an overview of experimental models to understand a complex volcanic instability application to mount etna italy abstract volcanic edifices are often unable to support their own load triggering the instability of their flanks many analogue models have been aimed especially in the last decade at understanding the processes leading to volcano flank instability general behaviors were defined and the experimental results were compared to nature however available data at well studied unstable volcanoes may allow a deeper understanding of the specific processes leading to instability providing insights also at the local scale etna italy constitutes a suitable example for such a possibility because of its well monitored flank instability for which different triggering factors have been proposed in the last two decades among these factors recent insar data highlight the role played by magmatic intrusions and a weak basement under a differential unbuttressing at the volcano base this study considers original and recently published experimental data to test these factors possibly responsible for flank instability with the final aim to better understand and summarize the conditions leading to flank instability at etna in particular we simulate the following processes a the long term activity of a lithospheric boundary as the malta escarpment separating the ionian oceanic lithosphere from the continental sicilian lithosphere below the most unstable east flank of the volcano b spreading due to a weak basement with different boundary conditions c the pressurization of a magmatic reservoir as that active during the 1994 2001 inflation period d dike emplacement as observed during the major 2001 and 2002 2003 eruptions the experimental results suggest that 1 the long term activity of a lithospheric tectonic boundary may create a topographic slope which provides a differential buttressing at the volcano base a preparing factor to drive longer term 10 5 years instability on the east flank of the volcano 2 volcano spreading 4 years has limited effect on flank instability at etna 3 magmatic intrusions 1 years both in the form of mogi like sources or dikes provide the most important conditions to trigger flank instability on the shorter term

on strike slip faulting in layered media summary we study the effects of structural inhomogeneities on the stress and displacement fields induced by strike slip faults in layered media an elastic medium is considered made up of an upper layer bounded by a free surface and welded to a lower half space characterized by different elastic parameters shear cracks with assigned stress drop are employed as mathematical models of strike slip faults which are assumed to be vertical and planar if the crack is entirely embedded within the lower medium case a a cauchy kernel integral equation is obtained which is solved by employing an expansion of the dislocation density in chebyshev polynomials if the crack is within the lower medium but it terminates at the interface case b a generalized cauchy singularity appears in the integral kernel this singularity affects the singular behaviour of the dislocation density at the crack tip touching the interface finally the case of a crack crossing the interface is considered case c the crack is split into two interacting sections each placed in a homogeneous medium and both open at the interface two coupled generalized cauchy equations are obtained and solved for the dislocation density distribution of each crack section an asymptotic study near the intersection between the crack and the interface shows that the dislocation densities for each crack section are bounded at the interface where a jump discontinuity is present as a corollary the stress drop must be discontinuous at the interface with a jump proportional to the rigidity contrast between the adjoining media this finding is shown to have important implications for the development of geometrical complexities within transform fault zones planar strike slip faults cutting across layer discontinuities with arbitrary stress drop values are shown to be admissible only if the interface between different layers becomes unwelded during the earthquake at the crack interface junction planar strike slip faulting may take place only in mature transform zones where a repetitive earthquake cycle has already developed if the rheology is perfectly elastic otherwise the fault cannot be planar we infer that strike slip faulting at depth is plausibly accompanied by en echelon surface breaks in a shallow sedimentary layer where the stress drop is lower than prescribed by the discontinuity condition while ductile deformation or steady sliding at depth may be accommodated by multiple fault branching or by antithetic faulting in the upper brittle layer endowed with lower rigidity but higher stress

dike deflection modelling for inferring magma pressure and withdrawal with application to etna 2001 case abstract we studied the stress effects of the topography load on dike propagation by considering the results from analogue experiments in addition we refined the results by applying numerical simulations using the finite element method fem in order to also consider the medium rheology and real topography we investigated the dike deflection observed during the final dike emplacement accompanying etna s 2001 eruption we cross related the information on the position of the dike from ground deformation modelling with the numerical simulation results with the aim of estimating the final excess pressure of the dike when it started to deflect which proved to be about 4 8 mpa assuming that the pressure decreases linearly with the volume of magma moving from the chamber into the dike we estimated 7 15 mpa as the initial overpressure accumulated at the intermediate magma chamber before its breakout although the previous modelling overestimated the stress the approach presented here leads to infer a compatible stress with the strength of the rocks

rheologic and structural controls on the deformation of okmok volcano alaska fems insar and ambient noise tomography 1 interferometric synthetic aperture radar insar data indicate that the caldera of okmok volcano alaska subsided more than a meter during its eruption in 1997 the large deformation suggests a relatively shallow magma reservoir beneath okmok seismic tomography using ambient ocean noise reveals two low velocity zones lvzs the shallow lvz corresponds to a region of weak fluid saturated materials within the caldera and extends from the caldera surface to a depth of 2 km the deep lvz clearly indicates the presence of the magma reservoir beneath okmok that is significantly deeper 4 km depth compared to previous geodetic based estimates 3 km depth the deep lvz associated with the magma reservoir suggests magma remains in a molten state between eruptions we construct finite element models fems to simulate deformation caused by mass extraction from a magma reservoir that is surrounded by a viscoelastic rind of country rock embedded in an elastic domain that is partitioned to account for the weak caldera materials observed with tomography this configuration allows us to reduce the estimated magma reservoir depressurization to within lithostatic constraints while simultaneously maintaining the magnitude of deformation required to predict the insar data more precisely the insar data are best predicted by an fem simulating a rind viscosity of 7 5 1016 pa s and a mass flux of 4 2 109 kg d from the magma reservoir the shallow weak layer within the caldera provides a coeruption stress regime and neutral buoyancy horizon that support lateral magma propagation from the central magma reservoir to extrusion near the rim of the caldera

time resolved seismic tomography detects magma intrusions at mount etna the continuous volcanic and seismic activity at mount etna makes this volcano an important laboratory for seismological and geophysical studies we used repeated three dimensional tomography to detect variations in elastic parameters during different volcanic cycles before and during the october 2002 january 2003 flank eruption well defined anomalous low p to s wave velocity ratio volumes were revealed absent during the pre eruptive period the anomalies trace the intrusion of volatile rich 4 weight percent basaltic magma most of which rose up only a few months before the onset of eruption the observed time changes of velocity anomalies suggest that four dimensional tomography provides a basis for more efficient volcano monitoring and short and midterm eruption forecasting of explosive activity

dyke intrusion model for the 1989 seismovolcanic activity off ito central japan in the last 10 years extensive earthquake swarms have occurred intermittently in the region east of izu peninsula central japan in july 1989 an active swarm again took place off ito city and among all past activities it was nearest to land and shallowest this activity eventually became a weak submarine eruption the first of its kind in this region associated with this event a borehole tiltmeter at 92 m depth installed several kilometers from the source area detected distinct continuous tilt change with the following features 1 tilt of 20 rad was observed within 1 week preceding the eruption 2 tilt change showed a good correlation to swarm activity 3 no obvious coeruption tilt change was observed on the basis of the tilt record and swarm distribution we constructed a dislocation model to interpret the seismovolcanic activity the model consists of two tensile faults each of which corresponds to magma intrusions in may and july and a right lateral reverse fault representing the largest earthquake m5 5 at 1109 lt on july 9 this model can simulate not only the above tilt data but also the record of a nearby dilatometer the results from daily laser distance measurements and daily global positioning system monitoring as well as results from other conventional distance surveys and leveling surveys in the surrounding region from this model we conclude that the intersection of the shear fault with the tensile fault caused magma to come up into soft sedimentary layers at the seabottom creating a lava dome later an instability brought about a magma phreatic explosion which did not generate any substantial crustal deformations at deeper levels

a seismic reflection and gloria study of compressional deformation in the gorringe bank region eastern north atlantic seismic reflection and gloria side scan sonar data obtained on rrs charles darwin cruise cd64 reveal new information on the styles of deformation in the gorringe bank region at the eastern end of the azores gibraltar plate boundary previous studies suggest that gorringe bank was formed by the overthrusting of a portion of the african plate upon the eurasian plate the new seismic data show however that the most intensely deformed region is located south of gorringe bank on the northern flanks of a nw se trending submarine ridge which includes the ampere and coral patch seamounts the deformation is expressed as long wavelength up to 60 km large amplitude up to 800 m folds in the sediments and underlying acoustic basement which in places are associated with one or more reverse faults and as a fabric of short wavelength folds up to 3 km with a ne trend in contrast the same sedimentary units when traced beneath the flanking plains are undeformed except for some faults with a small throw 30 m some of which offset the seafloor gloria data show that recent deformation is broadly distributed over the region structural trends rotate from 45 in the west to 70 in the east of the region nearly perpendicular to the nw verging plate motion vectors as determined from plate kinematic models flexure modelling suggests that a portion of gorringe bank has loaded 152 ma oceanic lithosphere and that a maximum of 50 km of shortening has occurred at gorringe bank since the mid miocene our observations support a model in which there is no single plate boundary in the region rather that the deformation is distributed over a 200 330 km wide zone

