a common feeding system of the ne and s rifts as revealed by the bilateral 2002 2003 eruptive event at mt etna sicily italy mount etna volcano is often characterized by bilateral eruptive events involving both the south s and the north east ne rifts the last event occurred in 2002 2003 from october 27 to january 28 a detailed stratigraphically time controlled sampling of lavas and tephra of the southern eruptive fissure was performed in order to 1 track the petrological features of products during the eruption and 2 integrate the results with those previously obtained on the ne rift whole rock composition and textural observations were implemented by major and minor element analyses of plagioclases in lavas and tephra from both sides of the volcano fractionation models constrained by mass balance major and trace elements and rayleigh calculations suggest that magmas are linked by the same liquid line of descent by fractionating 9 11 of a mineral assemblage of cpx 52 69 plg 21 41 and ol 7 46 these new data allowed us to identify at least two feeding episodes through the southern fissure and infer that high k2o porphyritic magmas emitted on both the s and ne rifts derives by fractionation from the same parent magma however lavas and tephra from the southern flank were slightly more primitive textural and petrological study of plagioclase moreover indicates that chemical physical conditions in the deep feeding system were similar for magmas erupting from both rifts as suggested by the presence of dissolved rounded cores in both lavas magmas evolved differently on the s and the ne rifts only at shallow levels comparison with published seismotectonic data supports the idea that the main magma feeding the eruption on october 27 ascended along the same pathway at depth and was intercepted by the fracture system of the s and ne rifts at shallow depth between 6 and 3 km b s l

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

multi parametric climatological analysis associated with global significant volcanic eruptions during 2002 2017 in this work we search for physical and chemical climatological anomalies preceding major volcanic explosive eruptions mostly vei volcanic explosivity index 4 occurred from 2002 to 2017 by applying two specific algorithms i e capri and means the former algorithm has been already used for a multi climatological analysis of the amatrice norcia 2016 2017 earthquake preparatory phase piscini et al in pure appl geophys 174 3673 3688 2017 here we analyse some climatological parameters for a three month period before each volcanic explosive eruption then we compare the behavior with the typical one of the past the analysis is applied to an area with dimensions comparable to the volcano crater because it is the increase of the magmatic camera activity that in turn can cause a temperature increase whose evidence could be detected at the surface slezin in j volcanol geotherm res 122 1 2 7 50 2003 while the use of a larger area would provide a greater probability of occurrence of other events e g other volcano eruption meteorological storms etcetera therefore a smaller area of study reduces the risk to get false alarms in particular we considered thermal skin temperature skt and total water vapour content tcwv from ecmwf european centre and aerosol optical thickness aot sulphur dioxide so2 and atmospheric dimethylsulphide dms are obtained from nasa merra 2 global modeling and assimilation data archive the latter compound was added in the analysis to check the validity of the method since we did not expect significant anomalies from this parameter the models above described are used for their temporal spatial completeness allowing performing time series analyses and for a real time monitoring on a global scale by simultaneous analysis we found for almost all volcanic eruptions some anomalies in about all analyzed parameters that precede by 75 days to 20 days the explosion these anomalies are not always simultaneous but we find an interesting synchronicity that probably reveals a correlation among the different datasets in addition the agung volcano which has recently started an eruptive activity 25 november 2017 without reaching a vei4 explosion has also been investigated the data related to this volcano present a small number of anomalies much lower than all attributed to the other analyzed explosive volcanoes and this is in high agreement with the low explosive nature of the agung volcano eruption we find that the occurrence of thermal anomalies typically preceding stratovolcano caldera eruptions seems to take place some days after so2 emissions the climatological anomalies that precede eruptions at high latitudes usually surround the volcano in a wider area outside the volcanic edifice we verify that the number of positive anomalies is systematically greater in the year that precedes the investigated eruption with respect to a quiet year of comparison with accuracy from 91 to 100 suggesting that the applied methods detected climatological anomalies likely related to imminent volcanic eruptions

a recent tectonic reorganization in the south central mediterranean abstract new geodetic data combined with seismicity geologic and geochemical information document a major tectonic reorganization in the central mediterranean around 0 8 0 5 ma when rapid trench migration and consequent tyrrhenian back arc extension which dominated the region s evolution since the tortonian 10 8 ma essentially stopped in response the african convergence in sicily was transferred to a back thrust in the southern tyrrhenian characterized by frequent m5 6 earthquakes in the last 20 years a diffuse transform boundary formed across northeastern sicily to connect the sicilian and calabrian plate boundaries causing opening of the messina straits home to large historical earthquakes and unusual volcanism in the aeolian island arc and the intraplate mount etna a divergence of the ionian region from the main part of africa with northeastward motions that reflect the joint influence of african push and hellenic slab pull and are transmitted to calabria and adria could explain motions observed in the sicily channel calabria and apulia as well as the high level of southeastern sicilian seismic activity

high precision locations of the microseismicity preceding the 2002 2003 mt etna eruption 1 to recognize possible signals of intrusive processes leading to the last 2002 2003 flank eruption at mt etna we analyzed the spatial pattern of microseismicity between august 2001 and october 2002 and calculated 23 fault plane solutions fpss for shocks with magnitude greater than 2 5 by applying the double difference approach of waldhauser and ellsworth 2000 on 3d locations we found that most of the scattered epicentral locations further collapse in roughly linear features high precision locations evidenced a distribution of earthquakes along two main alignments oriented ne sw to ene wsw and nw se matching well both with the known tectonic and volcanic lineaments of etna and fpss results moreover microseismicity and swarms located along the nnw sse volcano genetic trend suggest together with geodetic data and volcanological evidence that progressive magma refilling has occurred since february 2002

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

the shallow magma chamber of stromboli volcano italy in this work we integrate artificial and natural seismic sources data to obtain high resolution images of the shallow inner structure of stromboli volcano overall we used a total of 21 953 p readings from an active seismic experiment and an additional 2731 p and 992 s readings deriving from 269 local events the well defined vp vs and vp vs tomograms have highlighted the following i the region where magma cumulates at shallow depths 2 4 km below sea level bsl forming an elongated ne sw high velocity body vp 6 0 km s and vs 3 5 km s with a very fast velocity core 6 5 vp 7 0 km s of 2 km3 ii the presence of some near vertical pipe like structures characterized by relatively high p velocities values mainly linked to past activity e g strombolicchio and iii a near vertical pipe like volume with high vp vs 1 78 1 85 located beneath to the craters down to 1 0 km bsl overlying a deeper region 1 0 to 3 0 km bsl with low vp vs 1 64 1 69 interpreted as the actual and preferential pathway of magma toward the surface our results demonstrate the importance of combining passive and active seismic data to improve in a tomographic inversion the resolution of the volcanic structures and to discover where magma may be stored

volcanic coseismic and seasonal changes detected at white island whakaari volcano new zealand using seismic ambient noise ambient noise interferometry is becoming increasingly popular for studying seismic velocity changes such changes contain information on the structural and mechanical properties of earth systems application to monitoring however is complicated by the large number of processes capable of inducing crustal velocity changes we demonstrate this at white island volcano over a 10 year period containing multiple well documented eruptions using individual seismic stations we detect velocity perturbations that we ascribe to volcanic activity large earthquakes and seasonality distant seismic stations capture widespread nonvolcanic changes that are also present at the volcano comparison between velocity changes recorded by distant and local stations then allows us to distinguish volcanic phenomena from seasonality through this we resolve distinct features in ambient noise derived velocity changes that relate to volcanic unrest and a phreatic eruption illustrating the strength of the approach plain language summary detecting small changes in physical properties at volcanoes is important toward effectively forecasting volcanic eruptions one approach is to monitor the speed of seismic waves at the earth s surface which are sensitive to changes in the rock they pass through at volcanoes such changes may manifest through subsurface pressure increases preceding eruptions correctly interpreting these changes however is complicated many other nonvolcanic processes are also capable of producing similar wave speed perturbations at white island volcano new zealand we detect changes associated with volcanic activity large earthquakes and weather related processes using seismometers located on the volcano we demonstrate that volcanic and nonvolcanic features can be distinguished by comparing changes recorded at the volcano with those recorded at large distances where volcanic changes are not expected to be observed through this we resolve distinct differences that can be related to volcanic activity illustrating the strength of this approach

development and applications of double difference seismic tomography double difference dd tomography is a generalization of dd location it simultaneously solves for the three dimensional velocity structure and seismic event locations dd tomography uses a combination of absolute and more accurate differential arrival times and hierarchically determines the velocity structure from larger scale to smaller scale this method is able to produce more accurate event locations and velocity structure near the source region than standard tomography which uses only absolute arrival times we conduct a stability and uncertainty analysis of dd tomography based on a synthetic data set currently three versions of the dd tomography algorithms exist tomodd tomofdd and tomoadd tomodd assumes a flat earth model and uses a pseudo bending ray tracing algorithm to find rays between events and stations while tomofdd uses a finite difference travel time algorithm and the curvature of the earth is considered both codes are based on a regularly distributed inversion grid with the former for a local scale and the latter for a regional scale in contrast tomoadd adapts the inversion mesh to match with the data distribution based on tetrahedral and voronoi diagrams we discuss examples of applying dd tomography to characterize fault zone structure image high resolution structure of subduction zones and determine the velocity structure of volcanoes

