do transcurrent faults guide volcano growth the case of nw bicol volcanic arc luzon philippines this paper shows that although volcanoes can be aligned along transcurrent faults their growth can in reality be controlled by secondary structures that have a different orientation and kinematics assessing the relationships between local structures and volcano growth can be very useful for the evaluation of volcanic hazards and for economic purposes such as geothermal and hydrogeological exploration in the north western bicol volcanic arc luzon philippines the quaternary labo and caayunan volcanoes are aligned with the nw striking transcurrent philippine fault system they are exceptional examples of composite volcanoes mostly comprising lava domes where regional tectonic structures and hydraulic radial fracturing have alternated to control volcano growth field data and analogue modelling demonstrate that apical depressions affecting the domes reflect the geometry of magma feeding fractures these data together with alignments of domes and hot springs and other structural information suggest that magma rose at depth along the nw striking transcurrent faults but that in the uppermost crust magma rose along ne striking fractures parallel to the greatest principal stress

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

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

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

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

geometry and kinematics of the fault systems controlling the unstable flank of etna volcano sicily abstract an updated tectonic framework of etna s unstable flank has been defined as a result of multidisciplinary analyses carried out by integrating geological and geophysical data the different typologies of datasets have been analyzed and correlated in order to constrain the geometry and kinematics of the fault systems controlling the unstable flank of etna volcano and to better understand their complex relationship with the offshore morphostructures of the continental margin in particular we have considered as the main structural elements the following four fault systems pernicana ragalna tremestieri trecastagni and timpe slip rates and kinematics have been estimated in both long and short terms respectively from geological and seismotectonic geodetic data data integration has allowed defining five kinematic domains in the sliding flank of etna 1 the ne block bordered by the pernicana fault and characterised by the highest deformation velocities ground velocity progressively diminishes toward south with a clockwise rotation of the vectors defining 2 the block embracing the central part of the timpe system 3 the giarre wedge 4 the medium east block bounded by the s tecla and trecastagni faults and 5 the se block bordered by the hidden belpasso ognina tectonic lineament the dynamics of these blocks takes place through discontinuous movements sudden short term accelerations related to the magma intrusion are superimposed to a fairly constant mid term ese sliding the proposed comprehensive model of the unstable flank provides the basic input parameters for applying analytical models to flank dynamics of etna volcano

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

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

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

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

coseismic displacements and creeping along the pernicana fault etna italy in the last 17 years a detailed study of a tectonic structure on a volcano abstract the pernicana fault is a tectonic fault located on mt etna sicily movements across this structure have been monitored over the last 17 years by a levelling network operated by the osservatorio vesuviano during the monitoring period the network has recorded coseismic displacements associated with earthquakes of magnitude 4 5 as well as aseismic displacements we present a detailed analysis of the displacement data aimed at modelling the geometry and mechanism of this fault as well as the size and mechanisms of individual earthquakes we use for interpreting the displacement data two types of inverse methods the first is able to determine from ground deformation data the geometry mechanism and location of a system rectangular faults with homogeneous dislocation the second finds for a fixed fault system geometry the heterogeneous slip distribution giving the best fit to the data the total recorded displacements during the last 17 years are well described by a single homogeneous rectangular normal fault with dislocation and size corresponding to a magnitude 5 7 earthquake thus revealing intense dynamics along such a fault coseismic displacements for individual earthquakes of considerable magnitude account for about 30 of the total deformation when interpreted in terms of an homogenous slip fault as inferred from total deformation some aspects of the data are not well explained thus calling for heterogeneous slip models it is hence possible with a certain approximation to distinguish the slip distributions associated with individual earthquakes from the almost homogeneous slip resulting from the sum of coseismic and aseismic movements the inferred seismic moments for the two larger earthquakes that occurred along this fault are considerable higher than reported in seismic bulletins about 1 degree of magnitude the results obtained here support the important role of levelling data for the detailed study of a peculiar kind of tectonic structure on a volcano aimed at understanding the complex interaction between volcano dynamics and induced movements along well defined structures

