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

field evidence for flank instability basal spreading and volcano tectonic interactions at mt cameroon west africa the mt cameroon volcano is the highest and most active volcano of the cameroon volcanic line little geological information is available for improving the understanding of the structure of this large volcanic system and its relationship to regional tectonics after reviewing the tectonic evolution of the region the analysis of a digital elevation model and results from a field campaign dedicated to mapping geological structures in the summit area and at the se base of mt cameroon are presented mt cameroon is a lava dominated volcano with long steep over 30 flanks it is elongate parallel to its well defined rift zone the summit plateau is bordered by 10 m high cliffs formed by summit subsidence along normal faults geological profiles were measured along rivers cutting through a topographic step at the se base of mt cameroon this step is associated with deformed miocene sediments from the douala basin that are overlain by volcanic products weak sediments of this area are deformed by 050 060 and 020 030 trending asymmetrical folds verging toward the se and thrusts faults related to the spreading of the volcano over its mechanically weak substratum combined remote sensing and field observations suggest that spreading is accommodated by summit subsidence and flanks sliding both slow spreading movements and catastrophic collapses of the steep flanks are interpreted to result from complex interactions between the growing edifice repeated dyke intrusions the weak sedimentary substratum and tectonic structures

volcano tectonic controls and emplacement kinematics of the iriga debris avalanches philippines mt iriga in southeastern luzon is known for its spectacular collapse scar that was possibly created in 1628 ad by a 1 5 km3 debris avalanche the debris avalanche deposit dad covered 70 km2 and dammed the barit river to form lake buhi the collapse has been ascribed to a non volcanic trigger related to a major strike slip fault under the volcano using a combination of fieldwork and remote sensing we have identified a similar size older dad to the southwest of the edifice that originated from a sector oblique to the underlying strike slip fault both deposits cover wide areas of low waterlogged plains to a distance of about 16 km for the oldest and 12 km for the youngest hundreds of metre wide and up to 50 m high hummocks of intact conglomerate sand and clay units derived from the base of the volcano show that the initial failure planes cut deep into the substrata in addition large proportions of both dad consist of ring plain sediments that were incorporated by soft sediment bulking and extensive bulldozing an ignimbrite unit incorporated into the younger dad forms small less than 5 m high discrete hummocks between the larger ones both debris avalanches slid over water saturated soft sediment or ignimbrite and spread out on a basal shear zone accommodated by horst and graben formation and strike slip faults in the main mass the faults are listric and flatten into a well developed basal shear zone this shear zone contains components from the substrate and has a diffuse contact with the intact substrata long transport normal ridges in the distal parts are evidence of compression related to deceleration and bulldozing the collapse orientation and structure on both sectors and dad constituents are consistent with collapse being a response to combined transtensional faulting and gravity spreading iriga can serve as a model for other volcanoes such as mayon that stand in sedimentary basins undergoing transtensional strike slip faulting

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

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

analytical and 3 d numerical modelling of mt etna italy volcano inflation summary since 1993 geodetic data obtained by different techniques gps edm sar levelling have detected a consistent inflation of the mt etna volcano the inflation culminating with the 1998 2001 strong explosive activity from summit craters and recent 2001 and 2002 flank eruptions is interpreted in terms of magma ascent and refilling of the volcanic plumbing system and reservoirs we have modelled the 1993 1997 edm and gps data by 3 d pressurized sources to infer the position and dimension of the magma reservoir we have performed analytical inversions of the observed deformation using both spheroidal and ellipsoidal sources embedded in a homogeneous elastic half space and by applying different inversion methods solutions for these types of sources show evidence of a vertically elongated magma reservoir located 6 km beneath the summit craters the maximum elevation of topography is comparable to such depth and strong heterogeneities are inferred from seismic tomography in order to assess their importance further 3 d numerical models employing source parameters extracted from analytical models have been developed using the finite element technique the deformation predicted by all the models considered shows a general agreement with the 1993 1997 data suggesting the primary role of a pressure source while the complexities of the medium play a minor role under elastic conditions however major discrepancies between data and models are located in the se sector suggesting that sliding along potential detachment surfaces may contribute to amplify deformation during the inflation for the first time realistic features of mt etna are studied by a 3 d numerical model characterized by the topography and lateral variations of elastic structure providing a framework for a deeper insight into the relationships between internal sources and tectonic structures

