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

bayesian source inference of the 1993 1997 deformation at mount etna italy by numerical solutions summary deformation data collected at mount etna from 1993 to 1997 show that the inflation of the volcano edifice is accompanied by instability of the eastern flank we propose a 3 d finite element model including topography and lateral variations of elastic constants source parameters of the inflating source are constrained by a direct search followed by an appraisal stage of the sampled solutions the instability of the eastern flank is addressed using a kinematic approach consisting of a rigid body translation over a prescribed area the aim is to evaluate how source parameters are affected by sliding of the eastern flank when sliding is accounted for the inferred source location shifts 1 km se and its strength decreases by 20 per cent

ground deformation patterns on mount etna 1992 to 1994 inferred from gps data in this paper ground deformation that occurred on mount etna from 1992 1994 is studied using gps data first problems relating to data processing of the 1993 and 1994 surveys carried out on the whole of the mount etna gps network are considered care has been paid to the network adjustment step particularly in evaluating effects of the reference frame stability in finding final solutions comparison between survey results allows us to invert the strain tensor and to compute displacement vectors the latter when fully constrained solutions are available the comparisons lead to the conclusion that during the 1992 1994 period at least two sources were active the first was related to a shallow dyke that produced the 1991 1993 eruptive fissures the second deeper source was depleted during the 1991 1993 eruption and recharged between 1993 and 1994 local ground movements correlate spatially and temporally with seismic phenomena

relationship between petrologic processes in the plumbing system of mt etna and the dynamics of the eastern flank from 1995 to 2005 abstract mt etna volcano is located in a complex tectonic setting with large sectors of its eastern flank sliding seaward at different rates according to recent petrologic studies the etna s plumbing system has a multifaceted geometry variable in space and time and consisting of storage zones at different depths where magma ascending to the surface undergoes various processes mainly fractional crystallization and mixing in this framework we investigated a possible cause effect relationship between the flank displacement and pre eruptive magmatic processes in the shallow plumbing system furthermore a comparison between petrologic data and deformative patterns evidences that from 1995 to july 2001 the aforementioned pre eruptive magmatic processes did not significantly influence the volcano eastern flank dislocation which stayed slow and fairly regular by contrast the onset of the 2001 flank eruption leads to an acceleration of the movement as a consequence of the ascent of a primitive volatile rich sub aphyric basaltic magma from a deeper about 10 km b s l reservoir during the 2001 and 2002 03 activity at least for the decade 1995 2005 pre eruptive magmatic processes in the shallow portion

comparison between the 1994 2006 seismic and gravity data from mt etna new insight into the long term behavior of a complex volcano abstract we investigate the relationship between changes of the gravity field and the release of the seismic energy at mt etna over a 12 year period 1994 2006 during which the volcano exhibited different eruptive patterns over the two sub periods when intense gravity decreases occur centered on the upper southeastern sector of the volcano late 1996 to mid 1999 and late 2000 to mid 2001 the strain release curve displays neat long term accelerations with many hypocenters clustered in the volume containing the gravity source various evidences suggest that since 1994 and until the breakout of the 2001 eruption the eastern flank of etna remained peripheral to the lines of rise of the magma from the deep storage to the surface accordingly we hypothesize that rather than being directly associated to the migration of the magma the joint anomalies we found image phases of higher tensile stress on the upper southeastern sector associated to increase in the rate of microfracturing along the nnw sse fracture zone such an increase implies a local density gravity decrease and an increase in the release of seismic energy thus explaining the correlation we observe the second period of gravity decrease strain release increase culminated in the breakout of the 2001 flank eruption as a pressurized deeper magma accumulation used the inferred zone of increasing microfracturing as a path to the surface this eruption marks an important modification in the structure of etna s plumbing system as also testified by the absence of post 2001 long term gravity changes and accelerations in the strain release curve and the neat modification of the seismicity and ground deformation patterns we prove that joint microgravity and seismic studies can allow zones of the medium experiencing an increase in the rate of microfracturing to be identified months to years before a magma batch is conveyed through them to the surface setting off a lateral eruption

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

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

case history using time lapse vertical seismic profiling data to constrain velocity saturation relations the frio brine pilot co2 injection author s al hosni m caspari e pevzner r daley tm gurevich b abstract 2016 european association of geoscientists a engineers co2 sequestration projects benefit from quantitative assessment of saturation distribution and plume extent for field development and leakage prevention in this work we carry out quantitative analysis of time lapse seismic by using rock physics and seismic modelling tools we investigate the suitability of gassmann s equation for a co2 sequestration project with 1600 tons of co2 injected into high porosity brine saturated sandstone we analyze the observed time delays and amplitude changes in a time lapse vertical seismic profile dataset both reflected and transmitted waves are analyzed qualitatively and quantitatively to interpret the changes obtained from the vertical seismic profile we perform a 2 5d elastic finite difference modelling study the results show a p wave velocity reduction of 750 m s in the proximity of the injection well evident by the first arrivals travel time delays and amplitude change and reflected wave amplitude changes these results do not match with our rock physics model using gassmann s equation predictions even when taking uncertainty in co2 saturation and grain properties into account we find that time lapse vertical seismic profile data integrated with other information e g core and well log can be used to constrain the velocity saturation relation and verify the applicability of theoretical models such as gassmann s equation with considerable certainty the study shows that possible nonelastic factors are in play after co2 injection e g co2 brine rock interaction and pressure effect as gassmann s equation underestimated the velocity reduction in comparison with field data for all three sets of time lapse vertical seismic profile attributes our work shows the importance of data integration to validate the applicability of theoretical models such as gassmann s equation for quantitative analysis of time lapse seismic data

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

gps ground deformation patterns at mount st helens washington usa from 2004 to 2010 terra nova 24 148 155 2012 abstract gps measurements on mount st helens spanning the 2004 00 2010 85 time interval encompassing the 2004 2008 dome building eruption were analysed first a local reference frame was derived to isolate the volcanic ground deformation from the background tectonic pattern related to the interactions between the pacific juan de fuca and north american plates secondly the resulting ground deformation patterns were modelled to constrain magmatic sources results suggest a vertically elongated magma chamber centred at 8 9 km depth beneath the summit area that deflated during the beginning of the dome growth and inflated since january 2008 indicating that the same primary magma reservoir was active both during and after the eruption in a magmatic system that is persistent over the time

new behaviour of the piton de la fournaise volcano feeding system la reunion island deduced from gps data influence of the 2007 dolomieu caldera collapse after 15 months of summit deflation the unrest of piton de la fournaise renewed in august 2008 with several seismic crises and the re pressurization of the plumbing system the successive seismic crises sometime accompanied by ground displacements detected by gps were associated with inter eruptive dyke intrusions it was the first time since the implementation of the observatory that such successive inter eruptive magma migrations not reaching the surface were observed at piton de la fournaise the change in the volcano activity with an increase in the frequency of pure dyke intrusions have followed the dolomieu caldera collapse of april 2007 and reveals its strong influence on the new eruptive regime stress changes in the volcanic edifice have temporarily at least favoured the arrest of dykes in depth during these successive dyke intrusions magma stopped at shallow depth to form transitory magma storages before to erupt during three successive small summit eruptions september 21st october 2nd 2008 november 27th and december 14th 2008 february 4th 2009 the same kind of change in the pre eruptive and eruptive behaviour can be expected on other volcanoes having experienced a summit caldera collapse

