Project V4 Flank PROJECT V4 FLANK

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1 Project V4 Flank PROJECT V4 FLANK 259

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3 Project V4 Flank Coordinators: Project V4 - FLANK Hazards related to the flank dynamics at Mt. Etna Giuseppe Puglisi, Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania, Piazza Roma, 2, Catania, Italy, puglisi-g@ct.ingv.it Valerio Acocella, Dipartimento Scienze Geologiche Università Roma Tre, Largo S.L. Murialdo, 1, Roma, Italy, acocella@uniroma3.it Objectives Many active volcano flanks show clear evidence of an activity resulting from several causes including magma ascent along the feeding system and conduits, gravity force, local and/or regional tectonic activity. Such factors may interact in a complex way with each other and with the intrinsically complex volcano system. The result is quite often an increased difficulty of a straightforward interpretation of the observed phenomena (e.g., ground movement, seismicity) for an effective evaluation of the volcano hazards, as it was the case with Mount St. Helens volcano in Among the Italian volcanoes, Mount Etna shows the most relevant case of active flank dynamics along its East and South-East sectors, with some well-known seismogenic structures, such as the Pernicana fault, or highly evident morphologies, such as the Valle del Bove. Recent volcanic crises such as that of have been associated with seismic activity in the East sector of Mount Etna (e.g., Santa Venerina Santa Tecla fault) causing relevant concern and implying further troubles in the scientific and Civil Protection management of the crises. Despite the above evidences, the large scale eastern flank instability of Etna is still today the subject of debate, and in-depth dedicated research is necessary, with the aim of evaluating the influence of the geodynamic setting (geology, tectonics, etc.), its relationships with the volcano s activity and the related hazard. The aim of the present project is that of understanding the relationships between the preeruptive and eruptive dynamics, the shallow feeding system, and the tectonics on the East volcano sector. This will be achieved through i) a better definition of the structural and lithostratigraphic setting of the shallow portion of the volcano in critical sectors like those of the Timpe or the Rift; ii) an in-depth investigation of the dynamics of the main active tectonic structures; iii) the analysis of the relationships between volcanic activity and flank dynamics; iv) a detailed study of movements in the submerged sector of the volcano. A proposal for modification/innovation of the present monitoring system at Mount Etna will be a qualifying project outcome. This approach will allow improving the knowledge on the factors controlling flank instability at various scales on the volcano. This wide-ranging analysis of the flank dynamics at Mt. Etna will be also useful to define areas and processes relative to specific, potentially hazardous instabilities, from possible sudden, massive flank collapses of a portion of a volcano to localized creep-like movements. The research in the project will include the following steps: 261

4 262 a. integration of geo-volcanological, geophysical and geochemical data already available in order to define the areal extent of the volcano side subject to movements and plan geophysical investigation aimed at determining its thickness. b. Geo-volcanolgical studies on selected reference cases aimed at the definition of the relationships between the shallow feeding system and the flank dynamics. c. Geophysical and geochemical investigation (including the submerged portion of the volcano) aimed at a better characterization of the lithostratigraphic units and tectonic structures at depth, also addressed at the individuation of potential surface/s of instability. d. Modelling of geophysical, geochemical and geo-volcanological data aimed at establishing the relationships between magmatic and tectonic structures and their effects on the parameters recorded by the monitoring network. e. Formulating proposals for the improvement of the monitoring system. f. Study of systems for the evaluation of the hazard from flank dynamics related to the occurrence of volcanic and/or seismic events. Espected products Data employed in the project, organized in a GIS database. 3D definition of sectors of the volcano affected by flank dynamics. Characterization of geo-volcanological aspects of reference volcanic events and medium-long term evaluation of the effects on the flank dynamics, including the characterisation and analysis of time-space patterns of the geophysical and geochemical signals recorded. Numerical simulations aimed at defining relationships between pre-eruptive and eruptive dynamics and surface stress field. Detailed mapping of seismic hazard for the main active structures of the East sector of the volcano, including the relationships with the volcanic dynamics. Evaluation of the hazard deriving from flank dynamics at Mount Etna, and guidelines for a possible improvement of the monitoring system. Feasibility study for the realization of an interface at the Functional Center of DPC, to be agree upon with the same DPC, for the seismic hazard mapping described above. State of the art of the ongoing researches related to the present objectives The tectonic framework of Mt. Etna is dominated by a N-S trending direction of maximum compression, due to the Eurasia-Africa plates collision, and a related E-W trending direction of maximum extension, associated with the development of the Malta Escarpment, the possible surface expression of a tear in the subducting Ionian slab (see Bousquet and Lanzafame, 2004, for a review). Significant portions of the eastern and south-eastern flanks of the volcanic edifice are characterized by down-slope movements, occurring with extremely different rates, from mm/yr to cm/yr, up to m/week during some eruptive events. On the northern part of the eastern flank, there is a general agreement that the boundary of the unstable sector is represented by the E-W trending Pernicana Fault System, extending from the NE Rift to the coastline, with a predominant left-lateral motion. Here the flank shows a predominant ESE slip (Neri et al., 2004, and references therein). To the south, the slip of the flank appears less consistent, being directed towards SE and S, and controlled by several structures, with different geometry and kinematics.