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

a branched magma feeder system during the 1669 eruption of mt etna evidence from a time integrated study of zoned olivine phenocryst populations the 1669 eruption of mt etna was one of the most voluminous and devastating of its flank eruptions in historical times despite a large body of relevant research knowledge of the timing and duration of magma transfer and magma recharge through the internal plumbing system preceding and during the eruption is still limited to address that lack of knowledge we apply a three way integrated method linking systems analysis of crystals a time integrated study of zoned olivine populations and a forward modelling approach using thermodynamic calculations analysis of 202 olivine crystals erupted during the initial pre march 20 i e set1 and the final post march 20 i e set2 and mtrs stages of the eruption reveals the existence of three magmatic environments mes in which the majority of the olivine cores m 1 fo 75 78 and rims i e m 5 fo 51 59 and m 3 fo 65 69 formed application of the rhyolite melts software allowed us to constrain the key intensive variables associated with these mes we find that temperature water content and oxidation state vary between these mes application of diffusion modelling to the zoned olivine crystals allowed us to reconstruct the timing and chronology of melt and crystal transfer prior to and during the 1669 flank eruption we find that following the formation of the olivine cores m 1 fo 75 78 the reservoir m 1 was intruded by batches of more evolved degassed and possibly aphyric m 5 type magma commencing 1 center dot 5 years prior to eruptive activity this is the origin of the set1 olivine rims i e fo 51 59 in the months prior to eruption timescale data show that recharge activity along the newly established pathway m 1 m 5 increased notably starting in november 1668 only a few weeks after the first intrusive episode into the m 1 reservoir a second pulse of magma injections m 3 type magma occurred and a new pathway m 1 m 3 opened this is how the set2 olivine rims i e fo 65 69 formed for several weeks a bifurcated transport system with two dominant magma pathways developed along m 1 m 5 and m 1 m 3 dyke injections accompanied by vigorous seismicity in the days immediately before eruption the local magma transfer dynamics changed and the m 1 m 5 recharge activity slowed down as shown by a relative lack of crystals recording shorter timescales m 1 m 3 recharge however remained high and persisted following the eruption onset on march 11 during which the set1 lavas were drained we propose that the change of the local magma transfer dynamics might be linked to changes in the local stress field brought on during eruption this may potentially have been due to repeated dyke injections into etna s shallow plumbing system disrupting the early m 1 m 5 pathway and at the same time stabilizing the m 1 m 3 route as a dominant feeder this transfer of system feeding would reproduce the observed syn eruptive recharge and mixing in the weeks following eruption onset culminating in the eruption of the later set2 lavas

intrusive mechanisms at mt etna forerunning the july august 2001 eruption from seismic and ground deformation data in this work we present seismological and ground deformation evidence for the phase preparing the july 18 to august 9 2001 flank eruption at etna the analysis performed through data from the permanent seismic and ground deformation networks highlighted a strong relationship between seismic strain release at depth and surface deformation this joint analysis provided strong constraints on the magma rising mechanisms we show that in the last ten years after the 1991 1993 eruption an overall accumulation of tension has affected the volcano then we investigate the months preceding the 2001 eruption in particular we analyse the strong seismic swarm on april 20 24 2001 comprising more than 200 events mmax 3 6 with prevalent dextral shear fault mechanisms in the western flank the swarm showed a ca ne sw earthquake alignment which in agreement with previous cases can be interpreted as the response of the medium to an intrusive process along the approximately nnw sse volcano genetic trend these mechanisms leading to the july 18 to august 9 2001 flank eruption are analogous to ones observed some months before the 1991 1993 flank eruption and more recently in january 1998 before the february november 1999 summit eruption

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

volcanic tremor at mt etna italy preceding and accompanying the eruption of july august 2001 the july 17 august 9 2001 flank eruption of mt etna was preceded and accompanied by remarkable changes in volcanic tremor based on the records of stations belonging to the permanent seismic network deployed on the volcano we analyze amplitude and frequency content of the seismic signal we find considerable changes in the volcanic tremor which mark the transition to different styles of eruptive activity e g lava fountains phreatomagmatic activity strombolian explosions in particular the frequency content of the signal decreases from 5 hz to 3 hz at our reference station etf during episodes of lava fountains and further decreases at about 2 hz throughout phases of intense lava emission the frequency content and the ratios of the signal amplitude allow us to distinguish three seismic sources i e the peripheral dike which fed the eruption the reservoir which fed the lava fountains and the central conduit based on the analysis of the amplitude decay of the signal we highlight the migration of the dike from a depth of ca 5 km to about 1 km between july 10 and 12 after the onset of the effusive phase the distribution of the amplitude decay at our stations can be interpreted as the overall result of sources located within the first half kilometer from the surface although on a qualitative basis our findings shed some light on the complex feeding system of mt etna and integrate other volcanological and geophysical studies which tackle the problem of magma replenishment for the july august 2001 flank eruption we conclude that volcanic tremor is fundamental in monitoring mt etna not only as a marker of the different sources which act within the volcano edifice but also of the diverse styles of eruptive activity

crystal size distributions of plagioclase in lavas from the july august 2001 mount etna eruption during the 2001 eruption of mount etna two independent vent systems simultaneously erupted two different lavas the upper vents system uv opened between 3100 and 2650 m a s l emitted products that are markedly porphyritic and rich in plagioclase while the lower vents system lv opened at 2100 and 2550 m a s l emitted products that are sparsely porphyritic with scarce plagioclase in this study the crystal size distributions csds of plagioclase were measured for a series of 14 samples collected from all the main flows of the 2001 eruption the coefficient of r 2 determination was used to evaluate the goodness of fit of linear models to the csds and the results are represented as a grid of r 2 values by using a numerical code developed ad hoc r 2 diagrams suggest that the 2001 products can be separated into two main groups with slightly different characteristics plagioclase csds from the uvs can be modeled by three straight lines with different slopes while the plagioclase csds from the lvs are largely concave we have interpreted the csds of the uvs as representing three different populations of plagioclases i the large phenocrysts type i which started to crystallize at lower cooling rate in a deep reservoir from 13 to 8 months before eruption onset ii the phenocrysts type ii which crystallized largely during continuous degassing in a shallow reservoir and iii the microlites which crystallized during magma ascent immediately prior to the eruption the plagioclase csd curves for the lvs lava are interpreted to reflect strong and rapid changes in undercooling induced by strong and sudden degassing

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

seismic activity at cadamosto seamount near fogo island cape verdes formation of a new ocean island summary in global catalogues only a handful of earthquakes occurred at or near the cape verde islands the two most recent events occurring in 1998 and 2004 were observed in the southwest of the cape verde archipelago away from aerial volcanic centres event relocation suggests that both earthquakes may occur at the cadamosto seamount a 3 km tall submarine volcanic edifice to the southwest of the active volcanic islands of fogo swath mapping efforts revealed numerous small volcanic cones between the volcanic island of brava and the seamount and between fogo and brava the distribution of volcanic vents may support two plumbing systems one feeding fogo and volcanic cones between fogo and brava and another system feeding cadamosto seamount using ocean bottom seismic stations of opportunity deployed roughly a month after a mb 4 3 earthquake occurred in 2004 august near or at the cadamosto seamount we were able to locate local seismic activity clustering at the seamount we propose that these events reflect brittle rock failure due to magma redistribution in or near a central magma reservoir or more likely dyke intrusion the observations reported here suggest that cadamosto seamount is the seismically most active feature in the archipelago it might be reasonable to hypothesis that ongoing activity causes the cadamosto seamount to grow forming a new oceanic island in the future

integrating ambient noise with gis for a new perspective on volcano imaging and monitoring the case study of mt etna abstract the timely estimation of short and long term volcanic hazard relies on the availability of detailed 3d geophysical images of volcanic structures high resolution seismic models of the absorbing uppermost conduit systems and highly heterogeneous shallowest volcanic layers while particularly challenging to obtain provide important data to locate feasible eruptive centres and forecast flank collapses and lava ascending paths here we model the volcanic structures of mt etna sicily italy and its outskirts using the horizontal to vertical spectral ratio method generally applied to industrial and engineering settings the integration of this technique with web based geographic information system improves precision during the acquisition phase it also integrates geological and geophysical visualization of 3d surface and subsurface structures in a queryable environment representing their exact three dimensional geographic position enhancing interpretation the results show high resolution 3d images of the shallowest volcanic and feeding systems which complement 1 deeper seismic tomography imaging and 2 the results of recent remote sensing imaging the study recovers a vertical structure that divides the pre existing volcanic complexes of ellittico and cuvigghiuni this could be interpreted as a transitional phase between the two systems a comparison with recent remote sensing and geological results however shows that anomalies are generally related to volcano tectonic structures active during the last 17 years we infer that seismic noise measurements from miniaturized instruments when combined with remote sensing techniques represent an important resource to monitor volcanoes in unrest reducing the risk of loss of human lives and instrumentation

