slope the upper maximum had a potential temperature ranging from 4 2 4 6 c a core density of 1 5 34 56 and occurred at a depth of about 800m adjacent to the continental slope water with classical labrador sea water s characteristics occurs just above the cfc minimum between the upper and lower maxima and indicates that a significant volume of classical labrador sea water has not entered the region south of the grand banks for the last 3 decades the deep cfc maximum is from dense water overflowing the greenland iceland scotland ridge it occurred at about 3500m depth and had a potential temperature range of 2 02 2 18 c and a core density of 4 45 87 a source function of f 11 and f 12 for the deep maximum was estimated using temperature salinity and tracer data from previous studies the core of the dwbc defined by the deep cfc maximum was estimated to consist of roughly 2 3 gibbs fracture water and 1 3 denmark strait overflow water however 80 or more of the f 11 and f 12 signal was derived from denmark strait overflow water ages for the upper and lower cfc maxima in the dwbc were estimated from the cfc data these ages ranged from 11 12 years at the northernmost section to 18 years at the southernmost section for both features this corresponds to apparent mean current speeds of about 0 8cm s 1 for the upper maximum and 1 4cm s 1 for the deep maximum an age of 8 9 years with a corresponding apparent mean current speed of 2 2 2 5cm s 1 was also estimated for the deep cfc maximum from the observed increase in the f 11 concentration at 41 n between 1983 and 1986 the apparent mean current speeds are significantly less than current speeds measured with long term current meter moorings two reasons for this are 1 mixing between the dwbc core and adjacent water causes ages estimated from cfc data to be overestimated and hence the associated current speed to be underestimated pickart hogg and smethie 1989 and 2 water propagating along the western boundary spends some time in recirculation gyres the northern recirculation gyre south of the eastern north american continental margin is clearly apparent in the lateral distributions of f 11 and f 12 the apparent mean current speed in the northern recirculation gyre was estimated to be 1 3cm s 1 from the cfc data seaward of the dwbc north of the new england seamount chain high cfc low silica parcels of water were observed interspersed with low cfc high silica parcels of water along the bottom the high cfc low silica water is overflow water with a slightly greater component of denmark strait overflow water than contained in the dwbc deep cfc maximum the low cfc high silica water is of southern origin and has a component of antarctic bottom water

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

tomographic images and 3d earthquake locations of the seismic swarm preceding the 2001 mt etna eruption evidence for a dyke intrusion 1 on july 12 2001 mt etna experienced a sudden increase of seismic activity heralding one of the most intense eruptions of the past 30 years between july 12 and july 18 when the eruption started thousands of small magnitude earthquakes occurred and were recorded by a dense seismic network run by the istituto nazionale di geofisica e vulcanologia sezione di catania ingv ct hypocentral depths of earthquakes were very shallow mostly located above 3 km b s l and clustered near the summit area the high quality seismic dataset gives us the unique opportunity to study the process of magma migration before the eruption in this study we present the three dimensional earthquake locations and the velocity structure obtained by a tomographic inversion the shallowness of seismicity allowed us to enhance the details of the structure beneath the summit craters in a volume poorly defined by previous tomographic studies the presence of a high vp body previously observed at mt etna is confirmed at shallow depth beneath the southeastern part of the summit area the earthquakes preceding the eruption onset concentrated at its western border a low vp vs anomaly is found at 0 1 km depth just at the top of the volume where the magma intruded before the eruption this anomalous zone can be considered as molten material wealthy in gas the relocated seismicity occurs in a cylinder below the vents activated along the fracture system and exhibited an upward migration until the eruption all these results show evidence for the emplacement of a near vertical dyke striking about n s and a few kilometres south of the summit craters

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

a climatology of f region gravity wave propagation over the middle and upper atmosphere radar by observing the ionospheric f region simultaneously in multiple beams with the middle and upper atmosphere radar we have been able to track the passage of gravity waves and measure their propagation characteristics here we develop a climatology of wave propagation based on the observation of 58 daytime experiments conducted during 1986 1994 the thermosphere seems to be continuously swept by waves detectable by an incoherent scatter radar these waves generally come for hours on end from a consistent or slowly varying direction which can be any direction on a given day statistically the waves show a moderate preference for southward travel with this preference being reduced or shifted to southeastward travel during disturbed times on average the horizontal phase trace speed remains near 240 m s for all periods inspected 40 130 min this speed matches the behavior expected for lossless waves with 150 200 km vertical wavelength we find small variability in this relation for different times of day seasons solar and magnetic conditions and directions of wave travel though waves on disturbed days seem to travel moderately faster on solar minimum mornings

recent seismicity and tomographic modeling of the mount etna plumbing system the monitoring of seismic activity in eastern sicily southern italy has been recently improved in the framework of the poseidon project to investigate both tectonics and volcanic processes of mount etna this effort has produced a homogeneous and complete data set which we use to image the deep structure of the volcano and to define the space and time distribution of the recent seismicity encompassing the 1995 eruption diffuse eruptions between 1995 and 1997 a further magma intrusion started in 1997 and an increase of volcanic activity in july 1998 we inverted p wave arrival times from 307 selected local earthquakes to obtain a three dimensional velocity model of the volcano with a simultaneous inversion for hypocenters and velocity parameters the new tomographic images permit us to define the structure beneath the volcano from the surface down to 18 km depth the main structural feature revealed by our inversion is a high velocity body located beneath the central craters whose lateral extent increases from 6 km between 18 and 9 km depth to 12 km between 9 and 3 km depth near the surface the fast anomaly branches in two separate high vp regions which are located below the summit craters and the eastern flank valle del bove respectively the high velocity features are interpreted as high density cumulates of solidified magma that intruded the shallow crust we hypothesize that magma ascends the crust within the relatively small high velocity conduit below 9 km depth and is stored at depth shallower than 9 km within the broad high velocity region as also suggested by petrological data a sharp increase of seismicity in 1997 with earthquakes occurring at the border of the high velocity body suggests that mount etna sustained recent episodes of intrusions which possibly herald future eruptions no large low velocity anomaly interpretable as a melted magma chamber is imaged in the upper 18 km of the crust while a broad low velocity anomaly in the uppermost mantle revealed by regional seismic data possibly indicates the magma source region at depth earthquake occurrence from the deep source to the shallow intrusive area helps to trace the magma migration and the feeding of the volcanic system