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

transient creep of a composite lower crust 1 constitutive theory a composite model is proposed to describe the time dependent response of the earth s lower crust the motivation for such a model is twofold first new observations of widespread postseismic deformation indicate that the deep continental crust responds viscoelastically having both long and short term decay times second by any number of observationally based rationales the lower crust is compositionally and structurally heterogeneous over many length scales for heterogeneities that have much smaller characteristic lengths than the minimum deformation wavelength of interest the aggregate rheology can be described by composite media theory for wavelengths of the order of the thickness of the lower crust 25 40 km and larger composite theory may be applied to heterogeneities that are smaller than about several hundred meters or equivalent to the vertical extent of a thick lower crustal mylonitic shear zone the composite media theory developed here is constructed using both eshelby mori tanaka theory for aligned generalized spheroidal inclusions and a generalized self consistent method the inclusions and matrix are considered to be maxwellian viscoelastic a rheology that is consistent with past homogeneous models of postseismic stress relaxation the composite theory presented here introduces a transient response to a suddenly imposed stress field which does not appear in homogeneous maxwell models analytic expressions for the amplitude and duration of the transient and for the effective long and short term viscosities of the composite are given which describe the sensitivity to inclusion concentration to shape and to ratio of inclusion to matrix viscosity r

horizontal viscoelastic gravitational displacement due to a rectangular dipping thrust fault in a layered earth model calculations of horizontal displacements due to a rectangular finite thrust fault in a viscoelastic gravitational layered earth model are presented the earth model consists of a single elastic gravitational layer overlying a viscoelastic gravitational half space a review of the full three dimensional theoretical solutions is presented along with the explicit solutions for horizontal displacements several examples of computations for dipping faults with various angles and located at different depths are shown the results indicate that viscoelasticity introduces a long wavelength component into the interseismic deformation field which is not present in published elastic techniques and also that a proper consideration of gravity is necessary only for near field computations at longer periods of time a pattern is found in the cumulative displacement of cycled earthquakes which indicates that the viscoelastic displacements are visible for longer recurrence time events and that these may serve as a time index for the various stages between cycles

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

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

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

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

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

3d numerical deformation model of the intrusive event forerunning the 2001 etna eruption abstract 3d finite elements models were carried out in order to evaluate the ground deformation produced by the dike intrusion occurred at etna volcano in the 2001 the finite element method fem allows for considering the medium heterogeneity and the real topography of the volcano firstly we validated the method in a homogeneous elastic half space and compared the results with those obtained from analytical dislocation models we performed a convergence analysis to quantify the discretization errors which are sensitive to the size and quality of the mesh elements and can cause inaccurate numerical solutions secondly several numerical models were conducted to appreciate how the complex distribution of elastic medium parameters and the topography make the numerical results differ from the simple analytical solutions the numerical model which account for the real topography of etna volcano and medium heterogeneity well match the ground deformation observed at the gps stations between 11 and 16 july 2001 it appears that topography and heterogeneities provide more details about the ground deformation near the summit crater area that are missed when homogeneous half space models are used however only few discrepancies between the analytical and the numerical models are observed at the gps stations which coarsely sample the volcanic edifice far away from the summit craters

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

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

finite element model predictions of static deformation from dislocation sources in a subduction zone sensitivities to homogeneous isotropic poisson solid and half space assumptions 1 dislocation models can simulate static deformation caused by slip along a fault these models usually take the form of a dislocation embedded in a homogeneous isotropic poisson solid half space hipshs however the widely accepted hipshs assumptions poorly approximate subduction zone systems of converging oceanic and continental crust this study uses three dimensional finite element models fems that allow for any combination including none of the hipshs assumptions to compute synthetic green s functions for displacement using the1995 mw 8 0 jalisco colima mexico subduction zone earthquake and associated measurements from a nearby gps array as an example fem generated synthetic green s functions are combined with standard linear inverse methods to estimate dislocation distributions along the subduction interface loading a forward hipshs model with dislocation distributions estimated from fems that sequentially relax the hipshs assumptions yields the sensitivity of predicted displacements to each of the hipshs assumptions for the subduction zone models tested and the specific field situation considered sensitivities to the individual poisson solid isotropy and homogeneity assumptions can be substantially greater than gps measurement uncertainties forward modeling quantifies stress coupling between the mw 8 0 earthquake and a nearby mw 6 3 earthquake that occurred 63 days later coulomb stress changes predicted from static hipshs models cannot account for the 63 day lag time between events alternatively an fem that includes a poroelastic oceanic crust which allows for postseismic pore fluid pressure recovery can account for the lag time the pore fluid pressure recovery rate puts an upper limit of 10 17 m2 on the bulk permeability of the oceanic crust

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

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

the effects of topography on magma chamber deformation models application to mt etna and radar interferometry we have used a three dimensional elastic finite element model to examine the effects of topography on the surface deformation predicted by models of magma chamber deflation we used the topography of mt etna to control the geometry of our model and compared the finite element results to those predicted by an analytical solution for a pressurized sphere in an elastic half space topography has a significant effect on the predicted surface deformation for both displacement profiles and synthetic interferograms not only are the predicted displacement magnitudes significantly different but also the map view patterns of displacement it is possible to match the predicted displacement magnitudes fairly well by adjusting the elevation of a reference surface however the horizontal pattern of deformation is still significantly different thus inversions based on constant elevation reference surfaces may not properly estimate the horizontal position of a magma chamber we have investigated an approach where the elevation of the reference surface varies for each computation point corresponding to topography for vertical displacements and tilts this method provides a good fit to the finite element results and thus may form the basis for an inversion scheme for radial displacements a constant reference elevation provides a better fit to the numerical results

modelling of ground deformation and gravity fields using finite element method an application to etna volcano summary elastic finite element models are applied to investigate the effects of topography and medium heterogeneities on the surface deformation and the gravity field produced by volcanic pressure sources changes in the gravity field cannot be interpreted only in terms of gain of mass disregarding the ground deformation of the rocks surrounding the source contributions to gravity changes depend also on surface and subsurface mass redistribution driven by dilation of the volcanic source both ground deformation and gravity changes were firstly evaluated by solving a coupled axisymmetric problem to estimate the effects of topography and medium heterogeneities numerical results show significant discrepancies in the ground deformation and gravity field compared to those predicted by analytical solutions which disregard topography elastic heterogeneities and density subsurface structures with this in mind we reviewed the expected gravity changes accompanying the 1993 1997 inflation phase on mt etna by setting up a fully 3 d finite element model in which we used the real topography to include the geometry and seismic tomography to infer the crustal heterogeneities the inflation phase was clearly detected by different geodetic techniques edm gps sar and levelling data that showed a uniform expansion of the overall volcano edifice when the gravity data are integrated with ground deformation data and a coupled fem modelling was solved a mass intrusion could have occurred at depth to justify both ground deformation and gravity observations

models of ground deformation from vertical volcanic conduits with application to eruptions of mount st helens and mount etna we present simple analytical models of ground deformation from inflation of vertical volcanic conduits or pipes we compare three cases corresponding to 1 a pressurized pipe with closed end at the top that resists the internal pressure 2 a pressurized pipe with top open for which the internal deformation is mainly dislocation of the cylindrical walls and 3 a pipe shaped region that dilates for the closed pipe we use eshelby s inclusion theory to model deformation from a thin pressurized elongated prolate ellipsoid in a full space which we express in terms of double forces to satisfy surface boundary conditions we superimpose image solutions by using double forces derived from mindlin s half space solution for the point force for the open pipe we apply the volterra integral to dislocation across a cylindrical surface and generalize it to the half space using mindlin s point force solution these two solutions show marked differences from the line of dilatation solution ratios of maximum horizontal deformation to maximum vertical deformation for the pipe models are significantly greater than values for the center or line of dilatation models this and the more gradual fall off of the deformation with distance may be used as diagnostics for discriminating between pipe like sources and dilatational sources on volcanoes where both components of the deformation field are available as examples we compare the closed pipe model with deformation associated with dome building on mount st helens volcano and tilt predicted by the open pipe model with tilt measured during a period of explosive eruptive activity on mount etna sicily in 1995 comparison between model values and the measurements suggests that the effective elastic moduli of the volcanic cones are very low