5 Project V4 Flank Among these, are the NNW-SSE striking Timpe Fault System (TFS), considered as the onshore continuation of the Malta escarpment. This fault system is made up of several NNW-SSE-striking faults with transtensive dextral displacement and characterized by shallow seismicity (1-2 km of depth). The outermost structure confining the slip of the flank to the south is the N-S trending dextral Ragalna Fault (Neri and Rust, 1996). In addition, the slip of the SE flank of Etna is also characterized by the development of an E-W trending anticline, recognizable through InSAR data (Froger et al., 2001). These suggest that the fold, dissected by NW-SE trending dextral faults, probably continues off-shore. The spatial-temporal relationships between these different structures (faults, with various geometry and kinematics, and folds) are still poorly constrained. While the structure of the on-shore and shallower portion of the unstable flank is sufficiently known (even though more studies are needed to constrain the SE part), the deeper part of the unstable flank is still largely unknown. For example, different depths for its basal decollement(s) have been proposed. In fact, the base of the sliding sector has been inferred to lie at 1-2 km above sea level (asl) (Bousquet and Lanzafame, 2001), at 1-3 km below sea level (bsl) (Bonforte and Puglisi, 2003, Lundgren et al., 2005), at 5~6 km bsl (Borgia et al., 1992; Neri et al., 2004) and at both shallow and deep levels (Tibaldi and Groppelli, 2002). In addition, several authors have argued that the slip of the flank may result from shallower and deeper magma intrusion [e.g., Borgia et al., 1992; Lo Giudice and Rasà, 1992; Rust and Neri, 1996; Bonforte and Puglisi, 2003; Rust et al., 2005; Walter, 2005), suggesting a feed-back between gravity and magma emplacement within the volcano (McGuire et al., 1990). The unstable E flank of Etna is also characterized by a higher seismicity with regard to the rest of the volcano (Gresta et al., 1990). This recently culminated, during the eruption, in the destructive events of S. Venerina, characterized by shallow epicenters aligned along a NNW-SSE direction (Acocella et al., 2003). More in general, the eruption, characterized by pre-eruptive and syn-eruptive seismicity, also accompanying the slip of significant portions of the unstable flank, suggested the existence of complex relationships between volcanic, seismic and flank activity. The previously described state of the art deserves future investigations, summarized by the following key questions: - What is the spatial-temporal relationship between the different types of structures accommodating the slip of Mt. Etna flanks? - How deep is the flank slip? - What is the relationship between flank slip and volcanic activity? - What is the relationship between flank slip and seismic activity? - Which are the main factors controlling the flank instability? Description of the activities Project FLANK aims at minimizing the hazards related to the instability of Etna flanks. As shown in the previous section, this project will be focused on the E and S flanks, for which geological evidence of instability is widely proven. The hazards resulting from flank instability concern, in general, seismic and volcanic activity; therefore, most of the project is focusing at facing the hazard possibly deriving from these processes. However, in some cases, restricted to specific areas of the volcano, flank instability may lead to surface fracturing and/or creeping processes, as well as to the development of landslides. A part of this project will focus on the hazard deriving from surface fracturing, creep-like processes and landslides at selected areas. 263

6 In general, this Project will significantly rely on previously collected data, either those produced and available in a previous DPC-INGV project (e.g. the Etna V3_6 project, performed in ) and those available from the monitoring systems implemented on Mt. Etna from INGV, in the last decade. In fact, this combined dataset constitutes a massive amount of geological, geophysical and geochemical information, which largely waits to be analyzed and interpreted yet. The availability of such a large amount of data will permit to: 1) have a comprehensive and multidisciplinary view on the various processes characterizing flank instability; 2) analyze, integrate and merge the existing data, also focusing, for the first time, at defining the relationships between different datasets and processes; 3) highlight specific activities (surveys and /or modeling), which still have to be carried out in order to complete the data set or provide some unavailable parameters. In general, these activities will provide collecting all the required new data within the first part of the project, in order to interpret and make the data available to the project within the second part. In order to ensure coordination and cooperation with the Project V3 Lava, we intend, in agreement with the Lava Coordinators, to organize jointly the kick-off meeting of the two projects. Additional informal meetings between Task leaders of the two Projects will also take place with the same aim. To achieve its goal, the Project is structured in Tasks, each considering a specific expected product, listed in the Objectives section. In particular, Task 1 will be devoted to the implementation of the database into a GIS system. Task 2 will be devoted to the definition of the 3D geometry and structure of the portion of the volcano characterized by instability. Task 3 will be devoted to define the geo-volcanological processes and their relationships, also in the frame of the available geophysical and geochemical data, both on the long and the short term. Task 4 will be devoted to model (with constraints from Tasks 2 and 3) specific aspects of the instability of the flank, including stress, strain, triggering factors, cause/effect relationships, stability conditions. Task 5 will be devoted to produce (with constraints from Tasks 2, 3 and 4) detailed maps of seismic hazard, associated to the main structures of the unstable flank, and to evaluate the other hazards (volcanic, surface fracturing and creep) deriving from the instability of the flank. These results will be merged in a synthetic form in prototypal procedures for the evaluation of the hazard changes due to flank dynamics. The figure below offers a synthetic synoptic view of all the activities. The successive flow chart includes the roles of RU s in the different Project activities, and illustrates the finalization of the Project to a procedure for an integrated and multidisciplinary alert system related to flank dynamics at Mount Etna. The activities of Tasks 2, 3, 4 and 5 are grouped in WorkPakages in order both to facilitate the exchanges among different RUs involved in similar activities and improve the quality of the final products. A detailed description of the Tasks is provided below. 264