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

how a complex basaltic volcanic system works constraints from integrating seismic geodetic and petrological data at mount etna volcano during the july august 2014 eruption the petrological part of this study was supported by the fir 2014 research grant to marco viccaro from the university of catania italy grant number 2f119b title of the project dynamics of evolution ascent and emplacement of basic magmas case studies from eruptive manifestations of eastern sicily

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

post eruptive deformation associated with the 1986 87 and 1989 lava flows of etna detected by radar interferometry we analysed 92 interferograms produced using ers1 sar images taken on etna between may 1992 and october 1993 nineteen show a local subsidence in the eastern flank of the volcano correlated with the location of the 30 october 1986 1 march 1987 and 27 september 9 october 1989 lava flows using fringe unwrapping and data gridding techniques and assuming that over the sampled time window deformation was a linear function of time we derive a map of along range rate of motion the correlation between the deformation field and the area covered by recent lavas suggests that compaction of the lava flows continues several years after the eruptions the area of maximum subsidence 47 mm yr is localised at the narrowing of the 1989 flow between 1500 and 1700 m a s l we observe that subsidence extends outside the lava flows accounting for at least 12 mm yr assuming a relaxation process of the substrate in response to loading produced by recent lavas a simple 1d maxwell visco elastic model predicts a maximum subsidence rate of 25 mm yr and a relaxation time of about 3 5 years the relaxation time agrees with those derived from post eruptive displacements observed by levelling on etna and piton de la fournaise after several eruptions we conclude that at the time of our measurements 25 to 50 of the deformation was related to relaxation of the substrate and the other part due to compaction of the lava flows

analogue modeling of flank instability at mount etna understanding the driving factors 1 mount etna is characterized by significant flank instability whose triggering factors are still a matter of debate we use analog models to investigate the role of different factors in the models a cone and base of granular material simulate the volcanic edifice and its basement the asymmetric geometry of the basement simulates the topographic gradient around the volcano injections of silicone sets a and b and low viscosity vegetable oil set c simulate the pressurization of plutonic complex deep reservoirs and the emplacement of dikes respectively other experiments set d reproduce regional extensional tectonics in the last 105 years within layers with different cohesion simulating strength differences in the basement laser scanner and control points allow the tracking of surface deformation with submillimeter precision the asymmetric topography enhances flank instability on the side with the weakest confinement i e seaside providing the preparing factor for instability in sets a and b any type of pressurized reservoir enhances up to 10 times the amount of flank instability toward the seaside with respect to the other flanks of the volcano in set c dike emplacement enhances seaside flank instability up to 8 times regional tectonics and crustal layering in set d enhance flank instability up to 2 and 1 3 times respectively considering the duration and frequency of the simulated processes in nature we propose a semiquantitative evaluation and hierarchy of the factors controlling flank instability at etna magmatic activity point like source inflation and dike emplacement provides the most important triggering factor extensional tectonics in the last 105 years and crustal layering are more than 10 times less effective this study shows the importance of differential buttressing at the volcano base for flank instability this condition is an important indication to expect asymmetric activity in any volcano flank eruptions and deformation

assessing the reliability and consistency of insar and gnss data for retrieving 3d displacement rapid changes the example of the 2015 piton de la fournaise eruptions abstract insar and gnss are now the best and most developed techniques in the earth sciences to track deformation especially in volcanology in this study we assess the reliability and consistency of these two techniques for measuring 3 d ground displacements and not only the displacement in the direction of the insar line of sight on volcanoes during rapid changes the use of a large amount of satellite data x c l band as well as right and left looking acquisitions made it possible to retrieve the 3 d displacement components with an unprecedented accuracy we carry out this evaluation on the piton de la fournaise volcano where four eruptions occurred in 2015 the comparison between gnss and insar allows us i to describe the deformation pattern associated with these eruptions ii to quantify the discrepancies between insar and gnss and iii to discuss the limits and the complementarities of insar and gnss the ground deformation patterns associated with the four eruptions of piton de la fournaise in 2015 are typical of this volcano with decimeter ground displacements asymmetrically distributed along the dike path evidencing a preferential eastward motion particularly visible thanks to the broad spatial coverage of insar except for the ns component insar and gnss data are in overall agreement with most of the gnss insar residuals

subsidence and current strain patterns on tenerife island canary archipelago spain derived from continuous gnss time series 2008 2015 abstract in this paper we present the current crustal deformation model of tenerife island derived from daily cgps time series processing 2008 2015 our results include the position time series a global velocity estimation and the current crustal deformation on the island in terms of strain tensors we detect a measurable subsidence of 1 5 2 mm yr in the proximities of the canadas teide pico viejo ctpv complex these values are higher in the central part of the complex and could be explained by a lateral spreading of the elastic lithosphere combined with the effect of the drastic descent of the water table in the island experienced during recent decades the results show that the anaga massif is stable in both its horizontal and vertical components the strain tensor analysis shows a 70 nstrain yr e w compression in the central complex perpendicular to the 2004 sismo volcanic area and 50 nstrain yr sw ne extension towards the northeast ridge the residual velocity and strain patterns coincide with a decline in volcanic activity since the 2004 unrest

anisotropy repeating earthquakes and seismicity associated with the 2008 eruption of okmok volcano alaska 1 we use shear wave splitting sws analysis and double difference relocation to examine temporal variations in seismic properties prior to and accompanying magmatic activity associated with the 2008 eruption of okmok volcano alaska using bispectrum cross correlation a multiplet of 25 earthquakes is identified spanning five years leading up to the eruption each event having first motions compatible with a normal fault striking ne sw cross correlation differential times are used to relocate earthquakes occurring between january 2003 and february 2009 the bulk of the seismicity prior to the onset of the eruption on 12 july 2008 occurred southwest of the caldera beneath a geothermal field earthquakes associated with the onset of the eruption occurred beneath the northern portion of the caldera and started as deep as 13 km subsequent earthquakes occurred predominantly at 3 km depth coinciding with the depth at which the magma body has been modeled using geodetic data automated sws analysis of the okmok catalog reveals radial polarization outside the caldera and a northwest southeast polarization within we interpret these polarizations in terms of a magma reservoir near the center of the caldera which we model with a mogi point source sws analysis using the same input processing parameters for each event in the multiplet reveals no temporal changes in anisotropy over the duration of the multiplet suggesting either a short term or small increase in stress just before the eruption that was not detected by gps or eruption triggering by a mechanism other than a change of stress in the system

rapid deformation of kilauea volcano global positioning system measurements between 1990 and 1996 campaign global positioning system gps measurements from 1990 to 1996 are used to calculate surface displacement rates on kilauea volcano hawaii the gps data show that the south flank of the volcano which has generated several large earthquakes in the past 3 decades is displacing at up to 8 cm yr to the south southeast the summit and rift zones are subsiding with maximum subsidence rates of 8 cm yr observed a few kilometers south of the summit caldera elastic dislocation modeling of the gps data suggests that the active sources of deformation include deep rift opening along the upper east and east rift zone fault slip along a subhorizontal fault near the base of the volcano and deflation near the summit caldera a nonlinear optimization algorithm was used to explore the parameter space and to find the best fitting source geometry there is a broad range of model geometries that fit the data reasonably well however certain models can be ruled out including those that have shallow rift opening or shallow fault slip some offshore aseismic slip on a fault plane that dips between 258 north northwest and 88 south southeast is required best fitting slip and rift opening rates are 23 28 cm yr although rates as low as 10 cm yr are permitted by the data

