an overview of experimental models to understand a complex volcanic instability application to mount etna italy abstract volcanic edifices are often unable to support their own load triggering the instability of their flanks many analogue models have been aimed especially in the last decade at understanding the processes leading to volcano flank instability general behaviors were defined and the experimental results were compared to nature however available data at well studied unstable volcanoes may allow a deeper understanding of the specific processes leading to instability providing insights also at the local scale etna italy constitutes a suitable example for such a possibility because of its well monitored flank instability for which different triggering factors have been proposed in the last two decades among these factors recent insar data highlight the role played by magmatic intrusions and a weak basement under a differential unbuttressing at the volcano base this study considers original and recently published experimental data to test these factors possibly responsible for flank instability with the final aim to better understand and summarize the conditions leading to flank instability at etna in particular we simulate the following processes a the long term activity of a lithospheric boundary as the malta escarpment separating the ionian oceanic lithosphere from the continental sicilian lithosphere below the most unstable east flank of the volcano b spreading due to a weak basement with different boundary conditions c the pressurization of a magmatic reservoir as that active during the 1994 2001 inflation period d dike emplacement as observed during the major 2001 and 2002 2003 eruptions the experimental results suggest that 1 the long term activity of a lithospheric tectonic boundary may create a topographic slope which provides a differential buttressing at the volcano base a preparing factor to drive longer term 10 5 years instability on the east flank of the volcano 2 volcano spreading 4 years has limited effect on flank instability at etna 3 magmatic intrusions 1 years both in the form of mogi like sources or dikes provide the most important conditions to trigger flank instability on the shorter term

effects of the 1989 fracture system in the dynamics of the upper se flank of etna revealed by volcanic tremor data the missing link 1 fracture reactivation is a widespread process in nature even though evidence of magma induced reactivation is less documented here we provide evidence of the reactivation of a fracture system on the upper flank of the mt etna volcano and consider its possible implications in understanding the recent volcanic and tectonic activity a nnw sse trending fracture partly accompanied by magma emplacement in the form of a laterally propagating dike formed in 1989 on the upper se flank of etna lava effusions in 1991 1993 2001 and 2006 were associated with volcano tectonic vt seismicity and ground deformations on the upper part of the volcano which document the seismogenetic involvement of the 1989 fractures although without eruptive phenomena along the discontinuity in addition to the aforementioned episodes of vt seismicity differences in the characteristics of the background seismic radiation volcanic tremor were measured at stations close to these fractures during the eruptive activity on 24 november 2006 for which more detailed volcanological and seismological time histories are available moving on from these findings we analyze volcanic tremor data recorded close to the summit and along the s flank of the volcano to highlight the interactions between seismic radiation and the 1989 fracture system centroid location of volcanic tremor and wave field characteristics at stations of the permanent local seismic network of etna highlight the guidance role played by the 1989 fractures during the eruptive activity on 24 november 2006 in addition the collected data shed light on hitherto unknown structural features which appear to connect the volcano summit to the lower se slope and also play an important role in controlling the instability of the e flank more generally this study shows how 1 using an integrated approach it is possible to link apparently different features to a common structure showing uniform and distinct dynamics relevant at the volcano scale and 2 fracture reactivation can also occur by means of magma intrusion playing an important role in the transfer of magma within a volcanic edifice

shallow magma transport for the 2002 3 mt etna eruption inferred from thermal infrared surveys abstract the 26 october 2002 28 january 2003 eruption of mt etna volcano was characterised by lava effusion and by an uncommon explosivity along a 1 km long eruptive fissure on the southern upper flank of the volcano the intense activity promoted rapid growth of cinder cones and several effusive vents analysis of thermal images recorded throughout the eruption allowed investigation of the distribution of vents along the eruptive fissure and of the nature of explosive activity the spatial and temporal distribution of active vents revealed phases of dike intrusion expansion geometric stabilization and drainage these phases were characterised by different styles of explosive activity with a gradual transition from fire fountaining through transitional phases to mild strombolian activity and ending with non explosive lava effusion here we interpret the mechanisms of the dike emplacement and the eruptive dynamics according to changes in the eruptive style vent morphology and apparent temperature variations at vents detected through thermal imaging this is the first time that dike emplacement and eruptive activity have been tracked using a handheld thermal camera and we believe that its use was crucial to gain a detailed understanding of the eruptive event

spatiotemporal gravity variations to look deep into the southern flank of etna volcano 1 a 14 year long microgravity data set october 1994 to september 2007 collected along a 24 km east west trending profile of 19 stations was analyzed to detect underground mass redistributions related to the volcanic activity involving the southern flank of mt etna italy a multiresolution wavelet analysis was applied to separate the volcano related anomalies from the unwanted components the residual image having both spatial extension and temporal duration evidenced two complete gravity increase decrease cycles mainly affecting the central and eastern stations of the profile the first gravity increase early 1995 to the end of 1996 and decrease end of 1996 to late in 1998 cycle reached a maximum amplitude of approximately 90 gal the second gravity increase mid 1999 to mid 2000 and decrease mid 2000 to early 2004 cycle attained an amplitude of about 80 gal after about 5 years of a persistent negative gravity anomaly a new semicycle started at the end of 2006 and continued during the last survey carried out in september 2007 the density changes modeled over time since 1994 using a quadratic programming algorithm are mainly located at a depth of 2 4 km bsl in a region recognized to be a preferential pathway of magma rising and an intermediate zone of magma storage withdrawal the computed positive mass variations of about 105 109 kg were interpreted as magma accumulation while negative mass changes of about 120 109 kg were associated with either magma drainage or opening of new voids by tectonic stresses within a source volume where tensional earthquakes occurred

link between major flank slip and 2002 2003 eruption at mt etna italy 1 the 2002 2003 etna eruption is studied through earthquake distributions and surface fracturing in september 2002 earthquake induced surface rupture sinistral offset 0 48 m occurred along the e w striking pernicana fault pf on the ne flank in late october a flank eruption accompanied further 0 77 m surface rupturing reaching a total sinistral offset of 1 25 m the deformation then propagated for 18 km eastwards to the coastline sinistral offset 0 03 m and southwards along the nw se striking timpe dextral offset 0 04 m and later trecastagni faults dextral offset 0 035 m seismicity 4 km bsl on the e flank accompanied surface fracturing fault plane solutions indicate an overall ese wnw extension direction consistent with ese slip of the e flank also revealed by ground fractures a three stage model of flank slip is proposed inception september earthquake climax accelerated slip and eruption and propagation e and s migration of the deformation

the deformation offshore of mount etna as imaged by multichannel seismic reflection profiles abstract despite the clear evidence of active flank dynamics that is affecting the eastern side of mount etna the contribution of tectonic processes has not been yet understood so far the various models proposed to explain the observed flank deformation have been based on onshore structural data coming from the volcanic edifice the ionian offshore of mount etna has been only recently investigated using multichannel seismic profiles and offers the opportunity to image the structural features of the substrate of the unstable flank of the volcano this contribution aims at describing the deformation located offshore mount etna using multichannel seismic profiles recently acquired during three seismic surveys the onshore flank deformation of mount etna appears to be laterally confined by two tectonic guidelines trending roughly e w located to the north and south of the deforming flank the northern guideline in particular takes the surface expression of a sharp fault pernicana fault though often assumed that these boundary structures continue offshore as linear features connected to a frontal thrust ramp the occurrence of this simple offshore structural system has not been imaged in fact seismic data show a remarkable degree of structural complexity offshore mount etna the pernicana fault for instance is not continuing offshore as a sharp feature rather the deformation is expressed as ene wsw folds located very close to the coastline it is possible that these tectonic structures might have affected the offshore of mount etna before the pernicana fault system was developed less than 15 ka ago the southern guideline of the collapsing eastern flank of the volcano is poorly expressed onshore and does not show up offshore in fact seismic data indicate that the catania canyon a remarkable e w trending feature does not reflect a tectonic control seismic interpretation also shows the occurrence of a structural high located just offshore the edifice of mount etna whereas a complex deformation affects the boundary of this offshore bulge it shows only limited internal deformation part of the topography of the offshore bulge pre existed the constructional phase of mount etna being an extension of the hyblean plateau only in the northern part the bulge is a recent tectonic feature being composed by plio quaternary strata that were folded before and during the building of mount etna the offshore bulge is bounded by a thrust fault that can be related to the intrusion of the large scale magmatic body below mount etna

coupled magma chamber inflation and sector collapse slip observed with synthetic aperture radar interferometry on mt etna volcano 1 volcanoes deform dynamically due to changes in both their magmatic system and instability of their edifice mt etna features vigorous and almost continuous eruptive activity from its summit craters and periodic flank eruptions even though its shape is that of a large stratovolcano its structure features two rift systems and a flank collapse structure similar to hawaiian shield volcanoes we analyze european remote sensing ers satellite differential interferometric synthetic aperture radar insar data 1993 1996 for mt etna spanning its quiescence from 1993 through the initiation of renewed eruptive activity in late 1995 we use synthetic aperture radar sar data from both ascending and descending ers satellite tracks comparison of independent interferograms covering the first 2 years of the inflationary period shows a pattern consistent with inflation of the volcano calculation of the tropospheric path delay based on meteorological data does not change this interpretation interferograms from late summer 1995 1996 show no significant deformation joint inversion of interferograms from ascending and descending satellite tracks require both inflation from a spheroidal magmatic source located beneath the summit at 5 km below sea level and displacement of the east flank of etna along a basal decollement both sources of deformation were contemporaneous within the resolution of our data and suggest that inflation of the central magma chamber acted to trigger slip of etna s eastern flank these results demonstrate that flank instability and recharge of a volcano s magma system must both be considered toward understanding how volcanoes work and in their hazard evaluation