viscoelastic displacement and gravity changes due to point magmatic intrusions in a gravitational layered solid earth summary we present a method for the computation of time dependent geodetic and geophysical signatures deformation potential and gravity changes due to magmatic intrusions in a layered viscoelastic gravitational medium this work is an extension of a deformation model previously developed to compute effects due to volcanic loading in an elastic gravitational layered media the model assumes a planar earth geometry useful for near field problems and consists of welded elastic and viscoelastic layers overlying a viscoelastic half space every layer can either be considered elastic or viscoelastic the intrusion treated as a point source can be located at any depth in any of the layers or in the half space several examples of theoretical computations for different media are also presented we have found that in line with previous results obtained by other authors introducing viscoelastic properties in all or part of the medium can extend the effects displacements gravity changes etc considerably and therefore lower pressure increases are required to model given observed effects the viscoelastic effects seem to depend mainly on the rheological properties of the layer zone where the intrusion is located rather than on the rheology of the whole medium we apply our model to the 1982 1984 uplift episode at campi flegrei modelling simultaneously the observed vertical displacement and gravity changes the results clearly show that for a correct interpretation of observed effects it is necessary to include the gravitational field in the anelastic theoretical models this factor can change the value and pattern of time dependent deformation as well as the gravity changes explaining cases of displacement without noticeable gravity changes or vice versa cases with uplift and incremental gravity values and other cases the combination of displacement and gravity changes is found to be especially effective in constraining the possible characteristics of the magmatic intrusion as well as the rheology of the medium surrounding it

qp structure of mount etna constraints for the physics of the plumbing system 1 in this study we present the three dimensional qp structure of the mount etna volcano italy obtained by using local earthquake data the attenuation along ray paths t computed from the high frequency decay of velocity spectra is used to reconstruct the deep structure of the volcano down to 15 km depth the tomographic images reveal two broad low qp anomalies at 0 and 3 km depth located to the south and southwest of the summit area and extending at depth to the west of a central high qp anomaly located between 6 and 15 km depth the joint analysis of p wave attenuation and velocity allows us to better constrain the physics of the plumbing system the shallow low qp anomalies are associated with high vp anomalies beneath the top of the volcano and normal low vp toward its western borders we interpret the regions of low qp and normal low vp as shallow volumes where magmatic fluids are stored conversely the low qp high vp region may indicate intensely fractured rock volumes filled by fluids surrounding the magma branches at depth the low qp anomaly defines the path of the magma ascent to the west of an extremely high qp high vp volume located beneath the southeastern side of the summit area the high qp high vp body is interpreted to be the compact solidified high density intrusive body formed by nonerupted material during past volcano activity

crustal architecture and tectonic evolution of the gulf of cadiz sw iberian margin at the convergence of the eurasian and african plates 1 the gulf of cadiz located at the southwestern iberian margin is characterized by widespread seismicity compressional and strike slip fault plane solutions and by a large elongated positive free air gravity anomaly the gulf of cadiz gravity high gcgh multichannel seismic profiles across and along gcgh together with bathymetric and gravity data allow us to study in detail the tectonic architecture and crustal structure of the gulf of cadiz the upper shelf and slope of the gulf of cadiz includes the main structural domains of the betic fold and thrust belt in the middle part of the gulf the paleozoic basement crops out on the shallow guadalquivir bank and is associated with the largest signature of the gcgh whereas toward the outer part of the gulf the basement deepens progressively a large nw se normal fault and conjugate ne sw faults define a prominent basement high associated with the gcgh modeling of the gcgh suggests localized crustal thinning of 10 km along the central part of the gulf of cadiz probably generated during the mesozoic rifting episode between the iberian and african plates concentric wedges of fold and thrust belts and large allochthonous masses were emplaced in the gulf of cadiz during the neogene compressional phase the final emplacement of these units becomes progressively young from the se pre early langhian toward the foreland in the nw late tortonian seafloor surface ruptures pockmarks and submarine landslides provide evidence of active faulting in the gulf of cadiz to accommodate the present day convergence between the african and eurasian plates previously extensional faults have probably been reactivated and inverted at depth as suggested by the intermediate depth seismicity

an accurate and efficient method for including the effects of topography in three dimensional elastic models of ground deformation with applications to radar interferometry topography has a large effect on the results predicted by elastic surface deformation models in regions of significant relief in some cases topography may have more influence on the predicted deformation field than do model source parameters we have developed an approximate analytical technique for including topographic effects that retains most of the computational simplicity of elastic half space models while providing an accurate representation of topographic effects we use a series expansion of the elastic half space solution with a small slope approximation yielding a set of higher order corrections the integrated effect of these corrections is evaluated using fourier methods we investigate the effectiveness of our method by comparing predicted results for a tilted triaxial ellipsoid with those predicted by finite element models the resulting displacements and displacement gradients are in good agreement with finite element results both for relatively smooth topography synthetically generated and for the greater relief in the vicinity of mount etna volcano we then compare the results of our method with those predicted by traditional elastic half space models using different reference elevations and with a previously proposed method of estimating topographic effects our new method provides a significantly better fit to the finite element results than do the other methods our method is able to accurately portray both the number and the horizontal pattern of fringes in a synthetic interferogram when compared with finite element results in particular the method accurately represents the broadening of fringes that is observed in regions of high relief as well as reproducing the location of the fringe center and the topographically induced deviation of the fringes from a regular pattern elastic half space models typically show a fringe center that is displaced with respect to the finite element results indicating that parameter inversions based on such a model would provide incorrect estimates of the horizontal source position the lack of topographically generated fringe distortions in elastic half space results would also likely lead to inaccuracies in the predicted magnitude and orientation of proposed deformation sources our new technique over comes these limitations and should be useful when evaluating either traditional geodetic results or the greater areal coverage provided by interferometric observations

postseismic strain following the 1989 loma prieta earthquake from gps and leveling measurements postseismic deformation in the 5 years following the 1989 loma prieta earthquake has been measured with the global positioning system and precise leveling postearthquake velocities at distances greater than 20 km from the coseismic rupture are not significantly different from those observed in the 20 years prior to the earthquake however velocities at stations within 20 km of the rupture exceed preearthquake rates and exhibit unanticipated contraction normal to the strike of the san andreas fault system a combination of forward modeling and nonlinear optimization suggests that the observed postseismic deformations were caused by aseismic oblique reverse slip averaging 2 9 cm yr on the san andreas fault and or the loma prieta rupture zone and 2 4 cm yr reverse slip along a buried fault within the foothills thrust belt the best fitting sources of postseismic deformation are all located at depths of less than 15 km we find no evidence for accelerated flow or shear below the loma prieta rupture in the first 5 years following the earthquake the inferred postseismic slip is likely to have been caused by the coseismic stress change updip of the 1989 rupture

coupling of eruptions and earthquakes at mt etna sicily italy a case study from the 1981 and 2001 events 1 changes in coulomb failure stress cfs induced by dike propagation during two flank eruptions on mt etna 1981 and 2001 are calculated for the most seismically active faults on the east slope of the volcano the right lateral timpe fault system oriented nnw sse and the left lateral pernicana fault oriented e w calculations performed using coulomb 2 5 software indicate that intrusion of a nnw dike on the nw side of the volcano 1981 eruption rises cfs on both the timpe and pernicana faults in contrast intrusion of a n s dike at high elevation on the south flank 2001 eruption rises cfs only on timpe fault system these results are compatible with the observed pattern of seismicity but emphasize an extremely heterogeneous state of stress on the east flank of the volcano