active thrust tectonics in western sicily southern italy the 1968 belice earthquake sequence the 1968 belice earthquake sequence characterized by six main shocks with 5 m 5 4 represents the strongest seismic event recorded in western sicily in historical times the epicentral area is located in the belice valley a region lacking any topographic lineament likely to result from a fault with significant offsets of any kind instrumental data show that hypocentres of the major shocks are distributed along a roughly n dipping plane extending from about 36 km to 1 km depth fault plane solutions show pure thrusting mechanisms on n dipping ene trending planes or oblique slip with a right lateral component of motion along steep wsw dipping planes both as a result of approximate n s shortening the observed destruction indicates that isoseismal areas are elongated in an ene direction similarly the epiccntral distribution of events with m 4 outlines a roughly elliptical ene elongated area located 20 km nw of the sciacca rocca ficuzza thrust front this ene striking structure representing the regional morphotectonic feature closest to the epicentral area consists of two main imbricate fan systems in the southernmost system quaternary deposits tentatively dated as 1 0 0 7 myr old are involved in a large ramp anticline uplifting them to a maximum altitude of 346 m the occurrence of holocene lacustrine piggy back basins on the rear of this structure also indicates late quaternary activity of the underlying thrust seismological structural and morphotectonic observations suggest that multiple ruptures might have occurred during the 1968 sequence on a blind crustal thrust ramp located beneath the epicentral area slip propagated southwards along the shallow ramp flat system characterizing the thin skinned foreland fold and thrust belt of southwestern sicily being dispersed in flexural folding processes and diffuse strain along this path

seismic heterogeneity of mt etna structure and activity a dense seismic array maintained temporarily for 7 weeks provides an approach to deducing the 3 d heterogeneity of the structure of the upper crust beneath mt etna volcano from the inversion of p and s wave arrivals of local earthquakes independent data from a different source array geometry using waves generated by distant shots at sea confirm a main lateral variation a high velocity body underlies part of the volcano its contrast with the surrounding thick sedimentary pile and its location extending from the present summit to the southeast suggests that it may have been built by the development and migration of past eruptive centres followed by caldera collapse local low velocity anomalies near its sharp western edge may be associated with presently active features

three dimensional volcanic aerosol dispersal a comparison between multiangle imaging spectroradiometer misr data and numerical simulations 1 the three dimensional reconstruction of volcanic plumes is a central goal to enhance our understanding on dispersal processes in this paper we use data from the multiangle imaging spectroradiometer misr on board nasa s terra spacecraft combined with a stereo matching retrieval procedure we show the potential of misr in capturing important features of volcanic plumes like column height optical depth type and shape of the finest particles of two highly explosive eruptions occurring on mount etna in 2001 and 2002 this work tests how tephra dispersal models reconstruct the 3 d shape of volcanic clouds we compare misr data with fall3d an eulerian model for the transport and deposition of volcanic ash and aerosols coupled with the weather research and forecasting mesoscale meteorological model agreement between simulations and misr data is good regarding both events although it could be improved by increasing the accuracy of the meteorological data a better constraint on volcanological input parameters like the height of the eruptive column and improving our understanding of processes such as aggregation phenomena and volcanic cloud microphysics

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

the july august 2001 eruption of mt etna sicily the july august 2001 eruption of mt etna stimulated widespread public and media interest caused significant damage to tourist facilities and for several days threatened the town of nicolosi on the s flank of the volcano seven eruptive fissures were active five on the s flank between 3 050 and 2 100 m altitude and two on the ne flank between 3 080 and 2 600 m elevation all produced lava flows over various periods during the eruption the most voluminous of which reached a length of 6 9 km mineralogically the 2001 lavas fall into two distinct groups indicating that magma was supplied through two different and largely independent pathways one extending laterally from the central conduit system through radial fissures the other being a vertically ascending eccentric dike furthermore one of the eccentric vents at 2 570 m elevation was the site of vigorous phreatomagmatic activity as the dike cut through a shallow aquifer during both the initial and closing stages of the eruption for 6 days the magma column feeding this vent was more or less effectively sealed from the aquifer permitting powerful explosive and effusive magmatic activity while the eruption was characterized by a highly dynamic evolution complex interactions between some of the eruptive fissures and changing eruptive styles its total volume 25 106 m3 of lava and 5 10 106 m3 of pyroclastics was relatively small in comparison with other recent eruptions of etna effusion rates were calculated on a daily basis and reached peaks of 14 16 m3 s 1 while the average effusion rate at all fissures was about 11 m3 s 1 which is not exceptionally high the eruption showed a number of peculiar features but none of these except the contemporaneous lateral and eccentric activity represented a significant deviation from etna s eruptive behavior in the long term however the 2001 eruption could be but the first in a series of flank eruptions some of which might be more voluminous and hazardous placed in a long term context the eruption confirms a distinct trend initiated during the past 50 years toward higher production rates and more frequent eruptions which might bring etna back to similar levels of activity as during the early to mid seventeenth century

assessing the depth resolution of tomographic models of upper mantle structure beneath iceland 1 earlier inversions of body wave delay time data recorded during the icemelt portable broadband experiment imaged a cylindrical plume like low velocity anomaly extending to at least 400 km depth beneath iceland but the depth extent of the anomaly resolvable by tomography has recently been called into question we have performed several additional resolution tests to evaluate the depth resolution of tomographic models of the icelandic upper mantle the distribution of paths of body waves recorded by icemelt can distinguish among three different types of models a a wide and shallow anomaly b a narrow and deep anomaly and c a narrow and shallow anomaly while tomographic models contain an element of nonuniqueness these tests illustrate that the depth resolution of passive seismic experiments spanning subaerial iceland is adequate for distinguishing among alternative geodynamic models

evidence of multiple strain fields beneath the eastern flank of mt etna volcano sicily italy deduced from seismic and geodetic data during 2003 2004 we carried out a study of the seismicity and ground deformation occurring on mt etna volcano after the end of the 2002 2003 eruption and before the onset of the 2004 2005 eruption data were recorded by the permanent local seismic network run by istituto nazionale di geofisica e vulcanologia sezione di catania and by geodetic surveys carried out in july 2003 and july 2004 on the gps network most earthquakes were grouped in two main clusters located in the northeastern and southeastern sectors of the volcano the areal distribution of seismic energy associated with the recorded earthquakes allowed us to highlight the main seismogenic areas of mt etna in order to better understand the kinematic processes of the volcano 3d seismic locations were used to compute fault plane solutions and a selected dataset was inverted to determine stress and strain tensors the focal mechanisms in the northeastern sector show clear left lateral kinematics along an e w fault plane consistent with events occurring along the pernicana fault system the fault plane solutions in the southeastern sector show mainly right lateral kinematics along a nne and ene fault plane and left lateral kinematics along nw fault planes that together suggest roughly e w oriented compression surface ground deformation affecting mt etna measured by gps surveys highlighted a marked inflation during the same period and exceptionally strong seawards motion of its eastern flank the 2d geodetic strain tensor distribution was calculated and the results show mainly ene wsw extension coupled with wnw ese contraction indicating right lateral shear along a nw se oriented fault plane the different deformation of the eastern sector of the volcano as measured by seismicity and ground deformation must be interpreted by considering the different depths of the two signals seismic activity in the southeastern sector of volcano is located between 3 and 8 km b s l and can be associated with a very strong additional e w compression induced by a pressurizing source just westwards and at the same depth located by inverting gps data ground deformation in contrast is mainly affected by the shallower dynamics of the fast moving eastern flank which produces a shallower opposing e w extension the entire dataset shows that two different processes affect the eastern flank at the same time but at different depths the boundary is clearly located at a depth of 3 km b s l and could represent the decollement surface for the mobile flank