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

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

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

regional and local tectonics at erta ale caldera afar ethiopia erta ale volcano lies along the on shore red sea rift northern afar ethiopia separating the nubia and danakil plates erta ale has a nnwesse elongated caldera with a subvertical rim scarp hosting a lava lake structural field work was aimed at defining the deformation pattern around the caldera the caldera consists of along rim and across rim structures resulting from local and regional maximum extension wneesw stress fields respectively these structures cross cut each other at high angles suggesting that the two stress fields remain distinct each prevailing during rifting or caldera collapse the local along rim extensional fractures are gravity driven structures that formed due to the retreat of the caldera wall after collapse and are confined to the region of caldera subsidence the across rim structures are mainly located to the n and s of the caldera where they form rift zones each accommodating a similar amount of extension w6 3 m but displaying different trends and extension directions analogue models of interacting fractures are consistent with the southern rift being representative of the regional fault kinematics while the northern rift is a local perturbation resulting from the interaction between two right stepping rift segments along the erta ale range 2006 elsevier ltd all rights reserved

seismological features of the pernicana provenzana fault system mt etna italy and implications for the dynamics of northeastern flank of the volcano abstract the pernicana provenzana fault system is one of the most active tectonic systems of mt etna and it plays an important role in the dynamic of the eastern flank of the volcano earthquakes occurring close to this structural trend have reached magnitudes up to 4 2 sometimes with coseismic surface faulting and have caused severe damages to tourist resorts and villages in the vicinity of this structure in the last decade a large number of shocks sometimes in the form of swarms linked to pernicana provenzana fault system movements have been detected by the permanent local seismic network operating in eastern sicily in this paper we report on the detailed study of the seismic activity occurring during the 2000 2009 time span in the pernicana provenzana fault system area firstly we located 407 earthquakes using a standard location code and a 1d crustal velocity model we then applied two different approaches to calculate precise hypocenter locations of the events in particular a non linear code was adopted to obtain an estimate of the a posteriori probability density function in 3d space for the hypocenter location moreover a relative location of correlated event pairs was performed using the double difference method these two different location approaches allowed defining with good accuracy the most active and hazarding sectors of the structure the results of these precise locations showed a tighter clustering in the epicenters and in focal depths in comparison with standard locations earthquakes are located along the pernicana provenzana fault system and are mainly clustered in two zones separated by an area with very low rate of earthquakes occurrence but characterized by the highest energy release depths of the foci are very shallow ranging between the surface and about 3 km b s l kinematics of the pernicana provenzana fault system revealed by the fault plane solutions computed for the most energetic earthquakes highlights a predominant dip slip and left strike movements along e w oriented fault planes in agreement with field observations

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

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

magma storage eruptive activity and flank instability inferences from ground deformation and gravity changes during the 1993 2000 recharging of mt etna volcano abstract a long recharging period characterized mount etna volcano during 1993 2000 before the main explosive effusive 2001 and 2002 2003 flank eruptions the joint analysis of ground deformation and gravity data over the recharge period reveals that different phenomena occurred within etna s plumbing system and clearly indicates two phases spanning 1993 1997 and 1997 2000 respectively the first phase was characterized by magma storage and accumulation at an intermediate depth 2 6 km below sea level which provoked overall inflation and positive gravity changes during the second phase the magma started to rise and intrude at shallower levels favoring the movement of the unstable eastern flank which accelerated its sliding toward the east the shallower magma accumulation also caused the gas exsolution associated with increasing explosive activity at the summit craters negative gravity changes were detected during this phase the gravity measurements independent of the same result obtained by geochemical studies suggest that only 20 30 of the magma volumes supplied in the plumbing system were then erupted the complex dynamics of rising magma beneath mount etna makes ground deformation and gravity measurements complementary being able to detect different effects of magma emplacements beneath the surface our results also highlight how the joint use of ground deformation and gravity observations may be crucial in identifying the nature and rate of an impending period of volcanic eruptions

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

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

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

fem based inversion for heterogeneous fault mechanisms application at etna volcano by dinsar data summary a procedure based on the finite element method fem for high resolution geodetic data inversion was developed to estimate non uniform slip distribution during the 2002 september 22 m3 7 earthquake rupture occurring only one month before the 2002 2003 eruption of etna volcano fem generated synthetic green s functions are combined with an inverse algorithm to simulate deformation of the earthquake for a 3 d problem domain that takes into account heterogeneity of material properties in the volcanic edifice the inversion of dinsar data shows complex kinematics of the northeastern flank of the etna volcano involving the pernicana fault system we detailed the coseismic shear rupture mechanism and highlighted a tensile mechanism never observed before related to a first attempt of magma intrusion which preceded the following october 26 eruption