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

active stress map of italy we present a new map of the present day stress field in italy obtained from all the available data the map reports 200 horizontal stress directions inferred from 109 borehole breakout data 44 centroid moment tensor solutions 34 other focal mechanisms most of which are from polarity distributions seven stress inversions of microearthquake data two averages of t and p axes of earthquake focal mechanisms in zones of diffuse seismic activity and four fault slip data the integration of breakout data which yield horizontal stress directions with fault plane solutions which reflect the stress regime allows us to obtain an improved map of the present day stress in italy this stress field map can be used for a better comprehension of active tectonic processes for seismic hazard assessment and to foresee the behavior of faults recognized with other methods stress directions obtained from different data although relative to different depth intervals e g 0 7 km for breakouts and 0 20 km for most of the earthquakes and to different tectonic units are consistent since many regions in italy are characterized by an extensional stress regime we report the minimum horizontal stress shmin orientations the map shows that an extensional regime affects most of the apenninic belt conversely a compressional or transpressional regime characterizes the eastern alps the eastern side of the northern apennines and the southern tyrrhenian to northern sicily zone an abrupt change in stress directions marks the transition between northern and southern apennines suggesting that the two arcs are characterized by a different tectonic setting and recent evolution in this paper we report all the data analyzed to date with their geographic coordinates and average stress directions and we describe the main stress provinces in italy in the framework of the tectonic evolution of the region

improving seismic surveillance at mt etna volcano by probabilistic earthquake location in a 3d model the increasing accuracy of 3d velocity models developed recently for mt etna has enabled their use today in routine earthquake locations in this work we tested the potential and performance of a global search probabilistic earthquake lo cation method nonlinloc in a 3d velocity model to improve earthquake locations for seismic surveillance in addition nonlinloc hypocenter locations and those ob tained by standard iterative linear 3d locations simulps 14 have also been com pared to this end a dataset of 328 selected earthquakes occurring during the 2002 2003 etna flank eruption and the recent highest resolution 3d velocity model have been used the results revealed that the differences in hypocentral coordinates between the two methods are typically of the same order or smaller than the spatial location uncertainty to evaluate the consistency of results between the two 3d location algorithms synthetic datasets with real source receiver configuration are also considered furthermore by using nonlinloc we estimated the influence of the source receiver geometry on the quality of hypocenter locations if we vary the net work geometry in a dense and well distributed network like at etna reducing the number of stations by 20 and 50 it is significant that no large systematic hypo central shifts of the relocated earthquakes are observed if they occur within the net work nonlinloc is a fast and promising approach for automatic earthquake locations and surveillance purposes at mt etna because 1 it works well with a reduced num ber of seismic pickings which are usually available in the automatic locations 2 it is not particularly sensitive to tolerable levels of random noise in arrival times and 3 it produces full location uncertainty and resolution information with respect to standard iterative linear 3d locations

the role of crystallized magma and crustal fluids in intraplate seismic activity in talala region saurashtra western india an insight from local earthquake tomography abstract the talala region in saurashtra western india is one of the seismically active intraplate regions on the earth in recent past this region has been site of moderate magnitude earthquakes as well as swarm type earthquake activities to understand the processes of earthquake generation in this intraplate setting we constrained the earthquake distribution pattern along with the crustal seismic p wave velocity vp and vp vs variations using local earthquakes data we inverted 2470 p and 2230 s wave arrival times from 550 earthquakes which were recorded over 11 seismic stations during 2007 to 2012 the earthquakes distribution shows that the seismicity is following nne ssw trend extending for a distance of 25 km and up to 15 km in depth the seismic tomographic images show that the swarm type earthquake activities at shallower depths are mostly in the zone of lower vp and lower vp vs whereas the moderate magnitude earthquakes are occurring in a nw trending zone of higher vp and higher vp vs possibly indicating a zone of crystallized mafic magma which was transported from deeper earth this zone represents a pronounced heterogeneity and provides locale for stress accumulation in this region after 2001 bhuj earthquake mw 7 7 due to stress perturbation the nne ssw trending fault got activated and caused bigger earthquakes in this region moreover the crystallized mafic magma is possibly feeding fluids at shallower depths for causing the swarm type earthquake activities in this region

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

seismic hydraulic fracture migration originated by successive deep magma pulses the 2011 2013 seismic series associated to the volcanic activity of el hierro island in this manuscript we present a new interpretation of the seismic series that accompanied eruptive activity off the coast of el hierro canary islands during 2011 2013 we estimated temporal variations of the gutenberg richter b value throughout the period of analysis and performed high precision relocations of the preeruptive and syneruptive seismicity using a realistic 3 d velocity model our results suggest that eruptive activity and the accompanying seismicity were caused by repeated injections of magma from the mantle into the lower crust these magma pulses occurred within a small and well defined volume resulting in the emplacement of fresh magma along the crust mantle boundary underneath el hierro we analyzed the distribution of earthquake hypocenters in time and space in order to assess seismic diffusivity in the lower crust our results suggest that very high earthquake rates underneath el hierro represent the response of a stable lower crust to stress perturbations with pulsatory character linked to the injection of magma from the mantle magma input from depth caused large stress perturbations to propagate into the lower crust generating energetic seismic swarms the absence of any preferential alignment in the spatial pattern of seismicity reinforces our hypothesis that stress perturbation and related seismicity had diffusive character we conclude that the temporal and spatial evolution of seismicity was neither tracking the path of magma migration nor it defines the boundaries of magma storage volumes such as a midcrustal sill our conceptual model considers pulsatory magma injection from the upper mantle and its propagation along the moho we suggest within this framework that the spatial and temporal distributions of earthquake hypocenters reflect hydraulic fracturing processes associated with stress propagation due to magma movement

changes in heat released by hydrothermal circulation monitored during an eruptive cycle at mt etna italy the shallow vertical temperature profile has been measured in the proximity of an eruptive fissure far about 4 km north northeast from mt etna central craters the monitoring site was a steam heated soil lying between a group of flank fractures on the upper northeast flank of mt etna italy i e on the northeast rift we chose this area because it was close to an eruptive fissure that opened in 2002 and extended from about 2500 to about 1500 m a s l with our aim being to determine a connection between this fracture system and the ongoing volcanic activity heat flux anomalies from the ground from september 2009 to september 2012 were evaluated changes in the hydrothermal release which can be related to variations in volcanic activity are discussed and compared to the published geophysical data the heat flux ranges varied during the pre eruptive from about 7 to 38 w m 2 syn eruptive from about 3 to 49 w m 2 and post eruptive phases with the heat released being lowest at the latter phase from about 1 to 20 w m 2 moreover the heat flux time variation was strongly correlated with the eruption rate from the new southeast crater between january 2011 and april 2012 the migration of magma through active conduits acts as a changing heating source for steam heated soils located above the active fractures our findings suggest that tracking the heat flux above active fractures constitutes a useful investigation field for low cost thermal monitoring of volcanic activity time variations in their emissions could highlight the relationship between a hydrothermal circuit and the local network of fractures possibly indicating variation in the structural weakness of a volcanic edifice continuous monitoring of heat flux combined with a realistic model would contribute to multidisciplinary investigations aimed at evaluating changes in volcano dynamics

how to cope with volcano flank dynamics a conceptual model behind possible scenarios for mt etna abstract volcano flank dynamics poses a serious hazard also involving the inhabited lower slopes mt etna is a well studied unstable volcano and a significant amount of data has been collected on the dynamics of its eastern and southern flanks we first propose a conceptual model to describe and explain flank dynamics at etna we identify the preconditions as due to the differential unbuttressing conditions at the volcano base and the triggering factors as shallow magmatic sources dikes reservoirs evidence and parameters and or observations for flank dynamics are listed summarizing the 1994 2010 period of activity based on this we then propose a set of scenarios possibly occurring in case of unrest of the unstable flanks of mt etna flank unrest is a variation in the steady state condition of the volcano flanks possibly accompanied by significant ground deformation seismicity and eruptions the scenarios may provide a general reference and recommendation in case of five types of multi hazard processes related either as a cause or effect to flank dynamics 1 edifice inflation 2 emplacement of dikes along the ne and or s rifts 3 seismicity along pernicana fault system 4 seismicity on the s sector 5 seismicity along timpe fault system each scenario is analyzed and recommendations are given the scenarios may or may not be related to each other in the sense that the probability of occurrence of one scenario may or may not be contingent or dependent upon the prior occurrence of another these scenarios provide a qualitative analysis of the multi hazard processes related to flank dynamics a more quantitative i e probabilistic characterization is under consideration