7 Project V4 Flank Synthetic synoptic view of project activities 265

8 Flow chart of Project achievements and products 266

9 Project V4 Flank Task 1. GIS (Responsible: D. Reitano ) RU Participating: all The large amount of data which will be used in the FLANK Project, either already available at its onset (e.g. provided from the monitoring systems or previous projects) or resulting from the planned activities, are widely multidisciplinary. This task is aimed at implementing a web-gis infrastructure able to manage the different types of data; the webinterface will be user-friendly and able to guarantee different access levels, if necessary. It is planned that the web-gis will be also able to disseminate the main selected results of the project, in the case that the consortium wishes to present the project results to the wider scientific community. This activity will be carried out in cooperation with LAVA project, as it shares a large amount of data with the FLANK project. In particular, this cooperation mainly results from the activity of the RU11 (team 1). More in general, joint meetings (including the kick-off meeting) are planned between the LAVA and FLANK projects, as well as a continuous exchange of information and data. All RUs (Research Units) will implement their data sets into the database, at the onset of the project if these are already available, or during the project, if the data must be collected. Details on each data set type are provided into the applications of the different RUs (see below). ). The database will be implemented with the aim of ensure the maximum compatibility with the WOVOdat standards. Task 2. Geometry, kinematics and structure of the unstable flanks RU Participating: Valerio Cancella (RU-01), Andrea Argnani (RU-03), Francesco Chiocci (RU-05), Ornella Cocina (RU-06), Cinzia Federico (RU-07), Francesco Mazzarini (RU- 09), Giuseppe Puglisi (RU-11), Agata Siniscalchi (RU-12). The aim of this Task is to investigate the 3D structure (geometry and kinematics) of the unstable flanks of Etna, with particular attention to the definition of the associated deformations. This information will permit to: have a reference data set to evaluate any relationship between the structure of the flank and volcanic and seismic activity (Task 3); significantly constrain the results from numerical and analogue models (Task 4); provide the basic information for any hazard evaluation (Task 5). The Task is divided into 2 Work-Packages (WP): WP-2A, considering the surface features and WP-2B, considering the features at depth. WP-2A) Surface (Responsible: S. Branca) This WP aims at gathering all the available surface information regarding the slip of Etna flanks, both on-shore (i) and off-shore (ii). These two parts are characterized by the following features. i) Integration of the data concerning the main structural and kinematic features of the on-shore portion of the unstable flanks. Most of these data have been previously collected, largely by RU-11, even though focalized and local studies may be eventually carried in the first part of the research, to better define specific features. The data set to be analyzed and merged includes: field survey data (RU-11), gas emission data (RU-11, RU- 07), GPS, leveling and DinSAR data (RU-11), and SBAS velocity maps. The last one have been already produced and analyzed by the CNR-IREA institute of Napoli. While this institute will not be officially involved in the first stage of the project (appearing in RU-01, though), an ongoing collaboration with some of the researchers participating in this project will assure, under the responsibility of the coordinators, the availability of the SBAS 267

10 velocity maps. The aim of this part of the project is to provide a comprehensive multidisciplinary frame, including the area(s) characterized by a consistent slip, as well as the major and minor structures through which the motion occurs. ii) Interpretation and integration of different data sets, to identify the main geological and structural features of the proximal and distal of the unstable flank in the off-shore domain. These data sets include a detailed bathymetry (RU-05; RU-03) and seafloor sampling (RU-05), whose results will be related to the on-shore coastal portion, in collaboration with RU-11. Except for seafloor sampling, all of the remaining data sets have been already collected by the RUs. Seafloor sampling will be performed in the first part of the project, and will be focused at specific locations of particular interest. Attention will be devoted, in this part, to the definition of the main geological (nature and age of deposits) and structural (faults and folds) features characterizing the off-shore unstable portion, as well as the definition of its aerial extent. WP-2B) Depth (Responsible: O. Cocina) This WP aims at collecting new data and gathering them with all the already available information regarding the geometry of deep structures of Etna flanks. The activities will be carried out in this WP are the following. i) Interpretation and integration of all the available subsurface well-data on the onshore portion of the unstable flanks (RU-07). These will permit to define the main lithotypes at depth, including the configuration of the top of the sedimentary substratum, below the volcanic pile. Moreover, the well-data (most of them built for water purposes), in addition to the available spring data, will permit to define the depth, extent and volume of the main aquifer(s) of the E and S flanks. This evaluation will be particularly useful to best interpret the shallow geophysical results (resistivity and magnetotelluric), partly previously acquired and, partly, to be acquired in this project, from RU-12. Additionally it will represent an important data for the definition of the geological and hydrogeological model in performing the stress-strain analysis include in task 4 from RU-02. ii) Deeper geophysical analysis of the on-shore portion of the unstable flanks (RU-06). This will consist of the following two studies. Application and implementation of seismic tomography techniques for the definition of the 3D velocity tomography (V P and V P /V S tomographies) and attenuation structure (Qp models) of the deeper portion of the unstable area. High precision locations of seismic events also focused at recognizing the most important seismogenetic structures. This study will permit to evaluate the deeper structure of the on-shore unstable portion. iii) Resistivity and magnetotelluric properties of selected portions of the unstable flank (RU-12). This study will be characterized by the following two activities. Continuation of the previous promising studies along the Pernicana Fault (NE sector), which permitted to infer a possible depth for the basal decollement of the unstable sector; the aim of this activity, in the present project, is to provide definitive constraints on the structure and depth of the decollement in the northern part of the unstable flank. Definition of the relationships among different structures characterizing the slip of the SE flank (faults with different orientation), by constraining their deeper extent. All these data will be collected in the first part of the project and will be of particular interest to define the local extent of the on-shore structures, as well as the deeper extent of the unstable sector in the NE and SE portions of the volcano. This information will be particularly useful for Task 4 and, in part, for Tasks 3 and 5. iv) Interpretation of the existing data sets of seismic lines, devoted at understanding the deeper geology and structure of the off-shore portion of the eastern flank. In particular, two recently acquired seismic data sets are available: a shallower, high resolution, one (RU-09) and a deeper one (RU-03). While the first data set will permit to investigate the details of 268

