Fabrizio Ferrucci

Fast deformation processes and eruptive activity at Mount Etna (Italy)

The seismic and deformation patterns observed on Mount Etna before and during the 1991–1993 eruption, the third largest since the seventeenth century in terms of lava volume, are consistent with the regional tectonic framework of eastern Sicily. The pattern of the stress field acting on the intermediate and lower crust was defined at the local scale by focal mechanisms of microearthquakes occurring at depths between 10 and 25 km beneath the volcano. They provide evidence for a strike-slip compressional stress regime with the maximum compressive component acting approximately N-S. The fault plane solutions and the spatial and temporal distribution of seismicity indicate that usually sinistral shear ruptures occur along approximately NE-SW trending fault zones, while dip-slip ruptures affect approximately NNW-SSE trending fault zones. The latter include the avenues along which magma ascended during the 1991–1993 eruption. Seismic observations indicate a local inversion of the stress field acting on the upper crust (depth < ∼10 km) underlying Mount Etna, which was initiated less than 2 months before the eruptive event and disappeared with its end. This is consistent with a local tensile regime that favored the magma ascent through the shallow crust. The events preceding the eruption and accompanying its onset (tilt anomalies and seismic swarms) and those occurring shortly after its beginning (a mainshock-aftershock seismic sequence and associated coseismic tilts) provide important evidence for understanding the dynamics of the two main volcano-tectonic structures (NE-SW and NNW-SSE trending fault zones) and associated intrusive mechanisms on Etna. The shape and location of the eruption-feeding dike have been modeled from ground deformation data. This approximately NNW-SSE modeled dike, the seismicity, and the position of the fractures are consistent with the regional stress field characterized by σ1 oriented approximately N-S. The geophysical data presented and analyzed in the present paper strongly suggest an overall regional tectonic control as well as an active role for the intruding magma in the dynamics of the volcano.

Seismic activity accompanying the outbreak of the 1991–1993 eruption of Mt. Etna (Italy)

Abstract The character and location of seismic activity accompanying the onset of the 1991–1993 eruption at Mt. Etna are compatible with the surface evidence of the volcanic pile rupture. Both the epicentral distribution and the focal mechanisms of a swarm that occurred on December 14, 1991, agree with magma ascent occurring along the main NNW-SSE-trending structure of the volcano and the consequent opening of a system of effusive fissures with the same trend. A typical mainshock-aftershock sequence, recorded the day after and indicating transcurrent displacement occurring along the second-principal structure of Etna (NE-SW), depicts the tectonic response of the volcanic pile and the underlying basement to major stresses applied by the magma push.

Combined Use of SEVIRI and MODIS for Detecting, Measuring, and Monitoring Active Lava Flows at Erupting Volcanoes

Multispectral data acquired by Spinning Enhanced Visible and InfraRed Imager (SEVIRI) onboard the geostationary platform Meteosat Second Generation (MSG2), located at 0deg longitude, were analyzed to assess the payload suitability for quantitative volcano monitoring. In times of good infrared transparency of the troposphere, SEVIRI data proved particularly suited to detect the onset of effusive eruptions and to monitor the related lava flows with 15-min refresh rates. After development of a code allowing for fast automated processing of the 96 data streams downlinked daily by MSG2, thorough monitoring tests were carried out on the 2007 eruptions of Stromboli (Aeolian Islands, Italy) and Piton de la Fournaise (Reunion Island, France). The results in radiant flux and effusion rate provided by use of thermal, mid-, and short infrared bands of SEVIRI were validated by exploiting simultaneous MODIS overpasses by Terra and Aqua, up to four times daily.

SEVIRI Onboard Meteosat Second Generation, and the Quantitative Monitoring of Effusive Volcanoes in Europe and Africa

The spectral and radiometric performance of payload SEVIRI onboard the geostationary platform MSG-2, make its data particularly well suited not only to the detection of the onset of volcanic activity, but also to the measurement of thermal radiant fluxes and eruption rates. Thorough testing was carried out on two volcanoes - Stromboli (Aeolian Islands, Southern Italy) and Piton de la Fournaise (Reunion Island, northwestern Indian Ocean) - that mostly give rise to short-lived lava flows. Aimed to comply with the outstandingly high acquisition rate, we developed an ad-hoc code to automatically detect volcanic hot-spots, measure radiant fluxes, and derive lava volume effusion rates within the 15-minute interval between two SEVIRI data streams.

Automated, multi-payload, high-resolution temperature mapping and instant lava effusion rate determination at erupting volcanoes

We present a computing routine (MYVOL) specifically designed for volcano monitoring and, in particular, for the multi-platform, high-resolution, lava flow mapping and instantaneous effusion rate determination. The routine allows for the automated processing of data acquired by TM and ETM+ (onboard Landsat-5 and Landsat-7, respectively), ASTER (onboard TERRA), HRVIR and HRG (onboard SPOT-4 and SPOT-5, respectively). It was thoroughly tested on multi-scene sequences acquired 2000-2004 on four active volcanoes worldwide (Piton de la Fournaise, Réunion Island; Pu’u O’o, Hawaii; Mt.Etna and Stromboli, southern Italy). Here, we outline the results obtained by MYVOL on Hawaii and Stromboli, and discuss them in application to the performance analysis of ASTER (night-time and daytime) vs. ETM+ and TM (daytime scenes).

