formation of lava tubes and extensive flow field during the 1991 1993 eruption of mount etna detailed mapping during the 1991 1993 eruption of mount etna has shown that there is a relationship between tumuli ephemeral vents lava tubes and their parent lava flows during this eruption many tubes formed in stationary inflated a a lava flows ephemeral vents at the fronts of these stationary flows and above lava tubes fed secondary lava flows many of which subsequently developed new tubes the resulting complex network of tubes ephemeral vents and secondary flows was responsible for most of the widening thickening and lengthening of the 1991 1993 etna lava flow field the supply of relatively uncooled lava via tubes to distal parts of this flow field allowed lava to flow 3 km farther from the vent than the longest channel fed lava flow our observations suggest that lava tubes play a more important role in the formation of extensive a a flow fields on etna than has previously been recognized

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

fault imaging in sparsely sampled 3d seismic data using common reflection surface processing and attribute analysis a study in the upper rhine graben abstract cost reduction in seismic reconnaissance is an issue in geothermal exploration and can principally be achieved by sparse acquisition to address the adherent decrease in signal noise ratio the common reflection surface method has been proposed we reduced the data density of an existing 3d dataset and evaluated the results of common reflection surface processing using seismic attributes the application of the common reflection surface method leads in all cases to an improvement of the signal noise ratio the most distinct improvement can be seen in the low fold regions the improvement depends strongly on the midpoint aperture and there is a tradeoff between reflector continuity and horizontal resolution if small scale targets are to be imaged a small aperture size is necessary which may be far below the fresnel zone for a specific reflector the substantial reduction of the data density leads in our case to an irrecoverable information loss

tectonics of the tonga kermadec trench and ozbourn seamount junction area abstract seismic profiling together with seismic refraction data and dredging enabled us to study the upper crustal structure of the tonga kermadec trench and the ozbourn seamount junction area horst graben structures have been revealed both on the insular and oceanic slopes of the trench two systems of faults are characteristic one transverse and the other parallel to a general trend of the tonga kermadec trench grabens of the trench insular slope are partly compensated by sediments unlike those of the oceanic slope which are not ponded by sediments on both slopes the faults are normal this testifies to the extensional conditions within the upper crustal part of this region the tonga kermadec uplift insular slope of the trench has undergone intensive with amplitide to 5 7 km vertical movements uplifting and then subsidence in eocene oligocene pliocene and quaternary times

the volume and shape of the 1991 1993 lava flow field at mount etna sicily the 1991 1993 lava flow is the most voluminous flow erupted at mount etna sicily in over 300 years estimates of the volume obtained by various methods range from 205 106 m3 tanguy 1996 to over 500 106 m3 barberi et al 1993 this paper describes the results of an electronic distance measurement edm based field survey of the upper surface of the 1991 1993 flow field undertaken in 1995 the results were digitised interpolated and converted into a digital elevation model and then compared with a pre eruption digital elevation model constructed from a 1 25 000 contour map of the area based on 1989 aerial photographs our measurements are the most accurate to date and show that the 1991 1993 lava flow occupies a volume of 231 29 106 m3

horizontal lithosphere compression and subduction constraints provided by physical modeling physical modeling of the subduction is performed with a two layered mantle model elastico plastic lithosphere and low viscosity asthenosphere and is governed by the criteria of similarity compression of the lithosphere in the area of a passive continental margin has been shown to produce a buckling instability in the oceanic plate with wavelengths of 200 km on the average later a localization of deformation occurs in sagging at some distance from the margin where a strongly dislocated linear ridge is formed due to the thrusting the plate then experiences a failure along the inclined zone and subduction starts the inner trench slope which forms therefore has a scraped structure and include a block of crushed and dislocated oceanic crust and sediments in the lower section if there is an old inclined fault striking across the compression of an oceanic lithosphere it is on that fault that a subduction zone is initiated the inner trench slope has then a different structure and forms due to normal faulting in the frontal part of the overriding plate the formation of a subduction zone requires a compression that is smaller than that in the preceding case by a factor of 2 or 3 the subducting plate experiences an elastico plastic bending and under specific conditions thrusting along the zone dipping from under the overriding plate oceanward and crossing the entire lithosphere the best agreement between generalized relief in subduction zone in the model and nature is achieved when a shear yield limit s 1 3 108 pa modulus of elasticity e about a few times 1011 pa and a thickness h 60 km are adopted for the real lithosphere

