the influence of erosional processes on the visibility of permanent scatterers features from sar remote sensing on mount etna e sicily abstract analysis of 1549 dinsar interferograms covering the period from 2003 to 2010 has highlighted significant motion along the entire set of the active faults identified by advanced dinsar analyses i e permanent scatterers features psf affecting the mount etna volcano in eastern sicily in the analysed period the absence of significant seismicity producing co seismic ground deformation suggests that the overall deformation that has been recognized on the interferograms is to be associated with interseismic almost continuous creep which is well documented along most of the active faults according to field evidence the structures should accumulate displacements resulting in their permanent visibility on the interferograms progressively increases through time this expected behaviour has been recognised only for part of the entire set of structures other tectonic features in fact show episodic appearances alternating with periods of absence of ground displacement on the interferograms simulating a stick slip mechanism of deformation conflicting with field evidence this apparently incongruous behaviour can be interpreted as the result of topographic changes due to the combination of the tectonic displacements with related amounts of the differential erosion and deposition across the fault line the comparison between the history of the appearances and the monthly rainfall in the region seems to demonstrate that these structures appear when one of the two interacting processes governing the topographic changes around the fault i e tectonic vs erosional prevails over the other otherwise the same structures are not evident on the interferograms when the two components are in balance

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

decorrelation in interferometric radar echoes a radar interferometric technique for topographic mapping of surfaces implemented utilizing a single synthetic aperture radar sar system in a nearly repeating orbit is discussed the authors characterize the various sources contributing to the echo correlation statistics and isolate the term which most closely describes surficial change they then examine the application of this approach to topographic mapping of vegetated surfaces which may be expected to possess varying backscatter over time it is found that there is decorrelation increasing with time but that digital terrain model generation remains feasible the authors present such a map of a forested area in oregon which also includes some nearly unvegetated lava flows such a technique could provide a global digital terrain map

inflation leading to a slow slip event and volcanic unrest at mount etna in 2016 insights from cgps data global positioning system cgps data from mt etna between may 2015 and september 2016 show intense inflation and a concurrent slow slip event sse from 11 december 2015 to 17 may 2016 in may 2016 an eruptive phase started from the summit craters temporarily stopping the ongoing inflation the cgps data presented here give us the opportunity to determine 1 the source of the inflating body 2 the strain rate parameters highlighting shear strain rate accumulating along ne rift and s rift 3 the magnitude of the sse and 4 possible interaction between modelled sources and other flank structures through stress calculations by analytical inversion we find an inflating source 5 5 km under the summit 4 4 km b s l and flank slip in a fragmented shallow structure accommodating displacements equivalent to a magnitude mw 6 1 earthquake these large displacements reflect a complex mechanism of rotations indicated by the inversion of cgps data for strain rate parameters at the scale of the volcano these processes can be considered precursors of seismic activity in the eastern flank of the volcano but concentrated mainly on the northern boundary of the mobile eastern flank along the pernicana fault and in the area of the timpe fault system

monitoring landslides and tectonic motions with the permanent scatterers technique spaceborne differential synthetic aperture radar interferometry dinsar has already proven its potential for mapping ground deformation phenomena e g volcano dynamics however atmospheric disturbances as well as phase decorrelation have prevented hitherto this technique from achieving full operational capability these drawbacks are overcome by carrying out measurements on a subset of image pixels corresponding to pointwise stable reflectors permanent scatterers ps and exploiting long temporal series of interferometric data results obtained by processing 55 images acquired by the european space agency esa ers sar sensors over southern california show that the ps approach pushes measurement accuracy very close to its theoretical limit about 1 mm allowing the description of millimetric deformation phenomena occurring in a complex fault system a comparison with corresponding displacement time series relative to permanent gps stations of the southern california integrated gps network scign is carried out moreover the pixel by pixel character of the ps analysis allows the exploitation of individual phase stable radar targets in low coherence areas this makes spaceborne interferometric measurements possible in vegetated areas as long as a sufficient spatial density of individual isolated man made structures or exposed rocks is available the evolution of the ancona landslide central italy was analysed by processing 61 ers images acquired in the time span between june 1992 and december 2000 the results have been compared with deformation values detected during optical levelling campaigns ordered by the municipality of ancona the characteristics of ps gps and optical levelling surveying are to some extent complementary a synergistic use of the three techniques could strongly enhance quality and reliability of ground deformation monitoring d 2002 elsevier science b v all rights reserved