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

a fractal approach to the temporal distribution of microseismicity at the low eastern flank of mt etna during 1989 1994 abstract seismicity affecting the low eastern flank of mt etna shows clustering in time we analysed a catalog of microearthquakes recorded by the four stations of the osservatorio sismologico di protezione civile di acireale during the period 1989 1994 in general a strong deviation from periodic and random distribution was found the temporal clustering is scale invariant and a fractal dimension can be derived to characterize it fractal dimensions seem to be correlated to the beginning of two major eruptions

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

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

the volcano tectonic evolution of concepcion nicaragua we describe the evolution of concepcion volcano by integrating regional geology eruptive activity morphology stratigraphy petrology structure and active deformation data this nicaraguan volcano is set close to the back limb of the northwest trending tertiary rivas anticline a regional structure that bounds the southwest side of lake nicaragua concepcion rises 1 600 m above a 1 km thick sequence of quaternary lacustrine mud stones there is no record of volcanism in the lake prior to concepcion in addition the only nearby volcano maderas volcano has not deposited material on concepcion because of the trade winds thus concepcion and made ras too can be considered as pristine volcanic environments unaffected by other centres a topographic rise forms an annulus 20 km in diameter around the cone the rise is created by thrust related folds at the western base where the trade winds have accumulated a thick sequence of tephra and by mud diapirs at the eastern base where only lake mudstones are present four magmatic eruptive episodes exist in the stratigraphic record the first begins with primitive low alumina basalt and subsequently evolves to dacitic compositions the following three episodes begin with high alumina basalts and evolve only to silicic andesites the occurrence of the high alumina basalt after the first episode is indicative of crystal fractionation at lower crustal depths the first episode may be associated with a compressive phase of volcano evolution in this phase the edifice load compresses substrata allowing a longer magma residence time and differentiation in a shallow reservoir possibly located at the density contrast between the lake sediments and the tertiary flysch during the next three episodes the weak sediments below the volcano started to rupture and yield under its increasing load beginning a thrusting diapiring phase of volcano evolution because of outward thrusting vertical and horizontal stresses above the chamber were reduced allowing magma to erupt more easily and to reach a lesser degree of evolution if we consider the future evolution of concepcion the differentiation in the shallow reservoir has probably generated a cumulitic complex which eventually will start to deform and spread beginning another this time plutonic spreading phase this phase which may be beginning now could allow less evolved magmas to be erupted again four components influence the phases of volcano evolution 1 the regional geology that is the boundary condition of the environment 2 the substrata rheology that controls deformation 3 the load of the volcanic edifice and 4 the magma which provides the input of mass and energy our model of volcanic evolution suggests that concepcion is a complex geologic environment the volcanic activity tectonics and hazards can only be constrained through a complete knowledge of the many components of this environment

the valle del bove mount etna its origin and relation to the stratigraphy and structure of the volcano abstract the valle del bove is a major horseshoe shaped depression some 5 km in diameter and over 1000 m deep carved into the eastern flank of mount etna volcano the origin of the valle del bove has been a subject of debate for over a century but recent models relate it to the collapse of the ancient trifoglietto ii centre of etna either by caldera collapse or phreatomagmatic explosive activity careful morphological analysis shows the valle del bove to have formed after the post trifoglietto ii ellittico and leone centres and therefore to be considerably younger than the trifoglietto ii centre it has also been argued that the pyroclastic deposits that occur on the flanks of the volcano in close spatial relationship with the valle del bove were produced by the same event these pyroclastics are divided on the basis of age and composition into two groups the upper and lower tephra deposits the stratigraphy petrology and radiocarbon date of the lower tephra deposits indicate a trifoglietto ii age at least 20 000 years before the formation of the valle del bove the upper tephra deposits have a strong phreatomagmatic character and are closest in age to the valle del bove there is no evidence however to link them with its formation morphological study shows the valle del bove to consist of a series of coalescing scallops indicative of formation by landsliding the material removed by slope failure and subsequent fluvial transport followed a valley to the coast where it forms a fan shaped accumulation the chiancone consisting of volcaniclastics of fluvial and mudflow origin it is argued that the valle del bove did not result from simple caldera collapse but formed from a series of collapses caused by gravitational slope failure the chiancone is considered to be the product of this collapse