large scale deformation associated with ridge subduction summary continuum models are used to investigate the large scale deformation associated with the subduction of aseismic ridges formulated in the horizontal plane using thin viscous sheet theory these models measure the horizontal transmission of stress through the arc lithosphere accompanying ridge subduction modelling was used to compare the tonga arc and louisville ridge collision with the new hebrides arc and d entrecasteaux ridge collision which have disparate arc ridge intersection speeds but otherwise similar characteristics models of both systems indicate that diffuse deformation low values of the effective stress strain exponent n are required to explain the observed deformation deformation is somewhat insensitive to the vertically integrated strength of the arc inversely proportional to the argand number ar but indicates that the arc lithosphere is not extremely weak ar 100 low values of both ar and n suggest that the thermal structure is typical of cold or normal arcs and that deformation is dominated by flow in the lower crust and mantle in addition low values of n approaching newtonian flow may indicate that specific deformation mechanisms dictate deformation of the arc lithosphere possible mechanisms include low stress grain size dependent creep pyroxenite controlled rheology and mechanisms associated with water weakening changes in the boundary conditions greatly affect deformation within island arcs high rates of arc ridge intersection speed tonga louisville system yield arc parallel tension and crustal thickening in the wake of ridge subduction in contrast low rates of arc ridge intersection speed new hebrides d entrecasteaux system yield compressional deformation directly arcward of the collision zone and transverse strike slip faulting adjacent to the region of compressional deformation localized regions of extensional deformation along the frontal part of the arc adjacent to the collision zone may contribute to the formation of re entrants

coulomb theory applied to accretionary and nonaccretionary wedges possible causes for tectonic erosion and or frontal accretion based on observations from both modem convergent margins and sandbox modeling we examine the possible conditions favoring frontal accretion and or frontal and basal tectonic erosion mean characteristic parameters t t and are used to discuss the mechanical stability of 28 transects across the frontal part of convergent margins where the coulomb theory is applicable natural observations reveal that typical accretionary wedges are characterized by low tapers with smooth surface slope and subducting plate low convergence rates and thick trench sediment while nonaccretionary wedges display large tapers with irregular surface slopes and rough subducting plate high convergence rates and almost no trench fill sandbox experiments were performed to illustrate the effects of seamounts ridges in the subduction zone on the deformation of an accretionary wedge these experiments show that a wedge of sand is first trapped and pushed in front of the seamount which acts as a moving bulldozer this is followed by a tunnelling effect of the subducting seamount through the frontal wedge material which results in considerable sand reworking at an advanced subduction stage the d6collement jumps back from a high level in the wedge to its former basal position we conclude that a high trench sedimentation rate relative to the convergence rate leads to frontal accretion in contrast several conditions may favor tectonic erosion of the upper plate first oceanic features such as grabens seamounts or ridges may trap upper plate material during their subduction process second destabilization of the upper plate material by internal fluid overpressuring causing hydrofracturing is probably another important mechanism