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

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

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

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

dynamics of the eastern flank of mt etna volcano italy investigated by a dense gps network abstract mount etna has developed at the intersection of two regional tectonic lineaments the nnw sse trending hybleo maltese escarpment which separates the thick inland continental crust of the african platform from the ionian mesozoic oceanic crust and the ne sw messina fiumefreddo fault that marks a rift zone between south calabria and north eastern sicily extending as far as the mt etna area all tectonic features affect with outstanding surface features the eastern side of the volcano the eastern flank of the volcano is affected by a long term motion toward ese in 1997 in order to increase the detail of the ground deformation pattern on the lower eastern flank of mt etna a new gps network the ionica network was installed on this sector of the volcano this gps network consists of 24 stations and covers the lower eastern flank of the volcano from the town of catania to taormina and from the coastline up to an altitude of about 1300 m all the new stations consist in self centring benchmarks this kind of benchmark allows all station set up errors to be avoided before the merging of the ionica network to the frame of the global gps network of mt etna in june 2001 three surveys were carried out on this network in september 1997 august 1998 and january 2001 from the ground deformation pattern it is possible to distinguish two different sectors showing different characteristics of deformation the southern part of the network shows a more uniform distribution of the vertical motion with a mean se ward horizontal component while the northern one shows an heterogeneous vertical motion with a ese ward horizontal component furthermore a higher velocity is detected between 1997 and 1998 due to the additional stress induced by a shallow intrusion on the nw flank of the volcano the model resulting from data inversions defines a wide sliding plane beneath the entire eastern flank of the volcano with a low dip angle the expected velocity vectors fit well the observed ones even if the measured velocities are still quite higher than expected at lowermost stations the vertical inclination of the velocity vectors measured during the 1998 2001 period gradually decreases from west to east suggesting a sort of rotational movement of the south eastern flank interrupted by some anomalous vectors on the lower part that show higher vertical velocities these anomalies being located on a wedge defined by the intersection of the main nnw sse and ne sw fault systems and near the timpe faults are probably due to the activity of the vertical faults cutting the lower eastern flank of mt etna stations lying on the hanging wall and on the footwall of the timpe fault system are affected by similar horizontal displacements meaning that these structures are moving eastwards together with the sliding flank this evidence suggests that the timpe faults are probably second order structures with respect to the detachment surface these results depict a structural framework of the eastern flank of mt etna in which the low angle dislocation can be considered as a first order approximation of an actual listric plane and the current active part of the timpe fault system is confined above the detachment surface

composite ground deformation pattern forerunning the 2004 2005 mount etna eruption 1 after the end of the 2002 2003 eruption mount etna activity was characterized only by gentle degassing at the summit craters and some earthquake swarms suddenly an eruption started on 7 september 2004 in complete absence of summit crater volcanic activity seismicity or seismic tremor and ground deformation this is the first time that magma poured out passively without preeruptive and coeruptive volcanic and or geophysical phenomena the primary key to understanding this event is represented by the ground deformation pattern recorded through gps measurements during the year before the eruption the ground deformation shows inflation superimposed by a predominant eastward movement of the eastern sector at a rate never observed before in a noneruptive period the images from satellite radar interferometry confirmed this pattern the deformation field clearly shows that the maximum tension in the eastern sector of the volcano caused the opening of the eruptive fracture which favored the silent pouring out of already resident magma

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

seismic anisotropy time variations at mt etna this article has been accepted for publication in geophysical journal international the authors 2020 published by oxford university press on behalf of the royal astronomical society all rights reserved uploaded in accordance with the publisher s self archiving policy