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

volcaniclastic dykes tell on fracturing explosive eruption and lateral collapse at stromboli volcano italy abstract in the upper part of the stromboli volcano in the le croci and bastimento areas two dyke like bodies of volcanic breccia up to two metre thick crosscut and intrude the products of vancori and neostromboli volcanoes we describe the lithofacies association of these unusual volcaniclastic dykes interpret the setting of dyke forming fractures and the emplacement mechanism of internal deposits and discuss their probable relationships with the explosive eruption and major lateral collapse events that occurred at the end of the neostromboli period the dyke volcaniclastic deposits contain juvenile magmatic fragments pyroclasts suggesting a primary volcanic origin their petrographic characteristics are coincident with the neostromboli products the architecture of the infilling deposits comprises symmetrically nested volcaniclastic units separated by sub vertical boundaries which are parallel to the dyke margins the volcanic units are composed of distinctive lithofacies the more external facies is composed of fine and coarse ash showing sub vertical laminations parallel to the contact wall the central facies comprises stratified lithic rich breccia and lapilli tuff whose stratification is sub horizontal and convolute discordant to the dyke margins only at le croci dyke the final unit shows a massive tuff breccia facies the volcaniclastic dykes experienced a polyphasic geological evolution comprising three stages the first phase consisted in fracturing explosive intrusion related to magma rising and upward injection of magmatic fluids and pyroclasts the second phase recorded the dilation of fractures and their role as pyroclastic conduits in an explosive eruption possibly coeval with the lateral collapse of the neostromboli lava cone finally in the third phase the immediately post eruption mass flow remobilization of pyroclastic deposits took place on the volcano slopes

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

long term stress strain analysis of volcano flank instability the eastern sector of etna from 1980 to 2012 1 we investigated the evolution of seismicity and deformation in the unstable eastern flank of etna volcano over a 30 year period from 1980 to 2012 a significant temporal correlation has been revealed between periods of flank acceleration and intensified seismic activity by comparing seismicity along the northern border pernicana fault system of the sliding flank and the deformation of the eastern flank two marked phases have been observed in 1984 1986 and in the years following 2002 these two phases are separated by an intermediate phase from 1987 to 2001 in which the flank sliding slowed down and the seismicity dropped drastically this common temporal evolution in the deformation rate and seismic release supports the hypothesis that the seismicity in the northern border can be viewed as a marker of the response to accommodate the stress exerted by the traction of the eastern flank sliding this interplay has also been corroborated by finite element method numerical computations that highlight a good correlation between the seismicity pattern and areas of positive stress changes induced by the sliding surface the two intense phases of flank acceleration are representative of two main different sources volcano flank instability stretching the eastern sector in the first 1984 1986 phase and magmatic intrusions pushing the eastern flank seaward since the 2002 2003 eruption establishing the relationship between flank acceleration and seismic activation therefore contributes to understanding etna s mechanical behavior and provides insights into the processes regulating the unstable flank response

thermal weakening of the carbonate basement under mt etna volcano italy implications for volcano instability abstract the physical integrity of a sub volcanic basement is crucial in controlling the stability of a volcanic edifice for many volcanoes this basement can comprise thick sequences of carbonates that are prone to significant thermally induced alteration these debilitating thermal reactions facilitated by heat from proximal magma storage volumes promote the weakening of the rock mass and likely therefore encourage edifice instability such instability can result in slow gravitational spreading and episodic to continuous slippage of unstable flanks and may also facilitate catastrophic flank collapse understanding the propensity of a particular sub volcanic basement to such instability requires a detailed understanding of the influence of high temperatures on the chemical physical and mechanical properties of the rocks involved the juxtaposition of a thick carbonate substratum and magmatic heat sources makes mt etna volcano an ideal candidate for our study we investigated experimentally the effect of temperature on two carbonate rocks that have been chosen to represent the deep heterogeneous sedimentary substratum under mt etna volcano this study has demonstrated that thermal stressing resulted in a progressive and significant change in the physical properties of the two rocks porosity wet i e water saturated dynamic poisson s ratio and wet vp vs ratio all increased whilst p and s wave velocities bulk sample density dynamic and static young s modulus dry vp vs ratio and dry dynamic poisson s ratio all decreased at temperatures of 800 c the carbonate in these rocks completely dissociated resulting in a total mass loss of about 45 and the release of about 44 wt of co 2 uniaxial deformation experiments showed that high in situ temperatures 500 c significantly reduced the strength of the carbonates and altered their deformation behaviour above 500 c the rocks deformed in a ductile manner and the output of acoustic emissions was greatly reduced we speculate that thermally induced weakening and the ductile behaviour of the carbonate substratum could be a key factor in explaining the large scale deformation observed at mt etna volcano our findings are consistent with several field observations at mt etna volcano and can quantitatively support the interpretation of 1 the irregularly low seismic velocity zones present within the sub volcanic sedimentary basement 2 the anomalously high co 2 degassing observed 3 the anomalously high vp vs ratios and the rapid migration of fluids and 4 the increasing instability of volcanic edifices in the lifespan of a magmatic system we speculate that carbonate sub volcanic basement may emerge as one of the decisive fundamentals in controlling volcanic stability

geology and tectonics of the southwestern boundary of the unstable sector of mt etna italy abstract the etna volcano is known to be unstable and gradually moving downslope toward east and south the study of the local geology and structure of these unstable flanks and of their boundaries is important to understand the evolution of the flank instability and the stress field driving the spreading of the edifice in this paper we present the geological evolution of the lower south western sector of mount etna base on a detailed field survey at 1 10 000 scale this area located at the boundary of the unstable south eastern flank of the volcano is affected by the active ragalna fault and by distinctive eruptive fissures monte calvario formation 18 15 ka the monte calvario formation is made of viscous lavas often associated to breccia and autoclastic lava facies fed by a set of eruptive fissures ne sw oriented their emplacement occurred immediately before the ellitico caldera collapse marking a previously poorly constrained shift in the feeding system of the volcano the orientation of these eruptive fissures and lineaments and the geometry of the sedimentary substratum modeled from subsurface data indicate that the area was dominated by a local stress field consistent with the lateral spreading of mount etna since at least from the final ellittico phase about 18 ka with a nearly constant mean displacement rate these data give new insights into the geology and structure of the flank instability at etna the main geologic hazard of the studied area is not related to the opening of a new eruptive fissures but it is posed by the presence into il calvario quarry of fluoro edenite an asbestiform mineral that caused an high mortality rate for respiratory system cancer in biancavilla town in fact the monte calvario formation groups other eruptive fissures with similar volcanological and geochemical characteristics where hydrothermal alteration occurred with the likely formation of health threatening minerals