continuous soil radon monitoring during the july 2006 etna eruption 1 continuous soil radon monitoring was carried out near the southeast crater sec of mt etna during the 10 day july 2006 strombolian effusive eruption this signal was compared with simultaneously acquired volcanic tremor and thermal radiance data the onset of explosive activity and a lava fountaining episode were preceded by some hours with increases in radon soil emission by 4 5 orders of magnitude which we interpret as precursors minor changes in eruptive behavior did not produce significant variations in the monitored parameters the remarkably high radon concentrations we observed are unprecedented in the literature we interpret peaks in radon activity as due primarily to microfracturing of uranium bearing rock these observations suggest that radon measurements in the summit area of etna are strongly controlled by the state of stress within the volcano and demonstrate the usefulness of radon data acquisition before and during eruptions citation neri m b behncke m burton g galli s giammanco e pecora e privitera and d reitano 2006 continuous soil radon monitoring during the july 2006 etna eruption geophys res lett 33 l24316 doi 10 1029 2006gl028394

orthogonal intersections of megatrends in the western pacific ocean basin a case study of the mid pacific mountains abstract present day tectonic concepts of events on the western paleo pacific lithosphere must be assessed relative to new data data collected by the newer techniques of geophysical surveying reveal leaky fracture zones trending nnw sse and wsw ene non sequential in line ages on most seamount chains and orthogonal intersections of fracture zones the fracture zones meander braid merge splay start and stop at any place and are generally aligned with or contain linear chains of seamount the combination of these in line features is called megatrends when the geosat data are compared to the available bathymetry this seemingly jumbled tectonic structure is verified as the pole of rotation changes the stress field changes alignment to agree with the chandler wobble of earth younger megatrends propagating ever eastward cross the older already imprinted megatrends during the cretaceous the voluminous outpouring of igneous rock created the large pacific plateaus and rises where the megatrends active and inactive orthogonally intersected the magma floods at the intersections flowed outwardly and the outward flooding accounts for the fanning magnetic lineations around the manihiki magellan shatskiy and hess rises a case study of the mid pacific mountains mpm lying in the north central pacific ocean basin shows that the mpm formed about 125 110 ma by overprinting the orthogonal intersections of fracture zones at the molokai and easter krusenstern emperor megatrends and the murray and tubai mamua megatrends the mpm have been undergoing distortion into a vortex structure a feature which has been confirmed by updated bathymetry geosat altimetry data and drillsite information

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

geography and history of the louisville hotspot chain in the southwest pacific the louisville ridge is a 4300 km long late cretaceous and cenozoic hotspot chain the south pacific equivalent of the hawaiian emperor chain its northwestern end is being consumed by the tonga kermadec subduction zone but seabeam and magnetic mapping shows that the chain still includes more than 60 major volcanoes of both normal and reversed polarity distributed along a 75 km wide band that can be fitted to small circles about three successive poles of pacific plate hotspot rotation this band obliquely crosses fracture zones of the eltanin system but there is little interaction and no evidence of any genetic connection between the two structures forty of the louisville volcanoes grew above sea level and are preserved as high latitude i e coral free guyots they are spaced less than 100 km apart along most of the chain but there are none within 750 km of the inferred present location of the hotspot beneath a swell at the southeast end of the chain the rate of volcano building by the louisville hotspot declined sharply about 20 m y ago after being remarkably constant at 3 4 103 km3 m y for the previous 50 m y and none of the louisville volcanoes built during the past 10 12 m y the time of most profuse hawaiian volcanism has reached sea level however a seamount from which pleistocene lavas were dredged rises to within 540 m of the sea surface from the crest of the hotspot swell at 50 5 s 139 2 w guyot heights demonstrate that a hotspot swell several hundred meters high has persisted throughout the known life of the chain and sometimes had an isostatic depression on its loaded crest the depths of guyot shelf breaks increase systematically to the northwest from 530 to 2100 m proportional to the square root of volcano age with some scatter and tilting caused by plate boundary tectonism and local isostatic subsidence and uplift