atmospheric effects in interferometric synthetic aperture radar surface deformation and topographic maps interferogram images derived from repeat pass spaceborne synthetic aperture radar systems exhibit artifacts due to the time and space variations of atmospheric water vapor other tropospheric variations such as pressure and temperature also induce distortions but the effects are smaller in magnitude and more evenly distributed throughout the interferogram than the wet troposphere term spatial and temporal changes of 20 in relative humidity lead to 10 cm errors in deformation products and perhaps 100 m of error in derived topographic maps for those pass pairs with unfavorable baseline geometries in wet regions such as hawaii these are by far the dominant errors in the spaceborne imaging radar c and x band synthetic aperature radar sir c x sar interferometric products the unknown time delay from tropospheric distortion is independent of frequency and thus multiwavelength measurements such as those commonly used to correct radar altimeter and global positioning system gps ionospheric biases cannot be used to rectify the error in the topographic case the errors may be mitigated by choosing interferometric pairs with relatively long baselines as the error amplitude is inversely proportional to the perpendicular component of the interferometer baseline for the sir c x sar hawaii data we found that the best longest baseline pair produced a map supporting 100 m contouring whereas the poorest baseline choice yielded an extremely noisy topographic map even at this coarse contour interval in the case of deformation map errors the result is either independent of baseline parameters or else very nearly so here the only solution is averaging of independent interferograms so in order to create accurate deformation products in wet regions many multiple passes may be required rules for designing optimal data acquisition and processing sequences for interferometric analyses in nondesert parts of the world are 1 to use the longest radar wavelengths possible within ionospheric scintillation and faraday rotation limits 2 for topography maximize interferometer baseline within decorrelation limits and 3 for surface deformation use multiple observations and average the derived products following the above recipe yields accuracies of 10 m for digital elevation models and 1 cm for deformation maps even in very wet regions such as hawaii

very shallow dyke intrusion and potential slope failure imaged by ground deformation the 28 december 2014 eruption on mount etna on 28 december 2014 eruptive activity resumed at mount etna with fire fountain activity feeding two lava flows on the eastern and southwestern upper flanks of the volcano unlike all previous summit activity this eruption produced clear deformation at the summit of the volcano gps displacements and sentinel 1a ascending interferograms were calculated in order to image the ground deformation pattern accompanying the eruption the displacements observed by gps depict a local ground deformation pattern affecting only the upper part of the volcano despite snow cover on the summit differential interferometry synthetic aperture radar dinsar data allowed obtaining more detail on the ground deformation pattern on the upper eastern side of the volcano three dimensional gps displacements inversion located a very shallow ne sw intrusion just beneath the new southeast crater however this model cannot justify all the deformation observed by dinsar thus revealing a gravitational failure of the lava flow field

tectonic expression of an active slab tear from high resolution seismic and bathymetric data offshore sicily ionian sea subduction of a narrow slab of oceanic lithosphere beneath a tightly curved orogenic arc requires the presence of at least one lithospheric scale tear fault while the calabrian subduction beneath southern italy is considered to be the type example of this geodynamic setting the geometry kinematics and surface expression of the associated lateral slab tear fault offshore eastern sicily remain controversial results from a new marine geophysical survey conducted in the ionian sea using high resolution bathymetry and seismic profiling reveal active faulting at the seafloor within a 140 km long two branched fault system near alfeo seamount the previously unidentified 60 km long nw trending north alfeo fault system shows primarily strike slip kinematics as indicated by the morphology and steep dipping transpressional and transtensional faults available earthquake focal mechanisms indicate dextral strike slip motion along this fault segment the 80 km long sse trending south alfeo fault system is expressed by one or two steeply dipping normal faults bounding the western side of a 500 m thick 5 km wide elongate syntectonic plio quaternary sedimentary basin both branches of the fault system are mechanically capable of generating magnitude 6 7 earthquakes like those that struck eastern sicily in 1169 1542 and 1693

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

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

faulting on the western flank of mt etna and magma intrusions in the shallow crust surface deformations on the western flank of mt etna volcano spanning 1980 2004 have been analysed as they pertain to stress interactions between magma intrusions within the shallow crust along the s se rift and faulting sensitivity during this period an accurate analysis of strain parameters computed by inversion of sw electro optical distance data suggested that the observed strong displacements on this flank of the edifice can also be related to dextral shear movements along a roughly ne sw buried fault crossing the area covered

nonlinear subsidence rate estimation using permanent scatterers in differential sar interferometry discrete and temporarily stable natural reflectors or permanent scatterers ps can be identified from long temporal series of interferometric sar images even with baselines larger than the so called critical baseline this subset of image pixels can be exploited successfully for high accuracy differential measurements the authors discuss the use of ps in urban areas like pomona ca showing subsidence and absidence effects a new approach to the estimation of the atmospheric phase contributions and the local displacement field is proposed based on simple statistical assumptions new solutions are presented in order to cope with nonlinear motion of the targets

the global positioning system as a useful technique for measuring ground deformations in volcanic areas abstract in this paper the global positioning system technique for measuring ground deformations in volcanic areas is presented after an outline of the mathematical background the results of three years experience regarding the use of this technique on mt etna are reported the ground deformation patterns recorded between 1989 and 1991 are shown and discussed in the geodynamic framework which characterized mt etna in the time interval considered attention is focused on modeling a ground deformation episode which occurred on mt etna between 1990 and 1991 which contributed to characterizing the dynamic framework where the 1991 1992 eruptive event took place the deformation pattern mentioned has been interpreted by using a dislocation model the optimal solution for the inversion problem has been found by using an optimization approach based on the simplex method this solution agrees with the regional stress field whose compressive direction is nne ssw oriented