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

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

a late pleistocene intertidal boulder pavement from an isostatically emergent coast dundalk bay eastern ireland late pleistocene sequences around dundalk bay eastern ireland record glaciomarine sedimentation near the margin of a grounded ice lobe around 15 ka sp a coastal exposure at cooley point consists of four major facies deposited outside this ice limit 1 a basal mud facies deposited from sediment plumes accumulated following the initial ice marginal retreat inland it contains a well preserved arctic microfauna dominated by the foram elphidium clavatum and the ostracod roundstonia globulifera 2 a flat to undulating boulder facies pavement mostly one clast thick is found pressed into the mud and is characterized by bevelled and striated upper clast surfaces pavement attributes are a result of intertidal activity in a cold climate the boulder source is due to rafting by ice flees from glacigenic debris deposited during an ice advance 3 laminated sand facies drape the pavement and are a result of variable current activity 4 the overlying gravel facies is separated from the sand facies by a marine erosion surface the gravel facies is subaqueous channelized and is overlain by late glacial raised beach ridges locally the gravels have been deformed by ice pressure from partially floating ice flees facies changes record terrestrial submergence and provide evidence for changes in relative sea level during part of the last deglacial cycle the boulder pavement and deformed gravel facies suggest that ice flees and sea ice effects may be more common within stratigraphies along emergent coasts than previously thought though they have a low preservation potential extreme conditions during the deglacial favoured opportunistic microfaunas during mud deposition this event may be related to a major meltwater event within the irish sea basin

numerical evidence enabling reconciliation gravity and height changes in volcanic areas s u m m a r y gravity and height changes reflecting magma accumulation in subsurface chambers are evaluated using finite element models in order to resolve controversial relationships observed in some volcanic areas when significant gravity changes occur without any significant deformation or vice versa it is often difficult if not impossible to jointly explain the observations using the popular mogi model here we explore whether these discrepancies can be explained by magma compressibility and source geometry effects compression of resident magma and expansion of the chamber wall act concurrently to accommodate newly added magma gravityheight ratios are found to mainly depend on i geometry of the sources which control the volume expansion of the chamber ii magma compressibility which affects the contraction of the magma resident in the chamber and iii depth of the sources our numerical results show that when magma compressibility and non spherical sources are taken into account significant gravity variations can indeed be successfully reconciled with negligible height changes this may be the case at etna volcano where gravity changes about 40 gal without any significant deformation below 5 cm were observed during the 1994 1995 inflation period the numerical results point to the accumulation of a 1 4 1010 kg mass into an elongated source simulating a shallow storage region supplying the summit craters

elemental and isotope covariation of noble gases in mineral phases from etnean volcanics erupted during 2001 2005 and genetic relation with peripheral gas discharges abstract during 2001 2005 mount etna was characterized by intense eruptive activity involving the emission of petrologically different products from several vents which involved at least two types of magma with different degrees of evolution we investigated the ratios and abundances for noble gas isotopes in fluid inclusions trapped in olivines and pyroxenes in the erupted products we confirm that olivine has the most efficient crystalline structure for preserving the pristine composition of entrapped gases while pyroxene can suffer diffusive he loss both the minerals also experience noble gas air contamination after eruption helium isotopes of the products genetically linked to the two different magmas fall in the isotopic range typical of the etnean volcanism this result is compatible with the metasomatic process that the etnean mantle is undergoing by fluids from the ionian slab during the last ten kyr as previously inferred by isotope and trace element geochemistry significant differences were also observed among olivines of the same parental magma that erupted throughout 2001 2005 with 3he 4he ratios moving from about 7 0 ra in 2001 volcanites to 6 6 ra in 2004 2005 products changes in he abundances and isotope ratios were attributed to variations in protracted degassing of the same magma bodies from the 2001 to the 2004 2005 events with the latter lacking any contribution of undegassed magma the decrease in 3he 4he is similar to that found from measurements carried out every fifteen days during the same period in gases discharged at the periphery of the volcano to our knowledge this is the first time that such a comparison has been performed so in detail and provides strong evidence of the real time feeding of peripheral emissions by magmatic degassing

internal structure of piton de la fournaise volcano from seismic wave propagation and earthquake distribution abstract arrival times of seismic waves from local earthquakes are inverted for both locating the source and defining the 3 d velocity heterogeneity of piton de la fournaise the lateral heterogeneity of the 2632 m high edifice is resolved as a high velocity plug 1 5 km in diameter surrounded by a low velocity ring which may be interpreted as due to the construction of fournaise on the flank of the older volcano piton des neiges wave mode conversion detected on three component seismograms provides evidence for boundaries of contrasted velocities pre eruptive swarm earthquakes cluster in the high velocity zone under the dolomieu summit crater low strength and cohesion of the surrounding material account for the lack of seismicity for the final 1 3 km radial flow of magma to the vents in enclos fouque beneath the high velocity plug the existence of a body with low velocity for p and even for s waves is well constrained however the walls and base are poorly defined because of the lack of deep earthquakes for sampling the few earthquakes that are located in this depth region usually occur at a depth of around 1 5 km below sea level in the region of the cone this can be considered providing the upper constraint on the lower limit of the aseismic part of the low velocity body the coincidence in time of their occurrence with the swarms above sea level and the eruptions suggests magmatic activation of the low velocity aseismic volume 1 5 km below sea level under the high velocity plug of the cone further down the concentration of seismicity in two swarms between 2 and 4 km under the eastern flank does not allow the structure to be sampled effectively

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

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

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

temporal variations in gravity at mt etna italy associated with the 1989 and 1991 eruptions results are presented from 11 microgravity surveys on mt etna between 1987 and 1993 a period including the major 1989 and 1991 1993 flank eruptions and subordinate 1990 activity measurements were made with lacoste and romberg d 62 and d 157 gravity meters along a network around the volcano between 1000 and 1900 m a s l and since 1992 a n s summit profile gravity changes of as much as 200 gal were observed at scales from the size of the summit region to that of the volcano none was associated with significant changes in ground elevation the data show an increase in gravity for 2 years before the 1989 eruption the increase is attributed to the accumulation of magma 0 25 1 7 109 m3 in an elongate zone oriented nnw sse between 2 5 and 6 km below sea level part of this magma was injected into the volcanic pile to supply the 1989 and 1990 eruptions it also probably fed the start of the 1991 1993 eruption since this event was not preceded by significant gravity changes a large gravity increase up to 140 gal detected across the volcano between june and september 1992 is consistent with the arrival in the accumulation zone of 0 32 2 2 109 m3 of new magma thus favoring continued flank effusion until 1993 a large gravity decrease 200 gal in the summit region marked the closing stages of the 1991 1993 event and is associated with magma drainage from the upper levels of etna s central feeding system

spatio temporal evolution of volcano seismicity a laboratory study we report a laboratory and microstructural study of a suite of deformation experiments in which basalt from mount etna volcano is deformed and fractured at an effective confining pressure representative of conditions under a volcanic edifice 40 mpa particular attention was paid to the formation of a fracture and damage zone with which to stimulate coupled hydro mechanical interactions that create the various types of seismicity recorded on volcanic edifices and which usually precede eruption location of ae events through time shows the formation of a fault plane during which waveforms exhibit the typical high frequency characteristics of volcano tectonic vt earthquakes we found that these vt earthquakes were particularly pronounced when generated using dry samples compared to samples saturated with a pore fluid water vt events generated during deformation of water saturated sample are characterised by a distinctive high frequency onset and a longer low frequency coda exhibiting properties often seen in the field as hybrid events we present evidence that hybrid events are in fact the common type of volcanic seismic event with either vt or low frequency lf events representing end members and whose proportion depend on pore fluid being present in the rock type being deformed as well as how close the rock is to failure we find a notable trend of reducing instances of hybrid events leading up to the failure stage in our experiments suggesting that during this stage the pore fluid present in the rock moves sufficiently quickly to provide a resonance seen as a lf coda our data supports recent modeling and field studies that postulate that hybrid events generated in volcanic areas are likely to be generated through the interaction of hydrothermal fluids moving through a combination of pre existing microcrack networks and larger faults such as those we observe in forensic post test examination