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

experimental modelling of thin skinned shortening around magmatic intrusions magmatic intrusions can trigger thin skinned compression of the adjacent sedimentary cover by three processes a gravity gliding away from the topographic dome resulting from the ascending magma b fluid push from the rear resulting from forceful intrusion then lateral spreading of the magma and c increased loading by volcanic accumulation the applicability of the first two mechanisms gravity gliding and fluid push was tested using dynamically scaled experiments model results help to elucidate the kinematics and structural evolution of thrusts and folds formed by such processes and determine which geological parameters control the deformation style the results show that the presence of a weak layer within the sedimentary overburden is essential to form thrust and fold belts around the intrusion experiments suggest that although gravity gliding can dominate the early stages of deformation most of the deformation is caused by lateral spreading of the fluid magma pushing the adjacent sedimentary rocks models also suggest that true laccoliths can form only if the sedimentary section comprises a basal low viscosity stratum comparison with natural examples allows the evaluation of the applicability of experimental results

the role of transcurrent intra arc tectonics in the configuration of a volcanic arc summary field investigations show that plio quaternary mexican and quaternary ecuadorian volcanic arcs are coeval with intra arc transcurrent or transtensional tectonics with motions along faults parallel or subparallel to the arc this relationship can also be observed in the quaternary kamchatka arc these arcs have an anomalously wide distribution of volcanic centres which cannot be explained simply by a low dip in the subducting lithosphere comparison with the intra arc tectonics and geometry of other quaternary arcs reveals that strike slip fault zones parallel to the arc favour magma rising in a broad surficial zone and may channel magma feeding mainly huge stratovolcanoes

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

climate forcing of volcano lateral collapse evidence from mount etna sicily in this study we present evidence for early holocene climatic conditions providing circumstances favourable to major lateral collapse at mount etna sicily the volcano s most notable topographic feature is the valle del bove a 5 x 8 km cliff bounded amphitheatre excavated from the eastern flank of the volcano its origin due to prehistoric lateral collapse is corroborated by sturtzstrom deposits adjacent to the amphitheatre s downslope outlet but the age nature and cause of amphitheatre excavation remain matters for debate cosmogenic 3 he exposure ages determined for eroded surfaces within an abandoned watershed flanking the valle del bove support channel abandonment ca 7 5 ka bp as a consequence of its excavation in a catastrophic collapse event watershed development was largely dictated by pluvial conditions during the early holocene which are also implicated in slope failure a viable trigger is magma emplacement into rift zones in the eastern flank of a water saturated edifice leading to the development of excess pore pressures consequent reduction in sliding resistance detachment and collapse such a mechanism is presented as one potential driver of future lateral collapse in volcanic landscapes forecast to experience increased precipitation or melting of ice cover as a consequence of anthropogenic warming

volcano stratigraphy and physical characterization of the san mateo pomez unit cerritos member temascalcingo volcano central mexico abstract the temascalcingo volcano is a dacitic stratovolcano located at the eastern part of the acambay graben a tectonic basin in the central sector of the trans mexican volcanic belt tmvb which is an active mostly calc alkaline volcanic arc that crosses mexico from the pacific ocean to the gulf of mexico this study characterises the explosive activity of the san mateo pumice eruption that is the most recent and largest paroxysmal episode of this volcano and the last unit of the cerritos member indeed this eruption is associated with an undated debris avalanche event consisting of a major sector collapse developed on the western flank of the volcano stratigraphic data suggest a highly explosive eruption that generated a relatively thick up to 10 m and widespread pumice fallout deposit trending to the ne and an aerial distribution of at least 100 km2 this subplinian type eruption of vei 4 lasted about 9 h and produced a plume height up to 12 km above the vent i e 14 km above sea level this type of explosive eruption is relatively common in the tmvb so a comprehensive geological study with the corresponding numerical simulations like the one that was carried out contributes to the understanding of the explosive volcanism of modest size stratovolcanoes that are common in the tmvb