3 d finite element modelling of deformation and stress associated with faulting effect of inhomogeneous crustal structures summary modelling of deformation and stress caused by earthquake faulting or fault motion based on a homogeneous elastic half space model does not include crustal rigidity layering and lateral variations geological data and seismic surveys indicate that the crust is elastically inhomogeneous and that rigidity layering and heterogeneities are likely to affect the magnitude and pattern of deformation and stress we use the finite element method fem to investigate deformation and stress generated by strike slip tensile and thrust faulting considering rigidity layering in the crust for a fault with a dimension of 25 10 km and a slip value of 0 5 m cutting through the top 10 km of the crust the deformation and stress change associated with the three modes of faulting are calculated for an island arc crustal structure represented by three models of rigidity layering the results indicate i the maximum effect in horizontal displacements due to crustal layering for the investigated models is 19 7 mm and 28 8 mm for strike slip and tensile faulting respectively for thrust faulting the effect is up to 58 3 mm this remarkable effect is due to the offset of layers by thrust faulting which dynamically changes the crustal structure both horizontally and vertically ii the maximum effect in vertical deformation due to crustal rigidity layering for strike slip and tensile faulting is 5 mm in contrast the effect for thrusting is 30 3 mm iii the effect in the shear stress change at a depth of 7 5 km for the different styles of faulting ranges from 0 02 mpa to 0 10 mpa an additional modelling analysis of subduction thrusting at the japan trench with a detailed structural model based on seismic surveys further confirms the significant distortion caused by a homogeneous model that ignores crustal structural information overall the effect of crustal rigidity layering is at least 20 per cent for surface deformation and 15 per cent for stress changes at depth in light of the present accuracy of global positioning system gps observations 2 mm and the estimate of stress change required for earthquake hazard analysis ca 0 01 mpa the results from the numerical experiments indicate that crust inhomogeneity rigidity layering and lateral variations should be included in any quantitative models of faulting

the intrusive process leading to the mt etna 2001 flank eruption constraints from 3 d attenuation tomography 1 we have analyzed 291 shallow seismic events leading to the july 17 august 9 2001 flank eruption at mt etna volcano to obtain high resolution three dimensional 3 d images of seismic attenuation of p waves qp down to 2 km depth 2293 p wave spectra have been inverted for seismic attenuation to calculate t values considering a frequency independent q and a 2 type source model the 3 d tomographic images reveal an anomalous region of very low qp values between 10 and 30 located in the same place where the 2001 dike emplaced we interpret this anomaly as the effect of fluid intrusion magma rich in gas in the uppermost part of the etna volcano just before the 2001 eruption this confirms that attenuation is a physical parameter sensitive to the thermal state of crustal volumes through which seismic waves travel

thermomechanics of shallow magma chamber pressurization implications for the assessment of ground deformation data at active volcanoes abstract in this study we utilize thermomechanical models to investigate how magma chambers overpressurize as the result of either magmatic recharge or volatile exsolution by implementing an adaptive reservoir boundary condition we are able to track how overpressure dissipates as the magma chamber expands to accommodate internal volume changes we find that the size of the reservoir greatly impacts the resultant magma chamber overpressure in particular overpressure estimates for small to moderate sized reservoirs 1 10 km 3 are up to 70 lower than previous analytical predictions we apply our models to santorini volcano in greece where recent seismic activity and ground deformation observations suggested the potential for eruption the incorporation of an adaptive boundary condition reproduces mogi flux estimates and suggests that the magma reservoir present at santorini may be quite large furthermore model results suggest that if the magma chamber is 100 km 3 overpressures generated due to the high magma flux may not exceed the strength of the host rock thus requiring an additional triggering mechanism for eruption although the adaptive boundary condition approach does not calculate the internal evolution of the magma reservoir it represents a fundamental step forward from elastic mogi models and fixed boundary solutions on which future investigations of the evolution of the magma can be built

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

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

implications structurales et paleogeographiques de la presence de messinien a l ouest de gibraltar structural and paleogeographical implications of the existence of messinian layers west of gibraltar abstract a core sampled west of gibraltar shows at its base lower messinian sediments typical of the mediterranean area and at its top pleistocene sediments of atlantic type these observations lead us to consider the existence of a basin west of gibraltar which would have been isolated from the atlantic during the upper miocene though still communicating with the mediterranean through a south rifan strait the isolation of this basin during the messinian would be the result of the creation of a south iberian spur made up of the series folded during miocene events between the moroccan and iberian margins at about 9 w

temperature dependent viscoelastic modeling of ground deformation application to etna volcano during the 1993 1997 inflation period abstract we used the finite element method fem for modeling time dependent ground deformation due to volcanic pressure sources embedded in a viscoelastic medium especially in volcanic areas the presence of heterogeneous materials and high temperatures produce a lower effective viscosity of the earth s crust that calls for considering the thermal regime of crustal volume surrounding the magmatic sources we propose a thermo mechanical numerical model for evaluating the temperature dependency of the viscoelastic solution both temperature distributions and ground deformation are evaluated by solving an axi symmetric problem to estimate the effects of thermo viscoelastic response of the medium the thermo mechanical model permits to evidence that viscoelastic relaxation is responsible for significant time dependent variations in long term deformation these effects may be relevant for the interpretation and quantitative assessments of the pressure changes within magmatic sources with this in mind we reviewed the ground deformation observed on etna volcano during the 1993 1997 inflation period by setting up a fully 3d temperature dependent viscoelastic model since 1993 different geodetic measurements edm gps sar and leveling data identified an inflationary phase characterized by a uniform and continuous expansion of the overall volcano edifice that was not perturbed by eruptive activity the numerical model including significant viscoelastic material and reduced crustal rigidity around the magmatic source enables to produce deformation comparable with those obtained from elastic model requiring a significantly lower pressure for a purely elastic model with the same geometry and rigidity the pressure change necessary to describe the 1993 through 1997 inflation is around 320 mpa whereas for the viscoelastic model a pressure increase of about 200 mpa is required

nonlinear estimation of geometric parameters in fems of volcano deformation integrating tomography models and geodetic data for okmok volcano alaska 1 the internal structure loading processes and effective boundary conditions of a volcano control the deformation observed at the earth s surface using finite element models fems we simulate the response due to a pressurized magma chamber embedded in a domain having a distribution of elastic material properties we present the pinned mesh perturbation method pmp to automate the mesh generation process in response to perturbations of the position of a simulated magma chamber within an fem domain using insar observed deformation for the 1997 eruption of okmok volcano alaska as an example we combine pmp with nested monte carlo methods to estimate a set of linear and nonlinear parameters that characterize the depressurization and location of the magma chamber beneath okmok s caldera the three dimensional fems used in the pmp method simulate the distribution of material properties of tomography models and account for the irregular geometry of the topography and bathymetry the estimated depth of an assumed spherical magma chamber is 3527 54 55 m below sea level and is sensitive to the distribution of material properties this depth is consistent with lithostatic pressure constraints and very long period tremor observations the fit of this fem to the insar data is a significant improvement at the 95 confidence level compared to the fit of a corresponding fem having homogeneous material properties the methods presented here allow us to construct deformation models that integrate tomography models with geodetic observations in an effort to achieve a deeper understanding of active volcanoes

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

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

microbial community composition and biogeochemical processes in cold water coral carbonate mounds in the gulf of cadiz on the moroccan margin abstract this study reports on the microbial community composition of bacteria and archaea in a cluster of carbonate mounds located in the gulf of cadiz on the moroccan margin at water depths between 500 and 600 m amidst a field of mud volcanoes although nearly no live corals were observed on the mound surfaces gravity cores examined from both alpha and beta mound md 169 microsystems cruise cores md08 3218 and md08 3214 respectively display a high number of cold water coral fragments scleractinians throughout the cores molecular techniques using taxonomic 16s rrna gene pcr dgge and functional mcra and dsrab gene markers were applied to assess prokaryotic diversity this was compared with the distribution of total cell counts and a novel approach of atp activity measurements to identify microbial activity hot spots during core sub sampling despite broad similarities in the prokaryotic community at the two sites some differences were observed at specific depth intervals in correlation with differences in atp activity alpha and beta mound showed evidence for the presence of a shallow sulfate methane transition zone smtz with increased sulfate reduction rates indicating the presence of microbially mediated anaerobic oxidation of methane aom the key marker gene for methanotrophy and methanogenesis mcra was only found at alpha mound within the smtz where aom is occurring in contrast sulfate reducing prokaryotes dsrab were identified in cores from both mounds but at different depths correlating with increased atp activity and sr rates this study demonstrates that the cold water coral carbonate mounds of the pen duick escarpment host a diverse and metabolically active prokaryotic population although it remains unclear to what extent prokaryotes are important for the initiation of a cold water coral carbonate mound our results provide some evidence that microbes may play a role in the cementation of the mound sediment through microbially induced carbonate precipitation and thereby help preserve the mound structure