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

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

new insights into magma dynamics during last two eruptions of mount etna as inferred by geochemical monitoring from 2002 to 2005 two distinct eruptive events characterize the volcanic activity at mount etna during the 2002 to 2005 period we identified signals of magma ascent preceding these eruptions by geochemical monitoring of both chemical composition and he isotope ratio of gas emissions from five locations in the peripheral area of the volcano the geochemical signals are interpreted using the models proposed by caracausi et al 2003a 2003b and allow identification of episodes of magma ascent and estimation of the pressures of degassing magma as observed for the 2001 eruption caracausi et al 2003b magma ascent probably triggered the onset of the 2002 2003 eruption and minor events of magma ascent were observed between may and december 2003 in contrast to the previous two eruptions the 2004 2005 eruption was not preceded by significant geochemical signals of volcanic unrest suggesting that this eruption was mainly triggered by the failure of the upper portion of the volcanic edifice under the magmatic hydrostatic pressure in the conduits high 3he 4he ratio revealed new volatile rich magma accumulation the 2002 2003 eruption was preceded by a much shorter period of new magma accumulation from deep levels of the feeding system few minor signals of magma migration were detected at some of the sites during the months preceding the 2004 2005 eruption suggesting that the degassed 3he depleted magma resident in the volcanic conduits was not replaced by new volatile rich magma this is in agreement with the lack of explosive activity during the 2004 2005 eruption and with petrologic observations that the parent magma probably erupted in 2000 and 2001 new geochemical signals of magma ascent from the deep reservoir have been identified since june 2005 indicating that the volcanic activity of mount etna is evolving toward new pre eruptive conditions

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

multivariate time series clustering on geophysical data recorded at mt etna from 1996 to 2003 abstract time series clustering is an important task in data analysis issues in order to extract implicit previously unknown and potentially useful information from a large collection of data finding useful similar trends in multivariate time series represents a challenge in several areas including geophysics environment research while traditional time series analysis methods deal only with univariate time series multivariate time series analysis is a more suitable approach in the field of research where different kinds of data are available moreover the conventional time series clustering techniques do not provide desired results for geophysical datasets due to the huge amount of data whose sampling rate is different according to the nature of signal in this paper a novel approach concerning geophysical multivariate time series clustering is proposed using dynamic time series segmentation and self organizing maps techniques this method allows finding coupling among trends of different geophysical data recorded from monitoring networks at mt etna spanning from 1996 to 2003 when the transition from summit eruptions to flank eruptions occurred this information can be used to carry out a more careful evaluation of the state of volcano and to define potential hazard assessment at mt etna

volcanic spreading forcing and feedback in geothermal reservoir development amiata volcano italia abstract we made a stratigraphic structural and morphologic study of the amiata volcano in italy we find that the edifice is dissected by intersecting grabens that accommodate the collapse of the higher sectors of the volcano in turn a number of compressive structures and diapirs exist around the margin of the volcano these structures create an angular drainage pattern with stream damming and captures and a set of lakes within and around the volcano we interpret these structures as the result of volcanic spreading of amiata on its weak substratum formed by the late triassic evaporites burano anhydrites and the middle jurassic to early cretaceous clayey chaotic complexes ligurian complex regional doming created a slope in the basement facilitating the outward flow and spreading of the ductile layers forced by the volcanic load we model the dynamics of spreading with a scaled lubrication approximation of the navier stokes equations and numerically study a set of solutions in the model we include simple functions for volcanic deposition and surface erosion that change the topography over time scaling indicates that spreading at amiata could still be active the numerical solution shows that as the central part of the edifice sinks into the weak basement diapiric structures of the underlying formations form around the base of the volcano deposition of volcanic rocks within the volcano and surface erosion away from it both enhance spreading in addition a sloping basement may constitute a trigger for spreading and formation of trains of adjacent diapirs as a feedback the hot hydrothermal fluids decrease the shear strength of the anhydrites facilitating the spreading process finally we observe that volcanic spreading has created ideal heat traps that constitute todays exploited geothermal fields at amiata normal faults generated by volcanic spreading volcanic conduits and direct contact between volcanic rocks which host an extensive fresh water aquifer and the rocks of the geothermal field constitute ideal pathways for water recharge during vapour extraction for geothermal energy production we think that volcanic spreading could maintain faults in a critically stressed state facilitating the occurrence of induced and triggered seismicity

discrete monitoring of chemical parameters in ground waters of mt etna volcano 2000 2006 abstract three sites of groundwater captation on mt etna volcano namely currone ilice and pavone were sampled systematically for six years from 2000 to 2006 for the determination of the major ionic composition of water the monitored sites were chosen among those most representative of the geochemical characteristics of the groundwater systems of the volcano the period studied was characterized by several strong eruptions of mt etna both at its summit craters and along its flanks the overall composition of the waters sampled at currone and ilice falls in the group of bicarbonate alkaline earth compositions whereas those from pavone show a bicarbonate alkaline composition in all sites however some samples show input of chlorine sulfate alkaline waters likely due to interaction between fresh groundwater and either acidic waters from so2 polluted rainwater more evident at pavone or geothermal brines more evident at currone significant temporal variations affected in a more or less marked way all of the parameters measured at the three sites basic statistical correlations among the parameters at each site allowed to discover a general coherent temporal behavior of all major ions dissolved in mt etna s ground waters factor analysis allowed showing up to three main groups of parameters with similar temporal behavior depending on the site a first group was explained by interaction between volcanic ground waters and geothermal fluids a second group was related with leaching of the host volcanic rocks by co2 rich volcanic water a third group was explained as due to input of plume so2 derived sulfate through water recharge using normal probability plots for each parameter at the three sites it was possible to reveal different geochemical populations explained as background anomalous values and possibly outliers plotting the temporal patterns of all the monitored parameters versus the concurrent eruptive episodes at mt etna we discovered significant correlations that although with different intensity and rate depending on the parameter and on the site highlighted several geochemical processes induced by interaction between cold groundwater and magmatic hydrothermal fluids mostly following changes in the ground permeability of the volcanic pile these processes seemed to be enhanced during periods of shallow magma accumulation inside of the volcano that preceded summit or flank eruptions occurred at mt etna during the monitored period

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

intrusive mechanism of the 2008 2009 mt etna eruption constraints by tomographic images and stress tensor analysis abstract since january 2008 several geophysical parameters have evidenced a recharging phase at mt etna volcano culminating with an effusive eruption that began on may 13 2008 seismic activity recorded at mt etna from january 2007 to may 2008 was analyzed in order to provide seismological constraints to the volcano dynamics leading to the eruption a total of 336 selected earthquakes with m l 1 5 were used as data source for this study specifically we calculated 3d velocity and attenuation tomography including a 3d relocation of the events and we computed 53 selected fault plane solutions fpss that were used for stress tensor inversion the most important result obtained from the joint analysis of v p v p v s and p wave attenuation is an anomalous zone with normal to high v p values between 3 5 and 4 5 km s and low v p v s values 1 64 which partially overlaps with a low q p values 50 volume located along a ns trending channel beneath the central crater this can be interpreted as a shallow volume characterized by high temperature where the magma is located with the presence of supercritical fluids the analysis of seismic stress tensor evidenced an extensional regime in the depth range 3 13 km with a vertically oriented 1 this finding may suggest an extensional stress regime probably related to the kinematic response of the volcanic edifice to both a deep magmatic intrusion and a condition of decreased regional compressive stress facilitated by sliding processes of the eastern flank of the volcano

correlated morphological chemical and isotopic characteristics of hibonites from the murchison carbonaceous chondrite twenty four hibonite dominated refractory grains from the murchison carbonaceous chondrite have been identified from polished grain mounts of density separates and have been morphologically and chemically divided into three groups 1 14 colourless platy crystal fragments placs with less than 2 7 tio2 2 3 pleochroic blue aggregates bags which are composed of crystal plates and fragments and have tio2 concentrations between 5 1 and 6 5 3 six spinel hibonite spherules and crystal aggregates shibs often with spinel fe silicate and clinopyroxene rims the maximum tio2 concentrations of hibonite in the shibs ranges from 3 5 to 7 6 but the tio2 concentration in one grain was heterogeneous and ranged from 0 5 to 5 0 hibonite in all types is stoichiometric with ti and mg predominantly in a coupled substitution of mg2 and ti4 for 2al3 one grain with a rounded hibonite core does not clearly fit into the three designated groups the hibonites have been analysed by ion microprobe mass spectrometry for their mg and ti isotopic compositions twelve of the placs have 26al27al 0 ratios less than 1 10 5 but the other two placs have 26al27al 0 of 5 5 10 5 and 7 7 10 5 the excess 26mg may reflect initial mg isotopic heterogeneities in the source region of the placs or be the result of in situ26al decay in which case the distribution of 26al was heterogeneous three bags show substantial positive mass fractionation of mg one grain has excess 26mg while the other two have 26mg depletions the 26mg depletions indicate the preservation of mg isotopic anomalies in the bags but the excess 26mg in one grain could be due to in situ26al decay the six shibs have excess 26mg that is correlated with 27al24mg the mg isotopic systematics of the shibs are consistent with the in situ decay of 26al with 26al27al 0 of ca 5 10 5 the unclassified hibonite has a clearly resolved deficit in 26mg titanium isotopic anomalies are common in the hibonites measured here the largest anomalies are in 50ti with variations in 50ti48ti ranging from 50 to 16 relative to terrestrial smaller anomalies are present in 49ti and 47ti the ti isotopic compositions are not directly correlated with morphological type but the placs show the largest variations in isotopic composition whereas the shibs are generally close to terrestrial the presence of hibonite populations with distinct morphological chemical and mg isotopic systematics suggests that there were several hibonite formation episodes within the early solar system the hibonites probably formed by the melting of refractory dust aggregates during local transient thermal events