the exceptional activity and growth of the southeast crater mount etna italy between 1996 and 2001 between 1971 and 2001 the southeast crater was the most productive of the four summit craters of mount etna with activity that can be compared on a global scale to the opening phases of the pu u k paianaha eruption of k lauea volcano hawai i the period of highest eruptive rate was between 1996 and 2001 when near continuous activity occurred in five phases these were characterized by a wide range of eruptive styles and intensities from quiet non explosive lava emission to brief violent lava fountaining episodes much of the cone growth occurred during these fountaining episodes totaling 105 events many showed complex dynamics such as different eruptive styles at multiple vents and resulted in the growth of minor edifices on the flanks of the southeast crater cone small pyroclastic flows were produced during some of the eruptive episodes when oblique tephra jets showered the steep flanks of the cone with hot bombs and scoriae fluctuations in the eruptive style and eruption rates were controlled by a complex interplay between changes in the conduit geometry including the growth of a shallow magma reservoir under the southeast crater magma supply rates and flank instability during this period volume calculations were made with the aid of gis and image analysis of video footage obtained by a monitoring telecamera between 1996 and 2001 the bulk volume of the cone increased by 36 106 m3 giving a total 1971 2001 volume of 72 106 m3 at the same time the cone gained 105 m in height reaching an elevation of about 3 300 m the total dre volume of the 1996 2001 products was 90 106m3 this mostly comprised lava flows 72 106 m3 erupted at the summit and onto the flanks of the cone these values indicate that the productivity of the southeast crater increased fourfold during 1996 2001 with respect to the previous 25 years coinciding with a general increase in the eruptive output rates and eruption intensity at etna this phase of intense summit activity has been followed since the summer of 2001 by a period of increased structural instability of the volcano marked by a series of important flank eruptions

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

the three dimensional structure of kilauea volcano hawaii from travel time tomography a linear travel time tomography study of the most active shield volcano of the world kilauea volcano hawaii was undertaken to determine the lateral heterogeneities produced by its intricate magmatic and tectonic environment kilauea provides an ideal setting to do tomography because of its dense seismograph array and many local earthquakes that allow excellent ray coverage of complex subsurface features local p wave data from 12 295 events were inverted using a one dimensional layered velocity model inversions were done for two cell sizes 5 5 5 km and 1 1 1 km to resolve structural regions on different length scales this study provided a view of the average velocity variations relative to a one dimensional velocity model analysis and interpretation of the tomographic images allowed us to infer the following model the main shallow magma reservoir is delineated by a slow velocity region southeast of the summit from 0 to 2 km depth there is a distinct high velocity region centered northwest of the summit from 0 to 2 km depth that represents a cap of dense intrusive dikes surrounding the magma chamber we suggest that the shallow reservoir is a narrow compartmentalized region of sills and dikes centered just south southeast of halemaumau caldera below the main reservoir the summit is imaged as a slightly fast region from 5 to 10 km in the coarse model indicating that the main conduit is structurally defined by an intrusive dike complex until about 10 km the rift zones of kilauea are imaged as major high velocity entities widening to the south with depth until 6 km these fast anomalies are related to the sheeted dike complexes along the rifts on a finer scale slow anomalies suggest the presence of magma pockets centered at 0 2 km depth beneath mauna ulu makaopuhi and puu oo along the east rift zone erz two significant high velocity regions along the lower erz near kalalua and kaliu are inferred to represent intrusive barriers to magma injection along the shallow 0 4 km erz conduit the southwest rift zone may have an intrusive barrier related to a high velocity region just southwest of mauna iki the hilina and kaoiki fault zones are imaged as slow features at shallow depths 5 km related to the open fractures and scarps along the normal faults the koae fault system is imaged as a slightly fast shallow structure 6 km possibly related to intrusive diking from the adjacent rift zones that fill and may even induce the extensional structures associated with this complex fault zone continued inversions with the immense amount of seismic data collected for hawaiian events will allow the detailed development of a three dimensional structural model for kilauea such a model will be extremely useful to seismologists and petrologists alike for understanding the tectonic growth and magmatic evolution of this dynamic shield volcano

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

magmatic dike resonances inferred from very long period seismic signals very long period vlp signals showing simple decaying harmonic oscillations with periods near 10 seconds and lasting for about 300 seconds were observed in association with an earthquake swarm that occurred beneath hachijo island japan results from the source mechanism analysis and waveform simulation based on a fluid filled crack model consistently point to the resonance of a dike filled with a basaltic magma as the source of the vlp signals thus vlp signals can be used to probe the state of the fluid and dynamic processes within a volcanic system

detecting short term evolution of etnean scoria cones a lidar based approach the 2001 and 2002 2003 flank eruptions on mount etna italy were characterized by intense explosive activity which led to the formation of two large monogenetic scoria cones one from each eruption on the upper southern flank of the volcano continuous monitoring of etna especially during flank eruptions has provided detailed information on the growth of these cones they differ in genesis shape and size a set of high resolution 1 m digital elevation models dems derived from light detection and ranging lidar data collected during four different surveys 2004 2005 2006 and 2007 has been used to map morphology and to extract the morphometric parameters of the scoria cones by comparing lidar derived dems with a pre eruption 1998 10 m dem the volume of the two scoria cones was calculated for the first time comparison of the lidar derived dems revealed in unprecedented detail morphological changes during scoria cone degradation in particular the morphologically more exposed and structurally weaker 2002 2003 cone was eroded rapidly during the first few years after its emplacement mainly due to gravitational instability of slopes and wind erosion

volcanoes erupt stressed quartz crystals author s befus ks manga m stan c tamura n abstract 2019 american geophysical union all rights reserved volcanic eruptions are energetic events driven by the imbalance of magmatic forces the magnitudes of these forces remain poorly constrained because they operate in regions that are inaccessible either underground or dangerous to approach new techniques are needed to quantify the processes that drive eruptions and to probe magma storage conditions here we present x ray microdiffraction measurements of volcanic stress imparted as lattice distortions to the crystal cargo of magma from yellowstone and long valley eruptions elevated residual stresses between 100 and 300 mpa are preserved in erupted quartz multiple volcanic forces could be culpable for the deformation so we analyzed crystals from pyroclastic falls pyroclastic density currents and effusive lavas stresses are preserved in all quartz but cannot be attributed to differences in eruption style instead lattice deformation likely preserves an in situ measurement of the deviatoric stresses required for the brittle failure of viscous crystal bearing glass during ascent

petrology and sr nd isotope geochemistry of recent lavas from mt etna bearing on the volcano feeding system abstract the volcanic activity of mt etna during the period 1971 1987 has been investigated based on new volcanological petrographic geochemical and isotopic data the magma output rate since 1971 is much higher than that of the last 200 years marking a significant change in the feeding regime of mt etna the highest output rate has been observed for the 1981 eruption sub aphyric lavas emitted during the excentric activity of 1974 are the most primitive of those studied mg 57 55 the major and trace element chemistry of the lavas indicates limited differentiation by crystal fractionation mainly involving mafic phases nevertheless the observed variability of some ratios between highly incompatible elements suggests possible source heterogeneities the sr nd isotopic compositions range between 0 70362 0 70377 and 0 512829 0 512892 respectively with the lowest and highest 87sr 86sr ratios measured in the 1981 and 1974 lavas the observed isotopic variability is not due to late contamination processes but probably to the mantle source variations in sr and nd isotopic composition could indicate the lack of large magma chambers at any level in mt etna feeding system suggesting a model in which magma reaches the surface through a network of dikes where complete homogenization of different batches cannot be attained

incipient extension along the active convergent margin of nubia in sicily italy cefalu etna seismic zone 1 recent geodetic data are compatible with nne ssw tectonic extension at a rate of 5 mm yr in sicily southern italy within a broader region of net active compression along the nubian plate margin northern africa the structures that accommodate such extensional regime and its cause are still unknown from field structural surveys and seismological analyses the geometry kinematics structural architecture and seismic potential of an extensional seismic zone linking cefalu and mount etna in central eastern sicily are defined the zone includes high angle wnw striking normal and right lateral strike slip faults and subordinate north and nne striking strike slip faults either right or left lateral the occurrence of small discontinuous faults and the absence of related depressions and sedimentary basins suggest that the extensional regime is still in an incipient stage the ongoing seismic activity possibly reactivates preexisting faults instrumentally and historically recorded earthquakes are lower than about 6 in magnitude and destructive events are historically unknown since at least 1300 a d this apparent upper bound of earthquake magnitudes is consistent with the maximum magnitude values estimated from the length of the longest mapped faults and sources of seismic swarms which all together suggest a value between 6 and 6 5 as the maximum expected magnitude that can be proposed at the present stage of investigation for earthquakes in the study area lateral extension on preexisting faults and upwelling of melt mantle material beneath mount etna are considered viable processes to explain at least in part the active extensional tectonics along the cefalu etna seismic zone strike slip seismic faulting beneath mount etna may be part of a previously proposed diffuse transfer zone affecting northeastern sicily and including the tindari fault