the relationship between the north atlantic jet and tropical convection over the indian and western pacific oceans abstractboreal winter jet variability over the north atlantic is investigated using 40 yr european centre for medium range weather forecasts re analysis era 40 data where the variability is defined by the first eof of the zonal wind on seven vertical levels the principal component time series of this eof is referred to as the jet index a pattern correlation analysis indicates that the jet index more accurately describes intraseasonal north atlantic zonal wind variability than does the north atlantic oscillation nao a series of composite calculations of the jet index based on events of intraseasonal convective precipitation over the tropical indian and western pacific oceans reveals the following statistically significant relationships 1 negative jet events lead enhanced indian ocean precipitation 2 positive jet events lag enhanced indian ocean precipitation 3 positive jet events lead enhanced western pacific ocean precipitation and 4 negative jet events lag enhanced western pacific ocean p

geodetic analysis of dike intrusion and motion of the magma reservoir beneath the summit of kilauea volcano hawaii 1970 1985 we use leveling and trilateration data collected on kilauea volcano to constrain the location of deformation sources caused by magma accumulation intrusion and eruption for the 13 inflationary epochs examined combinations of an expanding point source and one or two opening rectangular dislocations mimic inflation of the summit reservoir and formation of dike s respectively the combined model adequately accounts for the deformation data and is consistent with the seismicity observed during each epoch for 10 deflationary epochs however the data require only a contracting point source confidence in these results is gained by noting that locations of the sources of both inflation and deflation are coincident within the observed uncertainties of the data the function of network geometry and the inversion procedure it appears therefore that magma accumulation at kilauea volcano may be characterized by the growth of dikes during inflation of the summit reservoir drainage of the reservoir on the other hand is not accompanied by significant closure of dikes in contrast to previous studies e g fiske and kinoshita 1969 dvorak et al 1983 that do not include the dislocation or dike growth component of summit magma accumulation and concluded that the source of inflation migrates over a 5 km2 area we find that a single magmatic reservoir source accounts for data collected during all inflationary and deflationary epochs results which compare favorably with those obtained from the point ellipsoid model can be used to estimate the distribution of stresses within the volcano in the near field of the source

toward a realistic deformation model of the 2008 magmatic intrusion at etna from combined dinsar and gps observations abstract the combination of i dinsar data capable of observing deformation pattern at a spatial resolution unachievable with other sparse geodetic measurements ii continuous gps data able to provide temporal constraints on source evolution and iii numerical modeling procedures appropriate to consider a non uniform opening distribution of a source embedded in a 3d heterogeneous medium allowed us to infer a complex and realistic deformation model of the magmatic intrusion that occurred in the northern flank of etna on 13 may 2008 numerical modeling of ground deformation data defines a near vertical dyke intruded for 2 5 km starting from a depth of 1400 m asl right below the summit craters and reaching shallow crust level in the northern flank from the estimated opening distribution of the propagating magma filled crack which reached a maximum value of about 2 m a volumetric expansion of crustal rocks of about 5 3 106 m3 was obtained also we clarified the temporal evolution of the northward magmatic intrusion which lasted just over 5 h with an initial magma propagation velocity of about 1 2 km h and decreased to about 0 24 km h as the driving pressure lowered due to the effusive activity started at southern vents

the effects of thermomechanical heterogeneities in island arc crust on time dependent preeruptive stresses and the failure of an andesitic reservoir using ground deformation data from soufriere hills volcano shv we present results from numerical modeling of the temperature and time dependent stress evolution in a mechanically heterogeneous crust prior to reservoir failure and renewed eruptive activity the best fit models do not allow us to discriminate between a magmatic plumbing system consisting of either a single vertically elongated reservoir or a series of stacked reservoirs a prolate reservoir geometry with volumes between 50 and 100 km3 reservoir pressure changes between 4 and 7 mpa and reservoir volume changes between 0 03 and 0 04 km3 with magma compressibility between 4 10 11 and 1 10 9 pa 1 provide plausible thermomechanical model parameters to explain the deformation time series around an order of magnitude less overpressure than is generally inferred from homogeneous elastic crustal models reservoir failure is predicted to occur at the crest of the reservoir except for reservoirs with highly compressible magma 4 10 9 pa for which subhorizontal sill formation is predicted upon reservoir failure introducing a deep crustal hot zone modulates the partitioning of strains into the hotter underlying crust and results in a further reduction in overpressure estimates to values of around 1 2 mpa upon reservoir failure deduced volume fluxes are consistent with constraints from thermal modeling of active subvolcanic systems and imply dynamic failure of a compressible magma mush column feeding eruptions at shv our interpretation of the results is that the combined thermomechanical effects of a deep crustal hot zone and hot encasing rocks around a midcrustal andesitic reservoir fundamentally alter the time dependent subsurface stress and strain partitioning upon reservoir priming these effects substantially influence surface strains recorded by volcano geodetic monitoring

magma faults and gravitational loading at mount etna the 2002 2003 eruptive period 1 mount etna is characterized by a complex structural setting that influences its evolution in order to understand how the interaction between dike forming intrusions and faulting influences the kinematics of the volcanic edifice we developed a numerical model it takes account of the topography the medium heterogeneities the gravitational loading and the most active crustal discontinuities a parameterization of the apparent coefficient of friction as a function of the depth has been considered in the range from 0 01 to 0 5 the density values used young s modulus and poisson s ratio range from about 1700 to 3200 kg m3 8 5 to 140 gpa and 0 15 to 0 35 respectively the model was applied to the 2002 2003 etna eruption the resulting deformation pattern was in agreement with the data provided by the continuous gps stations and the seismological knowledge obtaining displacements up to 1 m some discrepancies between the recorded ground deformation field and the modeled displacements allowed us to make some hypotheses on the volcano tectonic e g for the pernicana fault or regional tectonic origin acireale s alfio fault system of the crustal discontinuities moreover our results suggested that the pernicana fault is characterized by a very low apparent coefficient of friction less than 0 1 furthermore we evaluated the contribution of the gravitational loading and found that it implies a variation of about 10 of the overall deformation pattern our results clearly showed that the weight of the volcanic edifice acts in opposition to the magmatic intrusions conversely we found that the presence of medium heterogeneities may favor the eastern flank movements toward the se and the spreading of the summit area playing a fundamental role in ascending magma finally we investigated the shallow sliding model and found that dike forming intrusions produce negligible displacements less than 1 mm along the subhorizontal detachment surface therefore the gravitational loading during dike forming intrusions is not able to trigger sliding processes along this plane

deposit loading and its effect on co eruptive volcano deformation abstract erupting volcanoes commonly exhibit characteristic ground deformation that is typically interpreted in terms of pressure changes of magma reservoirs within the crust however other processes may also be significant since 1995 the soufriere hills volcano montserrat has erupted about 1 km3 of magma over five discrete extrusive phases with clear cycles of associated ground deformation recorded by gps here we consider the contribution to deformation by loading of the ground surface with erupted deposits we estimate topographic change and net deformation for the whole eruption to date between november 1995 and february 2010 we derive the surface load distribution using differenced digital elevation data which additionally enables us to constrain the budget of erupted lava about a third of the lava erupted from soufriere hills since 1995 remains in subaerial onshore deposits more than previously thought another third is emplaced immediately offshore and the remaining third has been transported further afield we combine the deposit thickness map with representative deposit densities to calculate surface load and model the deformation response using finite elements our results show that net displacements accumulated over 14 years on montserrat tens of centimetres could be explained by loading of erupted deposits on the flanks the proportion of the observed deformation that can be explained by loading alone depends on crustal rheology using rheology structures favoured in the literature our forward modelled displacements are remarkably similar to long term observations down to detail that we ascribe to localised load topography interaction results suggest that the shallow crust beneath montserrat is more compliant than usually assumed in geodetic models with more rigid rheology at depth loading is largely accommodated by elastic strain in the shallow crust top few kilometres with negligible contribution from intra crustal viscous flow over the time period investigated we thus infer that the role of stress transfer from the surface load in metering magma reservoir behaviour must be negligible but may influence degassing in the shallow conduit for example our findings suggest that when volcanic ground deformation accompanies a voluminous eruption geodetic model inversions will be misled if data are not appropriately corrected for the surface loading effect