soil gases and sar measurements reveal hidden faults on the sliding flank of mt etna italy abstract from october 2008 to november 2009 soil co 2 radon and structural field surveys were performed on mt etna in order to acquire insights into active tectonic structures in a densely populated sector of the south eastern flank of the volcano which is involved in the flank dynamics as highlighted by satellite data insar the studied area extends about 150 km 2 in a sector of the volcano where insar results detected several lineaments that were not well defined from previous geological surveys in order to validate and better constrain these features with ground data evidences soil co 2 and soil radon measurements were performed along transects roughly orthogonal to the newly detected faults with measurement points spaced about 100 m in each transect the highest co 2 values were found very close to the lineaments evidenced by insar observations anomalous soil co 2 and radon values were also measured at old eruptive fractures in some portions of the investigated area soil gas anomalies were rather broad over transects probably suggesting a complex structural framework consisting of several parallel volcano tectonic structures instead of a single one soil gas measurements proved particularly useful in areas at higher altitude on mt etna i e above 900 m asl where insar results are not very informative are fairly limited and allowed recognizing the prolongation of some tectonic lineaments towards the summit of the volcano at a lower altitude on the volcanic edifice soil gas anomalies define the active structures indicated by insar results prominently down to almost the coastline and through the northern periphery of the city of catania coupling insar with soil gas prospecting methods has thus proved to be a powerful tool in detecting hidden active structures that do not show significant field evidences

how to cope with volcano flank dynamics a conceptual model behind possible scenarios for mt etna abstract volcano flank dynamics poses a serious hazard also involving the inhabited lower slopes mt etna is a well studied unstable volcano and a significant amount of data has been collected on the dynamics of its eastern and southern flanks we first propose a conceptual model to describe and explain flank dynamics at etna we identify the preconditions as due to the differential unbuttressing conditions at the volcano base and the triggering factors as shallow magmatic sources dikes reservoirs evidence and parameters and or observations for flank dynamics are listed summarizing the 1994 2010 period of activity based on this we then propose a set of scenarios possibly occurring in case of unrest of the unstable flanks of mt etna flank unrest is a variation in the steady state condition of the volcano flanks possibly accompanied by significant ground deformation seismicity and eruptions the scenarios may provide a general reference and recommendation in case of five types of multi hazard processes related either as a cause or effect to flank dynamics 1 edifice inflation 2 emplacement of dikes along the ne and or s rifts 3 seismicity along pernicana fault system 4 seismicity on the s sector 5 seismicity along timpe fault system each scenario is analyzed and recommendations are given the scenarios may or may not be related to each other in the sense that the probability of occurrence of one scenario may or may not be contingent or dependent upon the prior occurrence of another these scenarios provide a qualitative analysis of the multi hazard processes related to flank dynamics a more quantitative i e probabilistic characterization is under consideration

contrasting triggering mechanisms of the 2001 and 2002 2003 eruptions of mount etna italy abstract mount etna produced two significant eruptions in 2001 and 2002 2003 which we have analysed using geological seismic and deformation data these eruptions showed some similarities such as the activating of two magmatic plumbing systems central lateral and eccentric but they differed in their triggering mechanisms while the 2001 eruption was largely the result of the emplacement of a n s eccentric dike independent from the central conduits consistent with e w regional extension the 2002 2003 eruption occurred in response to a major flank slip on the eastern and southeastern sides of the volcano this is demonstrated by the spatial and temporal distribution of seismicity and deformation preceding and accompanying the two eruptions during the months prior to the 2001 eruption most epicenters were concentrated on the southern flank at depths of 5 15 km below sea level during the 4 days before the eruption earthquake hypocenters migrated to shallower levels from 5 km bsl upward indicating the emplacement of the eccentric dike this is confirmed by the patterns of ground fracturing observed in the field and deformation documented by electronic distance measurements edm in contrast the months before the 2002 2003 eruption were characterised by shallower seismicity mainly concentrated along the active faults bordering the slipping flank sector flank slip accelerated in september 2002 and a second more vigorous acceleration of flank slip occurred on 26 27 october 2002 accompanying the opening of eruptive vents the very short 2 h seismic crisis preceding the onset of eruptive activity stands in neat contrast with the 4 days of intense seismicity before the 2001 eruption subsequently flank slip deformation extended all over the eastern and southeastern flanks of the volcano causing serious damage in this sector the events of 2001 2003 can be seen as a continuous chain of intimately interacting processes including regional tectonics magma accumulation and eruption and flank instability in this scenario the 2001 eruption led to increased flank instability that subsequently accelerated and culminated with the massive flank slip which in turn facilitated the 2002 2003 eruption this sequence of events points to a long term feedback mechanism between magmatism and flank instability at etna

etna 2004 2005 an archetype for geodynamically controlled effusive eruptions 1 the 2004 05 eruption of etna was characterised by outpouring of degassed lava from two vents within valle del bove after three months of eruption lava volumes were estimated to be between 18 5 and 32 106 m3 with eruption rate between 2 3 and 4 1 m3 s petrological analyses show that magma is resident in the shallow plumbing system emplaced during the last south east crater activity so2 flux data show no increase at the onset of the eruption and so2 hcl ratios in gas emitted from the eruptive fissure are consistent with a degassed magma no seismic activity was recorded prior to eruption unlike eruptions observed since the 1980 s the purely effusive nature of this eruption fed by a degassed resident magma and the fracture dynamics suggest that magmatic overpressure played a limited role in this eruption rather lateral spreading of etna s eastern flank combined with general inflation of the edifice triggered a geodynamically controlled eruption

dike emplacement and flank instability at mount etna constraints from a poro elastic model of flank collapse this work was funded by istituto nazionale di geofisica e vulcanologia ingv and the italian dipartimento per la protezione civile dpc dpc ingv project v4 flank

repeating volcano tectonic earthquakes at mt etna volcano sicily italy during 1999 2009 abstract repeating volcano tectonic vt earthquakes taking place at mt etna during 1999 2009 were detected and analyzed to investigate their behavior we found 735 families amounting to 2479 vt earthquakes representing 38 of all the analyzed vt earthquakes the number of vt earthquakes making up the families ranges from 2 to 23 over 70 of the families comprise 2 or 3 vt earthquakes and only 20 families by more than 10 events the occurrence lifetime is also highly variable ranging from some minutes to ten years in particular more than half of the families have a lifetime shorter than 0 5 day and only 10 longer than 1 year on the basis of these results most of the detected families were considered burst type i e show swarm like occurrence and hence their origin cannot be explained by a temporally constant tectonic loading indeed since the analyzed earthquakes take place in a volcanic area the rocks are affected not only by tectonic stresses related to the fairly steady regional stress field but also by local stresses caused by the volcano such as magma batch intrusions movements and gravitational loading we focused on the five groups of families characterized by the longest repeatability over time namely high number of events and long lifetime located in the north eastern eastern and southern flanks of the volcano unlike the first four groups which similarly to most of the detected families show swarm like vt occurrences group v located in the north eastern sector exhibits a more tectonic behavior with the events making up such a group spread over almost the entire analyzed period it is clear how both occurrence and slip rates do not remain constant but vary over time and such changes are time related to the occurrence of the 2002 2003 eruption finally by fpfit algorithm a good agreement between directions identified by nodal planes and the earthquake epicentral distribution was generally found