the unusual 28 december 2014 dike fed paroxysm at mount etna timing and mechanism from a multidisciplinary perspective between 2011 and 2013 there were 43 lava fountain episodes from mount etna s new south east summit crater nsec in 2014 this intense activity was supplanted by sporadic strombolian explosions and the opening of an eruptive fissure between july and august the only lava fountaining episode of the year occurred on 28 december this was characterized by the emplacement of a shallow dike that at the surface fed two distinct lava flows from an ene wsw trending eruptive fissure here we provide a detailed picture of the onset of the dike emplacement as well as the mechanism driving its migration using a multidisciplinary data set based on seismic geodetic geochemical and volcanological observations the dike emplacement was preceded by a pressurization of the magmatic plumbing system recorded from august 2014 on this pressurization has been modeled as a vertically elongated magmatic source located beneath the summit craters at 4 5 km below sea level from september to october magma rising was also detected by seismic and geochemical data that highlighted pressurization of the shallower portion of the plumbing system we suggest that the 28 december 2014 dike emplacement resulted from a modification of the preexisting nsec shallow plumbing system largely due to drainage of the main shallow conduit during the july august 2014 eruptive fissure activity such a structural modification might have created the conditions for magma emplacement as a dike like structure

ductile flow in sub volcanic carbonate basement as the main control for edifice stability new experimental insights abstract limestone in volcanic basements has been identified as a hazard in terms of edifice stability due to the propensity of calcite to decompose into lime and co2 at high temperatures 600 c causing a decrease in mechanical strength to date such hypotheses have been tested by experiments performed at ambient pressure the present work determines the mechanical strength of limestone under sub volcanic conditions of pressure and temperature and evaluates the effect of calcite decomposition to this end we use mt etna as a case study deforming sub etnean carbonate samples under triaxial compression using a paterson deformation apparatus we evaluate the effect of thermal decomposition of calcite on sample strength by comparing closed and open systems and measuring the permeability evolution under static conditions mechanical and micro structural observations at a constant strain rate of 10 5 s 1 and at a confining pressure of 50 mpa indicate that the rocks are brittle up to and including 300 c at higher temperatures the deformation becomes macroscopically ductile i e deformation is distributed throughout the sample the brittle to ductile transition is accompanied by an irreversible permeability decrease from 10 17 to 10 19 m 2 between 200 and 600 c we present new evidence that permanent change in permeability is due to ductile processes closing the initial pore space samples deformed at temperatures up to 900 c do not contain any decarbonation products at these temperatures permeability is sufficiently low to permit co2 pore pressures to increase thereby increasing local co2 fugacity which in turn strongly limits the decarbonation reaction we note that for non pure calcite rocks permeability might be sufficient to allow decarbonation reactions to occur as such variability in lithologies may slightly influence the efficiency of decarbonation reactions we conclude that in a closed system the instability of mt etna is related to high temperature induced ductile flow of basement limestone rather than chemical mineralogical changes this may have important implication for the stability of volcanoes within carbonate rich basement as carbonates become significantly weak at high temperatures which may increase the risk of sector collapse

an accurate and efficient method for including the effects of topography in three dimensional elastic models of ground deformation with applications to radar interferometry topography has a large effect on the results predicted by elastic surface deformation models in regions of significant relief in some cases topography may have more influence on the predicted deformation field than do model source parameters we have developed an approximate analytical technique for including topographic effects that retains most of the computational simplicity of elastic half space models while providing an accurate representation of topographic effects we use a series expansion of the elastic half space solution with a small slope approximation yielding a set of higher order corrections the integrated effect of these corrections is evaluated using fourier methods we investigate the effectiveness of our method by comparing predicted results for a tilted triaxial ellipsoid with those predicted by finite element models the resulting displacements and displacement gradients are in good agreement with finite element results both for relatively smooth topography synthetically generated and for the greater relief in the vicinity of mount etna volcano we then compare the results of our method with those predicted by traditional elastic half space models using different reference elevations and with a previously proposed method of estimating topographic effects our new method provides a significantly better fit to the finite element results than do the other methods our method is able to accurately portray both the number and the horizontal pattern of fringes in a synthetic interferogram when compared with finite element results in particular the method accurately represents the broadening of fringes that is observed in regions of high relief as well as reproducing the location of the fringe center and the topographically induced deviation of the fringes from a regular pattern elastic half space models typically show a fringe center that is displaced with respect to the finite element results indicating that parameter inversions based on such a model would provide incorrect estimates of the horizontal source position the lack of topographically generated fringe distortions in elastic half space results would also likely lead to inaccuracies in the predicted magnitude and orientation of proposed deformation sources our new technique over comes these limitations and should be useful when evaluating either traditional geodetic results or the greater areal coverage provided by interferometric observations

stress strain and mass changes at mt etna during the period between the 1991 93 and 2001 flank eruptions abstract during the 8 year period between the 1991 93 and 2001 flank eruptions the eruptive activity of mt etna was confined to the summit craters deformation and tomography studies indicate that this activity was fed by a magma accumulation zone centered ne of the summit at a depth of 5 to 9 km below sea level the most significant gravity changes measured during the same period were induced by mass redistributions at shallower depth below the southeastern flank of the volcano where minor ground deformation was observed i e vertical displacements within 2 cm the mismatch between the position of pressure and mass sources is difficult to explain under the assumption that both are directly related to magma dynamics past studies have suggested that the gravity changes observed during 1994 2001 may primarily reflect changes in the rate of microfracturing along the nnw sse fracture weakness zone fwz that crosses the se slope of etna we use the finite element method to shed new light on the complex relations between stress strain and mass changes that occurred at etna during the studied period in particular following previous results on the degradation of the mechanical properties of rocks we perform a set of simulations assuming that the part of the medium containing the fwz is characterized by a lower young s modulus than would be expected from interpolation of tomographic data we find that the presence of the fwz creates a distortion of the displacement field induced by the deeper pressure source locally resulting in a weak extensional regime this finding supports the hypothesis of a cause effect relationship between pressurization beneath the nw flank and tensile extension beneath the se slope of the volcano we propose that this extensional regime enhanced the propagation of pressurized gas that in turn amplified the tensile strain across the fwz we also find that decreasing the value of young s modulus in the fwz allows for a larger amount of extension at depth with no change in the magnitude of surface displacements this result provides an indication of how the changes in the rate of microfracturing at depth which are needed to induce the observed gravity changes might have occurred without large ground deformation

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

brittle creep in basalt and its application to time dependent volcano deformation time dependent brittle deformation is a fundamental and pervasive process operating in the earth s upper crust its characterization is a pre requisite to understanding and unraveling the complexities of crustal evolution and dynamics the preferential chemical interaction between pore fluids and strained atomic bonds at crack tips a mechanism known as stress corrosion allows rock to fail under a constant stress that is well below its short term strength over an extended period of time a process known as brittle creep here we present the first experimental measurements of brittle creep in a basic igneous rock a basalt from mt etna volcano under triaxial stress conditions results from conventional creep experiments show that creep strain rates are highly dependent on the level of applied stress and can be equally well fit by a power law or an exponential law with a 20 increase in stress producing close to three orders of magnitude increase in creep strain rate results from stress stepping creep experiments show that creep strain rates are also influenced by the imposed effective confining pressure we show that only part of this change can be attributed to the purely mechanical influence of an increase in effective pressure with the remainder interpreted as due to a reduction in stress corrosion reactions the result of a reduction in crack aperture that restricts the rate of transport of reactive species to crack tips overall our results also suggest that a critical level of crack damage is required before the deformation starts to accelerate to failure regardless of the level of applied stress and the time taken to reach this point the experimental results are discussed in terms of microstructural observations and fits to a macroscopic creep law and compared with the observed deformation history at mt etna volcano c 2011 elsevier b v all rights reserved