numerical inversion of deformation caused by pressure sources application to mount etna italy summary the interpretation of geodetic data in volcanic areas is usually based on analytical deformation models although numerical finite element fe modelling allows realistic features such as topography and crustal heterogeneities to be included the technique is not computationally convenient for solving inverse problems using classical methods in this paper we develop a general tool to perform inversions of geodetic data by means of 3 d fe models the forward model is a library of numerical displacement solutions where each entry of the library is the surface displacement due to a single stress component applied to an element of the grid the final solution is a weighted combination of the six stress components applied to a single elementsource the pre computed forward models are implemented in a global search algorithm followed by an appraisal of the sampled solutions after providing extended testing we apply the method to model the 1993 1997 inflation phase at mt etna documented by gps and edm measurements we consider four different forward libraries computed in models characterized by homogeneous heterogeneous medium and flat topographic free surface our results suggest that the elastic heterogeneities of the medium can significantly alter the position of the inferred source while the topography has minor effect

stick slip vs stable sliding fault behaviour a case study using a multidisciplinary approach in the volcanic region of mt etna italy abstract in active volcanic zones fault dynamics is considerably fast but it is often difficult to separate the pattern of nearly continuous large scale volcanic processes inflation deflation processes flank instability from impulsive episodes such as dyke intrusions or coseismic fault displacements at etna multidisciplinary studies on active faults whose activity does not strictly depend on volcanic processes are relatively few here we present the case study of the san leonardello fault an active structure located in the eastern flank of mt etna characterised by a well known seismic history this fault saw renewed activity in may 2009 when pre seismic creeping along the southern segment preceded an mw 4 0 earthquake in the northern segment followed by some twenty five aftershocks later in march april 2016 creep events reactivated the southern section of the same fault both the seismic and aseismic phenomena were recorded by the seismic and gnss networks of ingv osservatorio etneo and produced surface faulting that left a footprint in the pattern of ground deformation detected by the insar measurements we demonstrate that the integration of multidisciplinary data collected for volcano surveillance may shed light on different aspects of fault dynamics and allow understanding how coseismic slip and creep alternate in space and time along the strike moreover we use findings from our independent datasets to propose a conceptual model of the san leonardello fault taking into account behaviour and previous constraints from fault based seismic hazard analyses although the faulting mechanisms described here occur at a very small scale compared with those of a purely tectonic setting this case study may represent a perfect natural lab for improving knowledge of seismogenic processes also in other fault zones characterised by stick slip vs stable sliding fault behaviour

space geodetic evidence for multiple magma reservoirs and subvolcanic lateral intrusions at fernandina volcano galapagos islands 1 using interferometric synthetic aperture radar insar measurements of the surface deformation at fernandina volcano galapagos ecuador acquired between january 2003 and september 2010 we study the structure and the dynamics of the shallow magmatic system of the volcano through the analysis of spatial and temporal variations of the measured line of sight displacement we identify multiple sources of deformation beneath the summit and the southern flank at least two sources are considered to represent permanent zones of magma storage given their persistent or recurrent activity elastic deformation models indicate the presence of a flat topped magma reservoir at 1 1 km below sea level and an oblate spheroid cavity at 4 9 km b s l the two reservoirs are hydraulically connected this inferred structure of the shallow storage system is in agreement with previous geodetic studies and previous petrological analysis of both subaerial and submarine lavas the almost eight year long observation interval provides for the first time geodetic evidence for two subvolcanic lateral intrusions from the central storage system in december 2006 and august 2007 subvolcanic lateral intrusions could provide the explanation for enigmatic volcanic events at fernandina such as the rapid uplift at punta espinoza in 1927 and the 1968 caldera collapse without significant eruption

subsurface deformations in a layered elastic half space summary methods using the theory of dislocations to model deformations on the surface of a layered half space are extended to calculate deformation inside the medium the source may be of different type such as strike slip inclined dip slip and a centre of compression the method is exposed for point sources lame s constants for each layer may be chosen independently of each other the layers are assumed to be laterally homogeneous but may have different thickness results for different displacement components and depths are shown in comparison to an unlayered homogeneous half space the displacements obtained differ substantially depending on the distance from the source and on the contrast in lame s constants the method is useful in modelling deformation and tilt observed underground and related to seismic or aseismic sources at medium and far distances from the measuring device they also allow us to use information about the source and from superficial measurements to trace deformations down from the surface through the medium especially including layers with higher rigidity thus asperities may be simulated

effects of geological complexities on coseismic displacement hints from 2d numerical modelling by means of a 2d finite element procedure we tested how heterogeneities at the scale of seismogenic fault affect the displacement we defined one or more slip distributions for two typical normal faulting earthquakes in the central apennines computed the displacement occurred within different structures including lateral heterogeneities and compared the different displacement profiles to isolate the effect of the crustal structure to understand at what magnitude the heterogeneities affect the observation significantly we compared the predicted coseismic displacement with gps and dinsar data for the colfiorito 1997 earthquake we find that heterogeneities significantly affect the observable horizontal coseismic displacement for the larger magnitudes whereas for smaller quakes they affect horizontal displacement close to the fault trace only

the 24 december 2018 eruptive intrusion at etna volcano as revealed by multidisciplinary continuous deformation networks cgps borehole strainmeters and tiltmeters

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

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

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

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

mechanisms of low frequency variability in a simple model with orography abstract mechanisms of low frequency variability are examined in an extended run of a two level nonlinear global model with a single isolated mountain the presence of the mountain modifies the low frequency behavior compared with that in a zonally homogeneous model in two ways first slow variations in the zonally averaged circulation the zonal index are manifest as variability in the train of stationary waves generated by the orography second trains of low frequency rossby waves are modified by their propagation through the model s zonally asymmetric time mean flow these eddies become meridionally elongated at the jet entrance and zonally elongated at its exit allowing them to extract energy barotropically from the mean flow in the jet exit

a non linear geodetic data inversion using abic for slip distribution on a fault with an unknown dip angle summary we have developed a method of geodetic data inversion for slip distribution on a fault with an unknown dip angle a common strategy for obtaining slip distribution in previous studies is to first determine the fault geometry by minimizing the square misfit under the assumption of a uniform slip on a rectangular fault and then apply the usual linear inversion technique to estimate a slip distribution on the determined fault it is not guaranteed however that the fault determined under the assumption of a uniform slip gives the best fault geometry for a spatially variable slip distribution the inverse problem is non linear for cases with unknown fault geometries but the non linearity of the problems is actually weak when we can assume the fault surface to be a flat plane in particular when a clear trace of coseismic faults is observed on the earth s surface only the dip angle is an unknown parameter to determine the fault geometry then we regarded the dip angle as an hyperparameter that prescribed the structure of parametric models and obtained the best estimate of the dip angle using akaike s bayesian information criterion abic with the best estimate of the dip angle we can obtain the slip distribution on the fault based on the maximum likelihood principle we applied the method to the insar data of the 1995 dinar turkey earthquake and obtained a much lower dip angle than the previous analyses

how temperature dependent elasticity alters host rock magmatic reservoir models a case study on the effects of ice cap unloading on shallow volcanic systems abstract in geodynamic numerical models of volcanic systems the volcanic basement hosting the magmatic reservoir is often assumed to exhibit constant elastic parameters with a sharp transition from the host rocks to the magmatic reservoir we assess this assumption by deriving an empirical relation between elastic parameters and temperature for icelandic basalts by conducting a set of triaxial compression experiments between 200 c and 1000 c results show a significant decrease of young s modulus from 38 gpa to less than 4 7 gpa at around 1000 c based on these laboratory data we develop a 2d axisymmetric finite element model including temperature dependent elastic properties of the volcanic basement as a case study we use the snaefellsjokull volcanic system western iceland to evaluate pressure differences in the volcanic edifice and basement due to glacial unloading of the volcano first we calculate the temperature field throughout the model and assign elastic properties accordingly then we assess unloading driven pressure differences in the magma chamber at various depths in models with and without temperature dependent elastic parameters with constant elastic parameters and a sharp transition between basement and magma chamber we obtain results comparable to other studies however pressure changes due to surface unloading become smaller when using more realistic temperature dependent elastic properties we ascribe this subdued effect to a transition zone around the magma chamber which is still solid rock but with relatively low young s modulus due to high temperatures we discuss our findings in the light of volcanic processes in proximity to the magma chamber such as roof collapse dyke injection or deep hydrothermal circulation our results aim at quantifying the effects of glacial unloading on magma chamber dynamics and volcanic activity