understanding eruptive style variations at calc alkaline volcanoes the 1913 eruption of fuego de colima volcano mexico the 1913 sub plinian eruption of fuego de colima volcano mexico occurred after almost 100 years of effusive and minor vulcanian explosive activity which modulated dome growth and destruction dome extrusion persisted from 1869 to 1913 the transition to explosive eruption started on 17 january 1913 and it progressed in three phases 1 opening with the generation of block and ash flows 2 vent clearing with strong explosions that destroyed the summit dome and decompressed the magmatic system and 3 sustained column sub plinian fallout with final collapse producing pyroclastic density currents because of this succession of events the 1913 activity represents an excellent case study for investigating the eruptive style changes at calc alkaline volcanoes we investigated the conditions that led to eruptive style transition from effusive dome growth to explosive the final sub plinian fallout through steady state numerical simulations using subsurface data and independently inferred from volcanological data mass discharge rates as constraints results show good matches for hybrid geometrical settings of the shallow conduit feeding system i e dyke developing into a shallower cylindrical conduit and the magma chamber top at 6 km of depth the fragmentation level was shallower than 2 km as inferred from the lithics contained in the sub plinian fall deposits of phase 3 the most likely solution is represented by a dyke having major axis between 200 and 2000 m and the minor axis of 40 m the dyke cylinder transition was set at a depth of 500 m with a cylinder diameter of 40 m it emerges that at least two main mechanisms may be responsible for the effusive to explosive transition that led to the phase 3 of the 1913 eruption i an increase in magma chamber overpressure magmatic triggering or ii decrease of lithostatic stress acting on the volcano non magmatic triggering the former implies arrival into the magma chamber of a batch of fresh magma which can have volume between 10 and 200 106 m3 depending on the values of magma and host rock compressibility the latter requires decompression induced emptying of at least the equivalent of 1000 m of the magma column to produce the necessary unloading of the conduit feeding system a sudden jerk in the lateral spreading of the fuego de colima cone would be a reliable mechanism for decompressing the upper conduit and driving fragmentation processes over a time period of few hours the results are not conclusive on an internal magma chamber overpressure external lowering of lithostatic load or mixed internal and external trigger of the observed eruptive style transition this work highlights how different processes can have non linear cascade effects on close to equilibrium volcanic systems like fuego de colima volcano

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

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

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

time dependent deformation of the eastern flank of mt etna after slip or viscoelastic relaxation abstract major results of post intrusive gps monitoring of the 5 months encompassing and following the onset of 2002 03 mt etna eruption are presented and discussed here the overall ground deformation pattern is characterized by a time dependent relaxation function we evaluated two different parametrizations of relaxation functions each one linked to a different relaxation process i viscoelastic relaxation and ii after slip mechanism the former indicated that the process occurred within a weak layer characterized by viscosity values ranging between 7 1 1014 pa s and 1 3 1015 pa s the latter evidenced that frictional processes occurred beneath a layer of velocity strengthening having a thickness with values ranging between 0 4 km and 1 7 km either model may explain the observed time dependent deformation both from the statistical point of view and the comparison with geologic and seismic information although we are unable to favour one model rather than the other these results indicate that the mechanism responsible for the observed post intrusive deformation occurs within a sliding zone located inside the clayey sedimentary basement

the exceptional activity and growth of the southeast crater mount etna italy between 1996 and 2001 between 1971 and 2001 the southeast crater was the most productive of the four summit craters of mount etna with activity that can be compared on a global scale to the opening phases of the pu u k paianaha eruption of k lauea volcano hawai i the period of highest eruptive rate was between 1996 and 2001 when near continuous activity occurred in five phases these were characterized by a wide range of eruptive styles and intensities from quiet non explosive lava emission to brief violent lava fountaining episodes much of the cone growth occurred during these fountaining episodes totaling 105 events many showed complex dynamics such as different eruptive styles at multiple vents and resulted in the growth of minor edifices on the flanks of the southeast crater cone small pyroclastic flows were produced during some of the eruptive episodes when oblique tephra jets showered the steep flanks of the cone with hot bombs and scoriae fluctuations in the eruptive style and eruption rates were controlled by a complex interplay between changes in the conduit geometry including the growth of a shallow magma reservoir under the southeast crater magma supply rates and flank instability during this period volume calculations were made with the aid of gis and image analysis of video footage obtained by a monitoring telecamera between 1996 and 2001 the bulk volume of the cone increased by 36 106 m3 giving a total 1971 2001 volume of 72 106 m3 at the same time the cone gained 105 m in height reaching an elevation of about 3 300 m the total dre volume of the 1996 2001 products was 90 106m3 this mostly comprised lava flows 72 106 m3 erupted at the summit and onto the flanks of the cone these values indicate that the productivity of the southeast crater increased fourfold during 1996 2001 with respect to the previous 25 years coinciding with a general increase in the eruptive output rates and eruption intensity at etna this phase of intense summit activity has been followed since the summer of 2001 by a period of increased structural instability of the volcano marked by a series of important flank eruptions

fate of metals in coastal sediments of a mediterranean flood dominated system an approach based on total and labile fractions the dynamics of sediment bound metals cs cu ni pb ti and zn were studied off the tet river western gulf of lion a typical mediterranean coastal river punctuated by short and violent flash floods spatial and temporal sampling strategies were combined to elucidate the fate of these elements in response to both the riverine sediment input and the offshore transport of these sediments through hydrodynamics our results show the temporal entrapment of riverborne particles and associated metals consecutively to a major flood event in the nearshore sedimentary unit called prodelta here deposition and resuspension mechanisms define a sedimentological cycle that could be followed completely in this study in terms of speciation between reactive labile and residual fractions along the fluvio deltaic continuum our results show that cu pb and zn are the most labile potentially mobile metals in the river in accordance with their contributions from anthropogenic sources but in the marine surficial sediments two main behaviours can be discriminated when compared to the riverine suspended particulate matter while pb and zn depict rather a constant labile fraction cu is characterized by decreasing levels up to 50 difference in terms of environmental impact these contrasting trends have direct repercussions for the contaminant dispersal in the coastal area whereas pb and zn conserve their enhanced levels because of their stronger affinity with fine sediments cu is marked by the entire loss of its anthropogenic component that is progressively transferred to the dissolved phase likely mediated by organic ligands we ascribe these behaviours to different post depositional partition mechanisms with respect to oxidation of the particulate organic phase at the bottom sediment water interface also analysis of one sediment core from the prodelta indicates that these early diagenetic processes govern the chemical forms of land derived contaminants sequestrated in the nearshore sedimentary archives c 2011 elsevier ltd all rights reserved

deformation and eruptions at mt etna italy a lesson from 15 years of observations this work was partly funded by ingv and the italian dpc and was supported by asi the preview project and crdc amra dpc ingv flank project providing the funds for the publication fees

volcanomagnetic changes accompanying the onset of the 2002 2003 eruption of mt etna italy abstract remarkable changes in the local magnetic field were associated with the onset of the 2002 2003 flank eruption at mt etna after differential magnetic field measurements were filtered from the external noise by using adaptive filters we recognized two stages in the total intensity changes which are closely related to different volcanic events a rapid variations of about 4 5 nt associated with october 26 seismic swarm recorded beneath the summit craters b step like variations of 9 10 nt coincident with october 27 eruptive fissures opening up in the north flank these observations are generally consistent with those calculated from simple magnetic models of these volcanic processes in which the magnetic changes are generated by stress redistribution due to magmatic intrusions at different depth the magnetic data not only allow the timing of the intrusive event to be described in greater detail but also together with other volcanological and geophysical evidences permit some constraints to be set on the characteristics of propagation of a shallow dike firstly at around midnight on 26 october magma was rapidly injected to a depth of 3 4 km just below the summit craters secondly after 1 00 on 27 october continued intrusion magma occurred upward and culminated a few hundred meters below the free surface fractured along a n e direction thirdly at about 2 28 magma gave rise to an explosive fissural vent at the northern base of the ne crater near 3000 m a s l finally at about 5 00 the first eruptive fissure became active along the eastern border of the ne rift at 2500 m a s l the rate of growth of the magnetic anomalies moreover leads to the interpretation that the magmatic intrusion travelled northward from base of the ne crater to the ne rift at approximately 14 m min

micro porous pyroclasts reflecting multi vent basaltic andesite plinian eruptions at mt tongariro new zealand abstract mt tongariro is a multi vent volcanic complex in the central north island of new zealand constructed along the axis of an active graben its five largest known explosive eruption episodes occurred 11 000 years ago during a 200 year long paroxysm during these stable plinian and collapsing sub plinian columns erupted from multiple sequential and synchronous vents along the graben axis we examined the spatially varying eruption dynamics during the 200 year paroxysm through the lens of pyroclastic textures each eruption episode produced micro vesicular basaltic andesitic juvenile lapilli with high vesicle number densities and high groundmass crystallinity textural characteristics indicate that pressurisation via second boiling drove eruptions and rhyolite like melt viscosities promoted brittle failure highly variable and mingled textures within individual juvenile lapilli evidence diverse conditions developed across the conduit during the eruption foamy magma rose rapidly through the conduit core driving explosive vigour and dragged and sheared gas poor crystallised magma from the conduit margins consistent with the northward widening graben the most stable plinian eruptions occurred at northern vents under highest extensional stresses and possibly widest most stable conduits by contrast collapsing unstable eruption columns occurred at southern vents where mainly degassed and crystalline magma erupted at lower ejection rates through narrower unstable and shifting conduits these data collectively show how spatial variations in structure and tectonics may strongly influence explosive eruption style