11 Project V4 Flank the shallow structure, as well as the structural and stratigraphic relationships of the offshore flank, the second data set will permit to define the deeper structural and stratigraphic features, as well as the relationships with the regional tectonic structures, outcropping immediately to the south of the investigated area, along the Malta escarpment. Both data sets will be compared and integrated, in order to provide a general and consistent frame, through the experience of the researchers and geologists involved to analyze the seismic marine profiles and the morpho-bathymetric data, to define the structural features and the debris avalanched deposits. In addition, these results will be also integrated with those collected by RU-5, and subsequently with those available in the on-shore portion (RU-11). Task 3. Relationships between flank dynamics, eruptive activity and geophysics/geochemistry data RU Participating: Raffaele Azzaro (RU-04), Cinzia Federico (RU-07), Carlo Giunchi (RU-08), Giuseppe Nunnari (RU-10), Giuseppe Puglisi (RU-11). The aim of this Task is to define the possible cause/effect relationships between flank dynamics and magmatic activity, in broader terms. Therefore, this Task will consider the existence of any significant pattern in the geophysical, geochemical and geological (volcanological, petrological, structural) available dataset, in relation to the episodes of instability of the flanks of the volcano also considering available meteorological data. In general, this information will be particularly useful to better constrain and validate the numerical and analogue models of Task 4 and to provide an appropriate database for hazard evaluation in Task 5. This Task is divided into 2 Work-Packages (WP): WP-3A is focused on the Long- Term behavior and WP-3B on the Short-Term behavior. WP-3A) Long term (last years from catalogue data) (Responsible: G. Nunnari) i) Analysis of the historical seismicity, from catalogue data (RU-04). This will, first of all, permit to uniform, classify and parameterize the available dataset. Such an analysis will also permit to characterize the behavior of the main seismogenic faults, through the reconstruction of the curves of the seismic strain release, b value and occurrence models. These analyses are expected to indicate how the faulting processes relate to eruptive dynamics (emplacement of dykes) or larger-scale processes (instability of the flank, offshore tectonics). These data will be of crucial importance to evaluate the hazard deriving from seismic activity (Task 5). ii) Analysis of the historical volcanic events, as well as of the related products, to define the main eruptions, and associated features, related to the dynamics of the flank (UR-11). In particular, the relationships between summit and flank activity in the frame of the slip of the flanks (as during the occurrence of seismic events) will be investigated. The data will be analyzed, from a statistical point of view, in collaboration with RU-10. iii) Advanced statistical integrated analysis of the volcanic dataset provided by RU-04 and RU-11, to define the long-term reference volcanic events and any self-organization in volcanic activity related to flank slip (RU-10). Such an analysis will be focused on selforganized criticality theory (SOC), permitting to highlight possible behaviors, otherwise difficult to identify, given the complexity of the problem. These data will be of particular interest to constrain the models (Task 4) and evaluate the hazard deriving from seismic activity (Task 5). 269