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

the changing morphology of an open lava channel on mt etna an open channel lava flow on mt etna sicily was observed during may 30 31 2001 data collected using a forward looking infrared flir thermal camera and a minolta land cyclops 300 thermal infrared thermometer showed that the bulk volume flux of lava flowing in the channel varied greatly over time cyclic changes in the channel s volumetric flow rate occurred over several hours with cycle durations of 113 190 min and discharges peaking at 0 7 m3 s 1 and waning to 0 1 m3 s 1 each cycle was characterized by a relatively short high volume flux phase during which a pulse of lava with a well defined flow front would propagate down channel followed by a period of waning flow during which volume flux lowered pulses involved lava moving at relatively high velocities up to 0 29 m s 1 and were related to some change in the flow conditions occurring up channel possibly at the vent they implied either a change in the dense rock effusion rate at the source vent and or cyclic variation in the vesicle content of the lava changing its bulk volume flux pulses would generally overspill the channel to emplace p hoehoe overflows during periods of waning flow velocities fell to 0 05 m s 1 blockages forming during such phases caused lava to back up occasionally backup resulted in overflows of slow moving a that would advance a few tens of meters down the levee flank compound levees were thus a symptom of unsteady flow where overflow levees were emplaced as relatively fast moving p hoehoe sheets during pulses and as slow moving a units during backup small localized fluctuations in channel volume flux also occurred on timescales of minutes volumes of lava backed up behind blockages that formed at constrictions in the channel blockage collapse and or enhanced flow under around the blockage would then feed short lived wave like down channel surges real fluctuations in channel volume flux due to pulses and surges can lead to significant errors in effusion rate calculations

ducks low cost thermal monitoring units for near vent deployment abstract during 1999 we designed and tested a thermal monitoring system to provide a cheap robust modular real time system capable of surviving the hostile conditions encountered proximal to active volcanic vents in november 2000 the first system was deployed at pu u o o kilauea hawai i to target persistently active vents aside from some minor problems such as sensor damage due to tampering this system remained operational until january 2004 the success of the prototype system led us to use the blueprint for a second installation at stromboli aeolian islands italy this was deployed dug into a bomb proof bunker during may 2002 and survived the april 2003 paroxysmal eruption despite being located just 250 m from the vent in both cases careful waterproofing of connectors and selection of suitable protection has prevented water damage and corrosion in the harsh atmosphere encountered at the crater rim the pu u o o system cost us 10 000 and comprises four modules sensors transmission and power hub repeater station and reception site the sensor component consists of three thermal infrared thermometers housed in pelican cases fitted with germanium arsenide selenium windows two 1 field of view fov sensors allow specific vents to be targeted and a 60 fov sensor provides a crater floor overview a hard wire connection links to a pelican case housed microprocessor modem and power module from here data are transmitted via a repeater site to a dedicated pc at the hawaiian volcano observatory here data are displayed with a delay of 3 s between acquisition and display the modular design allows for great flexibility at stromboli 1 and 15 fov sensor modules can be switched depending changes in activity style and crater geometry in addition a direct line of site to the stromboli reception center negates the repeater site requirement reducing the cost to us 5500 for a single sensor system we have also constructed self contained units with internal data loggers for us 1500 unit these have been tested at kilauea stromboli etna masaya santiaguito fuego pacaya poas soufriere hills villarrica and erta ale these instruments have proved capable of detecting thermal signals associated with 1 gas emission 2 gas jetting events 3 crater floor collapse 4 lava effusion 5 lava flow in tubes 6 lava lake activity 7 lava dome activity and 8 crater lake skin temperature