fault propagation folds induced by gravitational failure and slumping of the central costa rica volcanic range implications for large terrestrial and martian volcanic edifices long sublinear ridges and related scarps located at the base of large volcanic structures are frequently interpreted as normal faults associated with extensional regional stress in contrast the ridges bordering the central costa rica volcanic range ccrvr are the topographic expression of hanging wall asymmetric angular anticlines overlying low angle thrust faults at the base of the range these faults formed by gravitational failure and slumping of the flanks of the range due to the weight of the volcanic edifices and were perhaps triggered by the intrusion of magma over the past 20 000 years the thrust fault underlying alajuela ridge rises from a depth of 700 m at a dip of 15 over a distance of a few kilometers it ramps up at 600 m depth on a 40 slope and terminates in the axis of the forward syncline 400 m below the surface the hanging wall of this fault has been thrusted about 200 m away from the volcanic range axis thrusting on the lower flanks of the ccrvr is compensated by extension on the range axis with formation of summit grabens shallow seismicity in the volcanic range suggests that thrusting is still active we postulate that at kilauea volcano hawaii the gravity and magma induced slumping of the southern flank on low angle thrust faults generates hanging wall anticlines similar to those observed in costa rica these anticlines are hypothesized to occur along the base of the volcano where the thrust faults ramp up toward the sea bottom ridges and scarps between 2000 and 5000 m below sea level are interpreted as the topographic expression of these folds we further suggest that the scarps of the ccrvr and kilauea are valid scaled terrestrial analogs of the perimeter scarp of the martian volcano olympus mons we suggest that the crust below olympus mons has failed under the load of the volcano triggering the radial slumping of the flanks of the volcano on basal thrusts the thrusting would have in turn formed the anticlinal ridges and scarps that surround the edifice the thrusting seems to be preferential toward the northwest and southeast and a northeast southwest rift zone seems to have developed perpendicular to the regional topographic gradient the thrust faults may extend all the way to the base of the martian crust about 40 km and they may have been active until almost the end of the volcanic activity we suggest that gravitational failure and slumping of the flanks of volcanoes is a process common to most large volcanic edifices in the ccrvr and at kilauea this slumping of the flanks is a slow intermittent process but it could evolve to rapid massive avalanching leading to catastrophic eruptions thus monitoring of uplift and displacement of the folds related to the slump tectonics could become an additional effective method for mitigating volcanic hazards

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

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

emplacement mechanisms of contrasting debris avalanches at volcan mombacho nicaragua provided by structural and facies analysis we study the lithology structure and emplacement of two debris avalanche deposits dads with contrasting origins and materials from the quaternary holocene mombacho volcano nicaragua a clear comparison is possible because both dads were emplaced onto similar nearly flat 3 slope topography with no apparent barrier to transport this lack of confinement allows us to study in nature the perfect case scenario of a freely spreading avalanche in addition there is good evidence that no substratum was incorporated in the events during flow so facies changes are related only to internal dynamics mombacho shows evidence of at least three large flank collapses producing the two well preserved debris avalanches of this study one on its northern flank las isletas directed northeast and the other on its southern flank el crater directed south other south eastern features indicate that the debris avalanche corresponding to the third collapse la danta occurred before las isletas and el crater events the materials involved in each event were similar except in their alteration state and in the amount of substrata initially included in the collapse while el crater avalanche shows no signs of substratum involvement and has characteristics of a hydrothermal weakening related collapse the las isletas avalanche involves significant substratum and was generated by gravity spreading related failure the latter avalanche may have interacted with lake nicaragua during transport in which case its run out could have been modified through a detailed morphological and structural description of the mombacho avalanches we provide two contrasting examples of non eruptive volcanic flank collapse we show that remarkably even with two distinct collapse mechanisms the debris avalanches developed the same gross stratigraphy of a coarse layer above a fine layer this fine layer provided a low friction basal slide layer whereas dad layering and the run outs are roughly similar the distribution of structures is different and related to lithology las isletas has clear proximal faults replaced distally by inter hummock depressions where basal unit zones are exhumed whereas el crater has faults throughout but the basal layer is hidden in the distal zone hummocky forms depend on material type with steep hummocks being formed of coherent lava units and low hummocks by matrix rich units in both avalanches extensional structures predominate the upper layers exclusively underwent longitudinal and lateral extension this is consistent with evidence of only small amounts of block to block interactions during bulk horizontal spreading the base of the moving mass accommodated transport by large amounts of simple shear we suggest that contractional structures and inter block collisions seen in many other avalanches are artifacts related to topographic confinement