petrologic evidence of a complex plumbing system feeding the july august 2001 eruption of mt etna sicily italy after the major 1991 1993 eruption mt etna resumed flank activity in july 2001 through a complex system of eruptive fissures cutting the ne and the s flanks of the volcano and feeding effusive activity fire fountains strombolian and minor phreatomagmatic explosions throughout the eruption magmas with different petrography and composition were erupted the vents higher than 2 600 m a s l hereafter upper vents uv erupted porphyritic plagioclase rich trachybasalt typical of present day summit and flank activity differently the vents located at 2 550 and 2 100 m a s l hereafter lower vents lv produced slightly more primitive trachybasalt dominated by large clinopyroxene olivine and uncommon minerals for etna such as amphibole apatite and orthopyroxene and containing siliceous and cognate xenoliths petrologic investigations carried out on samples collected throughout the eruption provided insights into one of the most intriguing aspects of the 2001 activity namely the coeval occurrence of distinct magmas we interpret this evidence as the result of a complex plumbing system it consists in two separate magma storage systems a shallow one feeding the activity of the uv and a deeper and more complex storage related to the activity of lv in this deep storage zone which is thermally and compositionally zoned the favourable conditions allow the crystallization of amphibole and the occurrence of cognate xenoliths representing wall cumulates throughout 2001 eruption uv and lv magmas remain clearly distinct and ascended following different paths ruling out the occurrence of mixing processes between them furthermore integrating the 2001 eruption in the framework of summit activity occurring since 1995 we propose that the 2001 magma feeding the vents lower than 2 600 m a s l is a precursor of a refilling event which reached its peak during the 2002 2003 etna flank eruption

bayesian inversion of 1994 1998 vertical displacements at mt etna evidence for magma intrusion summary we have developed a bayesian method for the inversion of static ground deformations at volcanic areas the method allows inference of the conditional probability density on the location and mechanism of point sources representing volcanic phenomena isotropic strain nuclei tensile faults embedded in homogeneous elastic media the method has been tested with simulated and real data from volcanic areas we have then analysed vertical displacements recorded at mt etna southern italy from 1994 to 1998 by high precision levelling measurements in this period had been carried out yearly so resulting displacements have been analysed both in consecutive periods and in the cumulative one measurement periods 1994 1995 and 1997 1998 show significant uplift of several centimetres the maximum cumulative displacement amounts to 6 5 cm with a trend similar to each of the two periods 1994 1995 and 1997 1998 the shape of displacement is well approximated by a circular symmetry thus allowing one to hypothesize an isotropic overpressure model as the source simulating magma intrusion at shallow depth the application of the inverse method gives the most probable location at about 4 5 km of depth b s l at about 1 5 km north of the central craters the 95 per cent of probability density is concentrated within a radius of about 0 5 km on the horizontal 1 km on depth the obtained results give important insight on the interpretation of recent eruptive episodes

imaging composite dike propagation etna 2002 case 1 late on the night of 26 october 2002 a dike intrusion started suddenly at mount etna producing intense explosive activity and lava effusion on the southern flank five to six hours afterward a long field of eruptive fractures propagated radially along the northeastern flank of the volcano producing marked variations at the permanent tilt network the dike propagation velocity was inferred by the associated seismicity we modeled the temporal evolution of the continuously recorded tilt data both during the vertical dike propagation on the high south flank on 26 october and during the radial propagation along the northeast flank between 27 and 28 october the reproduction of the recorded tilt signal allowed us to describe the geometry and characteristics of the two dikes in greater detail than the previous static inversion we deduced that the eruption was characterized by an unusual composite mechanism clearly showing a transition from a nearly pure opening mode displacement to a mechanism characterized by an equally strong normal dip slip component and a smaller left lateral strike slip component in this study we demonstrate the interaction between the final segment of the dike and a preexisting structure that was reactivated in response to the intrusion we show that tilt and its modeling represent a powerful tool to verify and constrain dike intrusions in detail

dislocation recovery in olivine under deep upper mantle conditions implications for creep and diffusion the kinetics of dislocation recovery in olivine have been studied up to 10 gpa and 1500 c using a multianvil apparatus dislocations in the 010 100 slip system were generated by high temperature deformation at room pressure and then the specimens were statically annealed at high pressures and temperatures the rate of dislocation recovery was measured as a function of pressure at controlled oxygen fugacity and oxide activity under anhydrous conditions microstructural observations indicate that dislocation recovery occurs through the climb of edge dislocations and hence is controlled by diffusion a small activation volume v 6 1 cm3 mol was obtained which is interpreted to be due to an interstitial mechanism of diffusion for the relevant transport limiting species oxygen or silicon combined with the previous observation of a small activation volume for mg fe diffusion we conclude that ionic diffusion in the olivine lattice in general has small activation volumes and therefore will not vary significantly with depth in the deep portions of the upper mantle we have estimated the relative importance of dislocation and diffusion creep in the upper mantle using the present result and the published results on creep parameters such as stress exponents grain size exponents and activation volume for dislocation creep the results suggest that the dominant creep mechanism may change from dislocation creep in the shallow upper mantle to diffusion creep in the deep upper mantle

crustal structure of the ionian margin of sicily etna volcano in the frame of regional evolution abstract crustal imaging could be achieved on normal incidence reflection profiles offshore eastern sicily by using industrial grade reflection seismic with improved marine sources thick recent sediments a reflective pile including the mesozoic deposits a transparent upper crust and a band of low frequency reflections attributed to the lower crust are imaged in the seismic sections the structure of the crust and its thickness show features inherited from the mesozoic evolution as a passive margin by which ionian basin crust was formed around the hyblean continental promontory of africa to constitute the southern plate in the later convergence with europe the seismic images are also marked by the lithospheric deformation due to the neogene overriding of the northern part of this paleomargin by the calabro peloritan block of european continental crust this transpressive motion may have been guided along the northern part of this paleomargin where the seismic profiles evidence a hinge line between the northward upslope of the moho of that old passive margin and its downslope to the present slab under the tyrrhenian sea etna volcano is located at the intersection of this mantle upwarp by a zone of active sea bottom normal faults which cut across the formerly constructed compressional belt the onset of its volcanic activity is roughly coeval with that of the cessation of interplate thrusting and could hence be related to a change of the coupling of the ionian slab this slab is now probably disconnected from the overriding plate and rolled back in front of the expanding hot tyrrhenian asthenospheric dome with the mobilisation of a viscous mantle material at depth an active lithospheric fault is here imaged which cuts over more than 100 km into the ionian basin the fault runs from the tyrrhenian margin in the sse direction of etna updip of the southwestern lateral edge of this slab leaving north eastward the extruded calabrian block and on its south westward edge the uplifted crust and mantle structures of etna along it the crust including the mesozoic and deeper layers has sagged vertically in the segment in front of the slab with a finite throw across the fault increasing from the basin towards etna

tomographic inversion of local earthquake data from the hengill grensdalur central volcano complex iceland parameters is generally low however a quantitative analysis of resolution provides an unambiguous assessment of well resolved volumes within the better resolved regions of the model the averaging volumes are 1 2 km and 2 4 km in vertical and horizontal extent respectively results of tomographic inversion image three distinct bodies of anomalously high velocity two of these extend from near the surface to a depth of about 3 km these high velocity volumes are located directly beneath the surface expressions of the extinct grensdalur volcano and the extinct husmuli basalt shield the third high velocity structure occurs in the depth range of 3 4 km but does not extend to the surface these three high velocity bodies are interpreted to be solidified magmatic intrusions relatively low velocities underlay limited portions of the trace of the present accretionary axis and a low velocity body is imaged in the roots of the active hengill volcano the volume of lower velocities located beneath the surface expression of the hengill volcano is interpreted to be a region of partial melt