radar interferometry and its application to changes in the earth s surface geophysical applications of radar interferometry to measure changes in the earth s surface have exploded in the early 1990s this new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by a spaceborne synthetic aperture radar at two distinct times the resulting interferogram is a contour map of the change in distance between the ground and the radar instrument these maps provide an unsurpassed spatial sampling density 100 pixels km 2 a competitive precision 1 cm and a useful observation cadence 1 pass month 1 they record movements in the crust perturbations in the atmosphere dielectric modifications in the soil and relief in the topography they are also sensitive to technical effects such as relative variations in the radar s trajectory or variations in its frequency standard we describe how all these phenomena contribute to an interferogram then a practical summary explains the techniques for calculating and manipulating interferograms from various radar instruments including the four satellites currently in orbit ers 1 ers 2 jers 1 and radarsat the next chapter suggests some guidelines for interpreting an interferogram as a geophysical measurement respecting the limits of the technique assessing its uncertainty recognizing artifacts and discriminating different types of signal we then review the geophysical applications published to date most of which study deformation related to earthquakes volcanoes and glaciers using ers 1 data we also show examples of monitoring natural hazards and environmental alterations related to landslides subsidence and agriculture in addition we consider subtler geophysical signals such as postseismic relaxation tidal loading of coastal areas and interseismic strain accumulation we conclude with our perspectives on the future of radar interferometry the objective of the review is for the reader to develop the physical understanding necessary to calculate an interferogram and the geophysical intuition necessary to interpret it

multiparametric study of the february april 2013 paroxysmal phase of mt etna new south east crater european fp7 med suv mediterranean supersite volcanoes grant number 308665 european research council european fp7 fp 2007 2013 erc grant number 279802 sigma sistema integrato di sensori in ambiente cloud per la gestione multirischio avanzata

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

deflation of mount etna monitored by spaceborne radar interferometry ground based measurements of volcano deformation can be used to assess eruptive hazard but require the costly and often hazardous installation and maintenance of an instrument network here we show that spaceborne radar interferometry which has already shown its utility in mapping earthquake related deformation1 can be used to monitor long term volcano deformation two families of synthetic aperture radar images acquired from ascending and descending orbits by the satellite ers 1 and looking at mount etna from opposite sides cover the time period from 17 may 1992 to 24 october 1993 and include the second half of etna s most recent eruption despite artefacts of the interferometric technique we can observe a volcano wide deflation which is an expected consequence of the eruption but which had not previously been appreciated we quantify it using a simple model based on the change of pressure in a sphere located in an elastic half space the modelled deformation increases linearly with time until the end of the eruption our results show that it will be possible to use this technique to detect the inflation of volcanic edifices that usually precedes eruptions

tectono stratigraphic evolution and architecture of the miocene rio del rey basin cameroon margin gulf of guinea the rio del rey basin located in the gulf of guinea is one of the two basins lining the cameroonian coast it evolved since the cenozoic in a tectono magmatic and seismic complex setting during the miocene this evolution was controlled by tectonics relative sea level changes basin filling and mantle dynamics two deposit megasequences of second order ms1 and ms2 were pointed out ms1 lower miocene aggradational and corresponding to the isongo turbidites deposited during a period of relative sea level drop registered two sequences of third order differentiated by the degree of channel incision s1a aquitanian burdigalian hardly incised and s1b serravallian moderately incised a double extension along n s burdigalian and ne sw serravallian directions responsible for a set of horsts and grabens high subsidence and depocentres trending nw se affected these sequences ms2 middle to upper miocene progradational and corresponding to deltaic alternations deposited during a period of creation of available space were controlled by the tilting wrenching a second stretching phase and low sedimentary filling ms2 recorded three cycles of 3rd order s2a lower tortonian s2b upper tortonian and s2c messinian differentiated by their morphology in ramp for s2a and s2b and slope for s2c the formation of grabens and horsts and the tilting of the margin coincide with the high activity of the cameroon volcanic line interpreted as a result of deep mantle dynamics affecting the inner congo craton lithosphere this architecture which differs from those of the other basins of the gulf of guinea partly explains the low oil production of this basin

ground deformation patterns at mt etna from 1993 to 2000 from joint use of insar and gps techniques abstract combined gps measurements and radar interferometry insar have been applied at mt etna to study the ground deformation affecting the volcano both over the long 1993 2000 and short term 1997 1998 and 1998 2000 the aim was to better understand the dynamics of the volcano during the magma recharging phase following the 1991 93 eruption since 1993 insar and gps data indicate that mt etna has undergone an inflation a deep intrusion was detected by insar on the western flank of the volcano between march and may 1997 in the following months this intrusion rose up leading to a seismic swarm occurring in january 1998 in the western sector this now shallow intrusion is confirmed by gps data from 1998 to 2000 a general deflation affecting the upper part of the volcano was detected over the whole study period a continuous eastward to south eastward motion of the eastern sector of the volcano was also evidenced the analytical inversions of gps data inferred a plane dipping about 12 ese located beneath the eastern flank of the volcano at a depth of 1 4 km b s l the movement along this plane is able to reproduce the observed south eastward motion of a sector bounded northward by the pernicana fault westward by the north east rift and the south rift and southward by the mascalucia tremestieri trecastagni fault system insar data have validated this model

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

fault creep and kinematics of the eastern segment of the pernicana fault mt etna italy derived from geodetic observations and their tectonic significance abstract aseismic fault displacements related to numerous fast slipping active faults are frequently observed on mt etna but the characteristics and the rate of displacements along with the behaviour of individual fault segments are poorly constrained to resolve this we installed two local geodetic networks in 1997 along the eastern segment of the pernicana fault one of the most active structures in the geodynamic framework of the volcano the networks are based on the electroptical distance measurements edm and global positioning system gps techniques and consist of four and six benchmarks respectively geodetic data confirm that the tectonic activity of the eastern pernicana fault is controlled by fault creep i e a near continuous stable sliding at a mean slip rate of 2 8 cm yr punctuated by aseismic displacement episodes the analysis of the strain tensor calculated from the edm and gps data indicates that deformation in the fault zone is related to a clear sinistral strike slip movement a more complete picture is obtained from the gps measurements for the rocca campana area where the main structure branches out eastward into a splay fault the inversion of 3d displacement vectors suggests a deformation model consisting of two principal sinistral strike slip faults with an oblique component of movement the maximum observed displacement 6 1 cm measured in the period april 1997 february 1999 is accommodated by the splay fault this finding corroborates the hypothesis that as proposed by the tectonic models in the literature the movement of the eastern segment of the pernicana fault is transferred easterly towards structures at a lower altitude along the same strike e g the fiumefreddo fault as a consequence the pernicana fault may constitute part of a continuous left lateral trans current zone which displaces the whole north eastern flank of mt etna