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

changes in the stress regime and displacement field in the interior of mount etna deduced from surface observations abstract if measurements of all three components of displacement at the surface of a mountain are available the stress strain relations of the theory of linear elasticity can be used as a simple approximation to obtain insight into changes that take place on a relatively short time scale in its interior if such a simple elastic model is employed interpolated values derived from these data can be used as boundary conditions at the surface of the mountain and then integrated downwards this procedure yields values for the internal displacements that take place from year to year from which changes in the internal stress distributions can be calculated the location of regions in which the solutions obtained by this approach give inappropriate results indicate where the assumptions of linear elasticity do not hold and so provide further evidence in the task of determining internal structure measurements are available from 1987 to 1992 for all three components of displacement at a substantial number of points on the surface of mount etna in intervals of not more than a year and the method was applied to them to obtain evidence of regions in the interior of the volcano deserving further study

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

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

evidence for magma carbonate interaction beneath syrtis major mars 1 we used three methods spectral index mapping linear spectral mixture analysis and factor analysis and target transformation to determine if carbonate decomposition products including lime cao periclase mgo portlandite ca oh 2 and brucite mg oh 2 are present on the surface of mars using an expanded spectral library that includes decomposition products of calcite and magnesite we deconvolved a binned emissivity data set from the mars global surveyor thermal emission spectrometer mgs tes the deconvolution model indicates that anhydrous carbonates are not present at kilometer scales above the tes detection limit however carbonate decomposition products may be present at or above the tes detection limit in northeast syrtis major and several other small regions on mars the model results are supported by spectral index mapping and factor analysis and target transformation of tes data in this region the volcanic setting of the detections may indicate the interaction of syrtis major lavas with subsurface carbonates or alternatively the eruption of carbonate bearing lavas that were subsequently devolatilized by impacts or later lava flows

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

remote sensing of damavand volcano iran using landsat imagery implications for the volcano dynamics abstract remote sensing techniques are applied to retrieve land surface temperature lst radiative heat flux rhf geothermal heat flux ghf and to map hydrothermal alteration zones around the damavand stratovolcano iran landsat enhanced thematic mapper plus etm day and nighttime images are used and merged to available geological data to identify thermal anomaly areas rhf is determined using the stefan boltzmann equation after preprocessing geometric radiometric and atmospheric correction and processing emissivity calculation and lst retrieval of thermal infrared bands in order to estimate ghf from daytime image solar radiation and albedo maps are generated to minimize these effects the ghf values are derived from nighttime image using the background subtraction technique using boolean operation only those pixels with the ghf values greater than 30 w m 2 obtained from daytime image and the ghf values greater than 10 w m 2 estimated from nighttime image are identified as thermal anomalies the geothermal areas are identified by combining the thermal anomaly map and other geological information thermal anomalies have close spatial correlation to faults thermal springs and high heat flow measurements from subsurface data and lithology some of the thermal anomalies and hydrothermal alteration areas also overlap active deformation areas this suggests role of heat and hydrothermal alteration on flank instability processes the thermal anomaly areas show an arc shaped pattern this pattern and the concentration of higher ghf areas in the eastern sector of the volcano are consistent with a release of fluids in a transition zone between a transpressional and a transtensional tectonic regime the combination of thermal infrared data with other geological information layers can be used to detect geothermal areas as well as to analyze the complex relationships among geothermal activity active tectonics and gravity instability processes on volcanoes