12 WP-3B) Short term ( , monitoring data) (Responsible: M. Neri) i) Assessment of a complete volcanological, geochemical and geophysical data-base. In particular, the volcanological data-set will investigate the relationship between magmatic activity (petrology of the erupted products, evaluation of the plumbing system) and flank dynamics (RU-11). The geochemical features will include studies of shallow magma degassing in soil and aquifer, through appropriate modeling (porosity and permeability, fluid circulation) (RU-07). The geophysical features will include the study of long-period LP earthquakes, as well as the definition of the polarization of earthquakes along the major faults on the unstable flanks, both able to cause significant damage (RU-08). These studies will be of particular importance for the analyses at points ii) and iii), as well as for Task 5 (in collaboration with RU-04, and RU-11). ii) Analysis of each data-set aimed at characterizing the relationships between each type of data and flank dynamics, e.g.: volcanological data (eruptive fracture distribution/evolution, time-evolution of chemical features of volcanic products and related erupted volumes), structural data (fault location, slip and size), geophysical data (time/spatial-evolution of geophysical data, including GPS, seismic, gravity and magnetic stations, definition of source mechanism of typical seismic events), geochemical data (time/spatial-evolution of geochemical data from soils, at specific locations, and plumes) (RU-11). This analysis will be performed in collaboration with RU-10. iii) Multidisciplinary review analysis of the different data-sets (volcanology, structure, geophysics, geochemistry), in relation to flank instability. This integrated study will be performed by RU-11, in collaboration with RU-10. It will lead to an advanced automatic multivariate statistical analysis, named data mining, consisting of the extraction of implicit and potentially useful information from large collections of data (RU-10, in collaboration with RU-11). Data mining will be focused on a selected database (namely seismic and High-Frequency GPS data) and, through the classification of events, aimed at identifying time/spatial patterns eventually related to the dynamics of the flank. The results of this study will be of particular importance for modeling validation, in Task 4, and hazard evaluation, in Task 5. Task 4. Modeling RU Participating: Valerio Acocella (RU-01), Tiziana Apuani (RU-02), Carlo Giunchi (RU-08), Francesco Mazzarini (RU-09), Giuseppe Nunnari (RU-10), Giuseppe Puglisi (RU-11). This Task is aimed at providing the required simulations for DPC to define the relationships between pre-eruptive and eruptive dynamics and the surface stress and strain distribution. This problem will be faced by using both numerical and analogue models. Both require an improvement of the knowledge of the basic parameters used in the models. Thus, the activities of this Task are grouped into 3 Work-Packages (WP): WP-4A (Definition of the parameters), WP-4B (Numerical models) and WP-4C (Analogue models). The results of this Task will be exploited into Task 5, to assess the seismic and volcanic hazard related to the flank dynamics. Moreover, consistent modeling results may also help in better constraining the interpretation of the models deriving from the geological and geophysical activities proposed in Task 2. WP-4A) Definition of the parameters (Responsible: M. Pompilio) Since the fundamental question of this Task is to assess the stress-strain relationship between the structure of the volcano and the dynamics of magmas within the volcanic reservoirs (in broad sense) or pathways, the basic parameters which will be investigated 270

13 Project V4 Flank in this WP are i) those characterizing the mechanic and rheologic properties of rocks forming the volcano and its basement and ii) those characterizing the pre-eruptive conditions of the magma. i) RU-08 will carry out tests to define both the physical properties (e.g. density and porosity) and the mechanical parameters (e.g. static elastic modules) of main lithotypes. These tests will provide also other information useful not only for the modeling, but also to improve the analysis and interpretation of studies on seismic anisotropies carried out in the Task 3; this is the case of the measurement of the seismic anisotropy of P ands waves. RU- 11 will provide an estimation of viscosity of sedimentary basement below selected areas of eastern flank (along the Pernicana Fault) by exploiting the GPS measurements collected during the eruption. The RU-2 will calibrate geotechnical models by integrating the results specific geotechnical and geomechanical laboratory tests with other tests, including those performed by RU-08. ii) The definition of the pre-eruptive conditions in terms of pressure, temperature and chemio- physical properties of magma will be achieved by petrologic study of products of relevant eruptions. In particular the evolution of processes of degassing, decompression and magma chamber refilling will be obtained from detailed studies of zoning of minerals of selected eruptions. Such estimates will be obtained using current thermodynamic modeling and results of experiments on phase-equilibria carried out by participants to RU- 09, during the previous DPC-INGV Etna Project. All the data will serve as input for numerical modeling (WP-4B). Further specific laboratory experiments will be carried out in order to improve the resolution of some parameters and to validate the above models. WP-4B) Numerical models (Responsible: C. Giunchi ) The relationships between pre-eruptive and eruptive dynamics and the surface stress and strain distribution will be investigated through three different approaches: i) one is aimed at modeling the geodetic data, to infer on the stress-strain relationship related to the flank dynamics; ii) the second deals with the relationships between magma equilibrium and flank dynamics; iii) the third investigates the critical conditions generating flanks instability through geotechnical modeling. i) Several recent studies, based on analytical modeling of ground deformations of Mt. Etna, allowed the identification of the major structures controlling the dynamics of the eastern and south-eastern flank. However, these analytical studies cannot give satisfactory answers in evaluating the cause-effect relationships among the intense geodetic strain pattern, the stress that magmatic structures produce or suffer, the stress field originating flank instability and the lively seismicity characterizing the eastern and southern flanks. Numerical models may give suitable answers to these questions, with potential applications to civil defence purposes. In this project, both Finite and Boundary Element Models (FEM and BEM) will be used to assess the distribution of the static stress, with particular care to its distribution along the main structures of the volcanic flanks. The 3D structural assessment resulting from Task 2 will allow improvement of the meshing of the numerical models. In particular, RU-08 will create a full model of the volcano, including topography, the principal volcanic and seismogenic structures and the appropriate rheological behaviors (e.g. anelasticity in proximity of volcanic sources). A sensitivity analysis will be also performed to evaluate the stability of the FEM approach as functions of assumed structural geometries and rheology. RU-11 will use FEM to compute synthetic Green s functions that will be combined with an inverse method to estimate the distribution of the dislocations of the main seismogenic structures; these results will allow computation of the Coulomb stress changes. The use of the BEM, which will be carried out by RU-10, may improve the efficiency of numerical approaches due to the reduced numbers of mathematical relations/parameters involved in this type of numerical modeling approach; specific 271