fault geometry and slip distribution of the 1999 chi chi taiwan earthquake imaged from inversion of gps data gps measurements of coseismic displacements from the 1999 chi chi taiwan earthquake are modeled using elastic dislocation theory we find that a single fault plane cannot fit the data but rather a curved fault surface consisting of multiple segments dipping 20 25 best fits the observations the model fault exhibits reverse and left lateral slip on a 75 km long n s trending segment and reverse and right lateral slip on a 25 km e w trending segment at the northern end of the rupture the 21 dipping e w segment is inconsistent with previous interpretations of high angle tear faulting

dynamics of low frequency variability barotropic mode the dynamics of low frequency variability is investigated in terms of sensitivity to the dependence of its relative zonal position of a single storm track in a simplified global circulation model a streamfunction tendency equation is derived that explicitly distinguishes between barotropic and baroclinic components one of the two low frequency patterns located in the center of the storm track grows barotropically and its decay is accomplished by low frequency eddy vorticity fluxes and the baroclinic contribution to the divergence term the growth and decay of the second pattern located at the downstream end of the storm track is dominated by nonlinear processes this indicates that the dynamical processes leading to growth and decay of low frequency patterns depend on the zonal position of the low frequency pattern relative to a storm track

the structure of the atlantic mediterranean transition zone from the alboran sea to the horseshoe abyssal plain iberia africa plate boundary abstract the diffusive plate boundary between iberia and africa has been analyzed by means of already published and new 28 multichannel seismic profiles covering most of the atlantic margins of sw spain and nw morocco this region includes the prolongation of the betic rifean tectonic units along the gibraltar arc one of the most characteristic units in the study area is the miocene seismically chaotic unit that has been divided in a tectonic and a gravitational domains in accordance to previous interpretation by torelli et al torelli l sartori r zitellini n 1997 the giant chaotic body in the atlantic ocean off gibraltar new results from a deep seismic reflection survey marine and petroleum geology 14 125 138 in this work we redefine the limits of both domains and rename them as the gulf of cadiz imbricate wedge and the horseshoe gravitational unit we interpret the gulf of cadiz imbricate wedge as a west migrating thick thrust system that build up in a relatively short period of time this unit constitutes the continuation of the miocene chaotic units observed onshore to the front of the external units in the betics and the rif the guadalquivir allochthonous unit and the rides prerifaines the horseshoe gravitational unit covering an approximate area of 18 000 km2 with a volume of around 23 000 km3 is interpreted as giant submarine debris flows sourced from the up building of the gulf of cadiz imbricate wedge surrounding basement highs and the continental iberian slope the fast westward migration of the flysch units the external units and the gulf of cadiz imbricate wedge from the early miocene to the late tortonian corresponds to a different tectonic process than the protracted but slow nnw to nw convergence of africa our interpretation favours the westward slab retreat theory to form the arcuate shape of the atlantic side of the iberia africa plate boundary the subduction mechanism as well as potential roll over was only active from late early miocene to late miocene spanning about 12 myr

hydrocarbon derived ferromanganese nodules in carbonate mud mounds from the gulf of cadiz mud breccia sediments and clasts as nucleation sites abstract more than 500 fe mn nodules were sampled during the anastasya 01 cruise tasyo project along the continental margin of the gulf of cadiz eastern central atlantic at the confluence of the mediterranean sea with the atlantic ocean where extensive nodule fields were discovered based on wide previous studies that included swath bathymetry multi channel and very high resolution seismic reflection gravimetry magnetism and underwater photography surveys nodules were collected at water depths ranging from 850 to 1000 m associated with hydrocarbon derived ankerite and dolomite chimneys and crusts thirty six selected samples among the various morphological types were used for the laboratory analysis of physical properties morphology colour surface texture sphericity weight and size mineralogy xrd optical and electronic microscopy and geochemistry xrf aas icp ms epma gc ms s c and o isotopes nodules show a wide range of sizes densities weights and morphologies nodules are formed of multiple millimetre thick layers of fe and mn oxyhydroxides surrounding the nucleus composed of early middle miocene plastic marl the textures developed by the fe and mn oxyhydroxides layers are massive laminated detrital and mottled to dendritic goethite lepidocrocite mn oxides 7 a manganates and 10 a manganates quartz and phyllosilicates are the main components accessory minerals are calcite dolomite siderite rhodochrosite kutnohorite pyrite chalcopyrite potassium feldspar zircon rutile ilmenite and chlorite fe mn carbonates from the siderite rhodochrosite continuous series are forming part of the marl nuclei framboidal filamentous and globular textures are observed in fe mn oxides and pyrite suggesting biogenic origin nodules show a high mean abundance of fe 38 6 moderate mn 6 0 and low contents of trace metals and rees compared to the average content of deep seabed polymetallic nodules from other oceanic areas the mn fe ratio ranges from 0 07 to 0 25 the studied nodules hold in their oxide layers hydrocarbons n alkanes derived from marine bacterial activity aromatic hydrocarbons in the form of phenanthrene are also present which is characteristic of mature petroleum the structure mineralogy and chemical composition in the studied nodules are similar to those of diagenetic hydrogenetic continental margin nodules rather than deep sea nodules we suggest that the formation of this type of nodule occurred through a combined diagenetic hydrogenetic growth process involving fluid venting from deep seated hydrocarbon reservoirs bio mineralization processes and bottom current erosion

data assimilation strategies for volcano geodesy abstract ground deformation observed using near real time geodetic methods such as insar and gps can provide critical information about the evolution of a magma chamber prior to volcanic eruption rapid advancement in numerical modeling capabilities has resulted in a number of finite element models targeted at better understanding the connection between surface uplift associated with magma chamber pressurization and the potential for volcanic eruption robust model data fusion techniques are necessary to take full advantage of the numerical models and the volcano monitoring observations currently available in this study we develop a 3d data assimilation framework using the ensemble kalman filter enkf approach in order to combine geodetic observations of surface deformation with geodynamic models to investigate volcanic unrest the enkf sequential assimilation method utilizes disparate data sets as they become available to update geodynamic models of magma reservoir evolution while the enkf has been widely applied in hydrologic and climate modeling the adaptation for volcano monitoring is in its initial stages as such our investigation focuses on conducting a series of sensitivity tests to optimize the enkf for volcano applications and on developing specific strategies for assimilation of geodetic data our numerical experiments illustrate that the enkf is able to adapt well to the spatial limitations posed by gps data and the temporal limitations of insar and that specific strategies can be adopted to enhance enkf performance to improve model forecasts specifically our numerical experiments indicate that 1 incorporating additional iterations of the enkf analysis step is more efficient than increasing the number of ensemble members 2 the accuracy of the enkf results are not affected by initial parameter assumptions 3 gps observations near the center of uplift improve the quality of model forecasts 4 occasionally shifting continuous gps stations to provide variability in the locations of observations results in better model predictions than utilizing fixed locations when the number of available instruments is limited 5 spotty insar data coverage on the flanks of a volcano due to topographic shadows and or atmospheric interference does not adversely impact the effectiveness of enkf if the available coverage is 50 and 6 snow or glacial obstruction in the center of uplift can adversely impact enkf forecasts by utilizing these strategies we conclude that the enkf is an effective sequential model data fusion technique for assimilating multiple geodetic observations to forecast volcanic activity at restless volcanoes

def3d a fem simulation tool for computing deformation near active faults and volcanic centers abstracts most analytical solutions of deformation near active and volcanic centers are limited to simple geometries and homogeneous media to solve more complex problems we have developed a fem software package called def3d for modeling deformation caused by earthquakes or magma chambers in laterally inhomogeneous media features presently available include modeling of split node technique equivalent body forces and surface tractions def3d presently supports the isotropic elastic and viscoelastic materials behaving as a maxwell body the program has been verified in various test cases by strict comparison with analytical solutions displacements following the 2008 wenchuan earthquake and magma induced surface deformation near changbaishan volcano are used to test the reliability of the software package