magma faults and gravitational loading at mount etna the 2002 2003 eruptive period 1 mount etna is characterized by a complex structural setting that influences its evolution in order to understand how the interaction between dike forming intrusions and faulting influences the kinematics of the volcanic edifice we developed a numerical model it takes account of the topography the medium heterogeneities the gravitational loading and the most active crustal discontinuities a parameterization of the apparent coefficient of friction as a function of the depth has been considered in the range from 0 01 to 0 5 the density values used young s modulus and poisson s ratio range from about 1700 to 3200 kg m3 8 5 to 140 gpa and 0 15 to 0 35 respectively the model was applied to the 2002 2003 etna eruption the resulting deformation pattern was in agreement with the data provided by the continuous gps stations and the seismological knowledge obtaining displacements up to 1 m some discrepancies between the recorded ground deformation field and the modeled displacements allowed us to make some hypotheses on the volcano tectonic e g for the pernicana fault or regional tectonic origin acireale s alfio fault system of the crustal discontinuities moreover our results suggested that the pernicana fault is characterized by a very low apparent coefficient of friction less than 0 1 furthermore we evaluated the contribution of the gravitational loading and found that it implies a variation of about 10 of the overall deformation pattern our results clearly showed that the weight of the volcanic edifice acts in opposition to the magmatic intrusions conversely we found that the presence of medium heterogeneities may favor the eastern flank movements toward the se and the spreading of the summit area playing a fundamental role in ascending magma finally we investigated the shallow sliding model and found that dike forming intrusions produce negligible displacements less than 1 mm along the subhorizontal detachment surface therefore the gravitational loading during dike forming intrusions is not able to trigger sliding processes along this plane

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

active spreading and regional extension at mount etna imaged by sar interferometry abstract large flank instability has been proposed by most recent authors as a major process in the dynamics of mount etna however several aspects of the models are still disputed such as the boundaries of the moving area and the driving force for the instability in this paper we present synthetic aperture radar interferometric data which allow us to identify two main sectors of active instability where the deformational process differs an eastern sector is bounded to the north by the pernicana provenzana fault to the west by the north rift zone and the south rift zone and to the south by the mascalucia tremestieri trecastagni fault system interferograms provide new data on the activity and extent of the southern boundary which was previously underestimated in this sector the structural features indicate an eastward sliding driven by e w regional extension which can be interpreted as a result of the retreating slab of the ionian subduction a second collapsing sector exists along the southern flank of mount etna where the interferograms show the presence of an active anticlinal ridge this ridge is interpreted as the result of southward gravity spreading over a basal decollement between etna and its plio quaternary basement and the hyblean platform the two sectors first became active in summer 1996 after the beginning of a new cycle of eruptive activity at the summit the activity was ongoing until january 1998 with the deformation rate ranging from 4 6 mm yr for the mascalucia tremestieri trecastagni faults to 12 mm yr for the anticlinal ridge

intrusion of eccentric dikes the case of the 2001 eruption and its role in the dynamics of mt etna volcano abstract the 2001 eruption represents one of the most studied events both from volcanological and geophysical point of view on mt etna this eruption was a crucial event in the recent dynamics of the volcano marking the passage from a period march 1993 june 2001 of moderate stability with slow continuous flank sliding and contemporaneous summit eruptions to a period july 2001 to present of dramatically increased flank deformations and flank eruptions we show new gps data and high precision relocation of seismicity in order to demonstrate the role of the 2001 intrusive phase in this change of the dynamic regime of the volcano gps data consist of two kinematic surveys carried out on 12 july a few hours before the beginning of the seismic swarm and on 17 july just after the onset of eruptive activity a picture of the spatial distribution of the sin eruptive seismicity has been obtained using the hypodd relocation algorithm based on the double difference dd technique modeling of gps measurements reveals a southward motion of the upper southern part of the volcano driven by a nnw sse structure showing mainly left lateral kinematics precise hypocenter location evidences an aseismic zone at about sea level where the magma upraise was characterized by a much higher velocity and an abrupt westward shift revealing the existence of a weakened or ductile zone these results reveal how an intrusion of a dike can severely modify the shallow stress field triggering significant flank failure in 2001 the intrusion was driven by a weakened surface which might correspond to a decollement plane of the portion of the volcano affected by flank instability inducing an additional stress testified by gps measurements and seismic data which led to an acceleration of the sliding flanks

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

vertical and lateral propagation of radial dikes inferred from the flow direction analysis of the radial dike swarm in komochi volcano central japan dikes with lateral and outward intrusion directions named l type dike and dikes with vertical and upward intrusion directions v type dike are recognized in a radial dike swarm of komochi volcano japan by the combined analysis of the preferred orientations of deformed vesicles and anisotropy of magnetic susceptibility ams intrusion directions of magmas were examined for 41 dike outcrops among them 19 dikes were classified as l type dike and 15 dikes were as v type the l type dikes distribute over the area of the dike swarm radiating from the central conduit which is named daikokuiwa stock and the v type dikes occur mainly in the peripheral portion of the volcano the l type dikes are characterized with evolved whole rock compositions similar to those of rocks consisting of the central conduit whereas the v type dikes have less fractionated composition and are enrich in mafic phenocryst as compared to the l type dikes the outward intrusion directions of the l type dikes and their petrological similarity to the rock of the central conduit indicate that these dikes intruded from the shallow part of the central conduit where the magmas underwent fractional crystallization and degassing the petrological characteristics of the v type dikes suggest that the less fractionated magma intruded directly from a magma chamber in which mafic phenocryst crystals accumulated the larger dike thickness and higher magnetic foliation of the v type dike as compared to the l type dike indicate higher magmatic overpressure which was possibly result of the direct connection to the pressurized magma chamber and vertical growth of the dikes with buoyant magma solidification of the central conduit is favorable for the accumulation of internal excess pressure in the magma chamber to break the wall rock fissure eruptions independent of the central conduit have occurred in many volcanoes and these fissure eruptions might be fed by the dikes directly propagated from the deeper magma chamber

three dimensional displacements of a large volcano flank movement during the may 2010 eruptions at pacaya volcano guatemala although massive flank failure is fairly common in the evolution of volcanoes measurements of flank movement indicative of instability are rare here 3 d displacements from airborne radar amplitude images derived using an amplitude image pixel offset tracking technique show that the west and southwest flanks of pacaya volcano in guatemala experienced large 4 m discrete landsliding that was ultimately aborted pixel offset tracking improved measurement recovery by nearly 50 over classic interferometric synthetic aperture radar techniques providing unique measurements at the event the 3 d displacement field shows that the flank moved coherently downslope along a complex failure surface involving both rotational and along slope movement notably the lack of continuous movement of the slide in the years leading up to the event emphasizes that active movement should not always be expected at volcanoes for which triggering factors e g magmatic intrusions and eruptions could precipitate sudden major flank instability

structural features of an active strike slip fault on the sliding flank of mt etna italy abstract the strike slip pernicana fault system pfs was activated along the eastern flank of mt etna during an earthquake in september 2002 and one month later during the eruption of the ne rift structural and volcanological data suggest that the pfs was activated as a result of the slide of the ne flank of etna this activation produced surface fracturing on walls and on paved and unpaved roads the segments of the pfs arranged in a right stepping en echelon configuration show a an inverse proportion between length and frequency b fractal behavior over scales of 10 2 10 1 m between their length overstep and overlap c consistent strike with regard to their fault array and d a progressive eastward decrease in the displacement along the smallest faults the consistent geometric and kinematic features of the pfs related to the sector collapse of etna are similar to those of faults in strike slip settings

thirty years of satellite derived lava discharge rates at etna implications for steady volumetric output 1 we present a 30 year long data set of satellite derived time averaged lava discharge rates tadr for mount etna volcano sicily italy spanning 1980 2010 and comprising 1792 measurements during 23 eruptions we use this to classify eruptions on the basis of magnitude and intensity as well as the shape of the tadr time series which characterizes each effusive event we find that while 1983 1993 was characterized by less frequent but longer duration effusive eruptions at lower tadrs 2000 2010 was characterized by more frequent eruptions of shorter duration and higher tadrs however roughly the same lava volume was erupted during both of these 11 year long periods so that the volumetric output was linear over the entire 30 year period increasing at a rate of 0 8 m3 s 1 between 1980 and 2010 the cumulative volume record can be extended back in time using data available in the literature this allows us to assess etna s output history over 5 centuries and to place the current trend in historical context we find that output has been stable at this rate since 1971 at this time the output rate changed from a low discharge rate phase which had characterized the period 1759 to 1970 to a high discharge rate phase this new phase had the same output rate as the high discharge rate phase that characterized the period 1610 1669 the 1610 1669 phase ended with the most voluminous eruption of historic times