Conclusion: recommendations and findings of the RED SEED working group

Abstract RED SEED stands for Risk Evaluation, Detection and Simulation during Effusive Eruption Disasters, and combines stakeholders from the remote sensing, modelling and response communities with experience in tracking volcanic effusive events. The group first met during a three day-long workshop held in Clermont Ferrand (France) between 28 and 30 May 2013. During each day, presentations were given reviewing the state of the art in terms of (a) volcano hot spot detection and parameterization, (b) operational satellite-based hot spot detection systems, (c) lava flow modelling and (d) response protocols during effusive crises. At the end of each presentation set, the four groups retreated to discuss and report on requirements for a truly integrated and operational response that satisfactorily combines remote sensors, modellers and responders during an effusive crisis. The results of collating the final reports, and follow-up discussions that have been on-going since the workshop, are given here. We can reduce our discussions to four main findings. (1) Hot spot detection tools are operational and capable of providing effusive eruption onset notice within 15 min. (2) Spectral radiance metrics can also be provided with high degrees of confidence. However, if we are to achieve a truly global system, more local receiving stations need to be installed with hot spot detection and data processing modules running on-site and in real time. (3) Models are operational, but need real-time input of reliable time-averaged discharge rate data and regular updates of digital elevation models if they are to be effective; the latter can be provided by the radar/photogrammetry community. (4) Information needs to be provided in an agreed and standard format following an ensemble approach and using models that have been validated and recognized as trustworthy by the responding authorities. All of this requires a sophisticated and centralized data collection, distribution and reporting hub that is based on a philosophy of joint ownership and mutual trust. While the next chapter carries out an exercise to explore the viability of the last point, the detailed recommendations behind these findings are detailed here.

Operational Integration of Spaceborne Measurements of Lava Discharge Rates and Sulfur Dioxide Concentrations for Global Volcano Monitoring

We present the rationale and the main initial achievements of the operational prototype of the first multi-method system for the real-time, unsupervised, quantitative monitoring of erupted masses simultaneously at all active volcanoes in Europe, Africa, the Eastern Antilles and the ocean islands. The system is structured as a multi-pole, geographically distributed system, where raw datasets from space payloads SEVIRI, MODIS, GOME-2, IASI and OMI are acquired at four downlink stations, distributed to, and automatically processed at six locations in four European nations, then returned to a central post-processor for real-time alert and Wide Area Network display. This architecture is aimed at optimizing quality and timeliness of the advanced methods run within it, and to let the inherent technical knowledge remain with inventors without concern for individual intellectual property. Before entering operations early in 2012, the system underwent extensive testing in 2011 during the major eruptions of Nabro (Eritrea) and Nyamulagira (DR Congo), which are presented here.

A neural approach to the integrated inversion of geophysical data of different types

Artificial neural networks (ANNs) have been employed for the inversion of the geometrical parameters of a magma-filled dike, which causes observable changes in various geophysical fields. The inversion approach, which is based on the function approximation capabilities of multilayer perceptrons (MLPs), is also carried out by a systematic search technique based on the simulated annealing (SA) optimization algorithm in order to emphasize the merits of the proposed strategy. It is shown that even if the SA approach guarantees a high degree of accuracy, it requires a considerable amount of time, incompatible with on-line applications. On the other hand, it is shown that MLPs, once correctly trained, can solve the inversion problem very fast and with an appreciable degree of accuracy. It is also demonstrated that an integrated approach involving geophysical data of different kinds allows for a more accurate solution than when ground deformation data alone is considered. The results given in the paper are supported by experiments carried out using an interactive software tool developed ad hoc, which allows both direct and inverse modeling of data related to the opening of a crack at the beginning and throughout a volcanic activity episode.

SIGRI Project: Products Validation Results

The pilot project SIGRI (Sistema Integrato per la Gestione del Rischio Incendi) of the Italian Space Agency aims at developing an integrated system for the management of wildfires. The system provides satellite-based products capable of assisting in all phases of fire combat activities: forecast, detection, damage assessment, and recovery. The SIGRI goals were achieved by implementing consolidated methodologies, and/or developing innovative tools and methods for the automated analysis of multispectral, Synthetic Aperture Radar, and non-EO data. This paper focuses on the testing and validation of algorithms developed during the final phase of SIGRI. The validation of the products generated is an important phase in which their potential is assessed, and algorithms are calibrated. We discuss the results of the validation process of the main chain of unsupervised products: Modified Fire Probability Index by multispectral moderate resolution data (prevention), early detection of fire Hot Spots by multispectral very-high temporal resolution data (response), and identification and mapping of Burn Scars (damage assessment) by high-spatial resolution electro-optical and Synthetic Aperture Radar data.

Southern Italy Burn Scar Mapping by MYME2 Procedure using IRS-P6 LISS3

The amount and frequency of occurrence of wildfires in southern Italy were exceptional during summer 2007. More than 7,000 major fire events are reported to have occurred from January to August 2007, for a total extent of burn surfaces exceeding 110,000 hectares (including all types of vegetation), half of which forested (vs. 12,621 hectares inventoried in the year 2006). The Calabria region, southern Italy, was the Italian hottest point for 2007, with 7,550 hectares of forest destroyed by the fire. Here, six scenes acquired by IRS-P6 LISS-3 on July 8th, August 25th, and September 18th, 2007, are analysed in combination with two sets of Landsat 5-TM and Terra-ASTER scenes acquired in 2006 for the high resolution mapping of burn scars.