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

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

magma dynamics in the shallow plumbing system of mt etna as recorded by compositional variations in volcanics of recent summit activity 1995 1999 describe the reactivation and the successive evolution of the shallow plumbing system of mt etna between the end of the largest flank eruption of the last three centuries 1991 1993 and the subterminal eruption from south east crater sec which occurred between february and mid november 1999 our analysis is based on observations of the volcanic activity and petrological studies of the erupted volcanics bulk rock mineral and glass compositions have been determined for more than 80 samples erupted from the four summit craters between october 1995 and february 1999 these data allow us to recognise significant compositional variations among the products of different craters in particular volcanics produced between 1995 and 1999 by bocca nuova bn voragine vor and north east crater nec show limited compositional variations and are similar to those observed during recent eruptions e g 1991 93 more primitive magmas have been produced during the more vigorous fire fountains episodes on the contrary the south east crater produced slightly more differentiated volcanics than those of the other summit craters following its reactivation november 1996 until the end of 1998 whole rock compositions of products from this crater show low cao al 2 o 3 whereas interstitial glasses have lower mgo and higher alkali contents than those from the other craters however since the beginning of 1999 and just before the start of the subterminal eruption from sec the volcanics erupted from this crater progressively changed in composition becoming similar to those of the other craters this trend indicates that within the conduits of the summit craters distinct thermal and fluid dynamical regimes can evolve controlling the cooling and crystallisation of etna magmas

spatial variation of seismic b values beneath makushin volcano unalaska island alaska abstract the frequency magnitude distribution was spatially mapped beneath makushin volcano unalaska island alaska using an earthquake catalog of 491 events that occurred between july 2001 and april 2005 an area of high seismic b values 2 0 is found 4 km east of makushin s main vent at a depth between 4 and 7 km the anomaly is statistically significant based on utsu s p test t utsu on seismicity in report of the joint research institute for statistical mathematics tokyo 1992 139 157 and is not data processing method or parameter dependent interestingly a recent insar interferometric study z lu j a power v s mcconnell c wicks jr d dzurism preeruptive inflation and surface interferometric coherence characteristics by satellite radar interferometry at makushin volcano alaska 1993 2000 j geophys res 107 2002 2266 doi 10 1029 2001jb000970 inferred a surface uplift of about 7 cm during the two year period prior to october 1995 centered approximately in the area with the observed anomalous b values the uplift was caused by the volume increase of an inferred magma chamber at a depth of about 7 km the close correspondence of the seismic and insar observations suggests that the heterogeneous area associated with the observed high b values is most likely the result of increased crack density associated with the magma chamber this study demonstrates the effectiveness of combining insar and seismological observations in locating magma chambers and areas of high heterogeneity in the crust

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

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

total volatile flux from mount etna 1 the total volatile tv flux from mount etna volcano has been characterised for the first time by summing the simultaneously evaluated fluxes of the three main volcanogenic volatiles h2o co2 and so2 so2 flux was determined by routine doas traverse measurements while h2o and co2 were evaluated by scaling multigas sensed h2o so2 and co2 so2 plume ratios to the uv sensed so2 flux the time averaged tv flux from etna is evaluated at 21 000 t day 1 with a large fraction accounted for by h2o 13 000 t day 1 h2o dominates 70 the volatile budget during syn eruptive degassing while co2 and h2o contribute equally to the tv flux during passive degassing the co2 flux was observed to be particularly high prior to the 2006 eruption suggesting that this parameter is a good candidate for eruption prediction at basaltic volcanoes

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

mapping of the b value anomalies beneath mt etna italy during july august 2001 lateral eruption 1 the pattern of b value of the frequency magnitude relation or mean magnitude has been analyzed as function of space beneath mt etna during the intense lateral eruption of july august 2001 the data used august 1999 august 2001 subdivided in the pre eruptive and eruption period show significant space variations in the b value for each of the two periods a volume of anomalously high b value can be observed in the southeastern flank of the volcano the anomalies located at 3 1 km b 1 84 0 20 and at about 1 1 km b 2 11 0 29 depth are interpreted as two different steps of a magma migration process ended with the july august 2001 eruption all the available geophysical evidences such as geodetic deformation measurements focal mechanism and tomographic studies support this interpretation

modeling the effects of eruptive and seismic activities on flank instability at mount etna italy 1 the identification and evaluation of trigger mechanisms for volcano flank instabilities and or collapse represent a key issue for risk assessment in densely populated volcanic areas as well as in long distance settings particularly in case of island or coastal volcanoes here we address quantitatively the effects of external seismic and inner magmatic forcing on the stress strain state associated to flank instabilities at mount etna sicily southern italy by means of a 2 d finite difference method numerical modeling modeled seismic actions include strong near field strong far field and low magnitude near field earthquakes magmatic actions consider the inner pressure changes induced by energetic lava fountains in the summit crater area and subvertical and oblique dike ascent below the summit area model results are validated in light of available monitoring data and recent eruptive activity numerical results show that the main strain effects are produced by high magnitude near field earthquakes expected return time of 103 yrs and by vertical uprise of a magma dike below the volcano summit area maximum displacements in the order of tens of centimeters may involve the summit area up to some 106 m3 m over some kilometers laterally stress releases up to 107 pa may affect a limited portion of the magmatic conduit thus favoring major effusive flank eruptions major catastrophic events such as volcano flank collapse should not be expected by applying either individually or combined the aforementioned actions

magma ascent and the pressurization of mount etna s volcanic system after a period of deflation during the 1991 1993 flank eruption mount etna underwent a rapid inflation seismicity and ground deformation show that since 1994 a huge volume of magma intruded beneath the volcano producing from 1998 onward a series of eruptions at the summit and on the flank of the volcano the last of these started on 27 october 2002 is still in progress and can be considered one of the most explosive eruptions of the volcano in recent times here we show how geodetic data and seismic deformation between 1994 and 2001 indicate a radial compression around an axial intrusion consistent with a repressurization of mount etna s plumbing system at a depth of 6 to 15 kilometers which triggered most of the seismicity and provoked the dilatation of the volcano and the recent explosive eruptive activity

fast deformation processes and eruptive activity at mount etna italy the seismic and deformation patterns observed on mount etna before and during the 1991 1993 eruption the third largest since the seventeenth century in terms of lava volume are consistent with the regional tectonic framework of eastern sicily the pattern of the stress field acting on the intermediate and lower crust was defined at the local scale by focal mechanisms of microearthquakes occurring at depths between 10 and 25 km beneath the volcano they provide evidence for a strike slip compressional stress regime with the maximum compressive component acting approximately n s the fault plane solutions and the spatial and temporal distribution of seismicity indicate that usually sinistral shear ruptures occur along approximately ne sw trending fault zones while dip slip ruptures affect approximately nnw sse trending fault zones the latter include the avenues along which magma ascended during the 1991 1993 eruption seismic observations indicate a local inversion of the stress field acting on the upper crust depth 10 km underlying mount etna which was initiated less than 2 months before the eruptive event and disappeared with its end this is consistent with a local tensile regime that favored the magma ascent through the shallow crust the events preceding the eruption and accompanying its onset tilt anomalies and seismic swarms and those occurring shortly after its beginning a mainshock aftershock seismic sequence and associated coseismic tilts provide important evidence for understanding the dynamics of the two main volcano tectonic structures ne sw and nnw sse trending fault zones and associated intrusive mechanisms on etna the shape and location of the eruption feeding dike have been modeled from ground deformation data this approximately nnw sse modeled dike the seismicity and the position of the fractures are consistent with the regional stress field characterized by 1 oriented approximately n s the geophysical data presented and analyzed in the present paper strongly suggest an overall regional tectonic control as well as an active role for the intruding magma in the dynamics of the volcano

spatial mapping of the b value at mount etna italy using earthquake data recorded from 1999 to 2005 1 the spatial pattern of the b value of the frequency magnitude relation has been analyzed using gridding techniques beneath mount etna italy a regional data set of 2900 events with md duration magnitude 1 5 up to 15 km depth occurring between august 1999 and december 2005 has been used two regions with an abnormally high b value have been found one centered beneath the southern part of the valle del bove above the 6 km below sea level bsl deep basement and the other beneath the summit region 2 km bsl east of the central craters we can infer that these high b value anomalies are regions of increased crack density and or high pore pressure related to the presence of nearby magma storage this interpretation is supported by all the available geophysical evidence such as tomographic studies and geodetic deformation measurements the data set has also been subdivided into five periods corresponding to different phases of volcanic activity 2001 preeruption 2001 eruptive 2002 2003 preeruption 2002 2003 eruptive and 2002 2003 posteruption the minimum magnitude of completeness mc and the b value were computed for each period a volume of anomalously high b values can be observed in each of these periods except for the 2002 2003 preeruption interval this approach has allowed the detection of the transient presence of magmatic intrusions during the various periods evaluated