application of the 3d common reflection surface stack workflow in a crystalline rock environment seismic data from crystalline or hardrock environments usually exhibit a poor signalto noise ratio due to low impedance contrasts in the subsurface moreover instead of continuous reflections we observe a lot of steeply dipping events resembling parts of diffractions the conventional seismic processing common midpoint stack and dip moveout is not ideally suited for imaging such type of data commonreflection surface stack processing considers more traces during the stack than common midpoint processing and the resulting image displays a better signal to noise ratio in the last decade the common reflection surface stack method was established as a powerful tool to provide improved images especially for low fold or noisecontaminated data the common reflection surface stack and all attributes linked to it are obtained using a coherence based automatic data driven optimization procedure in this work we applied the common reflection surface stack workflow to 3d crystalline rock seismic data which were acquired near schneeberg germany for geothermal exploration the common reflection surface stack itself provided an image of good signal to noise ratio however for data from environments with low acoustic impedance and poor velocity information coherence which is automatically obtained in the optimization procedure provides an alternative way to image the subsurface despite the reduced resolution for these data the coherence image provided the best results for an initial analysis utilized as a weight the coherence attribute can be used to further improve the quality of the stack by combining the benefits of a decreased noise level with the high resolution and high interference properties of waveforms we argue that these results may provide the best images in an entirely data driven processing workflow for the schneeberg data

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

deep seismic image enhancement with the common reflection surface crs stack method evidence from the aravalli delhi fold belt of northwestern india summary imaging of deep crustal features from narrow angle deep seismic reflection data especially from fold belt region has been a challenging task the common reflection surface crs stack is an alternative seismic imaging technique for multicoverage reflection data it is an automatic stacking process which does not require explicit knowledge of stacking velocity this crs stack is especially useful when the data quality is poor and foldage is low in this paper we demonstrate an application of the crs stack to a deep seismic reflection data set acquired across the aravalli delhi fold belt of the northwestern india which provides a seismic stack section with much improved signal to noise ratio comparing the conventional common midpoint cmp stack with the crs stack we find that the moho and other crustal reflections have been resolved clearly and the continuity of the reflectors has also been enhanced with the crs stack method the major findings from our crs processing include clear image of the moho discontinuity below the marwar basin and sandmata complex and prominent upper and mid crustal reflections our study for the first time images an extension of crustal scale jahazpur thrust below the sandmata complex which becomes listric at the moho some of the crustal features derived in this study were not identified in the earlier investigations using the cmp stack our study clearly demonstrates that the crs stacking method is more appropriate for imaging the crustal and subcrustal structures of the thrust fold belt region than the conventional cmp method where limited velocity information is available crustal thickness across the proterozoic orogenic aravalli delhi fold belt varies between 38 and 50km global correlation of the seismic results suggests no relation between crustal thickness and age of the crustal block but it depends on the thermorheological and tectonic history of the region palaeosignatures of the proterozoic subduction and collision processes are still preserved in major portion of the crust in this study area as well as in several parts of the world

data stacking beyond cmp stacking has been used in seismic data processing for a long time in fact stacked sections or volumes in 3d are standard deliverables in the industry and the concepts of common midpoint cmp gathers and normal moveout nmo correction are mentioned in almost every textbook on seismic processing although the general trend is toward prestack imaging either in time or in depth the construction of stacked sections remains an important step within the seismic processing flow since they are almost always the first available interpretable images of the subsurface

the initial phases of the 2008 2009 mount etna eruption a multidisciplinary approach for hazard assessment accepted for publication in journal of geophysical research copyright 2010 american geophysical union

velocity and event slope analysis using a model based common diffraction surface stack operator abstract over the last two decades scientists have introduced many ways to improve normal moveout velocity analysis by optimizing the resolution of the moveout velocity spectrum a graph that displays a coherence value for every tested velocity traveltime pair almost all of these methods have failed to enhance resolution when faced with low fold common midpoint gathers which might be caused by natural barriers or man made obstacles another problem is that many approaches are derived from very simple model assumptions that quickly break down for complex structures and do not provide enough model flexibility for an iterative and interactive velocity analysis in this paper we present a new velocity analysis method based on the model based common diffraction surface stack operator and apply it to two synthetic data sets one with locally sparse common midpoint coverage and one with a laterally variable complex geological structure we generate velocity spectra by calculating the semblance along spatial operators obtained for all possible emergence angles and an entire range of velocity models comparing the resolution of such velocity spectra with those obtained with the classical normal moveout velocity analysis shows in both two analysed cases that the stacking velocity can be estimated much more precisely the reasons for this are that the event dip is handled independently from the velocity and that the semblance is obtained for each zero offset sample over a group of neighbouring common midpoint gathers instead of just one