14 comparison among the results of the different RU involved in the numerical modeling of ground deformation will be performed. ii) Numerical models to simulate the relationship between magma and host-rock will be implemented by RU-09. Their aims are: understanding the pre-eruptive dynamics of magmas, considering also the role of the arrival of new gas-rich magma into the reservoir ; evaluating the effects of external perturbations of the stress in triggering magma convection and pressurization; estimating the effects on measured geophysical parameters induced by the simulated dynamics. This activity will be performed by using finite element numerical codes partially implemented and improved in previous INGV- DPC Projects. iii) RU-02 will implement numerical geotechnical models to evaluate the critical conditions able to generate flank instability. This approach will consist of a 3D modeling, successfully applied at Stromboli. This activity is aimed at defining the limit conditions for static and dynamic (magma-induced) equilibrium, as well as the possible failure surfaces, considering the different of various instability factors. These models will be partly based on the parameters defined in WP-4A. Particular attention will be given to study the role of porewater pressures on the instability of the flanks of the volcano, especially throughout the activities at the point i) and iii). In fact, porewater pressures changes have been suggested as one of the possible triggers for flank slip at many volcanoes (e.g. Kilauea, Capo Verde, Canaries; Cervelli et al., 2002, Elsworth and Day, 1999). WP-4C) Analogue models (Responsible: C. Giunchi ) Analogue models of flank instability will be performed to evaluate the possible role of topography, regional tectonics, magma emplacement (both dikes, at surface, and diapir-like bodies, at depth), presence of decollements or anisotropies (RU-1). These models will be validated by parallel-run numerical models (RU-1), sharing the same boundary conditions, for a better validation. Subsequently, the models will be compared to other numerical modes (UR-2, 8, 9, 11) and to the natural case (as derived from the constraints of Task 1 and Task 2), proposing a general comprehensive scenario relating flank slip to possible triggering factors. Task 5. Hazard (Responsible: R. Azzaro) 272 RU Participating: Raffaele Azzaro (RU-04), Giuseppe Puglisi (RU-11), all UR This Task will deliver the products aimed at assessing the hazard deriving from the flank dynamics and indicating the improvement/modification of monitoring system and surveillance activities to reduce such hazard. The activities of this Task are grouped into 3 Work-Packages (WP): WP-5A (Seismic Hazard) and WP-5B (Integrated hazard) and WP- 5C (Results for monitoring/surveillance activities). WP-5A) Seismic Hazard Seismic hazard is, by far, one of the most relevant natural hazards of the eastern and southern flanks of Mt. Etna. Although the magnitudes of the earthquakes has not exceeded 5, destructive events are relatively frequent (on average, the X degree of EMS on the eastern flank is reached every 20 years), due the shallow sources. RU-04 is responsible for the activities aimed at assessing the seismic hazard. The characterization of the seismic potential of the active faults on the eastern flank will contribute to define the more hazardous zones. The seismic potential will be evaluated by using both deterministic and probabilistic approaches, partially based on the results of Task 2 (for the dimension of the

15 Project V4 Flank faults) and Task 3 (for the estimation of the b-value of the Gutemberg-Richter relationship). Another preparatory study for seismic hazard assessment concerns the definition of the intensity decay, which will be achieved by probabilistic techniques based on appropriate analysis of earthquake database (which, in this project, will be extended up to XVII century). Two types of seismic hazard maps will be delivered: a set of seismic hazard maps, in terms of macroseismic intensity, for exposure times ranging from 5 to 50 years, and a set of time-dependent seismic hazard maps, computed for a few selected seismogenic faults of the eastern flank, by applying a method adopted in the previous INGV-DPC seismologic projects. WP-5B) Integrated hazard In this WP an analysis of the hazard deriving from the dynamics of the flanks of Etna will be performed. Beside seismic hazard (see WP-5A), the other main flank hazards are related to the opening of the fracture/eruptive fissure systems, the aseismic creep and the triggering of landslides. All these types of hazard will be investigated by RU-11, in general using information deriving from Tasks 2, 3 and 4. Furthermore, in this WP a preliminary evaluation will be performed, to assess a probabilistic hazard by using the event tree approach, in cooperation with LAVA project. The unstable portion of Mt. Etna is bounded to the west, by the NE and S rifts. Their activity, controlling the shallow rise of magma in the volcano, shows significant relationships with flank dynamics. The analyses of Task 3 and 4 will be integrated with a statistical analysis of the actual fracture/eruptive fissure system, to define the most suitable areas of the volcano where they may occur. This activity will benefit of the joint researches carried out in the frame of the LAVA project, based on probabilistic approaches, aimed at defining the probability of opening of new vents. However, in this project, only the relationships between volcanic activity and flank dynamics will be considered. Flank instability deriving from different processes (magma, seismicity, porewater pressure) will be also considered at smaller scales, defining the possible areas and mechanisms controlling the instability. These smaller-scale instabilities may range from collapses of portions of steepest flank of the volcano (e.g. collapses occurring in the Valle del Bove) to localized creep-like movements (as those observed along the Pernicana Fault). In particular, aseismic creep is relatively frequent on the eastern and southern flanks of Mt. Etna, along several faults systems related to flank instability. Creep processes may not have a primary importance for hazard assessment in uninhabited areas; however, they become significant when affecting crucial infrastructures or properties. Therefore, one of the aims of this activity will be the quantification (e.g. rate of movement, extent of the affected areas) of the creep processes near the principal life-lines (e.g. the Catania-Messina highway or the railway). On the eastern flank, a few well-known faults are related to flank activity. These, combined with local topographic conditions, enhance or trigger gravitational instabilities. This type of hazard will be systematically considered, evaluated and adequately mapped. The results of all the above described activities, together with the results of the seismic hazard assessment, will be integrated to assess a final volcano-hazard evaluation. WP-5C) Results for monitoring/surveillance activities This WP will produce two deliverables of the project. All RUs will be involved into their preparation. The first deliverable consists of a document indicating the guidelines for an eventual improvement of the monitoring system. This will consider all the results obtained in the project and the simulations in particular (Task 4), indicating the areas were the major 273