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

dynamic inversion of ground deformation data for modelling volcanic sources etna 1991 93 the 1991 93 etna eruption that represented the most important recent eruptive event both in terms of duration 472 days and total volume of erupted lava ca 250 106 m caused marked ground deformation measured by using different geodetic techniques such as edm gps levelling and tiltmetry an inversion termed dynamic because it took into account the sequence of events considering both the separate and cumulative effects of two sources a shallow tensile crack and a deeper ellipsoidal deflating source was performed it was based on 163 data collected by the different techniques plus 2 geometrical conditions for constraining the geometry of the crack on the surface the final solution furnished a good fit for all measurements defining a shallow tensile crack located inside the volcanic edifice which represents the effect of the intrusion and a depressuring body with centre at ca 3000 m b s l which could represent the centre of a generalized and more complex deflation of the volcanic edifice during the course of the eruption

dynamics of mount etna before during and after the july august 2001 eruption inferred from gps and differential synthetic aperture radar interferometry data we acknowledge the istituto nazionale di geofisica e vulcanologia the italian dipartimento per la protezione civile and the european community contract ingv dpc ur v3 6 36 and volume project for their economic contribution to this research the sar data are provided by esa esrin

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

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

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

the key role of vertical land motions in coastal sea level variations a global synthesis of multisatellite altimetry tide gauge data and gps measurements abstract this study aims to quantify the vertical motions driving the decadal coastline mobility and their uncertainty at global scale multisatellite altimetry is combined with tide gauges and global positioning system gps observations to evaluate the marine and crustal components of relative sea level variations vertical land motions and sea level variations are estimated simultaneously over the past 20 years for a network of 886 ground stations with accuracies better than 1 7 mm yr the altigaps database present significant interest both by its technical characteristics global coverage larger number of sites longer period of observation improved accuracy and by the novelty of the applications empowered altigaps offers the opportunity to look independently into the recent dynamic processes affecting the ocean and the interior of the earth here the role of vertical land motions in relative sea level variations is explored to better understand the natural hazards associated with sea level rise in coastal areas global evidence for the local variability in vertical land motions is provided which may either amplify or attenuate the apparent rise of the sea at the coast a set of 182 potential vulnerable localities are identified by large coastal subsidence 1 5 mm yr which increases by several times the effects of climate induced sea level rise for coastal management purposes both marine absolute sea level variations and crustal vertical land motions components of vertical coastal motions relative sea level variations should therefore be accounted for

towards more realistic values of elastic moduli for volcano modelling abstract the accuracy of elastic analytical solutions and numerical models widely used in volcanology to interpret surface ground deformation depends heavily on the young s modulus chosen to represent the medium the paucity of laboratory studies that provide young s moduli for volcanic rocks and studies that tackle the topic of upscaling these values to the relevant lengthscale has left volcano modellers ill equipped to select appropriate young s moduli for their models here we present a wealth of laboratory data and suggest tools widely used in geotechnics but adapted here to better suit volcanic rocks to upscale these values to the scale of a volcanic rock mass we provide the means to estimate upscaled values of young s modulus poisson s ratio shear modulus and bulk modulus for a volcanic rock mass that can be improved with laboratory measurements and or structural assessments of the studied area but do not rely on them in the absence of information we estimate upscaled values of young s modulus poisson s ratio shear modulus and bulk modulus for volcanic rock with an average porosity and an average fracture density quality to be 5 4 gpa 0 3 2 1 gpa and 4 5 gpa respectively the proposed young s modulus for a typical volcanic rock mass of 5 4 gpa is much lower than the values typically used in volcano modelling we also offer two methods to estimate depth dependent rock mass young s moduli and provide two examples using published data from boreholes within k lauea volcano usa and mt unzen japan to demonstrate how to apply our approach to real datasets it is our hope that the data and analysis presented herein will assist in the selection of elastic moduli for volcano modelling to this end we provide a microsoft excel spreadsheet containing the data and necessary equations to calculate rock mass elastic moduli that can be updated when new data become available the selection of the most appropriate elastic moduli will provide the most accurate model predictions and therefore the most reliable information regarding the unrest of a particular volcano or volcanic terrain

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

experimental study of the interplay between magmatic rift intrusion and flank instability with application to the 2001 mount etna eruption mount etna volcano is subject to transient magmatic intrusions and flank movement the east flank of the edifice in particular is moving eastward and is dissected by the timpe fault system the relationship of this eastward motion with intrusions and tectonic fault motion however remains poorly constrained here we explore this relationship by using analogue experiments that are designed to simulate magmatic rift intrusion flank movement and fault activity before during and after a magmatic intrusion episode using particle image velocimetry allows for a precise temporal and spatial analysis of the development and activity of fault systems the results show that the occurrence of rift intrusion episodes has a direct effect on fault activity in such a situation fault activity may occur or may be hindered depending on the interplay of fault displacement and flank acceleration in response to dike intrusion our results demonstrate that a complex interplay may exist between an active tectonic fault system and magmatically induced flank instability episodes of magmatic intrusion change the intensity pattern of horizontal flank displacements and may hinder or activate associated faults we further compare our results with the gps data of the mount etna 2001 eruption and intrusion we find that syneruptive displacement rates at the timpe fault system have differed from the preeruptive or posteruptive periods which shows a good agreement of both the experimental and the gps data therefore understanding the flank instability and flank stability at mount etna requires consideration of both tectonic and magmatic forcing

the inverse water wave problem of bathymetry detection the inverse water wave problem of bathymetry detection is the problem of deducing the bottom topography of the seabed from measurements of the water wave surface in this paper we present a fully nonlinear method to address this problem in the context of the euler equations for inviscid irrotational fluid flow with no further approximation given the water wave height and its first two time derivatives we demonstrate that the bottom topography may be reconstructed from the numerical solution of a set of two coupled non local equations owing to the presence of growing hyperbolic functions in these equations their numerical solution is increasingly difficult if the length scales involved are such that the water is sufficiently deep this reflects the ill posed nature of the inverse problem a new method for the solution of the forward problem of determining the water wave surface at any time given the bathymetry is also presented

characterization of seismicity at mt etna volcano italy by inter event time distribution abstract the space time inter event time iet distributions of earthquakes occurring from 1988 to 2011 at mt etna are analysed in order to identify the periodicity or stationary behaviour of seismicity and to correlate it with the volcano tectonic features of the region the comparison between iet distributions at etna with those obtained both for sicily and italy shows that iets at a larger scale are well modelled by a gamma distribution whereas at etna local scale they are characterised by a bimodal curve in which the two peaks are related to i the contribution of local seismic swarms with very short inter event times and ii the background regional stationary seismicity iet analysis is an important tool to investigate the behaviour of seismicity at different crustal levels in the etna region distinguishing sectors that are influenced by volcano dynamics or regional tectonics indeed the spatial variation of iet distributions obtained by analysing different etna crustal sectors shows that seismicity shallower than 5 km is almost entirely characterised by short inter event times and is mainly confined to the summit area for earthquakes deeper than 5 km occurring in the eastern flank of the volcano as well as in eastern sicily iet distributions are characterised by independent events which suggest that both areas are influenced by the same extensional regional regime by contrast iet distributions obtained for the western flank and north western sicily are marked by two peaks indicating that the compressional stress is acting in both areas

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

space time evolution of magma storage and transfer at mt etna volcano italy the 2015 2016 reawakening of voragine crater programma nazionale ricerche grant number pnra14 00011 university of catania fir 2014 grant numbers 2f119b pra 2016 18 22722132120

