Physical-Mathematical modeling and numerical simulations of stress-strain state in seismic and volcanic regions

The strain-stress state generated by faulting or cracking and influenced by the strong heterogeneity of the internal earth structure precedes and accompanies volcanic and seismic activity. Particularly, volcanic eruptions are the culmination of long and complex geophysical processes and physical processes which involve the generation of magmas in the mantle or in the lower crust, its ascent to shallower levels, its storage and differentiation in shallow crustal chambers, and, finally, its eruption at the Earth’s surface. Instead, earthquakes are a frictional stick-slip instability arising along pre-existing faults within the brittle crust of the Earth. Long-term tectonic plate motion causes stress to accumulate around faults until the frictional strength of the fault is exceeded. The study of these processes has been traditionally carried out through different geological disciplines, such as petrology, structural geology, geochemistry or sedimentology. Nevertheless, during the last two decades, the development of physical of earth as well as the introduction of new powerful numerical techniques has progressively converted geophysics into a multidisciplinary science. Nowadays, scientists with very different background and expertises such as geologist, physicists, chemists, mathematicians and engineers work on geophysics. As any multidisciplinary field, it has been largely benefited from these collaborations. The different ways and procedures to face the study of volcanic and seismic phenomena do not exclude each other and should be regarded as complementary. Nowadays, numerical modeling in volcanology covers different pre-eruptive, eruptive and post-eruptive aspects of the general volcanic phenomena. Among these aspects, the pre-eruptive process, linked to the continuous monitoring, is of special interest because it contributes to evaluate the volcanic risk and it is crucial for hazard assessment, eruption prediction and risk mitigation at volcanic unrest. large faults. The knowledge of the actual activity state of these sites is not only an academic topic but it has crucial importance in terms of public security and eruption and earthquake forecast. However, numerical simulation of volcanic and seismic processes have been traditionally developed introducing several simplifications: homogeneous half-space, flat topography and elastic rheology. These simplified assumptions disregards effects caused by topography, presence of medium heterogeneity and anelastic rheology, while they could play an important role in Moreover, frictional sliding of a earthquake generates seismic waves that travel through the earth, causing major damage in places nearby to the modeling procedure This thesis presents mathematical modeling and numerical simulations of volcanic and seismic processes. The subject of major interest has been concerned on the developing of mathematical formulations to describe seismic and volcanic process. The interpretation of geophysical parameters requires numerical models and algorithms to define the optimal source parameters which justify observed variations. In this work we use the finite element method that allows the definition of real topography into the computational domain, medium heterogeneity inferred from seismic tomography study and the use of complex rheologies. Numerical forward method have been applied to obtain solutions of ground deformation expected during volcanic unrest and post-seismic phases, and an automated procedure for geodetic data inversion was proposed for evaluating slip distribution along surface rupture

ABSOLUTE AND RELATIVE GRAVITY MEASUREMENTS AT ETNA VOLCANO (ITALY)

Employing both absolute and relative gravimeters, we carried out three hybrid microgravity surveys at Etna volcano between 2007 and 2009. The repeated measurements highlighted the spatio-time evolution of the gravity field associated with the volcanic unrest. We detected a gravity increase attained an amplitude of about 80 µGal on the summit area of the volcano between July 2008 and July 2009. The observed gravity increase could reflect mass accumulations into shallow magma storage system of the volcano located at 1÷2 km below sea level. We present here data and the advantages in using the combined approach of relative and absolute measurements performed at Etna volcano.PublishedSaint Petersburg, Russia2.6. TTC - Laboratorio di gravimetria, magnetismo ed elettromagnetismo in aree attiveope

Inflation Leading to a Slow Slip Event and Volcanic Unrest at Mount Etna in 2016: Insights From CGPS Data

Global Positioning System (CGPS) data from Mount Etna between May 2015 and September 2016 show intense inflation and a concurrent Slow Slip Event (SSE) from 11 December 2015 to 17 May 2016. In May 2016, an eruptive phase started from the summit craters, temporarily stopping the ongoing inflation. The CGPS data presented here give us the opportunity to determine (1) the source of the inflating body, (2) the strain rate parameters highlighting shear strain rate accumulating along NE Rift and S Rift, (3) the magnitude of the SSE, and (4) possible interaction between modeled sources and other flank structures through stress calculations. By analytical inversion, we find an inflating source 5.5 km under the summit (4.4 km below sea level) and flank slip in a fragmented shallow structure accommodating displacements equivalent to a magnitude Mw6.1 earthquake. These large displacements reflect a complex mechanism of rotations indicated by the inversion of CGPS data for strain rate parameters. At the scale of the volcano, these processes can be considered precursors of seismic activity in the eastern flank of the volcano but concentrated mainly on the northern boundary of the mobile eastern flank along the Pernicana Fault and in the area of the Timpe Fault System.Published12141-121494V. Dinamica dei processi pre-eruttiviJCR Journa

Probability hazard map for future vent opening at Etna volcano (Sicily, Italy).