stress field at a transcurrent plate boundary in the presence of frictional heat production at depth a model is proposed to study the modification of the stress field at a transcurrent plate boundary due to frictional heat production at depth two cases are considered a stable and a stretched lithosphere the model is applied to those weak faults where the dynamic friction is small compared to a static one if the deformation along the brittle portion of the fault is entirely accommodated by a series of seismic ruptures in a quasi static state where the fault has been moving for millions of years the long term thermal field perturbation due to these ruptures results in only a few degrees and can be neglected the boundary zone is considered as a viscoelastic body subject to a constant strain rate the lower section of the boundary is assumed to slip aseismically along a vertical transcurrent fault and to completely accommodate the plate motion while the upper section is locked the slipping zone is divided into a semi brittle zone placed between the isothermal surfaces of 300 c and 450 c and a ductile zone beneath the frictional heat is calculated by assuming a linearly decreasing friction in the semi brittle and a constant friction in the ductile zones the heat modifies the temperature field producing an upward movement of the semi brittle and ductile fault sections as a consequence the thickness of the brittle fault section is reduced and friction at the base of this section is less the stress field in the boundary zone is calculated as a function of time for different friction profiles and slip rates on the fault owing to heat production a greater stress concentration is produced on the brittle fault section while shear stress is lowered in regions occupied by the uplifted semi brittle layer these effects are found to be remarkable only in the case of a stable zone with a standard unperturbed geotherm while they are irrelevant in a stretched zone with a high geothermal gradient in any case the role of the semi brittle layer appears to be more prominent in the case of boundaries with higher slip rates due to the presence of higher stress values

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

high temperature experiments on the elastic and anelastic behaviour of magmatic rocks measurements of the complex shear modulus have been performed on various ultrabasic and basic rocks dunite peridotite gabbro and basalts and a synthetic forsterite at temperatures between 600 and 1500 c depending on the sample material and in the frequency range from 0 003 to 30 hz under forced torsional oscillations the maximum shear stress was 0 3 mpa and the strains were of the order 5 10 6 to 5 10 5 measurements of the electrical resistivity as a function of temperature have been carried out together with the mechanical experiments to indicate the beginning of partial melting the absolute values of the shear modulus below tm are comparable with the results of other authors the onset of melting shows up in a rapid decrease of both shear modulus and electrical resistivity at high temperatures t 0 8 tm the absorption factor q 1 follows a power law q 1 exp a rt with 0 15 0 30 and a between 100 and 200 kj mol 1 towards lower temperatures this high temperature background is superimposed by a flat absorption peak which shifts from high to low frequencies with falling temperature this peak can often be described by a lognormal distribution of simple relaxation processes with a standard deviation of about three and a mean relaxation time exp a rt with a 400 600 kj mol 1 above tm a third contribution to q 1 is observed that can be regarded as independent of frequency between 1 and 30 hz this last component which contributes 50 to the total absorption is attributed to the melt phase in the samples an explanation for the high temperature background and the peak is proposed which is based on the relaxation of pinned dislocation lines by some coupling mechanism via the reorganisation of the stress field with increasing deformation this process may be responsible for both features at very high temperatures and low frequencies a small influence of steady state flow on q 1 is observed and below t 0 6 tm thermal cracking or thermoelastic losses may contribute to q 1 the influence of lithostatic pressure on q 1 is estimated and the extrapolation of the experimental data to the p t conditions of the uppermost mantle are in good agreement with published earth models an attempt is made to establish a general q t relationship from the experimental data

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

effects of topography on the interpretation of the deformation field of prominent volcanoes application to etna we have investigated the effects of topography on the surface deformation field of volcanoes our study provides limits to the use of classical half space models considering axisymmetrical volcanoes we show that interpreting ground surface displacements with half space models can lead to erroneous estimations of the shape of the deformation source when the average slope of the flanks of a volcano exceeds 20 tilting in the summit area is reversed to that expected for a flat surface thus neglecting topography may lead to misinterpreting an inflation of the source as a deflation comparisons of mogi s model with a three dimensional model shows that ignoring topography may lead to an overestimate of the source volume change by as much as 50 for a slope of 30 this comparison also shows that the depths calculated by using mogi s solution for prominent volcanoes should be considered as depths from the summit of the edifices finally we illustrate these topographic effects by analyzing the deformation field measured by radar interferometry at mount etna during its 1991 1993 eruption a three dimensional modeling calculation shows that the flattening of the deflation field near the volcano s summit is probably a topographic effect

modeling of alos and cosmo skymed satellite data at mt etna implications on relation between seismic activation of the pernicana fault system and volcanic unrest abstract we investigate the displacement induced by the 2 3 april 2010 seismic swarm the largest event being of ml 4 3 magnitude by means of dinsar data acquired over the volcano by the cosmo skymed and alos radar systems satellite observations combined with leveling data allowed us to perform a high resolution modeling inversion capable of fully capturing the deformation pattern and identifying the mechanism responsible for the pfs seismic activation the inversion results well explain high gradients in the radar line of sight displacements observed along the fault rupture the slip distribution model indicates that the fault was characterized by a prevailing left lateral and normal dip slip motion with no fault dilation and hence excludes that the april 2010 seismic swarm is a response to accommodate the stress change induced by magma intrusions but it is due to the tectonic loading possibly associated with sliding of the eastern flank of the volcano edifice these results provide a completely different scenario from that derived for the 22 september 2002 m3 7 earthquake along the pfs where the co seismic shear rupture was accompanied by a tensile mechanism associated with a first attempt of magma intrusion that preceded the lateral eruption occurred here a month later these two opposite cases provide hints into the behavior of the pfs between quiescence and unrest periods at etna and pose different implications for eruptive activity prediction and volcano hazard assessment the dense pattern of ground deformation provided by integration of data from short revisiting time satellite missions together with refined modeling for fault slip distribution can be exploited at different volcanic sites where the activity is controlled by volcano tectonic interaction processes for a timely evaluation of the impending hazards

thermal weakening of the carbonate basement under mt etna volcano italy implications for volcano instability abstract the physical integrity of a sub volcanic basement is crucial in controlling the stability of a volcanic edifice for many volcanoes this basement can comprise thick sequences of carbonates that are prone to significant thermally induced alteration these debilitating thermal reactions facilitated by heat from proximal magma storage volumes promote the weakening of the rock mass and likely therefore encourage edifice instability such instability can result in slow gravitational spreading and episodic to continuous slippage of unstable flanks and may also facilitate catastrophic flank collapse understanding the propensity of a particular sub volcanic basement to such instability requires a detailed understanding of the influence of high temperatures on the chemical physical and mechanical properties of the rocks involved the juxtaposition of a thick carbonate substratum and magmatic heat sources makes mt etna volcano an ideal candidate for our study we investigated experimentally the effect of temperature on two carbonate rocks that have been chosen to represent the deep heterogeneous sedimentary substratum under mt etna volcano this study has demonstrated that thermal stressing resulted in a progressive and significant change in the physical properties of the two rocks porosity wet i e water saturated dynamic poisson s ratio and wet vp vs ratio all increased whilst p and s wave velocities bulk sample density dynamic and static young s modulus dry vp vs ratio and dry dynamic poisson s ratio all decreased at temperatures of 800 c the carbonate in these rocks completely dissociated resulting in a total mass loss of about 45 and the release of about 44 wt of co 2 uniaxial deformation experiments showed that high in situ temperatures 500 c significantly reduced the strength of the carbonates and altered their deformation behaviour above 500 c the rocks deformed in a ductile manner and the output of acoustic emissions was greatly reduced we speculate that thermally induced weakening and the ductile behaviour of the carbonate substratum could be a key factor in explaining the large scale deformation observed at mt etna volcano our findings are consistent with several field observations at mt etna volcano and can quantitatively support the interpretation of 1 the irregularly low seismic velocity zones present within the sub volcanic sedimentary basement 2 the anomalously high co 2 degassing observed 3 the anomalously high vp vs ratios and the rapid migration of fluids and 4 the increasing instability of volcanic edifices in the lifespan of a magmatic system we speculate that carbonate sub volcanic basement may emerge as one of the decisive fundamentals in controlling volcanic stability