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

episodic slow slip events and seaward flank motion at mt etna volcano italy abstract episodic aseismic slip events have recently been detected at a variety of tectonic and volcanic environments sparking the curiosity of seismic and geodetic communities here a sequence of 7 slow slip events occurring at mt etna since mid 2009 has been analyzed observed displacement fields evidence that the sequence involves two contiguous sectors of the unstable eastern flank delimited by the timpe faults the tectonic control played by these faults can also be recognized on the long term 2003 2015 velocity field elastic modelling of the long term velocity field infers a sub horizontal plane slightly dipping eastward and located within the sedimentary basement at shallow depth slip distribution models for each slow slip event highlight how the largest slip values were centred on the se edge of the sub horizontal plane during 4 events and on the ne edge during the remaining 3 ones the recognized events do not appear correlated with volcanic activity although there is a possible correlation between slow slip events and inflating episodes of the volcano

dynamic deformation of etna volcano observed by satellite radar interferometry satellite radar interferometry of mt etna volcano sicily italy reveals a sequence of deformation characterized by deflation during the end of the 1993 eruption inflation from 1993 1995 with an increase in the inflation rate immediately before its resumed eruptive activity in late 1995 this was followed by very low deformation levels during the following year the source of the deformation changed from a depth of 9 km during deflation to more than 11 14 km during the subsequent inflation consistent with a model in which deflation at shallower levels is followed by inflation at greater depth as the volcano system recharges from below before its next eruption this study demonstrates that radar interferometry provides an important contribution towards understanding the dynamic deformation of volcanoes by revealing large scale changes in their pre eruption deformation rates radar interferometry could play an important role in volcano eruption monitoring

the unstable eastern flank of mt etna volcano italy first results of a gnss based network at its southeastern edge abstract two small geodetic subnetworks were established in 2010 and in 2014 respectively along the southeastern edge of the unstable eastern flank of mt etna volcano these networks have been monitored since late 2014 with gnss techniques by the geomatic laboratory of earth science section of the university of catania the resulting horizontal velocity field allowed us to observe a westward decay of the rate and a different azimuthal pattern of motion between the two networks we suggest that both features are due to active deformation of the nizzeti faults we also observed that the deforming region is not entirely confined by the tremestieri san gregorio acitrezza fault zones but it extends southwards areal upgrades of the networks as well as the scheduling of measurements at least on a monthly basis will improve our knowledge of the current deformation pattern of the investigated area

large scale ground deformation of etna observed by gps between 1994 and 2001 we have processed thirty global positioning system gps campaigns carried out at etna from 1994 to early 2001 between the last two main flank eruptions of the mt etna sicily italy this rest period allowed us to investigate the deep magma plumbing system of the mt etna the temporal dynamics of twenty three points observed three times or more were analyzed all the time series show a first order linear trend during the five years period it suggests that the volcano was continuously deformed by the action of a deep source while a discrete activity of the volcano was observed at the summit we have interpreted the residual deformation field as the result of an major eastward motion of the eastern flank of the volcano

new dating of rapid vertical deformation of santa tecla fault scarps mt etna volcano sicily by lichenometry method abstract the eastern slope of mt etna is characterised by shallow seismicity originating from normal oblique faulting timpe fault system related to wnw ese regional extension recent research has demonstrated that in the fault population of mt etna s eastern flank the minimum earthquake magnitude that will have a ground rupture effect is ca 2 5 this system is characterised by high frequency seismic activity due to thinned seismogenic crustal layer this characteristic together with the high density of the fault segments does not always for identification of the segments responsible for the earthquake the earthquakes affecting the medium lower eastern flank have been historically reconstructed by macroseismic analysis and reported in a macroseismic database and in recent decades by instrumental seismic registration which provide the seismological parameters capable of evaluating focal mechanism hypocentre and relative algorithms related to geometric parameters which control the growth of fault segments in this paper we present a methodology to evaluate the age of the rapid exhumation of the free face fault plane of the nnw sse oriented normal fault segment named s tecla timpe fault system it consists of the measurement of the thalli species lichenometry method in order to evaluate the parameters which characterise their growth the seismic history of the s tecla fault indicates eight certain events from 1865 to 2005 with 3 4 4 7 magnitude de guidi et al 2012 and reference therein we found evidence of two different recent rapid vertical deformation events at the base of the s tecla fault escarpment the oldest 20 m long and 0 25 m in height and the youngest with a 0 02 m high nude surface exposed we have observed that there are thalli of xanthoparmelia conspersa ehrh ex ach hale colonizing part of the nude surface on the escarpment the results highlight that the oldest thalli was dated at 43 7 years old showing that rapid vertical deformation generated the surface where the thalli after 4 years took root the displacement of this surface could be related to the seismic events occurring on 3rd august 1973 3 8 m in s m ammalati area probably accompanied by intense post seismic deformation the second and last event could be attributable to a 3 1 m seismic event occurring on 25th september 2014 iside 2016

on precisely modelling surface deformation due to interacting magma chambers and dykes combined data sets of insar and gps allow us to observe surface deformation in volcanic settings however at the vast majority of volcanoes a detailed 3 d structure that could guide the modelling of deformation sources is not available due to the lack of tomography studies for example therefore volcano ground deformation due to magma movement in the subsurface is commonly modelled using simple point mogi or dislocation okada sources embedded in a homogeneous isotropic and elastic half space when data sets are too complex to be explained by a single deformation source the magmatic system is often represented by a combination of these sources and their displacements fields are simply summed by doing so the assumption of homogeneity in the half space is violated and the resulting interaction between sources is neglected we have quantified the errors of such a simplification and investigated the limits in which the combination of analytical sources is justified we have calculated the vertical and horizontal displacements for analytical models with adjacent deformation sources and have tested them against the solutions of corresponding 3 d finite element models which account for the interaction between sources we have tested various double source configurations with either two spherical sources representing magma chambers or a magma chamber and an adjacent dyke modelled by a rectangular tensile dislocation or pressurized crack for a tensile okada source representing an opening dyke aligned or superposed to a mogi source magma chamber we find the discrepancies with the numerical models to be insignificant 5 per cent independently of the source separation however if amogi source is placed side by side to an okada source in the strike perpendicular direction we find the discrepancies to become significant for a source separation less than four times the radius of the magma chamber for horizontally or vertically aligned pressurized sources the discrepancies are up to 20 per cent which translates into surprisingly large errors when inverting deformation data for source parameters such as depth and volume change beyond 8 radii however we demonstrate that the summation of analytical sources represents adjacent magma chambers correctly

tropospheric corrections of sar interferograms with strong topography application to etna the accuracy of spaceborne geodetic techniques including sar interferometry is limited by the time and spatial variation and altitude dependance of the propagation delay of electomagnetic waves in the lower troposphere particularly in mountainous areas in this paper we use a 1d model developed for tropospheric corrections of gps and doris measurements to correct sar data the differential tropospheric delay is computed at each pixel of the interferogram from ground temperature humidity and pressure using two empirical parameters calibrated from several radio soundings acquired in various latitude and climate conditions it is shown that with such a model given the 3300 meters topography of etna tropospheric variations can generate up to 4 phase rotations between the top and the bottom of the volcano in 16 out of the 20 interferograms processed with images acquired between august 1992 and october 1993 correction of the tropospheric effect reduces the number of fringes associated with the 1991 93 eruption from previous estimates the remaining deformation is consistant with a deforming source located at a depth of 14 1 km during the second half of the eruption the subsidence rate at the top of the volcano is roughly stable at 13 3 mm month these values are in good agreement with tiltmeter data collected on etna during the same period and with the estimated volume of erupted material no significant deformation can be observed during the last month of eruption inflation of the volcano seems to resume immediately after the end of the eruption at a rate of 3 mm month