long term record of co2 degassing along mt etna s flanks and its relationship with magma dynamics and eastern flank instability a record of soil co2 flux data on the lower flanks of mt etna measured from 1989 to 2008 is discussed in the framework of multidisciplinary observations including seismicity ground deformations and flank instability a huge increase in soil co2 fluxes appears to be related to the dynamics of magma ascent in the upper portions of the volcano 0 3 km and the intrusion of dykes along the southern rift as mainly observed before the 1991 93 eruption even after the 1991 93 eruption the recharge of the shallow central reservoir was accompanied by a long term increase in soil co2 degassing mainly in the southwestern area the 2001 eruption marked dramatic changes in the areal distribution of seismicity the deformation pattern and the soil co2 degassing indeed while the soil co2 degassing showed background values in the southwestern area it progressively increased in the eastern sector and along the pernicana fault this has been related to the marked sliding of the eastern flank since the 2002 03 eruption and the associated seismicity this study provides evidence that the extent of soil co2 degassing on the lower flanks of mt etna is controlled by 1 the volume of involved magma 2 the intrusion of dykes in the upper parts of the volcano and 3 fault movement and seismicity this implies that different degassing structures must be monitored simultaneously when attempting to understand the behavior of the volcano as a whole

superposed epoch analysis of the dayside ionospheric response to four intense geomagnetic storms 1 prompt daytime ionospheric responses are presented for the following four intense geomagnetic storms 29 october 2003 30 october 2003 20 november 2003 and 7 november 2004 we perform a superposed epoch analysis of the storms by defining the start time of the epoch when the kan lee interplanetary electric field proportional to the reconnection electric field first reaches 10 mv m during a period of continuously southward bz measurements from the gps receiver onboard the champ satellite at 400 km altitude indicate significant low to middle latitude daytime total electron content tec increases above the satellite within 1 2 h of the defined start time for three of the storms 1400 local solar time the 20 november 2003 data follow a different pattern the largest tec increases appear several hours 5 7 following the interplanetary magnetic field bz event onset tec data obtained from ground based gps receivers for the november 2003 storm tend to confirm a late tec increase for this storm at 1400 lt estimates of vertical plasma uplift near the equator at jicamarca longitudes 281 e using the dual magnetometer technique suggest that variability of the timing of the tec response is associated with variability in the prompt penetration of electric fields to low latitudes it is also found that for the november 2003 magnetic storm the cross correlation function between the sym h index and the interplanetary electric field reached maximum correlation with a lag time of 4 h such a large lag time has never been noted before the long delays of both the ionosphere and magnetosphere responses need to be better understood

a strong positive phase of ionospheric storms observed by the millstone hill incoherent scatter radar and global gps network 1 during geomagnetic storms the ionospheric f region electron density may be greatly increased or decreased which are termed positive storms or negative storms it is generally accepted that negative storm phases are caused by neutral composition changes in contrast different mechanisms have been proposed to explain the generation of positive storm phases in this paper we present observations of a strong positive storm at middle latitudes the millstone hill incoherent scatter radar detected significant increases of the midlatitude ionospheric f region electron density during a magnetic storm on 3 april 2004 the positive phase of the ionospheric storm started to occur in the morning sector 0912 lt at millstone hill and lasted for more than 10 hours compared with the quiet time ionosphere the daytime f peak altitude over millstone hill during the storm was 80 km higher the f region electron density was increased by a factor of 2 4 and the f region electron temperature was decreased by 1000 k or 40 the radar also measured an enhanced eastward electric field and a slightly more equatorward neutral wind global gps measurements show that total electron content tec was increased at middle latitudes and decreased at lower latitudes and the large tec enhancements occurred primarily in the atlantic sector we suggest that electric fields may play an important role in the generation of the observed positive storm phase the eastward electric field will cause increases in the midlatitude ionospheric electron density by moving the plasma particles upward and decreases in the equatorial ionospheric electron density by strengthening the fountain effect the daytime poleward wind was reduced or even reversed during the storm which may also contribute to the occurrence of the positive storm

relative importance of horizontal and vertical transports to the formation of ionospheric storm enhanced density and polar tongue of ionization there are still uncertainties regarding the formation mechanisms for storm enhanced density sed in the high and subauroral latitude ionosphere in this work we deploy the thermosphere ionosphere electrodynamic general circulation model tiegcm and gps total electron content tec observations to identify the principle mechanisms for sed and the tongue of ionization toi through term by term analysis of the ion continuity equation and also identify the advantages and deficiencies of the tiegcm in capturing high latitude and subauroral latitude ionospheric fine structures for the two geomagnetic storm events occurring on 17 march 2013 and 2015 our results show that in the topside ionosphere upward e b ion drifts are most important in sed formation and are offset by antisunward neutral winds and downward ambipolar diffusion effects in the bottomside f region ionosphere neutral winds play a major role in generating seds sed signature in tec is mainly caused by upward e b ion drifts that lift the ionosphere to higher altitudes where chemical recombination is slower horizontal e b ion drifts play an essential role in transporting plasma from the dayside convection throat region to the polar cap to form tois inconsistencies between model results and gps tec data were found 1 gps relative tec difference between storm time and quiet time has holes in the dayside ion convection entrance region which do not appear in the model results 2 the model tends to overestimate electron density enhancements in the polar region possible causes for these inconsistencies are discussed in this article

three dimensional p wave velocity structure of mt etna italy the three dimensional p wave velocity structure of mt etna is determined to depths of 15 km by tomographic inversion of first arrival times from local earthquakes recorded by a network of 29 permanent and temporary seismographs results show a near vertical low velocity zone that extends from beneath the central craters to a depth of 10 km this low velocity region is coincident with a band of steeply dipping seismicity suggesting a magmatic conduit that feeds the summit eruptions the most prominent structure is an approximately 8 km diameter high velocity body located between 2 and 12 km depth below the southeast flank of the volcano this high velocity body is interpreted as a remnant mafic intrusion that is an important structural feature influencing both volcanism and east flank slope stability and faulting

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

volcano tectonic activity along structures of the unstable ne flank of mt etna italy and their possible origin abstract we describe the prehistoric historic activity of the main and minor volcano tectonic structures of the northeastern flank of mt etna giving new data which provide a clearer view of how destabilized volcanoes react to magma pressure and gravity forces data are mostly based on new lithostratigraphic surveys and on offset measurements of late pleistocene holocene deposits and historic man made features the north east rift ne rift is a volcanic rift that has guided mostly explosive but also secondary effusive activity since the end of the pleistocene monogenetic cones and explosive craters are strongly elongated and aligned along 66 main surface fractures and several others hidden but inferred from sinkhole alignments the opening direction is locally oblique with a left lateral component in the north eastern segment of the rift at the ne tip of the rift the movements are relieved by the normal left lateral pernicana fault pf an 11 km long structure comprising e w fault segments connected by right stepping en echelon faults our study demonstrates that the very high slip rates at a centennial scale of these structures are well constrained and similar ne rift 0 6 1 8 cm a pf 0 5 2 2 cm a and have been also recognized in the latest pleistocene holocene 2 7 cm a the e w fiumefreddo fault ff has normal left lateral kinematics and a historic slip rate of 0 1 cm a ripa della naca faults strike ne and are covered by unfaulted