Mount Etna is a composite stratovolcano located along the Ionian coast of eastern Sicily. The frequent occurrence of flank eruptions (at an interval of years), mostly concentrated along the NE, S and W rift zones leads to a high volcanic hazard that, linked with intense urbanization, poses a high volcanic risk. In the framework of the project PON SIGMA (Integrated Cloud-Sensor System for Advanced Multirisk Management), we develop a near real-time computer-assisted analysis and probabilistic evaluations that provides the identification of the areas prone to the highest vent opening hazard. A longterm volcanic hazard assessment, mainly based on the past flank activity of the Mt. Etna volcano, is the basic tool for the evaluation of this risk. Then, a reliable forecast of where an impending eruption will occur is needed. The use of a code such BET_EF (Bayesian Event Tree_Eruption Forecasting) delivers a long-term hazard map, that, if additional data are provided, switches into a short-term future vent opening map. The present application is based on incoming seismic and ground deformation data. Analytic inversion of high frequencies deformation data is performed to find the key parameters of a magmatic source in an elastic, isotropic and homogeneous half-space. Seismic data allow us to set the boundary of the investigated area. The inversion is performed by using the genetic algorithms (GAs) approach, a well-known search technique widely used to solve optimization problems and categorized as global search heuristics (Goldberg, 1989). Hence the magmatic source is located, a forward model is computed to evaluate the deformation field over Mt. Etna surface. Therefore, for each cell, the displacement vector modulus is estimated and the density probability function is calculated. A higher probability value matches with the cells with larger modulus, whereas lower estimate is found where the modulus is close to zero, being the sum of the probability values normalized to one over the investigated area. We modelled the final intrusion of the May 2008 – July 2009 flank eruption at Mt. Etna, whose onset was preceded by an intense seismic swarm and marked by ground deformation recorded at GPS stations. The future vent forecast highlights the area with higher probability, increasing the difference in relative values between that zone and the rest of the volcano edifice. It is worthy notice that a good accordance is evident if the highest probability area is compared with the real vent occurrence.PublishedNicolosi (Catania), Italy4V. Vulcani e ambientereserve

Probability hazard map for future vent opening at Etna volcano (Sicily, Italy).

Mount Etna is a composite stratovolcano located along the Ionian coast of eastern Sicily. The frequent occurrence of flank eruptions (at an interval of years), mostly concentrated along the NE, S and W rift zones leads to a high volcanic hazard that, linked with intense urbanization, poses a high volcanic risk. In the framework of the project PON SIGMA (Integrated Cloud-Sensor System for Advanced Multirisk Management), we develop a near real-time computer-assisted analysis and probabilistic evaluations that provides the identification of the areas prone to the highest vent opening hazard. A longterm volcanic hazard assessment, mainly based on the past flank activity of the Mt. Etna volcano, is the basic tool for the evaluation of this risk. Then, a reliable forecast of where an impending eruption will occur is needed. The use of a code such BET_EF (Bayesian Event Tree_Eruption Forecasting) delivers a long-term hazard map, that, if additional data are provided, switches into a short-term future vent opening map. The present application is based on incoming seismic and ground deformation data. Analytic inversion of high frequencies deformation data is performed to find the key parameters of a magmatic source in an elastic, isotropic and homogeneous half-space. Seismic data allow us to set the boundary of the investigated area. The inversion is performed by using the genetic algorithms (GAs) approach, a well-known search technique widely used to solve optimization problems and categorized as global search heuristics (Goldberg, 1989). Hence the magmatic source is located, a forward model is computed to evaluate the deformation field over Mt. Etna surface. Therefore, for each cell, the displacement vector modulus is estimated and the density probability function is calculated. A higher probability value matches with the cells with larger modulus, whereas lower estimate is found where the modulus is close to zero, being the sum of the probability values normalized to one over the investigated area. We modelled the final intrusion of the May 2008 – July 2009 flank eruption at Mt. Etna, whose onset was preceded by an intense seismic swarm and marked by ground deformation recorded at GPS stations. The future vent forecast highlights the area with higher probability, increasing the difference in relative values between that zone and the rest of the volcano edifice. It is worthy notice that a good accordance is evident if the highest probability area is compared with the real vent occurrence

Probability hazard map for future vent opening at Etna volcano (Sicily, Italy).