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

feeding system and magma storage beneath mt etna as revealed by recent inflation deflation cycles 1 ground deformation at mt etna detected by three gps surveys carried out in 2004 2005 and 2006 is analyzed the data set encompasses the 2004 2005 eruptions and foreruns those of 2006 a wide deflation of the entire volcano was detected from 2004 to 2005 accompanying the 2004 2005 eruption conversely an evident inflation phase from 2005 to 2006 followed this eruption and preceded the 2006 one in both cases the deflation inflation cycle was accompanied by a continuous seaward motion of the eastern flank we inverted both data sets 2004 2005 deflation and 2005 2006 inflation using an optimization algorithm based on the genetic algorithm ga in order to detect the ground deformation sources the wide contraction measured during the eruption reveals the drainage of a sill shaped magma reservoir located by data inversions at a depth of about 4 5 km b s l the pressurizing source modeled for the 2005 2006 time interval indicates a refilling of the shallower near vertical plumbing system of the volcano this could indicate a change in the geometry of the feeding system active after the 2004 2005 eruption with a new and shallower magma storage that could have enabled the resumption of volcanic activity that was observed at summit craters in 2006 these results improve the imaging of the plumbing system of mt etna volcano

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

structural assessment of mount etna volcano from permanent scatterers analysis a study of the deformation pattern of mount etna volcano based on the results from the permanent scatterers ps technique is reported ground motion data provided by the interferometric synthetic aperture radar insar ps technique from 1995 to 2000 are compared and validated by gps data an analysis of the ascending and descending line of sight los components of ground velocities has yielded detailed ground deformation maps and cross sections this analysis allows detection and constraint of discontinuities in the surface velocity field los velocities have then been combined to calculate the vertical and horizontal e w ground velocities a wide inflation of the edifice has been detected on the western and northern flanks over an area of about 350 km2 a seaward motion of the eastern and southern flanks has also been measured ps data allows the geometry and kinematics of the several blocks composing the unstable flanks to be defined even in the highly urbanized areas and their displacement rates have been measured with millimeter precision this analysis reveals the extension of some features beyond their field evidences and defines new important features the results of this work depict a new comprehensive kinematic model of the volcano highlighting the gravitational reorganization of the unbuttressed volcanic pile on its slippery clay basement on the southern flank but an additional drag force due to a strong subsidence of the continental margin facing the etna volcano is necessary to explain the ps velocity field observed on the eastern flank

scaled experiments of volcanic spreading experiments were conducted to study the spreading of volcanic constructs volcanoes are simulated by a sand cone and the volcanic substratum is simulated by a sand layer brittle substratum overlying a silicone layer ductile substratum similarity conditions between natural volcanoes and experimental prototypes led to the definition of dimensionless numbers experiments determine values which predict whether or not spreading takes place of particular importance are the ratio between the thickness of the brittle substratum and the height of the volcano 2 and the brittle ductile ratio of the substratum 3 2 indicates that the volcano must be large enough to break the substratum before spreading occurs whereas 3 controls the style of deformation during spreading these dimensionless numbers change with time reaching values that tend toward those observed for stable configurations experimental values are compared with those from well constrained natural examples it is found that an essential requirement for volcanic spreading is the presence of a low viscosity layer within the substratum flow of the weak layer away from the excess load is responsible for the spreading the overlying edifice displays radial intersecting grabens due to concentric stretching dissected summit areas concentric zones of thrusts and folds form in the substratum around the edifice and diapirs of the ductile substratum rise within the fault zones