high resolution mapping of tec perturbations with the gsi gps network over japan two dimensional total electron content tec perturbations over japan are mapped with the geographical survey institute gsi gps network geonet gps earth observation network its spatial resolution is 0 15 latitude 0 15 longitude and temporal resolution is 30 seconds two dimensional tec observations with these high resolutions revealed spatial structures and temporal evolutions of traveling ionospheric disturbances tids in the nighttime mid latitude ionosphere on july 03 1997 a preliminary result of the tec perturbation mapping indicates that it would be a strong tool to investigate the ionospheric structures in detail coordinated observations with other ionospheric observation techniques such as incoherent scatter is radars airglow imagers and ionosondes are needed to clarify the vertical structure of the ionosphere

storm time dependence of equatorial disturbance dynamo zonal electric fields we use jicamarca radar observations of f region vertical plasma drifts and auroral electrojet indices during 1968 1988 to study the characteristics and temporal evolution of equatorial disturbance dynamo zonal electric fields these electric fields result from the dynamo action of storm time winds and or thermospheric composition changes driven by enhanced energy deposition into the high latitude ionosphere during geomagnetically active conditions the equatorial vertical drift perturbations last for periods of up to 30 hours after large increases in the high latitude currents on the average this process can be described by two basic components with time delays of about 1 12 hours and 22 28 hours between the high latitude current enhancements and the equatorial velocity perturbations our data indicate strong coupling between dynamo processes with different timescales the short term disturbance dynamo drives upward equatorial drifts eastward electric fields at night with largest amplitudes near sunrise and small downward drifts during the day these perturbation drifts are in good agreement with results from the blanc richmond disturbance dynamo theory the dynamo process with time delays of about a day drives upward drift velocities at night with largest values near midnight and downward drifts in the sunrise noon sector in this case the amplitudes of the disturbance drifts maximize during geomagnetically quiet times preceded by strongly disturbed conditions we also present results of a new equatorial storm time dependent empirical model which illustrate the characteristics of the vertical disturbance dynamo drifts

importance of gravitational spreading in the tectonic and volcanic evolution of mount etna the interaction between gravity and thermal effects largely determines the structural and magmatic evolution of volcanic constructs at scales spanning several orders of magnitude from small cones to the oceanic crust1 3 although gravitational spreading is a direct consequence of this interaction and a fundamental process in volcano growth it is rarely recognized as such here we describe a striking example of this process at etna volcano in italy the volcano and its clay rich substratum are slowly spreading towards the east and south driven by gravity spreading produces extensional structures in the summit region and contpressional structures at the base of the volcano eastward movement of the volcanic edifice over a stationary magma supply may be the cause of an apparent westward migration of volcanic activity as gravitational spreading seems to control the location and magnitude of shallow seismicity and flank eruptions an appreciation of its effects could become an essential element of future volcanic hazard evaluation our model proposed here for etna may also be relevant to a reinterpretation of the geological history of a number of other volcanoes

roots of etna volcano in faults of great earthquakes abstract results from several seismic methods allow us to sketch the deep structure of etna and its ionian margin under etna a volume of high velocity material is found in a structurally high position the emplacement of this suggests spreading of the surrounding medium just offshore down to the east normal faults penetrate through the upper crust the deeper crustal structure beneath appears upwarped from the basin towards etna juxtaposed with the crust of sicily a thinner crust reaches from the ionian basin under etna and the mantle is upwarped in such a structure magma can then be viewed as a melted lens capping a mantle upwarp at shallow depth rather than in an intracrustal chamber this reduces the conflict between estimates of its volume from excess output of volatiles and short residence times a link in time is indicated between volcanic and seismic activity at a large scale over the millennium the reported ends of episodes of high output rates of magma are followed by the reported occurrences of magnitude 7 earthquakes which caused destruction in southeastern sicily several steep active normal fault have been imaged to a depth of 10 km the crust up to 30 km offshore of the cities of catania and augusta which may be fault planes for such large earthquakes they expand and prolongate the system of the timpe faults on the eastern flank of etna thus linking large scale tectonics offshore with the volcano etna developed together with normal faulting upwarp and spreading during the recent evolution of the former ionian subduction activation of the material at depth at the lateral edge of the slab by vertical motion with extension above could produce the peculiar type of etna magmatism

location and orientation of eruptive fissures and feederdykes at mount etna influence of gravitational and regional tectonic stress regimes abstract lava extrusion from fissures on the flanks of the etna volcano is a common feature of recent activity as evidenced by the eruptions of 1971 1981 1983 and 1985 and was of similar importance during prehistoric times we propose here a model within which the location and orientations of the large majority of historic eruptive fissures on etna s flanks together with their feeder dykes are explained within the framework of a gravitational stress regime stress orientations within this regime are controlled largely by the gross morphology of the volcano but are significantly modified by local topographic anomalies we propose that the gravitational stress regime largely supercedes an earlier developed regional tectonic stress regime which still operates in the sub volcanic basement and may remain the dominant control of eruptive fissure and feeder dyke disposition at lower altitudes on the flanks the proposed model is supported by 1 detailed examination of fissure locations and orientations and the relationship between fissure azimuths and topography 2 precise horizontal distance measurement and vertical ground deformation studies of a recent eruption and 3 qualitative physical modelling experiments in which coloured water is injected into solidified gelatine solutions representing variously shaped volcanic constructs a cautious approach is advocated when extrapolating trends of spatially limited fissure segments for the purpose of locating potential sites of magma ascent and implications of the model for hazard analysis are outlined

mount etna dense array local earthquake p and s tomography and implications for volcanic plumbing inversion for the three dimensional velocity structure of mount etna is performed with a data set of arrival times of p and s waves of local earthquakes from temporary dense arrays of three component seismographs a high v p body revealed by the original tomography without nearby stations is confirmed and its image is sharpened using new velocity constraints provided by refraction data synthetic tests of v p and v p v s and comparison with an independent artificial source tomography with a fundamentally different geometry consistently calibrate the significance threshold of the resolution indicators the trustworthy part of the image shows a high v p body centered under the southern part of valle del bove above the 6 km below sea level deep basement which extends towards sea level and may be rooted in or through the crust it has a large contrast of over 1 km s with the surrounding sediments and sharp lateral limits and can thus be regarded as made of intrusive material of magmatic origin the massive high v p body is heterogeneous in v p v s the regions inside it where v s is relatively low can then be suspected of containing a proportion of melt or be fractured and act as pressure links or transport zones such features may be structurally linked and appear to be activated in eruptive phenomena by taking into account the heterogeneities in structure and physical state retrieved by seismic tomography a succession of seismic events deformational episodes and geochemical variation in lavas can be discussed with respect to the well observed eruptions