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

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

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

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

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

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

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

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

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

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

chemical heterogeneity of mt etna magmas in the last 15 ka inferences on their mantle sources abstract primitive basaltic magmas are crucial in the study of the geochemical heterogeneity documented in etna magmas and their inferred mantle sources we undertook a systematic sampling of the less evolved basalts mg 50 erupted over the last 15 ka a time period which corresponds to the activity of the youngest volcanic edifice of mt etna complex i e mongibello volcano we focused on lava flows and pyroclastites emplaced during deep dyke fed ddf eruptions which were driven by the rapid ascent of deeply rooted magma intrusions that bypassed the shallow plumbing system of the volcano all the samples were analyzed by the same laboratory to avoid analytical bias to build a comprehensive dataset on their major and trace element compositions and to propose a coherent framework for interpreting the geochemical fingerprints of present day etna basalts trace element modeling together with literature data for sr isotopes gave insight into long term magmatic processes related to different melting degrees of the heterogeneous mantle beneath mt etna ddf magma batches provide good snapshots of their mantle source heterogeneities that point to the variable involvement of clinopyroxenitic lithology rb 87 sr cl rich fluid component s possibly controlled by their source mineralogy and slab derived fluids selectively enriched in alkalis rb k the ongoing alkali rb k enrichment of the present day magmas well manifest since the 1970s is decoupled from that of sr and cl we propose that this process is linked to mantle source composition and is concomitant with changes in both volcanological and seismotectonic patterns of the volcano there is no time evolution of ddf magma chemistry

frequency distribution of felt earthquakes abstract seismic intensity is a measure of how seismic ground motion is felt for a particular earthquake using the intensity data of the japan meteorological agency jma for the last 32 years we report that the number of felt earthquakes exponentially decays as the function of the observed maximum intensity the slope of this exponential relation is approximately 0 6 with some variability and this is roughly in accord with the gutenberg richter law of seismicity and existing empirical relations among intensity magnitude of earthquakes and hypocentral distance the number of felt earthquakes does not increase in proportion to a large increase of observation sites during this period

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

volcanism in compressional tectonic settings is it possible 1 this study presents the first field evidence of emplacement of a huge stratovolcano within contractional tectonics in spite of the widely accepted idea that volcanism can develop only in extensional or transcurrent tectonic settings el reventador volcano ecuador started to grow 0 32 ma bp and is still active during pre el reventador times its substratum has been affected by n s to nne striking reverse faults during late pleistocene holocene some reverse faults with the same orientations were still active locally with a component of right lateral strike slip motions seismicity shows widespread events with intensity up to 6 9 mw and compression some of these faults cut the volcano creating differential uplift along n s to nne trending tectonic blocks hypocenter swarms and field data indicate east vergent basal thrusting under the volcano and n s trending fault propagation folds to the east a model for magma migration in this setting is proposed suggesting that similar cases of volcanism within a dominantly contractional tectonic regime may be more frequent than previously thought

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

insight into mt etna italy kinematics during the 2002 2003 eruption as inferred from seismic stress and strain tensors 1 seismic activity linked to the 2002 03 mt etna eruption was investigated by analyzing the md 2 3 earthquakes the results of 3d relocation were used to compute fault plane solutions and a selected dataset was inverted to determine stress and strain tensors the analysis revealed a complex kinematic response of the eastern flank dominated by fast stress propagation and reorientation we hypothesize that a vertical dike intruded the southern flank generating an extensional regime that triggered a radial intrusion in the northeast sector of the volcano the combined effects gave rise to a rotation of the stress tensor that controlled the activation of the pernicana fault system the volcanic and tectonic interactions produced a second reorientation of the stress tensor causing a structural response in the southeast lower flank the overall result of the deformation processes observed during the eruption was an e w extension on the eastern flank of the volcano

flank instability structure of mt etna inferred by a magnetotelluric survey this paper presents a magnetotelluric mt survey of the unstable eastern flank of mt etna we take thirty soundings along two profiles oriented in the n s and nw se directions and from these data recover two 2d resistivity models of the subsurface both models reveal three major layers in a resistive conductive resistive sequence the deepest extending to 14 km bsl the shallow layer corresponds to the volcanic cover and the intermediate conductive layer corresponds to underlying sediments segmented by faults these two electrical units are cut by e w striking faults the third layer basement is interpreted as mainly pertinent to the apennine maghrebian chain associated with sw ne striking regional faults the detailed shapes of the resistivity profiles clearly show that the ne rift is shallow rooted 0 1 km bsl thus presumably fed by lateral dikes from the central volcano conduit the nw se profile suggests by a series of listric faults reaching up to 3 km bsl then becoming almost horizontal toward the se the resistive basement dramatically dips from 3 km to 10 km bsl in correspondence with the timpe fault system several high conductivity zones close to the main faults suggest the presence of hydrothermal activity and fluid circulation that could enhance flank instability our results provide new findings about the geometry of the unstable etna flank and its relation to faults and subsurface structures

deformed symmetrical volcanoes analog modeling of volcanic cones traversed by strike slip faulting was conducted and the cones were analyzed for deformation characteristics the study shows that symmetrical volcanoes that have undergone basal strike slip offset may be deformed internally without manifesting any change in their conical shape volcanoes deformed by strike slip faulting may already have well developed fractures in their interior yet still appear as a symmetrical cone exhibiting concentric contours when viewed on a topographic map moreover slight changes in the basal shape of the cone induced by strike slip movement can be restored by the relatively faster resurfacing and reshaping processes from the deposition of younger eruptive products these findings pose a subtle but significant point in the assessment of volcanic landslide hazards not all perfect cones are undisturbed the detection of concealed deformation is important because fractures induce further instability in volcanoes and act as slip planes during volcano collapse events there are many examples of symmetrical volcanoes in nature the faultless appearance of such perfect cones can be misleading which requires careful attention in hazards assessment