volcanic unrest leading to the july august 2001 lateral eruption at mt etna seismological constraints abstract a close relationship between earthquake swarms volcanic eruptions and ground deformation at mt etna was well documented shortly before the beginning of the july august 2001 eruption past experiences at this volcano suggest how magma dike intrusion in the shallow crust or in the upper part of the volcanic pile normally occurs after several years months of internal recharging since seismic investigations provide a means to study the scale and origin of stress perturbations at active volcanoes allowing to better investigating the preparation phase of an eruption in this paper we performed a close examination of the seismic activity recorded at mt etna in the months preceding the 2001 eruption and in particular between november 2000 and july 2001 after integrating data recorded by the two networks operating during that time and run by the istituto internazionale di vulcanologia and sistema poseidon we relocated 522 earthquakes by using the tomodd code in a 3d velocity model and then we computed their fault plane solutions the application of different selection criteria enabled obtaining a good quality revised data set consisting of 111 fault plane solutions the high precision locations identified well defined seismic clusters in different periods suggesting a link with the magma migration from a depth of 8 13 km b s l towards shallower zones moreover the computed maximum compressive stress axis as inferred from earthquake focal mechanisms indicated a roughly w e oriented 1 this findings reflect an overpressure of the mid to shallow crust due to the progressive magma uprising in central portion of the volcano and also highlighted a rotation of the local stress field with respect to the regional one n s trending in addition p axis distribution pointed out the presence of a center of pressure located to the south of the central craters these results provide particularly compelling evidence for a direct causal link between pressurization of the mid level volcanic plumbing system by ascending magma and precursory local stress field reorientations demonstrating that seismological analysis can be used to detect subtle local stress changes that herald eruptive activity

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

magma intrusion mechanisms and redistribution of seismogenic stress at mt etna volcano 1997 1998 terra nova 23 339 348 2011 abstract several volcanoes worldwide have shown changes in their stress state as a consequence of the deformation produced by the pressurization of a magmatic body this study investigated seismic swarms occurring on the western flank of mt etna in january 1997 january 1998 integrating seismic observations and geodetic data we constrained the seismogenic fault system and on the basis of stress tensor inversion and shmax analyses we inferred an inflating pressure source located at 5 5 km b s l beneath the west portion of summit area evaluation of coulomb failure stress related to the proposed model showed how a large part of the seismogenic fault underwent a significant coulomb failure stress increase 500 kpa we inferred the presence of a sub vertical faulted region potentially weak n50 e oriented beneath the western sector of mt etna this structure could be brought closer to failure thereby generating seismic swarms as the effect of elastic stress transfer induced by movement and or overpressure of magmatic masses within the upper crust under the volcano

volcanic deformation and flank instability due to magmatic sources and frictional rheology the case of mount etna summary the overall picture of mount etna deformation emerging since a couple of decades of geodetic surveys shows effects of magma accumulation characterized by inflation deflation cycle accompanied by a sliding instability of the southeast flank whose manifestation is an increase in the horizontal deformation away from the volcano summit this is a very interesting case to test whether advanced models taking into account topography internal structure and frictional rheology may contribute to a better understanding of the complex interplay among mechanical response magmatic activity and gravitational load occurring in a volcanic system using finite element numerical models we make predictions of surface displacements associated with a simple expansion source and with a dike like vertical discontinuity a new methodology is developed to initialize the lithostatic stress field according to the material and geometrical complexities of the models considered our results show that while an amplification of the horizontal displacement can be easily obtained up to a maximum distance of 10 km from the source we have not been able to find any configuration to extend further this signal for the case of mount etna this suggests that the large horizontal displacements observed in the east flank along the coast cannot be directly related to magma accumulation below the volcano s summit

gravity and magma induced spreading of mount etna volcano revealed by satellite radar interferometry 1 mount etna underwent a cycle of eruptive activity over the past ten years here we compute ground displacement maps and deformation time series from more than 400 radar interferograms to reveal mount etna s average and time varying surface deformation from 1992 to 2001 we find that during this time interval it experienced magmatic inflation and radial spreading to the west south and east steady relative motion between the west and south flanks and between the east and north flanks during this time interval suggests they are related to gravitational spreading of the volcanic edifice time series analysis shows that growth of a southeastern basal anticline began with the end of magma recharge in 1995 thus showing a direct link between deep seated magma intrusions and edifice spreading these observations support a complex mode of radial gravitational collapse underlain by deeper magma driven basal spreading although ultimately the two must be related

elastic moduli evolution and accompanying stress changes with increasing crack damage implications for stress changes around fault zones and volcanoes during deformation summary the elastic moduli of rock in areas susceptible to crack damage such as within fault zones or volcanic edifices can be subject to large modifications knowledge of how elastic moduli may vary in such situations is important for both the reliable modelling of volcano deformation and stability and for linear and non linear elastic crack models for earthquake rupture furthermore it has previously been shown that changes in elastic moduli can induce changes in the stress field surrounding faults here we report both uniaxial experimental measurements of changes in elastic moduli during increasing amplitude cyclic stressing experiments on a range of different rock types basalts sandstones and granite and the results of modelled stress modifications the trend in elastic moduli evolution with increasing damage was remarkably similar for each rock type with the exception of essentially crack free intrusive basalt that exhibited very minor changes in general young s modulus decreased by between 11 and 32 per cent and poisson s ratio increased by between 72 and 600 per cent over the total sequence of loading cycles these changes are attributed to an increasing level of anisotropic crack damage within the samples our results also show that acoustic emission ae output during any loading cycle only commenced when new crack damage was generated this corresponded to the level of stress where ae ceased during the unloading portion of the previous cycle using the multilayer elastic model of faulkner et al we demonstrate that the damage induced changes in elastic moduli also result in significant decreases in differential stress increases in mean stress and rotation of the applied greatest principal stress relative to the orientation of the mechanical layering the similar trend in the evolution of the elastic moduli of all the rocks tested suggests that stress modification in the damage zone of faults might take the same form regardless of the lithology through which the fault runs these observations are discussed in terms of their applicability to both fault zones and deformation at volcanoes

pressurization and depressurization phases inside the plumbing system of mount etna volcano evidence from a multiparametric approach during 2013 mount etna volcano experienced intense eruptive activity at the summit craters foremost at the new southeast crater and to a minor degree at the voragine and bocca nuova bn which took place in two cycles february april and september december in this work we mainly focus on the period between these cycles applying a multiparametric approach the period from the end of april to 5 september showed a gradual increase in the amplitude of long period lp events and volcanic tremor a slight inflation testified by both tilt and gps data and a co2 flux increase such variations were interpreted as due to a gradual pressurization of the plumbing system from the shallowest part where lp and volcanic tremor are located down to about 3 9 km below sea level pressure source depths obtained by both geodetic and co2 data on 5 september at the same time as a large explosion at bn we observed an instantaneous variation of the aforementioned signals decrease in amplitude of lp events and volcanic tremor slight deflation and co2 flux decrease and the activation of a new infrasonic source located at bn in the light of it the bn explosion probably caused the instantaneous end of the pressurization and the opening of a new vent at bn that has become a new steady source of infrasonic events this apparently slight change in the plumbing system also led to the gradual resumption of activity at the new southeast crater culminating with the second lava fountain cycle of 2013

interpretation of ground surface changes prior to the 2010 large eruption of merapi volcano using alos palsar aster tir and gas emission data abstract understanding precursory signals is essential to forecast eruptions hazards and mitigate risks satellite observations have been shown to increasingly contribute to this goal we use differential inteferometric synthetic aperture radar d insar and sar backscattering intensity data from alos palsar to define a time series of ground surface displacements for the 2006 2010 inter eruptive period at merapi volcano we correlate trends in the displacement data to trends for summit temperature determined using data from the aster sensor and to gas emission data we show that processing of the satellite data must be performed carefully before meaningful interpretations can be drawn for example after careful removal of the topographic effect on phase delays we detect only subtle inter eruptive episodes of cyclic deformation in the d insar and sar backscattering data these small mostly sub centimeter displacements contrast with meter scale pre eruptive displacements along an electronic distance measurement edm line on the south flank of the volcano we suggest that this difference is a consequence of localized movement within the summit area a result that has important implications for understanding merapi s structure for monitoring network design and for eruption forecasting although small merapi s inter eruptive deformation cycles are also seen in thermal data from aster and gas emissions accordingly we interpret these cycles as the result of successive movement of individual magma batches migrating upward from deeper to shallower storage systems located along a ne dipping conduit in view of magma migration prior to eruptions these cycles may also serve as a precursory signal for large eruptions at merapi such as the one that took place in early november 2010