s cl f degassing pattern of water rich alkali basalt modelling and relationship with eruption styles on mount etna volcano abstract our knowledge of the degassing pattern of sulphur chlorine and fluorine during ascent and eruption of basaltic magmas is still fragmental and mainly limited to water poor basalts here we model and discuss the pressure related degassing behaviour of s cl and f during ascent differentiation and extrusion of h2o co2 rich alkali basalt on mount etna sicily as a function of eruptive styles our modelling is based on published and new melt inclusion data for dissolved volatiles co2 h2o s cl f in quenched explosive products from both central conduit 1989 2001 and lateral dyke 2001 and 2002 eruptions pressures are obtained from the dissolved h2o and co2 concentrations and vapour melt partition coefficients of s cl and f are derived from best fitting of melt inclusion data for each step of magma evolution this allows us to compute the compositional evolution of the gas phase during either open or closed system degassing and to compare it with the measured composition of emitted gases we find that sulphur chlorine and fluorine begin to exsolve at respective pressures of 140 mpa 100 mpa and 10 mpa during etna basalt ascent and are respectively degassed at 95 22 55 and 15 upon eruption pure open system degassing fails to explain gas compositions measured during either lateral dyke or central conduit eruptions instead closed system ascent and eruption of the volatile rich basaltic melt well accounts for the time averaged gas composition measured during 2002 type lateral dyke eruptions s cl molar ratio of 5 1 35 bulk cl loss extensive magma fragmentation during the most energetic fountaining phases enhances cl release 55 and produces a lower s cl ratio of 3 7 as actually measured comparatively slower magma rise in the central conduits of etna favours both sulphide saturation of the melt and greater chlorine release 55 resulting in a distinct s cl evolution path and final ratio in eruptive gas in both eruption types any previous bubble melt separation at depth leads to increased s cl and s f ratios in emitted gas high s cl ratios measured during some discrete eruptive events can thus be explained by transitions from closed deep to open shallow system degassing with differential gas transfer extending down to 2 km depth below the vents this depth coincides with the base of the volcanic pile where structural discontinuities and the high magma vesicularity 60 may favour separate gas flow finally the excess s cl f gas discharge through etna summit craters during non eruptive periods requires a mixed supply from shallow magma degassing in the volcanic conduits and deeper derived so2 rich bubbles from the sub volcano plumbing system our modelling provides a useful reference framework for interpreting the monitored variations of s cl and f in mount etna gas emissions as a function of volcanic activity more broadly the observations made for s cl and f degassing on etna may apply to other basaltic volcanoes with water rich magmas such as in arcs

patterns in the recent 2007 2008 activity of mount etna volcano investigated by integrated geophysical and geochemical observations 1 seismic deformation and volcanic gas observations offer independent and complementary information on the activity state and dynamics of quiescent and eruptive volcanoes and thus all contribute to volcanic risk assessment in spite of their wide use there have been only a few efforts to systematically integrate and compare the results of these different monitoring techniques here we combine seismic volcanic tremor and long period seismicity deformation gps and geochemical volcanic gas plume co2 so2 ratios measurements in an attempt to interpret trends in the recent 2007 2008 activity of etna volcano we show that each eruptive episode occurring at the southeast crater sec was preceded by a cyclic phase of increase decrease of plume co2 so2 ratios and by inflation of the volcano s summit captured by the gps network these observations are interpreted as reflecting the persistent supply of co2 rich gas bubbles and eventually more primitive magmas to a shallow depth of 1 2 8 km asl magma storage zone below the volcano s central craters ccs overpressuring of the resident magma stored in the upper ccs conduit triggers further magma ascent and finally eruption at sec a process which we capture as an abrupt increase in tremor amplitude an upward 2800 m asl and eastward migration of the source location of seismic tremor and a rapid contraction of the volcano s summit resumption of volcanic activity at sec was also systematically anticipated by declining plume co2 so2 ratios consistent with magma degassing being diverted from the central conduit area toward sec

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

mt etna volcano modelling of ground deformation patterns of recent eruptions and considerations on the associated precursors abstract the study of the ground deformation associated with the recent eruptions of the etna volcano 1981 1989 1991 93 furnished the opportunity to observe different behaviour relating to the eruptive activity and suggested different feeding and penetration mechanisms inside the volcano edifice in particular the analytical modelling of geodetic data was applied to study the strain sources of these eruptions by the application of single and multiple source models i e composed of two single sources in particular a single tensile dislocation was used to model the se fracture associated with the 1989 eruption a double tensile dislocation was adopted to interpret and model the deformation pattern of the 1981 eruption a double source composed of a tensile dislocation for the final eruptive fracture and a depressuring body for the deflation during the eruption course was considered for the 1991 93 eruption the results of this modelling show that however the final uprising system i e the tensile mechanisms inside the volcano edifice involved the same structure oriented approximately nnw sse this structure was activated by different eruption mechanisms with associated different deformation patterns during these three recent eruptions a review of the methodologies applied and main results obtained in modelling of different sources and mechanisms is presented here the analysis of the deformation data and the performed modelling evidence that the associated precursors can strongly change for the different eruptions in addition the implications both in terms of how the volcano works and in terms of ground deformation precursors are discussed

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

insights into magma and fluid transfer at mount etna by a multiparametric approach a model of the events leading to the 2011 eruptive cycle 1 since the second half of the 1990s the eruptive activity of mount etna has provided evidence that both explosive and effusive eruptions display periodic variations in discharge and eruption style in this work a multiparametric approach consisting of comparing volcanological geophysical and geochemical data was applied to explore the volcano s dynamics during 2009 2011 in particular temporal and or spatial variations of seismicity volcano tectonic earthquakes volcanic tremor and long period and very long period events ground deformation gps and tiltmeter data and geochemistry so2 flux co2 flux co2 so2 ratio were studied to understand the volcanic activity as well as to investigate magma movement in both deep and shallow portions of the plumbing system feeding the 2011 eruptive period after the volcano deflation accompanying the onset of the 2008 2009 eruption a new recharging phase began in august 2008 this new volcanic cycle evolved from an initial recharge phase of the intermediate shallower plumbing system and inflation followed by i accelerated displacement in the volcano s eastern flank since april 2009 and ii renewal of summit volcanic activity during the second half of 2010 culminating in 2011 in a cyclic eruptive behavior with 18 lava fountains from new southeast crater nsec furthermore supported by the geochemical data the inversion of ground deformation gps data and the locations of the tremor sources are used here to constrain both the area and the depth range of magma degassing allowing reconstructing the intermediate and shallow storage zones feeding the 2011 cyclic fountaining nsec activity

buoyancy controlled eruption of magmas at mt etna buoyancy controls the ability of magma to rise its ascent rate and the style of the eruptions geophysical geological and petrological data have been integrated to evaluate the buoyancy of magmas at mt etna the density difference between host rocks and magmas is mainly related to the amount of h2o dissolved in the magma and to the bubble liquid separation processes in the depth interval 22 2 km b s l highly hydrated h2o 3 basaltic magmas or mixtures of bubbles liquid have positive buoyancy and rise rapidly conversely bubble depleted liquids with an intermediate h2o content 1 5 having neutral buoyancy will spread out and form magmatic reservoirs at different depths until cooling crystallization further modify composition and density these different processes account for the magma compositions location of magmatic reservoirs as determined by geophysical methods and the complex eruptive cycles slow effusions fire fountains and plinian eruptions that have been observed in the history of the volcano

magma transport and storage at mt etna italy a review of geodetic and petrological data for the 2002 03 2004 and 2006 eruptions abstract a detailed reconstruction of magma movements within the plumbing system of mt etna volcano has been made by reviewing the eruptions occurring during the october 2002 december 2006 period the availability of continuous gps data allowed detecting at least ten different ground deformation stages highlighting deflationary and inflationary episodes as well as the occurrence of a shallow dike intrusion these data have been coupled with the available petrological datasets including major trace elements and sr nd pb isotope compositions for the volcanic rocks erupted in the 2002 2006 period we identified two main magmatic reservoirs located at different depths along the plumbing system of the volcano the former is located at a depth of 7 km bsl and fed the 2001 and 2002 03 eruptions while the latter located from 3 5 to 5 5 km bsl fed the 2004 05 and 2006 eruptions petrological characteristics of emitted products have been correlated with the inflation vs deflation cycles related to the identified sources providing evidence for changes through time of the evolutionary degree of the erupted magmas along with variations in their geochemical feature finally we suggest that a modification of the deep plumbing system of the volcano might have occurred during the 2002 03 eruption as a consequence of the major seaward motion of the eastern flank of the volcano