detecting short term evolution of etnean scoria cones a lidar based approach the 2001 and 2002 2003 flank eruptions on mount etna italy were characterized by intense explosive activity which led to the formation of two large monogenetic scoria cones one from each eruption on the upper southern flank of the volcano continuous monitoring of etna especially during flank eruptions has provided detailed information on the growth of these cones they differ in genesis shape and size a set of high resolution 1 m digital elevation models dems derived from light detection and ranging lidar data collected during four different surveys 2004 2005 2006 and 2007 has been used to map morphology and to extract the morphometric parameters of the scoria cones by comparing lidar derived dems with a pre eruption 1998 10 m dem the volume of the two scoria cones was calculated for the first time comparison of the lidar derived dems revealed in unprecedented detail morphological changes during scoria cone degradation in particular the morphologically more exposed and structurally weaker 2002 2003 cone was eroded rapidly during the first few years after its emplacement mainly due to gravitational instability of slopes and wind erosion

seismic tomography of etna volcano abstract a 3 d velocity model beneath etna volcano has been obtained through inversion of p wave arrivals of local earthquakes about 300 seismic events distributed around this volcano from surface up to a depth of 20 km have been used to infer the p wave velocity structure high p wave velocity bodies have been found in the upper portion of the volcanic edifice in a region where positive values of bouguer anomalies have previously been found low velocity bodies are identified at depths lower than 10 km and may be related to magmatic reservoirs the spatial pattern of these deeper velocity anomalies appears to be correlated at surface with the distribution of spatter cones in the nw quadrant a high velocity anomaly is correlated to the presence of a deeper seismicity the distribution of relocated hypocenters is not homogeneous but shows some features apparently related to the presence of magmatic bodies

regional scale tectonic evolution and the seismic velocity structure of the lithosphere and upper mantle the mediterranean region we present a numerical modeling approach designed for the verification of tectonic reconstructions and for a quantitative analysis of the seismic velocity structure of the lower lithosphere and upper mantle in this forward modeling procedure we use published reconstructions of the tectonic evolution of a region to predict the thermal structure from which we calculate physical quantities like p wave velocity basin subsidence and basement heat flow we show an application of this approach to two reconstructions of the late mesozoic and cenozoic evolution of the mediterranean region the resulting synthetic velocity models are tested against seismological models of the mantle structure obtained independently by delay time tomography subsidence and heat flow predictions are compared with actual observations to further constrain the geological assumptions underlying the forward models the mantle models predicted from reconstructions of the evolution of the mediterranean region correlate with major features in the tomographic images from our model results we conclude that the present distribution of seismic velocities in the mediterranean region is largely determined by the tectonic evolution during at least the last 40 m y this means we can verify processes represented in different tectonic scenarios with the seismologically determined velocity structure seen from a different perspective the model results contribute to understanding the causes of the velocity structure imaged by delay time tomography by showing how the tectonic evolution results in this structure

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

quaternary normal faulting in southeastern sicily italy a seismic source for the 1693 large earthquake summary we present geological and morphological data combined with an analysis of seismic reflection lines across the ionian ovshore zone and information on historical earthquakes in order to yield new constraints on active faulting in southeastern sicily this region one of the most seismically active of the mediterranean is avected by wnw ese regional extension producing normal faulting of the southern edge of the siculo calabrian rift zone our data describe two systems of quaternary normal faults characterized by diverent ages and related to distinct tectonic processes the older nw se trending normal fault segments developed up to 400 kyr ago and striking perpendicular to the main front of the maghrebian thrust belt bound the small basins occurring along the eastern coast of the hyblean plateau the younger fault system is represented by prominent nnw sse trending normal fault segments and extends along the ionian ovshore zone following the ne sw trending avola and rosolini ispica normal faults these faults are characterized by vertical slip rates of 0 7 3 3 mm yr 1 and might be associated with the large seismic events of january 1693 we suggest that the main shock of the january 1693 earthquakes m 7 could be related to a 45 km long normal fault with a right lateral component of motion a long term net slip rate of about 3 7 mm yr 1 is calculated and a recurrence interval of about 550 50 yr is proposed for large events similar to that of january 1693

earlier alkaline and transitional magmatic pulsation of mt etna volcano abstract the observation of glass inclusions with alkalic and transitional compositions in single olivine crystals from aci castello hyaloclastites indicates that small volumes of alkalic melts preceded tholeiite eruptions during the onset of mt etna volcanism the gradual shift in composition from alkalic to transitional melts is explained by simple partial melting of a compositionally uniform source with the degree of melting increasing by a factor of 3 4 during this early melting process such variation controls both the chemical and mineralogical signatures of emitted lavas the source shows trace element and isotopic signatures which may be representative of a himu type plume for etnean lavas

paleo environmental and volcano tectonic evolution of the southeastern flank of mt etna during the last 225 ka inferred from the volcanic succession of the timpe acireale sicily abstract the tectonic escarpments locally known as timpe cut a large sector of the eastern flank of etna and allow an ancient volcanic succession dating back to 225 ka to be exposed geological and volcanological investigations carried out on this succession have allowed us to recognize relevant angular unconformities and volcanic features which are the remnants of eruptive fissures as well as important changes in the nature composition and magmatic affinity of the exposed volcanics in particular the recognition in the lower part of the succession of important and unequivocal evidence of ancient eruptive fissures led us to propose a local origin for these volcanics and to revise previous interpretations which attributed their westward dipping to the progressive tectonic tilting of strata these elements led us to reinterpret the main features of the volcanic activity occurring since 250 ka bp and their relationship with tectonic structures active in the eastern flank of etna we propose a complex paleo environmental and volcano tectonic evolution of the southeastern flank of mt etna in which the timpe fault system played the role of the crustal structure that allowed the rise and eruption of magmas in the above considered time span

petrologic evidence of a complex plumbing system feeding the july august 2001 eruption of mt etna sicily italy after the major 1991 1993 eruption mt etna resumed flank activity in july 2001 through a complex system of eruptive fissures cutting the ne and the s flanks of the volcano and feeding effusive activity fire fountains strombolian and minor phreatomagmatic explosions throughout the eruption magmas with different petrography and composition were erupted the vents higher than 2 600 m a s l hereafter upper vents uv erupted porphyritic plagioclase rich trachybasalt typical of present day summit and flank activity differently the vents located at 2 550 and 2 100 m a s l hereafter lower vents lv produced slightly more primitive trachybasalt dominated by large clinopyroxene olivine and uncommon minerals for etna such as amphibole apatite and orthopyroxene and containing siliceous and cognate xenoliths petrologic investigations carried out on samples collected throughout the eruption provided insights into one of the most intriguing aspects of the 2001 activity namely the coeval occurrence of distinct magmas we interpret this evidence as the result of a complex plumbing system it consists in two separate magma storage systems a shallow one feeding the activity of the uv and a deeper and more complex storage related to the activity of lv in this deep storage zone which is thermally and compositionally zoned the favourable conditions allow the crystallization of amphibole and the occurrence of cognate xenoliths representing wall cumulates throughout 2001 eruption uv and lv magmas remain clearly distinct and ascended following different paths ruling out the occurrence of mixing processes between them furthermore integrating the 2001 eruption in the framework of summit activity occurring since 1995 we propose that the 2001 magma feeding the vents lower than 2 600 m a s l is a precursor of a refilling event which reached its peak during the 2002 2003 etna flank eruption