prestack time migration by common migrated reflector element stacking abstracttime migration is an attractive tool to produce a subsurface image because it is faster and less sensitive to velocities errors than depth migration however a highly focused time image is only achievable with well determined time migration velocities therefore a refinement of the initial time migration velocities often is required we introduced a new technique for prestack time migration based on the common migrated reflector element stack of common scatterpoint gathers including an automatic update of time migration velocities the common scatterpoint gathers are generated using a new formulation of the double square root equation that is parametrized with the common offset apex time the common migrated reflector element stack is a multiparameter stacking technique based on the taylor expansion of traveltimes of time migrated reflections in the paraxial vicinity of the image ray our 2d synthetic and field data examples demonstrated that the proposed method provides updated time migration

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

common reflection surface stack imaging of the proterozoic chambal valley vindhyan basin and its boundary fault in the northwest india constraints on crustal evolution and basin formation

detachment depth revealed by rollover deformation an integrated approach at mount etna this work was partially funded by ingv and the dpc ingv project flank and partially by the asi srv project

a chronology of the 1991 to 1993 mount etna eruption using advanced very high resolution radiometer data implications for real time thermal volcano monitoring between december 1991 and march 1993 a continuous effusive eruption at mount etna built a 7 6 km2 lava flow field flows extended to within 1 km of the town of zafferana before a successful artificial diversion was carried out higher up the volcano during this eruption the spaceborne advanced very high resolution radiometer avhrr acquired 308 images on which the activity could be detected since these data can be freely and directly available such coverage potentially allows regular real time monitoring ground observations and a flow map that we produced using a spot image and electronic distance measurement allowed us to develop and test data extraction techniques avhrr radiance maps were consistent with known locations of surface activity these documented the transition from channel to tube fed phases the changing threat to zafferana and flow diversion quantitative analysis of the avhrr data enabled estimation of active lava area thermal flux effusion rates and total flow field volume our estimates for eruption rate and total flow field volume 5 6 to 7 6 m3 s and 220 106 to 300 106 m3 respectively are in agreement with published ground based estimates of 5 8 m3 s and 235 106 m3 these correlations demonstrate the high degree of confidence that can now be placed in interpretations of avhrr time series for eruptions where ground based data are scanty

earthen barriers to control lava flows in the 2001 eruption of mt etna abstract preceded by four days of intense seismicity and marked ground deformation a new eruption of mt etna started on 17 july and lasted until 9 august 2001 it produced lava emission and strombolian and phreatomagmatic activity from four different main vents located on a complex fracture system extending from the southeast summit cone for about 4 5 km southwards from 3000 to 2100 m elevation a s l the lava emitted from the lowest vent cut up an important road on the volcano and destroyed other rural roads and a few isolated country houses its front descended southwards to about 4 km distance from the villages of nicolosi and belpasso a plan of intervention including diversion and retaining barriers and possibly lava flow interruption was prepared but not activated because the flow front stopped as a consequence of a decrease in the effusion rate extensive interventions were carried out in order to protect some important tourist facilities of the sapienza and mts silvestri zones 1900 m elevation from being destroyed by the lava emitted from vents located at 2700 m and 2550 m elevation thirteen earthen barriers with a maximum length of 370 m height of 10 12 m base width of 15 m and volume of 25 000 m3 were built to divert the lava flow away from the facilities towards a path implying considerably less damage most of the barriers were oriented diagonally 110 135 to the direction of the flow they were made of loose material excavated nearby and worked very nicely resisting the thrust of the lava without any difficulty after the interventions carried out on mt etna in 1983 and in 1991 1992 those of 2001 confirm that earthen barriers can be very effective in controlling lava flows