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

ground deformation modeling of flank dynamics prior to the 2002 eruption of mt etna on 22 september 2002 1 month before the beginning of the flank eruption on the ne rift an m 3 7 earthquake struck the northeastern part of mt etna on the westernmost part of the pernicana fault in order to investigate the ground deformation pattern associated with this event a multi disciplinary approach is presented here just after the earthquake specific gps surveys were carried out on two small sub networks aimed at monitoring the eastern part of the pernicana fault and some baselines belonging to the northeastern edm monitoring network of mt etna were measured the leveling route on the northeastern flank of the volcano was also surveyed furthermore an investigation using sar interferometry was performed and also the continuous tilt data recorded at a high precision sensor close to the epicenter were analyzed to constrain the coseismic deformation the results of the geodetic surveys show a ground deformation pattern that affects the entire northeastern flank of the volcano clearly shaped by the pernicana fault but too strong and wide to be related only to an m 3 7 earthquake leveling and dinsar data highlight a local strong subsidence up to 7 cm close to the pernicana fault significant displacements up to 2 cm were also detected on the upper part of the ne rift and in the summit craters area while the displacements decrease at lower altitude suggesting that the dislocation did not continue further eastward three dimensional gps data inversions have been attempted in order to model the ground deformation source and its relationship with the volcano plumbing system the model has also been constrained by vertical displacements measured by the leveling survey and by the deformation map obtained by sar interferometry

active tectonic features and structural dynamics of the summit area of mt etna italy revealed by soil co2 and soil temperature surveying project cgl2005 07509 cli ministry of education and science of spain dpc ingv project flank istituto nazionale di geofisica e vulcanologia osservatorio etneo sezione di catania

squeesar and gps ground deformation monitoring of santorini volcano 1992 2012 tectonic implications abstract the santorini volcanic complex svc has been in a dormant state for the last 60 years until january 2011 when upward influx of magma reawakened the volcano with intense radial ground deformation and inter caldera seismicity that lasted until january 2012 but declined afterwards this paper aims to study the ground deformation and the inferred tectonic implications of the svc for the period 1992 2012 mainly based on the squeesar technique and dgps campaign results of our local network which incorporates available data on internet from several continuous gps stations established on the island the spatial deformation of the svc during the quiet period 1992 2010 was deduced by joint analysis of ers1 and 2 and envisat it was found that the intra caldera palaea kammeni shield volcano was being uplifted 2 3 mm yr with increasing rate whilst the adjacent nea kammeni shield volcano was being subsided up to 6 mm yr with increasing rate the rest of the svc showed a velocity field varying from 1 to 2 mm yr indicating a rather linear deformation during that period the results from the gps network are in full agreement with the squeesar results based on the results of squeesar analysis of 12 envisat images and dgps cgps data to end 2012 the deformation for the unrest period 2011 2012 was non linear being characterized by strong radial deformation in the northern part of the caldera 50 120 mm yr and accelerating values 130 mm yr 2 combined gps squeesar mogi modeling indicated a source located north of nea kammeni at a shallow depth however a progressively decreasing rate in deformation was noted at most gps cgps station components after january 2012 indicating magma settlement consistent with the constantly decreasing rate of the inter caldera seismicity the faulting features seem to have a key role in the evolution of the deformation which continues up the end 2012 but at a very low level

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

a multidisciplinary study of an active fault crossing urban areas the trecastagni fault at mt etna italy abstract the trecastagni fault is a nnw sse tectonic structure in the densely inhabited southern flank of mt etna characterised by evident morphological scarps and movements of normal and right lateral type that directly affect roads and buildings the fault is affected by continuous dynamics with intermittent accelerations accompanied with shallow seismicity it has an important role in the instability affecting mt etna s south eastern flank and represents part of the southern boundary of the unstable sector the motion of the fault between 2005 and 2011 has been analysed by using a multi disciplinary approach involving terrestrial and satellite ground deformation data active monitoring systems able to investigate the fault in detail are extensometers a levelling network and insar two episodes of acceleration were recorded at the end of 2009 and during 2010 data evidences that the acceleration episodes affected only portions of the fault and that stress may accumulate and be periodically released although both magmatic processes inflation or intrusive episodes and flank dynamics influence the occurrence of the tf acceleration episodes the dragging effect of the overall seaward sliding of the south eastern flank is evident and it causes the subsidence of the hangingwall accumulating stress on the fault that is periodically seismically released

discrimination of geophysical phenomena in satellite radar interferograms various geophysical phenomena are recorded in the interference patterns formed by differencing two synthetic aperture radar sar images the fringes generated by the topographic relief can be removed using a digital elevation model dem the remaining fringes map the change in satellite to ground range which occurred between the acquisition times of the two images by comparing different pairs of images spanning different intervals of time it is possible to discriminate between geophysical signal and interferometric artifact here we apply this pair wise logic to the area around the 1992 landers california earthquake using sar images acquired by the ers 1 satellite the range varies with time as a constant step impulsive or sloping function examples of each type include a dem error an aftershock two atmospheric perturbations and postseismic afterslip respectively their signatures are identified and separated using the pair wise logic