geometry of the neotectonic stress field in southern italy geological and seismological evidence the neotectonic regime in southern italy has been evaluated by making a comparison between all the available structural and seismological data the area investigated can be subdivided into four distinct zones which are characterized by different stress regimes in the southern apennines the tensile axis of the stress field is oriented approximately ne sw while the maximum principal stress 1 is subvertical in northern calabria the tensile axis is ese wnw and the 1 axis is almost vertical in the catanzaro trough both the tensile axis and the 1 axis are subhorizontal and act e w and n s respectively finally the strait of messina zone is characterized by a tensile axis oriented e w and by 1 being subvertical

tectonic control on the eruptive dynamics at mt etna volcano sicily during the 2001 and 2002 2003 eruptions abstract the eruptive events of the july august 2001 and october 2002 january 2003 at mt etna provide new insights for reconstructing the complex geometry of the feeding system and their relationship to regional tectonics the 2001 eruption took place mainly on the upper southern sector of the volcano the eruption was preceded by a large earthquake swarm for a few days before its onset and accompanied by ground deformation and fracturing the development of surface cracking along with the seismic pattern has allowed us to recognize three distinct eruptive systems the sw ne nnw sse and n s systems which have been simultaneously active such eruptive systems are only the upper portions of a complex feeding system that was fed at the same time by two distinct magmas the sw ne and nnw sse systems connected with the se crater conduit were fed by magma coming from depth whereas the n s system served instead as an ascending pathway for an amphibole bearing magma residing in a shallow reservoir the eruptive activity started again on october 2002 on the ne rift zone where about 20 eruptive vents were aligned between 2500 and 1900 m a s l and on the southern flank from the central crater to the montagnola the onset of eruptive activity was accompanied by a seismic swarm as in the 2001 eruptive event two independent feeding systems formed characterized by distinct magmas the sw ne system controlled the feeding of the northeast rift and was accommodated by left lateral displacement along the wnw ese trending pernicana fault the n s system fed the eruptions on the southern flank moreover the associated crustal deformation triggered seismic reactivation of tectonic structures in the eastern flank of the volcano and offshore these two last eruptions indicate that at mt etna the ascent of magma as well as the accommodation of deformation is strongly dominated by local extensional structures that are connected to a regional tectonic regime

the role of the pernicana fault system in the spreading of mt etna italy during the 2002 2003 eruption flank instability and collapse are observed at many volcanoes among these mt etna is characterized by the spreading of its eastern and southern flanks the eastern spreading area is bordered to the north by the e w trending pernicana fault system pfs during the 2002 2003 etna eruption ground fracturing along the pfs migrated eastward from the ne rift to as far as the 18 km distant coastline the deformation consisted of dextral en echelon segments with sinistral and normal kinematics both of these components of displacement were one order of magnitude larger 1 m in the western previously known portion of the pfs with respect to the newly surveyed 9 km long eastern section 0 1 m this eastern section is located along a pre existing but previously unknown fault where displaced man made structures give overall slip rates 1 1 9 cm year only slightly lower than those calculated for the western portion 1 4 2 3 cm year after an initial rapid motion during the first days of the 2002 2003 eruption movement of the western portion of the pfs decreased dramatically while parts of the eastern portion continued to move these data suggest a model of spreading of the eastern flank of etna along the pfs characterized by eruptions along the ne rift instantaneous short lived meter scale displacements along the western pfs and more long lived centimeter scale displacements along the eastern pfs the surface deformation then migrated southwards reactivating one after the other the nnw sse trending timpe and trecastagni faults with displacements of 0 1 and 0 04 m respectively these structures along with the pfs mark the boundaries of two adjacent blocks moving at different times and rates the new extent of the pfs and previous activity over its full length indicate that the sliding eastern flank extends well below the ionian sea the clustering of seismic activity above 4 km b s l during the eruption suggests a deep decollement for the moving mass the collected data thus suggests a significant movement volume 1 100 km3 of the eastern flank of etna both on shore and off shore

two step development of geomagnetic storms using the dst index more than 1200 geomagnetic storms from weak to intense spanning over three solar cycles have been examined statistically interplanetary magnetic field imf and solar wind data have also been used in the study it is found that for more than 50 of intense magnetic storms the main phase undergoes a two step growth in the ring current that is before the ring current has decayed significantly to the prestorm level anew major particle injection occurs leading to a further development of the ring current and making dst decrease a second time thus intense magnetic storms may often be the result of two closely spaced moderate storms the corresponding signature in the interplanetary medium is the arrival of double structured southward imf at the magnetosphere

volatile rich magma injection into the feeding system during the 2001 eruption of mt etna italy its role on explosive activity and change in rheology of lavas the explosive behavior and the rheology of lavas in basaltic volcanoes usually driven by differentiation can also be significantly affected by the kinetics of magma degassing in the upper portion of the feeding system the complex eruption of 2001 at mt etna italy was marked by two crucial phenomena that occurred at the laghetto vent on the southern flank of the volcano 1 intense explosive activity and 2 at the end of the eruption emission of a lava flow with higher viscosity than flows previously emitted from the same vent here we investigate the hypothesis that these events were driven by the injection of volatile rich magma into the feeding system the input and mixing of this magma into a reservoir containing more evolved magma had the twofold effect of increasing 1 the overall concentration of volatiles and 2 their exsolution with consequent efficient vesiculation and degassing this led to an explosive stage of the eruption which produced a 75 m high cinder cone efficient volatile loss and the consequent increase of the liquidus temperature brought about the nucleation of fe oxides and other anhydrous crystalline phases which significantly increased the magma viscosity in the upper part of the conduit leading to the emission of a high viscosity lava flow that ended the eruption the 2001 eruption has offered the opportunity to investigate the important role that input of volatile rich magma may exert in controlling not only the geochemical features of erupted lavas but also the eruption dynamics these results present a new idea for interpreting similar eruptions in other basaltic volcanoes and explaining eruptions with uncommonly high explosivity when only basic magmas are involved

seismic tomography of the crust underneath the etna volcano sicily abstract a new tomographic inversion of the velocity structure and hypocenter parameters has been carried out in the etna area using a remarkably larger seismic dataset than used in the previous investigations the obtained v p and v p v s space distributions allow us to detail the already known structural features and to find new velocity anomalies a major aseismic high velocity body is recognized in the upper 10 km beneath the central crater area and the southeastern flank of the volcano interpreted as high strength magmatic rocks such as cumulites dike structures etc a high level of seismic activity and low v p values are found immediately to the west and the east of the high velocity body suggesting the presence of highly fractured weakness zones which also taking into account the local distribution of seismogenic stress can be supposed to include paths for magma rising and stationing clear evidence is also found of a shallow aseismic low velocity zone beneath the volcano s southwestern flank corresponding to the volume where previous investigators hypothesized the presence of a magma chamber on the grounds of geodetic data and seismic b value mapping