actively growing anticlines beneath catania from the distal motion of mount etna s decollement measured by sar interferometry and gps we used sar interferometry and gps to measure the rise of an anticline beneath the urban area of catania italy which originates from outward thrusting above the basal decollement of etna volcano the anticline grows at a rate of over 0 015 m a 1 of se thrusting and about 0 007 m a 1 of relative uplift by relating this growth to the simultaneous extension measured at the summit of the volcano we demonstrate the occurrence of active volcanic spreading this process may exert a control on eruptions earthquakes sector collapses and landslides

dispersion index of topographic surfaces abstract the dispersion index d of topography is introduced this index is a geomorphic parameter which characterizes each point of topography with respect to the stability instability of the steepest descent path sdp originating from it the procedure for calculating d is based on the assessment of sdp variations as the initial topography is also varied within a given elevation h while a length scale l defines the maximum extent of the sdp as a result d can be derived for different ranges h and different bandwidths l since at each point the gravitational force would direct a surface flow along the sdp d appears to have a strong influence on the behavior of gravity driven mass flows influencing local topographic widening spreading or channelization considering mount etna italy as a test case we present maps of d for h 3 m and l 1 2 4 and 8 km demonstrating also the relationship between the range h 3 m and etnean lava flows focusing on the 2001 lava flow we show that the presented maps of d besides being a tool for viewing morphologies have interesting applications for hazard assessment related to lava flows

structural features of the 2007 stromboli eruption abstract on 27 february 2007 two ne sw and nnw sse dike fed effusive vents opened to the north at 650 and 400 m above sea level asl of the summit craters at stromboli forming a fissure parallel to the inner walls of the sciara del fuoco sdf sector collapse depression the formation of these vents was soon followed by rapid subsidence of the summit crater area this partly obstructed the central conduit temporarily choking the fissure and increasing the deformation of the upper part of sdf the reactivation of the nnw sse vent and the opening of a new vent located at 500 m asl fed by a second dike released the internal pressure and surface deformation ceased the eruption then continued again from the 400 m vent after a summit explosion on 15 march until ending in early april after a progressive decrease of magma output repeated ne sw dike intrusions have occurred in recent years close to the upper se limit of the sdf in that zone named bastimento the eruptive fractures traced the discontinuities that borders the sdf increasing the risk of triggering new sector collapse whereas the ne sw trending structures lie along the regional volcano structural trend of the aeolian arc through stromboli the nnw sse vents are oblique to this trend and may be controlled by the anomalous stress field within the unstable flank of the sdf another fundamental aspect of the 2007 eruption is the collapse of the central conduit due to the rapid and deep magma drainage linked to the opening of the 400 m vent the intrusion of dikes and development of flank vents during the 2007 eruption could possibly have triggered catastrophic landslides and related tsunami or eruptive paroxysms but the opening of new effusive vents released the internal pressures diminishing the hazard

how do volcanic rift zones relate to flank instability evidence from collapsing rifts at etna 1 volcanic rift zones characterized by repeated dike emplacements are expected to delimit the upper portion of unstable flanks at basaltic edifices we use nearly two decades of insar observations excluding wintertime acquisitions to analyze the relationships between rift zones dike emplacement and flank instability at etna the results highlight a general eastward shift of the volcano summit including the northeast and south rifts this steady state eastward movement 1 2 cm yr is interrupted or even reversed during transient dike injections detailed analysis of the northeast rift shows that only during phases of dike injection as in 2002 does the rift transiently becomes the upper border of the unstable flank the flank s steady state eastward movement is inferred to result from the interplay between magmatic activity asymmetric topographic unbuttressing and east dipping detachment geometry at its base this study documents the first evidence of steady state volcano rift instability interrupted by transient dike injection at basaltic edifices

magma ascent and the pressurization of mount etna s volcanic system after a period of deflation during the 1991 1993 flank eruption mount etna underwent a rapid inflation seismicity and ground deformation show that since 1994 a huge volume of magma intruded beneath the volcano producing from 1998 onward a series of eruptions at the summit and on the flank of the volcano the last of these started on 27 october 2002 is still in progress and can be considered one of the most explosive eruptions of the volcano in recent times here we show how geodetic data and seismic deformation between 1994 and 2001 indicate a radial compression around an axial intrusion consistent with a repressurization of mount etna s plumbing system at a depth of 6 to 15 kilometers which triggered most of the seismicity and provoked the dilatation of the volcano and the recent explosive eruptive activity

modeling the effects of eruptive and seismic activities on flank instability at mount etna italy 1 the identification and evaluation of trigger mechanisms for volcano flank instabilities and or collapse represent a key issue for risk assessment in densely populated volcanic areas as well as in long distance settings particularly in case of island or coastal volcanoes here we address quantitatively the effects of external seismic and inner magmatic forcing on the stress strain state associated to flank instabilities at mount etna sicily southern italy by means of a 2 d finite difference method numerical modeling modeled seismic actions include strong near field strong far field and low magnitude near field earthquakes magmatic actions consider the inner pressure changes induced by energetic lava fountains in the summit crater area and subvertical and oblique dike ascent below the summit area model results are validated in light of available monitoring data and recent eruptive activity numerical results show that the main strain effects are produced by high magnitude near field earthquakes expected return time of 103 yrs and by vertical uprise of a magma dike below the volcano summit area maximum displacements in the order of tens of centimeters may involve the summit area up to some 106 m3 m over some kilometers laterally stress releases up to 107 pa may affect a limited portion of the magmatic conduit thus favoring major effusive flank eruptions major catastrophic events such as volcano flank collapse should not be expected by applying either individually or combined the aforementioned actions

the failed eruption of mt etna in december 2005 evidence from volcanic tremor analyses 1 strong changes in seismic radiation comparable to those preceding and or accompanying eruptive activity in recent years were recorded at mt etna volcano italy from november 2005 to january 2006 the amplitude of volcanic tremor peaked in mid december 2005 after a continuous slow increase from august 2005 onward during which neither effusive nor paroxysmal activity was observed by volcanologists and alpine guides during this time span the centroid locations of volcanic tremor moved toward the surface more and more clustered below the summit craters the application of pattern classification analysis based on self organizing maps and fuzzy clustering to volcanic tremor data highlighted variations in the frequency domain as well these changes were temporally associated with ground deformation variations as indicative of a mild inflation of the summit of the volcano and with a conspicuous increase in the so2 plume flux emission overall we interpret this evidence as the result of recharging of the volcanic feeder at depth 3 km below sea level during which magma did not reach the shallow plumbing system

high spatial resolution radon measurements reveal hidden active faults on mt etna radon emissions are frequently monitored in volcanically and tectonically active areas in order to reveal changes in soil degassing as radon acts a tracer for the more abundant co2 degassing commonly observed in such areas between july 2002 and may 2003 a series of discrete measurements of radon concentrations in soil were made with high spatial resolution similar to5 100 m in the santa venerina area on mt etna these measurements revealed well defined linear anomalies that we interpret as being caused by active faults whose higher porosity than surrounding soils allows an increased co2 flux carrying radon from beneath these faults were not visible at the surface and were therefore revealed at high spatial resolution by our radon survey our hypothesis that the positive anomalies are attributable to active faults was strengthened by the observation of concentrated damage along this geometry during the earthquakes that struck this area in late october 2003

dynamics of 2004 2005 mt etna effusive eruption as inferred from petrologic monitoring 1 from early september to early november during the 2004 2005 mt etna effusive eruption petrologic monitoring was enabled by near vent sampling of erupting lava and onsite sem eds capabilities at ingv ct significant differences in composition and temperature of lava erupted from 2920 2620 m and 2820 2320 m vents attest to variably evolved shallow magmatic conditions within a geometrically complex storage volume the petrography and glass compositions of water quenched samples indicate that the magma feeding the 2004 2005 activity was likely to have been stored in the shallow plumbing system during the 2000 and 2001 activity where it experienced volatile loss and extensive crystallization both geophysical and petrologic data suggest that this eruption was not triggered by the intrusion of a new dike from depth but it was more likely that existing shallow magma reservoirs were passively mobilized and erupted in response to edifice deformation