16 changes in the geophysical/geochemical signals are expected, and the integrated hazard assessment provided in the above two WPs of Task 5. The second deliverable consists of prototypal procedures to be used by the Operations Centre of DPC in case of unrest along the unstable flanks, highlighting possible changes in hazard as a function of the changes in the state of the flank dynamics. These include volcanic hazard (opening of fissures and fractures), seismic hazard (occurrence of earthquakes) and stability hazard (creep-like movements, sudden, mass movements, localized landslides). In particular, if the project (Task 3) will identify specific relationships between seismic and volcanic activity, the procedures should consider these results, possibly by identifying type-events, trying to estimate of the type of hazard and its occurrence probability, considering certain boundary conditions. The details of this deliverable will be agreed with the DPC. 274

17 Project V4 Flank 4. List of deliverables First Year Task 1 - GIS 1. Database structure assessment; Site realization; Database integration (UR-11). Task 2. Geometry, kinematics and structure of the unstable flanks WP-2A) Surface 1. Map of integrated (on-shore and offshore) structural features (1: scale) and map of selected features (1:10.000) (UR-05 and UR-11); 2. Integration of all the shallow water available data (UR-05 and UR-11); 3. Report on the oceanographic cruise with the R/V Universitatis (UR-05); 4. Structural analysis derived from the integration of surface surveys, geodetic data and soil gas surveys (UR-11); 5. Definition of the main tectonic features related to flank slip (UR-11). WP-2B) Depth 6. Analysis of seismic data, mostly marine seismic profiles, in order to identify and correlate the main seismostratigraphic units. Identification and correlation of the main tectonic structures on seismic profiles (UR-03); 7. Mapping of the distribution of the large-scale mass-wasting deposits located offshore the eastern flank of Mt. Etna (UR-03); 8. Build-up of a relative chronology of tectonic activity and stratigraphic events. Attempt of correlation of the identified seismic units to the onshore stratigraphic units of known age (UR-03); 9. Data analysis of seismic data sets; 1D Vp and Vp/Vs models (UR-06); 10. Physical model of the volcano, with the identification of zone of different permeability (UR-07); 11. Elaboration of some off-shore seismic lines across the possible prolongation of the Mascalucia-Trecastagni faults. Analysis and interpretation of elaborated seismic lines (UR-09); 12. MT and SP data acquisition in the northeastern flank; ERT profiles (acquisition and modeling) on the southern flank (UR-12); 13. Integrated interpretation of the previous resistivity model with velocity and density models (UR-12). Task 3. Relationships between flank dynamics, eruptive activity and geophysics/geochemistry data WP-3A) Long-term 14. Extension of the macroseismic catalogue from 1650 to 1831 (UR-04); 15. Analyses on fault behavior: strain release and b value (UR-04); 16. New insights about self organized critical (SOC) behaviors of volcanic areas (UR-10); 17. Preliminary definition of the main eruptive events and their volcanological features related to the flank dynamic (UR-11). 275

18 WP-3B) Short-term 18. New algorithms to process continuous GPS and seismic signals (UR-10); 19. Petrologic data set of selected volcanics from Summit Craters (UR-11). Task 4. Modeling WP-4A) Definition of the parameters. 20. Rock mechanical characterization of selected sites for modeling activities. Physical and mechanical characterization of the main Etna lithotypes, and definition of lithotechnical units (UR-02 and UR-08); 21. Microstructural characterization of the natural lithologies investigated (UR-08); 22. Definition of secondary seismic anisotropy (Voids space+texture) (UR-08); 23. Petrologic study of products of selected recent eruptions (UR-09); 24. Estimate of relevant pre-eruptive conditions within magmatic reservoirs feeding recent eruptions. Development of combined analytical methods to obtain detailed zoning profile in minerals (UR-09); 25. Inversion of time-dependent relaxation models by using GPS data time series (UR-11). WP-4B) Numerical models 26. First stress-strain numerical models of the unstable Etna flanks (UR-02); 27. Preliminary 3D FE model of the unstable flanks of Mt. Etna. Study of the role of different sources (summit eruptions, deep pressurized reservoirs, regional tectonic stresses) on the structural discontinuities and flank instability (UR-08); 28. System definition for the simulations of magma and rock dynamics. First simulations on magma/rock dynamics (UR-09); 29. New algorithms to compute the Coulomb stress changes in the eastern flank of Mt Etna (UR-10); 30. Developing and testing the FEM geodetic inversion procedure and numerical code for evaluating the viscoelastic deformation (UR-11). WP-4C) Analogue models 31. Set up of the experimental apparatus for analogue modeling (RU-01); 32. Definition of the input parameters (derived from WP 2B and 4A) and production of the experiments simulating flank slip. Run of the numerical experiments (RU-01). Task 5. Hazard WP-5A) Seismic Hazard 33. Seismic potential of faults: deterministic approaches (RU-04); 34. New probabilistic relationships of intensity attenuation (RU-04). WP-5B) Integrated hazard 35. Preliminary results of the parameterization of creep and landslide areas for volcano-structural hazard evaluations (RU-11); 276