global positioning system phase fluctuations at auroral latitudes using observations of a diversity of propagation paths of global positioning system satellites from each of 11 high latitude stations it was possible to determine the behavior pattern for the development of phase fluctuations in the auroral and subauroral irregularity regions the coverage comprised a large range of longitudes and latitudes with all data measuring the same parameter i e phase fluctuations starting with characteristics of the irregularity development on magnetically quiet days it was noted that the start and stop times of phase fluctuations correlated with the entry and exit into the irregularity oval maximum occurrence of phase fluctuation took place near magnetic midnight during magnetic storms the irregularity oval expands equatorward and poleward and phase fluctuations increase in intensity using the time difference of the development of irregularities between stations considerably separated in longitude the conclusion was reached that during a magnetic storm there is a long time feeding of the turbulent energy that develops irregularities in the oval while the geographic position of the station relevant to the oval is important during storms the dynamics of each storm modifies the simple behavior shown during quiet times observations at corrected geomagnetic latitudes 80 indicate that phase scintillation intensities were lower than those in the oval during both quiet and disturbed conditions in years of low solar flux since the technique yields a measure of total irregularity intensity for the total propagation path it was not possible solely from these data to determine the altitude of the irregularities in case studies it was found that during magnetically quiet periods when irregularities are noted on propagation paths in the irregularity oval f layer critical frequencies and thicknesses were greater than those of the e layer during magnetic storm periods e layer critical frequencies are for various periods of time greater than those of the f layer during storms there are probably contributions from both layers with different mechanisms for the development of irregularities operating as a function of time storm development and latitude

ground deformations and volcanic processes as imaged by cgps data at mt etna italy between 2003 and 2008 1 we analyze the kinematic and crustal deformations of mt etna from 2003 to 2008 as imaged by the mt etna continuous gps cgps network etn net through a careful analysis of gps time series six coherent phases of crustal deformations have been identified three inflation phases and three deflation phases superimposed on a major inflation of the volcanic edifice since 2001 the inversions of gps velocities have enabled 1 a better understanding of the evolution of the volcanic sources acting beneath the volcano 2 analysis of the strain rate patterns and 3 a delineation of potential coupling between volcanic sources and the observed ground deformations the modeling of the pressure sources has shown a separation between inflation and deflation sources the deflation sources show an upward migration from 5 5 toward 2 0 km b s l while the inflation sources are located within 5 5 and 4 0 km b s l our results indicate that the kinematic and ground deformations of the mid upper eastern flank are driven by the interplay between the effect of the magmatic sources and a southeastward motion furthermore clockwise rotations have been detected that prevailed over the eastern motion of the flank during the inflation phases preceding the 2004 2005 and 2006 eruptions finally the accordance between the higher geodetic shear strain rates and the area with the highest seismic energy release shows that measured geodetic shear strain rates can provide useful information on the potential occurrence of seismic activity

analysis of the global ionospheric disturbances of the march 2015 great storm the global ionospheric storm in march 2015 was investigated using data from over 3000 gps stations worldwide in this study total electron content tec rate of tec rot and rot s standard deviation roti as well as the second order difference operator tect were considered as main characteristic methods to distinguish ionosphereic disturbances the results show that 1 based on the multiple methods above we all observed that for the first time there were three equatorward traveling ionospheric disturbances tids in the main phase of this storm in north america the disturbance zone expanded to 40 n the disturbance periods and ae peak stages were roughly synchronous we suggest that these three tids were induced by the propagation of agws to low latitudes under the action of ae 2 the most intense positive storm occurred over south america and the south atlantic over 300 enhancement 00 00 05 00 ut march 18 whereas a negative storm was observed in the corresponding region of the nh such inverse hemispheric asymmetry in intensity and structure can be explained by the variations of the thermospheric composition the imf by component and the geomagnetic intensity 3 on march 18 a negative storm dominated globally except at certain low latitudes and tended to propagate equatorward and decay with time which could be largely attributed to the storm circulation theory and the evolution of the negative storm was further characterized by the fof2 variations of ionosondes

penetration of magnetospheric electric fields to the equator during a geomagnetic storm 1 penetration of the magnetospheric electric field to the equatorial ionosphere was examined for the geomagnetic storm on 6 november 2001 by analyzing the difference in magnitude of the geomagnetic storm recorded at the dayside geomagnetic equator yap 0 3 gml and low latitude okinawa 14 47 gml the penetrated electric field caused the dp2 currents at the equator i e eastward currents during the main phase of the storm while the overshielding currents i e westward currents dominated during the recovery phase it is shown that the ring current started to develop simultaneously with the onset of the equatorial dp2 within the temporal resolution of a few minutes these results imply prompt transmission of the dawn to dusk convection electric field to the inner magnetosphere as well as to the equatorial ionosphere it is found that the equatorial dp2 started to decrease one hour after the onset of the ring current development indicating shielding effects becoming effective at the equator during the latter half of the storm main phase the dp2 was then overwhelmed by the overshielding which resulted in the counter electrojet cej in the beginning of the storm recovery phase the image magnetometer chain data indicate that the westward auroral electrojet aej in the dawn sector was driven over midlatitude centered at 57 corrected geomagnetic latitude cgml during the main phase while the aej shifted rapidly poleward to the auroral latitude centered at 67 cgml in the beginning of the recovery phase the overshielding must be caused by the abrupt poleward shift of the rl facs as inferred from the poleward shift of the aej in addition to the decrease in their magnitude due to the decrease in magnitude of the southward imf the geomagnetic storm at the dayside geomagnetic equator was enhanced in amplitude with the ratio of 2 7 as compared with the geomagnetic storm at low latitude this amplification is a result of both effects of the dp2 currents and the cej associated with the main and recovery phases respectively it is suggested that the electric field associated with the dp2 currents contributed to the development of the ring current during the main phase while the overshielding electric field may contribute to cease developing the ring current during the recovery phase

mechanisms for ground surface fracturing and incipient slope failure associated with the 2001 eruption of mt etna italy analysis of ephemeral field data abstract during the july august 2001 eruption of mt etna development of extensional fractures faults and grabens accompanied magma intrusion and subsequent volcanic activity during the first days of the eruption we performed an analysis of attitude displacement and propagation of fractures and faults exposed on the ground surface in two sites torre del filosofo and valle del leone located along the same fracture system in the region surrounding the valle del bove depression on the eastern flank of mt etna fractures and faults formed as the consequence of a shallow intruding dyke system that fed the several volcanic centres developed along the fracture system the investigated sites differ in slope attitude and in geometrical relationships between fractures and slopes in particular the fracture system propagated parallel to the gentle slope