long term dynamics across a volcanic rift 21 years of microgravity and gps observations on the southern flank of mt etna volcano abstract in this paper an integrated analysis of microgravity and ground deformation measurements at mt etna is performed over a 21 years time span 1994 2014 a period encompassing several flank and summit eruptions data were collected along a common gravity and ground deformation network located on the volcano s southern flank to monitor the dynamics of the main volcanic and tectonic processes gravity variations have first been corrected for the free air effect using the vertical deformation and the experimental vertical gravity gradients measured at each station the free air corrected gravity changes were then reduced for seasonal fluctuations mainly imputable to water table fluctuations and for high frequency variations noise this long term dataset constitutes a unique opportunity to examine the behavior of mt etna in a period in which the volcano exhibited different styles of activity characterized by recharging flank eruptions and fountaining episodes at summit craters the joint analysis highlights common periods in which gravity and deformation underwent contemporaneous changes occurring mainly in the central and eastern stations of the profile specifically it was possible to distinguish three different sectors showing significant deformation and gravity patterns a western sector lying west of the south rift a central one between the south rift and the 1989 fracture zone and an eastern one lying east of the 1989 fracture system the data shows that the deflation dynamics accompanying the eruptive phases mainly affect the western portion of the profile gradually disappearing toward east where the more constant sliding dynamics dominates this pattern defines a transition zone corresponding to the sector comprised between the south rift and the 1989 fracture furthermore it was also possible to detect at least three main magma charging phases in 1996 2000 and 2011 which preceded and accompanied the onset of intense flank eruptions and lava fountaining activity at the summit craters

static stress changes induced by the magmatic intrusions during the 2002 2003 etna eruption 1 the shallow intrusive processes that occurred during 2002 2003 etna eruption as well as the complex interaction between the magma intrusive events and the tectonic response of the volcano s eastern flank are investigated with numerical deformation modeling and the estimation of changes in the static coulomb stress ground deformation and volcanologic evidence clearly indicate a composite mechanism of intrusion on both the southern and northeastern flanks of the volcano geodetic data inversions have been based on a homogeneous elastic half space model although geological data and seismic tomography indicate that mt etna is elastically inhomogeneous and that rigidity layering and heterogeneities are likely to affect the magnitude and pattern of the deformation field to account for topographic effects as well as a complicated distribution of material properties we use the finite element method fem to provide a more realistic model the presence of medium heterogeneity strongly affects the amplitudes of the static stress changes seismicity matches well the areas of positive increase in the static stress caused by the intrusive events along the southern and northeastern flanks the changes in the state of stress generated by the southern dike produce an extensional stress field that favors magma propagation along the north east rift the highest seismic releases were associated with the activation of two fault systems the timpe fault system and the pernicana fault the static stress changes resolved onto these faults indicate that the magma intrusions on the southern and northeastern flanks encouraged these seismogenic structures to slip

anatomy of an unstable volcano from insar multiple processes affecting flank instability at mt etna 1994 2008 1 volcano deformation may occur under different conditions to understand how a volcano deforms as well as relations with magmatic activity we studied mt etna in detail using interferometric synthetic aperture radar insar data from 1994 to 2008 from 1994 to 2000 the volcano inflated with a linear behavior the inflation was accompanied by eastward and westward slip on the eastern and western flanks respectively the portions proximal to the summit showed higher inflation rates whereas the distal portions showed several sectors bounded by faults in some cases behaving as rigid blocks from 2000 to 2003 the deformation became nonlinear especially on the proximal eastern and western flanks showing marked eastward and westward displacements respectively this behavior resulted from the deformation induced by the emplacement of feeder dikes during the 2001 and 2002 2003 eruptions from 2003 to 2008 the deformation approached linearity again even though the overall pattern continued to be influenced by the emplacement of the dikes from 2001 to 2002 the eastward velocity on the eastern flank showed a marked asymmetry between the faster sectors to the north and those largely inactive to the south in addition from 1994 to 2008 part of the volcano base south west and north lower slopes experienced a consistent trend of uplift on the order of 0 5 cm yr this study reveals that the flanks of etna have undergone a complex instability resulting from three main processes in the long term 103 104 years the load of the volcano is responsible for the development of a peripheral bulge in the intermediate term 101 years observed from 1994 to 2000 inflation due to the accumulation of magma induces a moderate and linear uplift and outward slip of the flanks in the short term 1 year observed from 2001 to 2002 the emplacement of feeder dikes along the ne and south rifts results in a nonlinear focused and asymmetric deformation on the eastern and western flanks deformation due to flank instability is widespread at mt etna regardless of volcanic activity and remains by far the predominant type of deformation on the volcano

modeling of alos and cosmo skymed satellite data at mt etna implications on relation between seismic activation of the pernicana fault system and volcanic unrest abstract we investigate the displacement induced by the 2 3 april 2010 seismic swarm the largest event being of ml 4 3 magnitude by means of dinsar data acquired over the volcano by the cosmo skymed and alos radar systems satellite observations combined with leveling data allowed us to perform a high resolution modeling inversion capable of fully capturing the deformation pattern and identifying the mechanism responsible for the pfs seismic activation the inversion results well explain high gradients in the radar line of sight displacements observed along the fault rupture the slip distribution model indicates that the fault was characterized by a prevailing left lateral and normal dip slip motion with no fault dilation and hence excludes that the april 2010 seismic swarm is a response to accommodate the stress change induced by magma intrusions but it is due to the tectonic loading possibly associated with sliding of the eastern flank of the volcano edifice these results provide a completely different scenario from that derived for the 22 september 2002 m3 7 earthquake along the pfs where the co seismic shear rupture was accompanied by a tensile mechanism associated with a first attempt of magma intrusion that preceded the lateral eruption occurred here a month later these two opposite cases provide hints into the behavior of the pfs between quiescence and unrest periods at etna and pose different implications for eruptive activity prediction and volcano hazard assessment the dense pattern of ground deformation provided by integration of data from short revisiting time satellite missions together with refined modeling for fault slip distribution can be exploited at different volcanic sites where the activity is controlled by volcano tectonic interaction processes for a timely evaluation of the impending hazards

a pilot gis database of active faults of mt etna sicily a tool for integrated hazard evaluation abstract a pilot gis based system has been implemented for the assessment and analysis of hazard related to active faults affecting the eastern and southern flanks of mt etna the system structure was developed in arcgis environment and consists of different thematic datasets that include spatially referenced arc features and associated database arc type features georeferenced into wgs84 ellipsoid utm zone 33 projection represent the five main fault systems that develop in the analysed region the backbone of the gis based system is constituted by the large amount of information which was collected from the literature and then stored and properly geocoded in a digital database this consists of thirty five alpha numeric fields which include all fault parameters available from literature such us location kinematics landform slip rate etc although the system has been implemented according to the most common procedures used by gis developer the architecture and content of the database represent a pilot backbone for digital storing of fault parameters providing a powerful tool in modelling hazard related to the active tectonics of mt etna the database collects organises and shares all scientific currently available information about the active faults of the volcano furthermore thanks to the strong effort spent on defining the fields of the database the structure proposed in this paper is open to the collection of further data coming from future improvements in the knowledge of the fault systems by layering additional user specific geographic information and managing the proposed database topological querying a great diversity of hazard and vulnerability maps can be produced by the user this is a proposal of a backbone for a comprehensive geographical database of fault systems universally applicable to other sites

magma transport and storage at mt etna italy a review of geodetic and petrological data for the 2002 03 2004 and 2006 eruptions abstract a detailed reconstruction of magma movements within the plumbing system of mt etna volcano has been made by reviewing the eruptions occurring during the october 2002 december 2006 period the availability of continuous gps data allowed detecting at least ten different ground deformation stages highlighting deflationary and inflationary episodes as well as the occurrence of a shallow dike intrusion these data have been coupled with the available petrological datasets including major trace elements and sr nd pb isotope compositions for the volcanic rocks erupted in the 2002 2006 period we identified two main magmatic reservoirs located at different depths along the plumbing system of the volcano the former is located at a depth of 7 km bsl and fed the 2001 and 2002 03 eruptions while the latter located from 3 5 to 5 5 km bsl fed the 2004 05 and 2006 eruptions petrological characteristics of emitted products have been correlated with the inflation vs deflation cycles related to the identified sources providing evidence for changes through time of the evolutionary degree of the erupted magmas along with variations in their geochemical feature finally we suggest that a modification of the deep plumbing system of the volcano might have occurred during the 2002 03 eruption as a consequence of the major seaward motion of the eastern flank of the volcano