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

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

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

relevance of the chiancone volcaniclastic deposit in the recent history of etna volcano italy abstract the chiancone ch deposit is a volcaniclastic fan on the eastern flank of mt etna it crops out from the exit of the depression of the valle del bove 350 m a s l to the sea in an area which covers about 40 km 2 with a maximum thickness of about 30 m and a slope of 3 4 towards the east the total volume of the deposit is unknown because the base does not crop out but some geophysical data suggest a maximum thickness of about 300 m leading to an estimated maximum volume of about 12 km 3 which is comparable to the volume of the valle del bove vdb since this horseshoe shaped valley is considered to be the ch s source region a study of this deposit may allow an understanding of the mechanisms responsible for the origin of the vdb on the basis of stratigraphic and sedimentary studies we divided the ch sequence into two main parts the basal portion lithofacies 1 is visible only along the coast and has a width of about 6 5 km a thickness of 1 4 m and appears as an indurated horizontal deposit with a flat locally eroded upper surface we consider lithofacies 1 as a huge mud flow which may be associated with an important eruptive event the upper part lithofacies 2 5 is mainly composed of fluvial beds 63 of measured thicknesses that we attribute to events reworking the previously deposited layers the less abundant 23 very coarse grained lenses were caused by fluvial floods thin and discontinuous pyroclastic layers are accidentally 3 interbedded into the sequence the upper portion of the ch sequence is up to 30 m thick and formed after 7590 130 yr b p as established by our new radiocarbon dating when the chemical data obtained on lava blocks sampled from lithofacies 1 4 are compared with products of older eruptive centres it may be argued that the major direction of transport occurred from west to east and involved erosion of those old eruptive centres which were located in the central northern part of the vdb our data suggest the occurrence of an important eruptive event at least 7590 yr b p which may be associated with the deposition of the huge basal mud flow this event was followed by fluvial reworking and deposition at a rate of at least 4 mm yr extending this deposition rate to the whole thickness of the ch deposit 300 m would imply a maximum age of 80 000 70 000 yr b p however the deposition rate of the hidden part of the ch deposit was almost certainly much greater than 4 mm yr implying an age for the onset of the ch sequence significantly less than 80 000 70 000 yr b p this very strongly suggests that the trifoglietto volcano which is older than 80 000 yr was not involved in the opening of the vdb and the formation of the ch deposit it also suggests that the first event of the opening of the vdb was much older than the 5000 yr proposed by some authors it is possible that the ch was deposited during or slightly later than the life span of the ellittico volcano 40 000 15 000 yr b p

conditions favouring catastrophic landslides on tenerife canary islands catastrophic failures of volcano flanks represent one of the most hazardous geological phenomena these immense mass movements originate either by increasing the destabilizing forces driving forces or by reducing the strength of the materials involved or both the study of large volcanic landslides on tenerife suggests that the presence of weak residual soils palaeosols in combination with the pre existence of deep narrow canyons created by fluvial erosion have played a fundamental role in the initiation of large scale sector collapses of the volcanic edifice regardless of the triggering mechanism considered residual soils strongly reduce the material strength during undrained loading while pre existing canyons control the lateral limits of the landslide the existence of a wet climate in some sectors of the island favours these circumstances

ground deformation monitoring at mt etna evidence for dyke emplacement and slope instability ground deformation monitoring at mount etna has successfully enabled the sub surface paths of two shallow feeder dykes to be traced and their dimensional parameters depths and departures from the vertical to be constrained determinations of horizontal movement have recorded the displacement by 3 6 m maximum of a rim segment of the valle del bove flank caldera due to dilation associated with dyke emplacement adjacent to the rim over the period 1981 to 1989 small scale collapse along this rim segment associated with the opening of the 1989 fissure points to increasing slope instability and highlights the potential for major failure and debris avalanche generation