damping of large scale traveling ionospheric disturbances detected with gps networks during the geomagnetic storm 1 large scale traveling ionospheric disturbances lstids during the geomagnetic storm on 22 september 1999 were studied using total electron content tec data from the gps earth observation network geonet in japan international gps service igs and continuously operating reference stations cors in the united states the damping rates of the lstids were precisely derived in several local time sectors and were found to depend on values of the background tec this indicates that the dominant physical mechanism of the lstids damping is the ion drag effect by the background ionosphere the high resolution tec data from geonet revealed that two successive lstids were damped significantly as they traveled equatorward in the dawn sector the ratio of the perturbation component of tec to the background component i i0 decreased exponentially with the damping rate of 0 89 1000 km and 0 77 1000 km we studied also the amplitude of i i0 at high latitudes using igs data and found that the damping rates of lstids at high latitudes tended to be smaller than those at midlatitudes global tec observations during this geomagnetic storm by the igs and cors networks detected that several lstids propagated also equatorward in the afternoon sector and in the night sector the lstids in the afternoon sector were most damped with the damping rate of 1 04 1000 km which corresponds to the e folding length of 961 km the damping rate of lstids in the night sector was found to be small the lstids had a tendency to be damped rapidly in the regions where background tec was large this dependence of the damping rate on latitude and local time indicates that this intense damping of lstids was caused mainly by the ion drag effect that is proportional to the ion collision frequency the relation between the damping rates and the background tec derived from the observation are consistent with those estimated with a theoretical calculation of the gravity wave damping by the ion drag effect the worldwide distribution of gps receivers enabled us to estimate the longitudinal extent of these lstids the zonal width of lstids in the dawn sector was narrower than 45 in longitude 2 900 km around 55 n and wider than 20 in longitude 1 800 km around 40 n these widths were narrower than those reported in previous studies

review of seismological studies at mount etna this paper reports the present state of seismological research at mt etna a schematic classification of the earthquakes that occur on the volcano is proposed based on both seismogram and spectrum features we have made both focal solutions and estimates of earthquake source parameters stress drop values between 2 and 20 bars and small source dimensions the crust of etna thus appears as an extremely heterogeneous medium that does not permit great stress accumulation the coexistence of an extensional regime with an older and deeper compressive one seems confirmed at depths greater than about 7 km eruptive and seismic phenomena occur mainly along the principal structural trends of the volcano but often the directions of the eruptive fractures and the earthquake concentration during the same eruption do not coincide tectonics seem to play an important role in controlling seismo volcanic behaviour

constraints on the seismotectonics of the central mediterranean from very long baseline interferometry summary very long baseline interferometry vlbi determined site velocities from seven stations in western europe reveal a stable continental platform north of the alps deformations between sweden germany and spain can not exceed 2 mm yr south of the alps significant motions are occurring with respect to stable europe two sites east of the apennine mountains on peninsular italy have north easttrending velocities which increase from 2 mm yr l in the north at medicina to 6 mm yr l in the south at matera in contrast the vlbi site in the south eastern corner of sicily is moving 7 mm yr i to the north north west these velocities are largely explained if southern sicily is attached to a north westerly moving african plate and the eastern portion of the italian peninsula forms part of a hypothesized adriatic sea crustal block which is rotating counter clockwise with respect to europe about a pole near the alps such an explanation is consistent with the styles of the larger historical earthquakes of the region which show ne sw extension across the apennines north south convergence across the alps and ne sw compression in coastal yugoslavia the adria plate model generates 1 5 2 2 x 10l8 nm yr l of potential earthquake moment along the northern and central apennines historical records suggest that 30 60 per cent of this moment is released seismically based on a direct strain rate measurement recurrence intervals for italian earthquakes south of medicina are estimated to be 12 46 yr for m6 5 quakes and 35 143 years for m7 0 quakes

recent and active tectonics in the calabrian arc southern italy normal faulting which has developed since the middle pleistocene with an overall ese wnw extension is the dominant mode of deformation which has characterized the calabrian arc up to the present quaternary normal faults extend for a total length of about 180 km along the inner side of the arc the different normal fault segments which during the pleistocene controlled the evolution of the main marine sedimentary basins are varying in length from 10 to 20 km and have fault escarpments showing a very young morphology which define the fronts of the major mountain ranges of the arc the morphological features of the fault escarpments suggest slip rates of 0 8 1 1 mm yr for the last 700 k y and values of 0 6 0 9 mm yr for the last 120 k y indicating a uniform rate of faulting since the middle pleistocene crustal seismicity and the mesoseismic areas of historical large events 6 5 m 7 1 which occurred in the calabrian arc are located within a narrow belt along the hanging walls of the quaternary normal fault segments this suggests that the normal faults which dissect the inner side of the calabrian arc may be seismically active

geospace system responses to the st patrick s day storms in 2013 and 2015 this special collection includes 31 research papers investigating geospace system responses to the geomagnetic storms during the st patrick s days of 17 march 2013 and 2015 it covers observation data assimilation and modeling aspects of the storm time phenomena and their associated physical processes the ionosphere and thermosphere as well as their coupling to the magnetosphere are clearly the main subject areas addressed this collection provides a comprehensive picture of the geospace response to these two major storms we provide some highlights of these studies in six specific areas 1 global and magnetosphere plasmasphere perspectives 2 high latitude responses 3 subauroral and mid latitude processes 4 effects of prompt penetration electric fields and disturbance dynamo electric fields 5 effects of neutral dynamics and perturbation and 6 storm effects on plasma bubbles and irregularities we also discuss areas of future challenges and the ways to move forward in advancing our understanding of the geospace storm time behavior and space weather effects

oblique rifting in salina lipari and vulcano islands aeolian islands southern italy a structural analysis carried out on the volcanic products of the islands of salina lipari and vulcano aeolian archipelago points out that the large scale tectonic setting is dominated by nw se trending right lateral extensional strike slip faults and by n s to ne sw trending normal faults and fractures this fault pattern generates pull apart type structures developing between different right hand overlapping fault segments and a characteristic extensional imbricate fan geometry at the tip of the major strike slip faults all the structures representing the surface expression of an active crustal discontinuity which controls the evolutionary history of the magmatism of the three islands are kinematically compatible with a n100 e extension related to a rifting process affecting southern italy

the feeding of the eruptive activity of etna volcano the regional stress field as a constraint to magma uprising and eruption an analysis of the structural lineaments as observed on the middle and upper slopes of etna volcano was made with the aim of checking stress distribution within the volcanic structure

geomorphology and seismotectonic elements in the giarre area sicily a morphostructural analysis has been performed on the eastern flank of mt etna located between the towns of st alfio and linera and the ionian sea the research has been carried out through analysis of aerial photographs and has allowed recognition of morphoneotectonic elements such as some scarps with rectilinear trend laterally becoming morphological flexures according to the lithology anomalies in the hydrographic network such as rectilinear tracts of drainage valleys with simple or double bends hanging valleys and truncated valleys narrow deeply engraved valleys with meanders and fluvial captures all these elements are caused by a fault system oriented nnw sse with a mainly vertical component seismic events with very shallow foci have been recorded in the study area these earthquakes triggered several small landslides on the fault scarps and large series of coseismic and coaxial fractures it is possible to show that the morphostructures examined have been reactivated during many of the seismic events that have occurred in the area the combination of these elements verifies that the morphostructures have a real neotectonic cause which is associated with uplifts which have occurred in the area at different times