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

dynamics of mount etna volcano inferred from static and kinematic gps measurements 1 ground deformations measured on mount etna from late 1995 to mid 1998 using gps observations are analyzed four gps surveys were carried out during the considered period in 1995 the gps network consisted of 18 stations on the volcanic edifice and 6 stations around it during the 1996 survey 22 new monuments were added along a n s profile crossing the summit craters area this profile was surveyed by a semikinematic method allowing greater spatial detail to be achieved on the uppermost part of the volcano the comparisons between the gps surveys are reported here in terms of horizontal and vertical displacements for each station and also in terms of areal dilatation and strain distribution this last parameter continues its ascending trend at a rate of 5 strain yr 1 already shown in the previous period after the end of the 1991 1993 flank eruption inversion of the ground deformation patterns permits investigation of the evolution of both the position and dynamics of magma reservoirs beneath the volcano consistently associated with a general eastward sliding of its eastern sector this study allows us to define the nonuniqueness of ground deformation sources through the investigated period suggesting that the plumbing system of the volcano is made up of a complex system of single intrusions occurring at different times

a joint inversion of ground deformation and focal mechanisms data for magmatic source modelling the paucity of geodetic data acquired on active volcanoes can make the understanding of modelling magmatic systems quite difficult in this study we propose a novel approach which allows improving the parameter estimation of analytical models of magmatic sources e g shape depth dimensions volume change etc by means of a joint inversion of surface ground deformation data and p axes of focal plane solutions the methodology is first verified against a synthetic dataset of surface deformation and strain within the medium and then applied to real data from an unrest episode occurred before the may 13 2008 eruption at mt etna italy the main results clearly indicate the joint inversion improves the accuracy of the estimated source parameters by about 70 the statistical tests indicate that the source depth is the parameter with the highest increment of accuracy in addition a sensitivity analysis confirms that displacements data are more useful to constrain the pressure and the horizontal location of the source than its depth while the p axes better constrain the depth estimation

mt etna 2001 eruption new insights into the magmatic feeding system and the mechanical response of the western flank from a detailed geodetic dataset abstract in the last decades the increasing availability of comprehensive geodetic datasets has allowed for more detailed constraints on subsurface magma storage and conduits at several active volcanoes worldwide here by using a large dataset of geodetic measurements collected between early january 2001 and august 2001 we identified at least six different deformation stages that allow us to quantify the surface deformation patterns before during and after the 2001 mt etna volcanic eruption our results are largely in agreement with previous works e g the presence of a deep inflating source and a shallow dike located beneath the north western and upper southern flanks of the volcano respectively however we provide 1 finer resolution of the temporal activity of these magmatic sources leading to 2 new evidence related to the evolution of the magmatic system and the mechanical response of the western flank in particular during the pre eruptive phase results and analysis show a clear change in the ground deformation pattern of the volcano in response to the 20 24 april 2001 seismic swarm that occurred beneath the western flank evolving from a volcano wide inflation to a slight deflation of the summit area we suggest that the source responsible for the volcano wide inflation beginning in the fall of 2000 experienced a drastic reduction in the inflation rate in response to this seismic swarm moreover we provide evidence for the presence of a new inflating source located beneath the upper southern flank at a depth of 7 0 km bsl that triggered both the occurrence of the 20 24 april 2001 seismic swarm and led to the rapid ascent of magma upward to the surface after 12 july the lower vents system was fed by fresh magma rising from this source the presence of this inflating source is inferred by 1 seismological and volcanological observations coming from the 2001 eruption and 2 seismological constraints coming from a previous similar episode that occurred at etna during the 1993 1998 period furthermore both shallow deflations observed after the 20 24 april 2001 seismic swarm and during the first day of the eruption also could be due to the deflation of two adjacent portions of the same shallow 2 km bsl reservoir such reservoirs would feed the activity that occurred at the south east crater after january 2001 and the activity of the upper vents system during the july august eruption in agreement with petrochemical observations through an updated revision of the available data we shed some light on the relevance of pre eruptive activity patterns an important element for an effective volcano monitoring

shear response to an intrusive episode at mt etna volcano january 1998 inferred through seismic and tilt data abstract the space time evolution of a seismic swarm m d max 3 7 occurring on 9 14 january 1998 at mt etna volcano is analysed the hypocentral pattern and most reliable focal mechanisms indicate that seismic activity during 10 14 january mainly occurred within a fault zone located in the volcano s western flank the fault showed an approximately ne sw overall trend and shallow rupture mode of right lateral strike slip type it is noteworthy that earthquakes occurring during the initial phase 9 january of the swarm showed prevalent dip slip rupture mechanisms which are consistent with tensile opening of an approximately nnw sse trending fault zone this nnw sse structural lineament belongs to a regional lithospheric structure which has also been identified as a main volcano genic structural trend of mt etna the observed continuous tilt data are not explainable by the seismic slip associated with strain released along the ne sw structure however an intrusive source would be compatible with the rupture mechanisms observed during the initial phase of the swarm and could explain the observed tilt therefore we evidence that an intrusive episode occurred along the nnw sse structure starting 9 january and during the following days it forced the ne sw fault system to work in a right lateral mode these mechanisms leading to the february november 1999 summit eruption are analogous to the ones observed before the 1991 93 eruption

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

volcano wide fringes in ers synthetic aperture radar interferograms of etna 1992 1998 deformation or tropospheric effect mount etna 3300 m is the volcano that has been first and most studied by differential synthetic aperture radar previous papers gave evidence for a large scale deformation of the entire edifice consistent with unrest episodes but with a poor fit with classical elastic models also atmospheric effects on mountainous areas are known to be very significant accordingly interferograms may reflect both deformation and tropospheric effects we investigate here the possibility of evaluating and correcting tropospheric effects directly from the interferograms from 38 ers synthetic aperture radar ascending scenes taken from 1992 to 1999 we have computed 238 interferograms the amount of data allows us to analyze how the coherence is maintained over long periods of time and thus how it reveals the location of permanent scatters from a simple analysis of phase elevation relation we give evidence for the clear difference in pattern between stratified tropospheric effects and large scale deformation produced by a source in a three dimensional elastic body with topography using combination of inversion processes we analyze both deformation source and tropospheric effects for the complete set of 238 interferograms finally time evolution of the parameters and modeling probability estimation are retrieved for each sar image estimated relative change in tropospheric delay varies in time from 2 7 to 3 0 1 2 fringes they are consistent with other tropospheric estimations at etna based on ground met and global positioning system observations on the same period of time magmatic volume variations remain below error bars and thus cannot be estimated properly finally some of the interferograms may be entirely explained by the difference in tropospheric conditions between the two acquisition periods without the need to invoking a deformation of the volcano

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