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

early deformations at a submarine compressive front the quaternary catania foredeep south of mt etna sicily italy abstract in the catania foredeep south of mt etna oil drilling has revealed the existence at depth of an allochthonous complex emplaced during the middle quaternary at the surface outcropping middle quaternary marine marly clays and sands display complex deformations which are partly synsedimentary and which can be correlated with the emplacement of this allochthonous complex most of these deformations are thought to result from gravitational gliding of slope sediment apron this process probably facilitated by high pore pressure would be in particular the cause of a semi penetrative shear deformation with an eastward vergence in the clays thus our study rules out the classical view of a shallow pre etnean gulf that was steadily filled in before emerging some 400 000 to 300 000 years ago this particular example of neotectonics shows the precocity and complexity of deformations occurring in sediments deposited along the compressive margin of a foreland basin or similarly at an accretionary prism front

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

geochemical investigations applied to active fault detection in a volcanic area the north east rift on mt etna sicily italy geochemical investigations were performed on the northeast rift of mt etna a prominent volcanic structure of this volcano low temperature fumaroles were found on the upper part of this area and the isotopic compositions of c co2 and he suggest a likely magmatic origin of the emitted gases on the contrary very low degassing was found in the lower part of the ne rift with co2 concentrations generally very close to those in air this pattern is probably due to sealing of the eruptive fissures by the repeated injections of magma solidified into dikes and by consequent shallow hydrothermal alteration of the fissured rocks due to residual magma degassing high soil co2 concentrations were also found in an elongated area parallel to the ne rift and located immediately to the east of it the geometry of these anomalies suggests the existence of several hidden faults sub parallel to the ne rift and likely connected to the pernicana fault system this latter structure seems to merge with the ne rift at the altitude where the fumarole emissions are located the hidden structures together with the pernicana system and the ne rift represent the western and northern boundaries of a large eastward collapsing sector of mt etna

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

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

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

time seismicity patterns affecting local and regional fault systems in the etna region preliminary results for the period 1874 1913 an analysis of time correlation function and fractal dimension has been performed on the seismic activity that affected mt etna volcano italy during 1874 1913 in order to investigate the behaviour of some suspected magma controlling regional fault systems the time span considered has been characterized by intense seismic and volcanic activity with eight flank eruptions mainly occurring along the same north south fissure system the analysis of historical sources has been used to revise and improve the seismic catalogue all macroseismic information has been reinterpreted using the new european macroseismic scale 1998 ems the results contribute to the definition of the seismic behaviour of some regional fault systems relevant to the geodynamics of the area and provide some insights into the dynamic processes of mt etna volcano

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

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

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

application of gravity and deep dipole geoelectrics in the volcanic area of mt etna sicily abstract the structural pattern of the basement of the mt etna volcano is studied by combining results from new gravity and deep dipole geoelectric field data at first the bouguer map was separated into regional and residual contour maps by a 50 km cut off wavelength then by the geoelectric interpretation n s and e w resistivity cross sections were elaborated which were used as guidelines for modelling gravity residuals after observing a close correspondence between bouguer anomalies and resistivity classes by a trial and error adjustment to the relationship between resistivity and density a 3 d block model of the basement was finally constructed which consistently matched with both gravity and geoelectric information content two main conclusions emerged from the combined interpretation the first is the presence of diffuse inhomogeneities in the upper portion of the basement down to an average depth of 2 km below sea level in contrast with the regularity of the explored underlying portion the second is the absence of geophysical markers suggesting the existence of a large magmatic chamber down to about 3 km below sea level