The frequent flank eruptions occurrence at Mt. Etna lead to a high volcanic hazard that, linked to a population of nearly one million people dwell on its flanks, poses a high volcanic risk. In the framework of the project PON SIGMA (Integrated Cloud-Sensor System for Advanced Multirisk Management), we developed a near real-time computer-assisted analysis and probabilistic evaluations that provide the identification of the areas prone to the highest vent opening hazard. The use of a code such BET_EF (Bayesian Event Tree_Eruption Forecasting) provide us a long-term hazard map mainly based on the past behaviour of the Etna volcano. The near real-time additional seismic and ground deformation data allow the long-term hazard map switches into a short-term future vent opening one. The short-term future vent opening was computed starting from the evaluation of deformation field over Etna surface. Analytical inversion of deformation and seismic data is performed to find the parameters of a magmatic source in an elastic, isotropic and homogeneous half-space and forward model is performed to compute the displacement field over Etna surface. We modelled the final intrusion of the Mount Etna May 2008 eruption that was accompanied by a violent seismic swarm and marked by ground deformation recorded at GPS stations. Results suggest a good accordance between the higher probability area and the real vent occurrence.PublishedSan Francisco, USA2V. Dinamiche di unrest e scenari pre-eruttiviope

Procedura near real-time per la valutazione dell’hazard da eruzioni laterali all’Etna (Sicilia, Italia)

L’Etna è uno stratovulcano composito situato lungo la costa ionica della Sicilia. Le frequenti eruzioni laterali (soprattutto lungo i Rift NE, S e O) fanno sì che ad esso sia associata una elevata pericolosità vulcanica. Se valutiamo anche l’elevato tasso di urbanizzazione dei suoi fianchi risulta evidente il notevole valore esposto al pericolo. Nel quadro del progetto PON SIGMA (Integrated Cloud-Sensor System for Advanced Multirisk Management), abbiamo sviluppato un’analisi in tempo quasi reale e completamente automatizzata volta alla valutazione delle aree soggette alla più alta probabilità di apertura di bocche effusive (vent) e il corrispondente hazard relativo all’accadimento di eruzioni effusive. L’algoritmo bayesiano BET_EF (Bayesian Event Tree_Eruption Forecasting), basato sull’albero degli eventi, è, nel nostro approccio, utilizzato inizialmente per la valutazione di una mappa di pericolosità a lungo termine sulla base dell’attività effusiva degli ultimi 4000 anni. L’analisi e l’inversione dei parametri monitorati in tempo reale, quali, ad esempio, dati sismici e sorgenti di tremore vulcanico, permette di valutare la funzione di densità di probabilità (PDF) a breve termine. Un’ulteriore applicazione dell’algoritmo BET_EF fornisce uno scenario, in termini di mappa di pericolosità, a breve termine per le simulazioni delle colate laviche. L’output della seconda applicazione del BET_EF costituisce l’input per simulare una serie di colate laviche e valutare il relativo hazard, definito in termini di impatto sul territorio. Allo scopo di testare limiti e utilità del nostro approccio integrato, abbiamo utilizzato, come test case, la fase intrusiva iniziale dell’eruzione laterale accaduta all’Etna nel maggio 2008. La previsione di apertura di vent evidenzia la zona con maggiore probabilità e, dall’analisi dei risultati, si nota un buon accordo tra l’area a probabilità più alta e la posizione effettiva del vent. È stata eseguita una serie di 200 simulazioni di colate per valutare le aree soggette a più alta probabilità di invasione lavica. Infine, è stata valutata la densità dei flussi simulati e i valori più alti sono risultati in accordo con l’area effettivamente coperta dal campo lavico dell’eruzione considerata.progetto PON01_00683 SIGMA (Sistema Integrato di sensori in ambiente cloud per la Gestione Multirischio Avanzata)Published6V. Pericolosità vulcanica e contributi alla stima del rischioJCR Journa

Probability hazard map for future vent opening at Etna volcano (Sicily, Italy).

The frequent flank eruptions occurrence at Mt. Etna lead to a high volcanic hazard that, linked to a population of nearly one million people dwell on its flanks, poses a high volcanic risk. In the framework of the project PON SIGMA (Integrated Cloud-Sensor System for Advanced Multirisk Management), we developed a near real-time computer-assisted analysis and probabilistic evaluations that provide the identification of the areas prone to the highest vent opening hazard. The use of a code such BET_EF (Bayesian Event Tree_Eruption Forecasting) provide us a long-term hazard map mainly based on the past behaviour of the Etna volcano. The near real-time additional seismic and ground deformation data allow the long-term hazard map switches into a short-term future vent opening one. The short-term future vent opening was computed starting from the evaluation of deformation field over Etna surface. Analytical inversion of deformation and seismic data is performed to find the parameters of a magmatic source in an elastic, isotropic and homogeneous half-space and forward model is performed to compute the displacement field over Etna surface. We modelled the final intrusion of the Mount Etna May 2008 eruption that was accompanied by a violent seismic swarm and marked by ground deformation recorded at GPS stations. Results suggest a good accordance between the higher probability area and the real vent occurrence