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

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

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

a syn eruptive ground deformation episode measured by gps during the 2001 eruption on the upper southern flank of mt etna ground deformation occurring on the southern flank of mt etna volcano during the july august 2001 eruption was monitored by gps measurements along an e w profile crossing the fissure system this profile was measured eight times during the eruption using the stop and go semi kinematic technique horizontal and vertical displacements between gps surveys are reported for each station the most significant event is a deformation episode occurring during the first week of the eruption between 25 27 july displacements were measured on benchmarks close to the eruptive fissure and the tensile 1989 fracture data inversions for measured displacements were performed using the okada model the model shows the narrowing of the 2001 dyke accompanied by a dextral dislocation along an east dipping fault parallel to the 1989 fracture

correction for interferometric synthetic aperture radar atmospheric phase artifacts using time series of zenith wet delay observations from a gps network 1 radar interferograms provide precise millimeter level measurements of crustal deformation at fine resolution over wide areas the dominant error source in many interferograms results from spatial heterogeneity of the wet component of atmospheric refractivity resulting in excess path length of the radar signal propagating through the neutral atmosphere in this report we introduce a method to compensate for atmospheric phase artifacts in a radar interferogram using spatially interpolated zenith wet delay zwd data obtained from a network of global positioning system gps receivers in the region imaged by the radar our method based on taylor s frozen flow hypothesis uses gps data recorded prior to and after the individual radar acquisition times to infer denser spatial networks of control points for interpolation than is suggested by the sparse and irregular spatial distribution of gps receivers we test this approach by correcting phase fluctuations observed in a radar interferogram over an area covered by the southern california integrated gps network stations using maps of atmospheric delay interpolated from the denser network of gps zwd measurements generated by our method we find that the largest improvement results from removing an altitude dependent model derived from the gps data the uncorrected interferogram in our example has an rms fluctuation of 16 1 mm which falls to 8 6 mm after the altitude correction a map derived from zwd measurements recorded only at the instances of radar acquisition reduced overall fluctuations in the data from 8 6 to 8 1 mm rms while using the inferred denser network reduces the error further to 7 5 mm rms most of this residual variation is due to decorrelation of the signal and does not result from atmospheric propagation however after smoothing to remove decorrelation noise the residual drops from 4 7 to 3 9 mm gps stations only and then to 2 7 mm rms when the denser network algorithm is used

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

bioindication of volcanic mercury hg deposition around mt etna sicily mt etna is a major natural source of hg to the mediterranean region total mercury concentrations hg tot in castanea sativa sweet chestnut leaves sampled 7 13 km from etna s vents during six campaigns in 2005 2011 were determined using atomic absorption spectroscopy hg tot in c sativa was greatest on etna s se flank reflecting hg deposition from the typically overhead volcanic plume hg tot also showed hg accumulation over the growing season increasing with leaf age and recent eruptive activity hg tot in c sativa was not controlled by hg tot in soils which instead was greatest on etna s nw flank and was correlated with the proportion of organic matter in the soil org an elevated hg tot org ratio in soils on etna s se flank is indicative of increased hg deposition this ratio was also found to decrease with local soil ph suggesting that hg deposited to the low ph and organic poor soils on etna s se flank may not be retained but will instead be released to groundwater or re emitted to the atmosphere these results show that the deposition of volcanic hg