the geometry of volcano flank terraces on mars abstract flank terraces are subtle expansive structures on the slopes of many large martian shield volcanoes several terrace formation hypotheses including self loading lithospheric flexure magma chamber tumescence volcano spreading and shallow gravitational slumping have been suggested terraces are not readily visible on photogeological data consequently terrace geometry has not yet been comprehensively described terrace provenance therefore is poorly understood we used three dimensional mars orbiter laser altimeter mola data to characterise the geometry of these elusive structures with a view to understanding better the role that flank terraces play in the tectonic evolution of volcanoes on mars terraces have a broad convex upward profile in section and a systematic fish scale imbricate stacking pattern in plan they are visible at all elevations on at least nine disparate martian volcanoes terrace like features also occur on three shield volcanoes on earth an observation not recorded before analysis of a suite of morphometric parameters for flank terraces showed that they are scale invariant with similar proportions to thrust faults on earth we compared predicted formation geometries to our terrace observations and found that only lithospheric flexure can fully account for the morphology distribution and timing of terraces as a volcano flexes into the lithosphere beneath it its upper surface will experience a net reduction in area resulting in the formation of outward verging thrusts we conclude therefore that flank terraces are fundamental volcanotectonic structures that they are the surface expressions of thrust faults probably formed by lithospheric flexure and that they are not restricted to mars

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

control of rock rheology on deformation style and slip rate along the active pernicana fault mt etna italy abstract the already known part of the active left lateral strike slip pernicana fault on the eastern flank of mt etna volcano has a holocene high slip rate of 1 5 2 7 cm yr but its surface trace abruptly disappears eastward approaching the lower slope of the volcano using geological geomorphological and structural surveys we found that the pernicana deformation zone extends 8 km further to the east beyond this point through a different mechanism as the thickness of the volcanic pile decreases the single e w to ese striking main fault plane gives way to a set of faults arranged in a splay structure which partitions the fault motion here slip rates are 0 4 to 1 4 cm yr on each fault further east where the lava succession is very thin and unfaulted we suggest that lavas are decoupled from plastic deforming sub etnean clay deposits which absorb the strain or that lavas have a too low mass to slide on the very lowest slope of the volcano i e further east lavas are once again thicker and the pernicana deformation zone behaves at the surface once again in a brittle manner locally known as the fiumefreddo fault with a low slip rate of

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

debris avalanche deposits of the milo lahar sequence and the opening of the valle del bove on etna volcano italy previously undescribed debris avalanche deposits occur in two locations downslope from the open end of the valle del bove these outcrops comprise unstratified ungraded deposits of metre scale lava blocks in a matrix of weathered and fractured lava clasts the avalanche deposits are unconformably overlain by matrix to clast supported conglomerates representing debris flow and interbedded fluvial deposits that constitute most of the milo lahar sequence we present evidence that the milo lahar sequence which crops out just at the exit of the valle del bove formed during the opening and enlargement of this depression the presence of the avalanche deposits at the base of the milo lahar sequence indicates that catastrophic landslides were involved in the formation of the valle del bove the composition of lavas in the debris avalanche deposits is similar to that of most of the ellittico volcanic sequence exposed along the northern wall of the valle del bove radiocarbon dates of 8400 and 5300 years bp from the base and top respectively of the debris flow sequence indicate that the milo lahars are correlative with the exposed part of the chiancone deposit the basal lahars of the chiancone which contain lava blocks whose compositions partially overlap that of blocks in the avalanche deposits may have formed by water concentration in the distal end of the avalanche causing transformation to debris or alternatively by reworking of the avalanche deposit

volcanic edifice weakening via devolatilization reactions summary edifice instability that can result in catastrophic flank collapse is a fundamental volcanic hazard the subvolcanic basement can encourage such instability especially if it is susceptible to mechanical weakening by devolatilization reactions near magmatic temperatures for this reason understanding how the physical and chemical properties of representative lithologies deteriorate at high temperatures is potentially highly relevant for volcanic hazard mitigation this is particularly true for sedimentary rock commonly found underlying volcanic edifices worldwide that undergo rapid deterioration even under modest temperatures therefore here we present the first experimental study of devolatilization reactions induced by magmatic temperatures on sedimentary rock comprising a subvolcanic basement our results show that for a marly limestone representative of the basement at mt etna devolatilization reactions namely the dehydroxylation of clay minerals and the decarbonation of calcium carbonate result in a dramatic reduction of mechanical strength and seismic velocities these temperature driven reactions can promote volcanic instability at stresses much lower than previously estimated

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

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