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

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

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

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

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

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

probabilistic seismic hazard at mt etna italy the contribution of local fault activity in mid term assessment abstract in this work we tackle the problem of seismic hazard at etna deriving from the recurrent seismogenic activity of local faults by adopting two independent methods based on probabilistic approaches we assess the hazard in terms of macroseismic intensity and represent the occurrence probability calculated for different exposure times both on maps and at fault scale seismic hazard maps obtained by applying the site approach through the sasha code and a new probabilistic attenuation model indicate the eastern flank of the volcano as the most hazardous with expected intensity i exp in 50 years i e the standard exposure time adopted in the seismic regulations ranging from degrees ix to x ems in shorter exposure periods 20 10 5 years values of i exp up to ix are also reached in the same area but they are clearly determined by the earthquakes generated by the timpe fault system in order to quantify the contribution of local seismogenic sources to the hazard of the region we reconstruct the seismic history of each fault and calculate with sasha the probability that earthquakes of a given intensity may be generated in different exposure times results confirm the high level of hazard due to the s tecla moscarello and fiandaca faults especially for earthquakes of moderate intensity i e vi i 0 vii with probabilities respectively exceeding 50 and 20 in 10 years and 30 and 10 in 5 years occurrence probability of major events i 0 viii at the fault scale has also been investigated by statistics on intertimes under stationary assumptions we obtain a probability of 6 8 in 5 years for each structure by introducing the time dependency time elapsed since the last event occurred on each fault through a bpt model we identify the moscarello and s tecla faults as the most probable sources to be activated in the next 5 years 2013 2017 this result may represent a useful indication to establish priority criteria for actions aimed at reducing seismic risk at a local scale

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

using tetraether lipids archived in north sea basin sediments to extract north western european pliocene continental air temperatures the pliocene is often regarded as a suitable analogue for future climate due to an overall warmer climate 2 3 c coupled with atmospheric co2concentrations largely similar to present values 400 ppmv numerous pliocene sea surface temperature sst records are available however little is known about climate in the terrestrial realm here we generated a pliocene continental temperature record for northwestern europe based on branched glycerol dialkyl glycerol tetraether brgdgt membrane lipids stored in a marine sedimentary record from the western netherlands the total organic carbon toc content of the sediments and its stable carbon isotopic composition 13corg indicate a strong transition from primarily marine derived organic matter om during the pliocene to predominantly terrestrially derived om after the transition into the pleistocene this trend is supported by the ratio of branched and isoprenoid tetraethers bit index the marine terrestrial transition indicates a likely change in brgdgt sources in the core which may complicate the applicability of the brgdgt paleotemperature proxy in this setting currently the application of the brgdgt based paleothermometer on coastal marine sediments has been hampered by a marine overprint here we propose a method to disentangle terrestrial and marine sources based on the degree of cyclizationof tetramethylated brgdgts rings using a linear mixing model based on the global soil calibration set and a newly developed coastal marine temperature transfer function application of this method on our brgdgt record resulted in a corrected terrestrial temperature record matterr this latter record indicates that continental temperature were 12 14 c during the early pilocene and 10 5 12 c during the mid pilocene pollen based terrestrial temperatures estimate from nortern and central europe furthermore two colder 5 7 c periods in the pilocene maytterr record show that the influence of pilocene glacials reached well into nw europe

continental margin large scale instability controlling the flank sliding of etna volcano abstract etna volcano is affected by a downward sliding of its eastern flank as rapid as a few cm year whose nature is highly debated recently collected marine geological and geophysical data allows a detailed image of the morphostructural setting of the continental margin facing the volcano here a large bulge offsets the margin that is deeply affected by widespread semicircular steps interpreted as evidence of large scale gravitational instability such features permeate the whole margin and extend inshore to the volcano sector where the larger ground deformations are measured both submarine instability and subaerial flank sliding are bounded by two regional tectonic lineaments interpreted as weakness lines these cross the coastline to accommodate the basinward movement of this large sector of the continental margin topped by the etna volcanic pile the new data allows re interpreting the tectonic setting of the coastal belt and proposing a novel structural model highlighting the active role of the continental margin instability to drive the seaward sliding of the volcano s eastern flank this model may suggest why a very active basaltic volcano has so unusually developed in front of an active thrust belt

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

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

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