experimental study on ultrasonic velocity and anisotropy of tectonically deformed coal abstract tectonically deformed coal tdc is defined as coal formed by various tectonic stresses as one of the key concerns in the formation and recovery of coal bed methane cbm from the tectonic deformation coal seams the texture and fractures of tdc present various features in different deformation environments and as a result the physical properties change therefore the identification of tdc is significant and can be obtained from the physical properties in this study fourteen representative tdc and two undeformed coal samples from the suzhou mining area in the east of north china plate were collected to investigate the geophysical recognition parameters of tdc by elastic properties such as the velocities p and s waves elastic parameters v p v s and poisson s ratio and velocity anisotropies the results show that the elastic properties of undeformed coal and tdc samples from different deformation environments exhibit significant difference normally the velocities and elastic parameters of undeformed coal have the highest values while the velocity anisotropy has the lowest value in brittle deformation environment the velocity and elastic parameters decrease while the velocity anisotropy ascends with increased deformation extent for the tdc samples from shear deformation environment the velocity anisotropies present the significant high values among the selected tdc samples in plastic deformation environment the elastic parameters gradually decrease with the deformation extent ascending while the velocity anisotropies are relatively high among the elastic properties the v p v s poisson s ratio and velocity anisotropy are sensitive to deformation type and extent of coal samples furthermore the development characteristics of coal structural fractures have a significant impact on the elastic properties of measured coal samples from different deformation environments in summary the results may provide reference parameters for future studies in cbm rock physics from the tectonic deformation coal seams

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

analysis of satellite and in situ ground deformation data integrated by the sistem approach the april 3 2010 earthquake along the pernicana fault mt etna italy case study abstract etna is known worldwide as one of the most studied and monitored active volcanoes flank instability along the eastern and southern portions of mt etna has been observed and measured thanks to geodetic networks and insar data analysis the spreading area is bordered to the north by the east west pernicana fault system pfs whose dynamics is often linked with the eruptive activity as recently observed during the 2002 2003 eruption a seismic sequence occurred from april 2 3 2010 along the pfs with very shallow a few hundred meters mainshocks of magnitude 4 3 and 3 6 explosions and ash emissions at the summit craters followed this swarm culminating a few days later april 7 8 despite their small magnitude the earthquakes caused damage and significant surface fracturing along the pfs in order to investigate and measure the deformations in the near field of the earthquakes the sistem integration approach has been exploited the sistem enabled integrating geodetic in situ ground deformation measurements gps and leveling with satellite interferometric measurements envisat and alos in order to obtain high resolution 3d displacement maps allowing to overcome the limitations of each technique and take advantage of the particular features of each of them the integrated ground deformation field evidenced that the medium behave elastically we inverted the sistem results using an optimization algorithm based on the genetic algorithm ga in order to model the kinematics of the pfs associated to seismic swarm the results are in good agreement with the field evidence and improved the knowledge on the kinematics of the pfs and mt etna s unstable flank

intrusive mechanism of the 2002 ne rift eruption at mt etna italy modelled using gps and gravity data summary microgravity and gps data collected at mt etna during a 1 yr time interval encompassing the 2002 ne rift eruption are analysed the common gps gravity profile traverses the summit area of mt etna between the summit craters about 3000 m and the northernmost tip of the eruptive fractures 2500 m displacements up to 2 m in both the horizontal and vertical directions and gravity variations up to 350 gal after having removed the effect of elevation changes observed during this period are among the largest ever recorded at etna displacements and gravity changes have been modelled separately assuming a magma influx from the summit feeder pipe to the ne rift models obtained through surface deformation data partially overlap with those explaining the gravity data but in general are narrower and extend to a greater depth the discrepancies found between gravity and deformation models are significant and can be regarded as due to the different structural features encountered by the intruding magma during its downslope propagation along the ne rift in particular on the grounds of our result we infer that both the eastward sliding of the east flank of the volcano and the curved shape of the ne rift influenced the 2002 intrusive process

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

interaction between magma intrusion and flank dynamics at mt etna in 2008 imaged by integrated dense gps and dinsar data 1 global positioning system gps and differential interferometric synthetic aperture radar dinsar data collected from july 2007 to july 2008 on mt etna are analyzed to define the dynamics preceding and accompanying the onset of the eruption on 13 may 2008 short and long term comparisons have been made on both gps and radar data covering similar time windows thanks to the availability of three gps surveys the year before the eruption onset an increase in the seaward movement of the ne flank of the volcano has been detected in the few months before the dike intrusion the gps ground deformation pattern also shows a slight inflation centered on the western side of the volcano in the preeruptive long term comparison from july 2007 to may 2008 the gps has been integrated with dinsar data by the sistem approach to take advantage of the different methodologies and provide high spatial sampling of the 3 d ground displacement pattern we inverted the sistem results to model the pressure source causing the observed preeruptive inflation the subsequent emplacement of the eruptive dike was imaged by two gps surveys carried out on a dense network over the uppermost part of the volcano on 6 and 13 may i e a few days before and a few hours after the beginning of the eruption we inverted this comparison to define the position geometry and kinematics of the dike the dike intrusion was also imaged by dinsar data with temporal baselines of 2 3 months which confirm strong displacements localized on the summit area rapidly decreasing toward the middle flanks of the volcano as detected by very short term gps data furthermore the comparison between dinsar and gps data highlighted the presence of a depressurizing source localized beneath the upper southwestern area acting just after the dike intrusion finally the long period 1 year gps and dinsar data were integrated by sistem to finely depict the 3 d ground deformation pattern with the highest spatial resolution the long period data allowed the complex kinematics of the volcano to be finely imaged and highlighting the interaction between flank dynamics and magma injection