19 Project V4 Flank Second Year Task 1 - GIS 36. Data representations, web interfaces, GIS; Final documentations; manuals (UR- 11); 37. Collection of the data sets for populating the database (all RU). Task 2. Geometry, kinematics and structure of the unstable flanks WP-2A) Surface 38. Report on scuba and ROV survey on selected targets (UR-05); 39. Characterization of the nature of possible mud volcanoes in the offshore Pernicana Fault (UR-05); 40. Mapping and characterization of the tectonic elements cropping out on the coastal zone (on land and offshore) (UR-05); 41. Analysis of the samples collected in the first-year cruise, and of all the collected geophysical data (UR-05); 42. Interpretation of the offshore structural elements and of tectonic/large-scale instability features possibly driving the movement of the eastern flank of the volcano (UR-05); 43. Correlation between on- and off-shore tectonic structures and their relationship to the eastern flank dynamic (UR-11). WP-2B) Depth 44. Mapping of fault surfaces at depth on seismic profiles, to outline fault geometry. Interpretation of tectonic structures at a large scale (UR-03); 45. Depth conversion of selected seismic profiles, to obtain a realistic geometry of fault planes and a more accurate volume estimate of the offshore mass-wasting deposits (UR-03); 46. Tectonic model describing the deformation affecting the offshore flank within the regional tectonics frame (UR-03); 47. 3D numerical models of P- and S- wave velocities and of Qp and Qs (UR-06); 48. Precise locations on selected earthquake clusters occurring nearby seismogenic structures (UR-06); 49. Database of earthquake locations relative to the period , including the 2004 summit eruption (UR-06); 50. Vertical and spatial distribution of the main fluid pathways (UR-07); 51. Elaboration of some seismic lines across the possible off-shore continuation of the Pernicana Fault. Analysis and interpretation of elaborated seismic lines. Correlation of observed structures with other seismic surveys (UR-09); 52. MT data acquisition along the Mascalucia-Acireale profile (UR-12); 53. Map of distribution of the geoelectrical strikes at different estimated depth (UR- 12); 54. SP map and Resistivity model (2D o 3D) for the areal survey in NE Rift area (UR-12); 55. Resistivity model across the MT profile Mascalucia-Acireale and its integrated interpretation of the profile (UR-12). 277

20 Task 3. Relationships between flank dynamics, eruptive activity and geophysics/geochemistry data 278 WP-3A) Long-term Analyses on fault behavior: occurrence models, Montecarlo simulations of earthquake catalogues (UR-04); 57. Algorithm for measuring time series similarities, classification and clustering (UR-10); 58. Recognition of the eruptive processes of the past 3-4 centuries related to the activation of the main seismogenic faults (UR-11). WP-3B) Short-term 59. Simulation of the effect of of the variation of the mass rate and/or pressure on shallow geochemical manifestations during the past volcanic activity (UR-07); 60. Simulation of the effects of fluid mass rate and/or pressure on rock characteristics (UR-07); 61. Map of directions of polarization. Attenuation of volcanic LP earthquakes (UR- 08); 62. Pattern recognition techniques to analyze multivariate time-series (UR-10); 63. Time-related petrologic sequence correlated with other temporally constrained data-set concerning geology, geophysics and geochemistry of gases (UR-11); 64. Results of the review and the re-interpretation of eruptive and deformative events during the period (detailed results of specific volcanic events) (UR-11). Task 4. Modeling WP-4A) Definition of the parameters. 65. Dynamic elastic moduli for lava flows at increasing effective pressure. Microstructural characterization of the experimental products. Definition of Primary seismic anisotropy (Texture) (UR-08); 66. Evaluation of elastic and geometrical parameters of the Pernicana area and comparison with available geological and geophysical information (UR-11); 67. Petrologic study of products of relevant historical eruptions. Interpretation of zoning profile in minerals. Reconstruction of the crystallization history within the magma chamber (RU-08). WP-4B) Numerical models 68. Comparison between numerical models and data from other research units on deformation field for further development of numerical models, with different input parameters (UR-02); 69. Definition of the geometry of the potential decollement surfaces (UR-02); 70. Simulations of magma/rock dynamics with external triggers, and definition of the expected geophysical signals (RU-08). 71. Refinement of the 3D FE model including anelastic rheologies. Application of the 3D model predictions to the and activity (RU-08). 72. BEM modeling for simulation of relationships between pre-eruptive, eruptive dynamics and superficial stress fields (UR-10); 73. Coulomb stress change maps on seismogenic structures (UR-11); 74. Numerical code for evaluating the thermoelastic deformation (UR-11); 75. FEM geodetic data inversion code (UR-11).