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

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

the morphostructural setting of mount etna sedimentary basement italy implications for the geometry and volume of the volcano and its flank instability abstract the reinterpretation of more than 2500 subsurface data consisting of geoelectric and borehole prospecting undertaken at mount etna allows reconstructing the contour map of the sedimentary basement this reconstruction highlights a complex asymmetric topography due to the inhomogeneous long term updoming of the region and the interrelationship between the development of the drainage network and flank instability these different processes have produced a major morphological difference between the eastern sector characterised by a 17 km wide horseshoe shaped depression and the other flanks formed by palaeovalleys the origin of the wide horseshoe shaped depression can be attributed to the large scale flank instability processes involving the entire continental margin in the etna offshore this depression of the etna basement was generated by a series of coalescent landslides before the beginning of the eruptive activity of the timpe phase more than 220 ka ago this wide depression is the main cause of the flank instability that produced the gravitational slope failures of the valle del bove about 10 ka ago regarding mt etna s geometry we have estimated a total volume of about 532 km 3 that was emplaced during the past 330 ka resulting in an average rate of volcanic output of 0 0016 km 3 a the reconstruction of the temporal variation of the average eruptive rate highlights a drastic increase of volcanism during the last 100 ka in response to the gradual stabilization of the plumbing system in the etna region that led to the build up of the composite stratovolcano structure the data presented in this paper represent the state of knowledge of the sedimentary basement of etna which can be used for future studies aimed at developing a detailed understanding of the deep structure of the volcano s unstable flanks

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

high resolution aeromagnetic anomaly map of mount etna volcano southern italy abstract a high resolution aeromagnetic survey of mount etna volcano was carried out by the airborne geophysics science team of istituto nazionale di geofisica e vulcanologia ingv aimed at producing the most detailed magnetic anomaly map existing so far for this area two datasets of the total intensity of the earth s magnetic field were collected at different altitudes to take into account the huge topographic variations of etna volcano that reaches elevations above 3300 m asl one level was flown at the altitude of 2200 m whereas a second one over the central part at about 3500 m of altitude since the region is characterized by a large presence of strongly magnetized volcanic products the survey was carried out acquiring profile lines only in order to optimize the resources from the residual magnetic anomaly analysis we inferred two main trending lineaments 35 n and 0 n that are related to regional tectonic stress field and we interpret the main magnetic anomaly as the effect of thickness variation of magnetized volcanic products due to the complex pre volcanic basement morphology of etna

the cryptic summit graben of mt etna volcano abstract previous studies have inferred the likelihood of a summit graben at mt etna but until now there has been no direct observation or evidence of such a feature here the results of 43 years of deformation measurements at the summit are reported in which the presence of an actively forming north south graben 1 5 km wide is evident with a maximum subsidence of nearly 4 m in 43 years its bounding faults have in most places been hidden by the eruptive deposits of 190 summit eruptions but horizontal measurements across these faults show a maximum value of nearly 9 m of east west extension most of the subsidence and extension has taken place during the injection of eruption feeder dykes with extreme values for single events of 1 7 m subsidence during the injection of the 2002 2003 dyke and 4 4 m extension across the 1989 feeder dyke but subsidence and extension continues to take place slowly during inter eruptive periods analogue modelling indicates that its origin is probably a consequence of the gravitational spreading and downslope sliding of the etna edifice on its clay rich substrate aided by magmatic pressure from feeder dykes intruded into individual faults and by downward pressure from surface loading of erupted lava this study clarifies the way in which the mechanism of gravitational spreading is maintained throughout the lifetime of this and other spreading volcanoes and rifts on earth and mars

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