Synthesis of global satellite observations of magmatic and volcanic deformation: implications for volcano monitoring & the lateral extent of magmatic domains

Global Synthetic Aperture Radar (SAR) measurements made over the past decades provide insights into the lateral extent of magmatic domains, and capture volcanic process on scales useful for volcano monitoring. Satellite-based SAR imagery has great potential for monitoring topographic change, the distribution of eruptive products and surface displacements (InSAR) at subaerial volcanoes. However, there are challenges in applying it routinely, as would be required for the reliable operational assessment of hazard. The deformation detectable depends upon satellite repeat time and swath widths, relative to the spatial and temporal scales of volcanological processes. We describe the characteristics of InSAR-measured volcano deformation over the past two decades, highlighting both the technique’s capabilities and its limitations as a monitoring tool. To achieve this, we draw on two global datasets of volcano deformation: the Smithsonian Institution Volcanoes of the World database and the Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics volcano deformation catalogue, as well as compiling some measurement characteristics and interpretations from the primary literature. We find that a higher proportion of InSAR observations capture non-eruptive and non-magmatic processes than those from ground-based instrument networks, and that both transient ( 5 years) deformation episodes are under-represented. However, satellite radar is already used to assess the development of extended periods of unrest and long-lasting eruptions, and improved spatial resolution and coverage have resulted in the detection of previously unrecognised deformation at both ends of the spatial scale (~ 10 to > 1000 km²). ‘Baseline’ records of past InSAR measurements, including ‘null’ results, are fundamental for any future interpretation of interferograms in terms of hazard‚ both by providing information about past deformation at an individual volcano, and for assessing the characteristics of deformation that are likely to be detectable (and undetectable) using InSAR. More than half of all InSAR deformation signals attributed to magmatic processes have sources in the shallow crust (< 5 km depth). While the depth distribution of InSAR-derived deformation sources is affected by measurement limitations, their lateral distribution provides information about the extent of active magmatic domains. Deformation is common (24% of all potentially magmatic events) at loci ≥5 km away from the nearest active volcanic vent. This demonstrates that laterally extensive active magmatic domains are not exceptional, but can comprise the shallowest part of trans-crustal magmatic systems in a range of volcanic settings

Geomática aplicada al análisis de riesgos geológicos

Tesis por compendio de publicaciones[ES]Esta Tesis Doctoral se ha realizado mediante el formato de compendio de artículos, con objetivos claramente diferenciados y concatenados entre sí con el fin de ampliar el conocimiento sobre la implementación de nuevas metodologías en Geomática Aplicada utilizando información de uso público para la gestión de la peligrosidad natural en la reducción del Riesgo Geológico. Se ha puesto énfasis en hacer conocer a la comunidad los beneficios de analizar los riesgos geológicos con anticipación para identificarlos espacialmente y establecer correcciones estructurales como criterio de prevención, lo que implica elaborar previamente mapas de zonas susceptibles a movimientos en masa, inundaciones, erosión hídrica, mapas sismo-tectónicos-volcánicos y de problemas geotécnicos, a partir de la Geomática Aplicada (Teledetección, Sistemas de Información Geográfica y Modelación Numérica) e información espacial georeferenciada. Se desarrollan en esta Tesis cinco métodos geomáticos aplicados a la reducción del riesgo geológico, validados mediante su aplicación en diferentes riesgos geológicos de varias regiones de Ecuador[EN][EN]This Doctoral Thesis has been carried out through the compendium format of articles, with clearly differentiated and concatenated objectives in order to expand knowledge on the implementation of new methodologies in Applied Geomatics using information of public use for the management of natural hazard in the reduction of Geological Risk. Emphasis has been placed on making the community aware of the benefits of analyzing geological risks in advance to spatially identify them and establish structural corrections as a prevention criterion, which implies preparing previously maps of areas susceptible to mass movements, floods, water erosion, Earthquake-tectonic-volcanic maps and geotechnical problems, from Applied Geomatics (Remote Sensing, Geographic Information Systems and Numerical Modeling) and georeferenced spatial information. Five geomatic methods applied to the reduction of geological risk are developed in this thesis, validated by their application to different geological risks in various regions of Ecuador

Using Seismic Signals to Forecast Volcanic Processes

One of the ultimate aims in volcanological research is to be able to forecast the timing, location and intensity of a volcanic eruption with confidence. Prior to many volcanic eruptions, an acceleration in geophysical precursors (seismicity, deformation, gas emissions) is observed, suggesting the potential for this as a forecasting tool. The Failure Forecast Method (FFM) relates an accelerating precursor to the timing of failure by an empirical power law, with failure being defined in this context as the onset of an eruption. Previous applications of the FFM have used a wide variety of accelerating time series, often generating questionable forecasts with large misfits between data and the forecast, as well as the generation of a number of different forecasts from the same data series. This research presents an alternative approach applying the FFM using it in combination with a cross correlation technique which identifies seismicity from the same active source mechanism and location. Isolating a single system at depth avoids additional uncertainties introduced by averaging data over a number of different accelerating phenomena, and consequently reduces the misfit between the data and the forecast. Similar seismic waveforms are identified in the precursory accelerating seismicity to dome collapses at Soufriere Hills volcano, Montserrat in June 1997, July 2003 and February 2010. These events were specifically chosen since they represent a spectrum of collapse scenarios at this volcano. The use of similar seismicity as a forecasting tool for collapses in 1997 and 2003 greatly improved the forecasted timing of the dome collapse, as well as improving the confidence in the forecast, thereby outperforming the classical application of the FFM. The dome collapse event of 2010 could not successfully be forecast using the FFM since no acceleration in seismicity was observed. Use of the FFM requires the assumption that the accelerating seismicity at depth forms a direct and causal link to the dome collapse at the surface. Collapse triggers can be either internal (e.g. the movement of magma) or external (e.g. rainfall). For the first time within a volcanic environment, the use of grey incidence analysis quantitatively recognised that the most influential parameters for affecting the likelihood of a dome collapse at Soufriere Hills were internal; and particularly important was the effect of low frequency seismicity, which may induce instability through an increase in pore fluid pressures related to the movement of magma and hydrothermal fluids from depth. Finite Element Modelling of the stability of the volcanic dome in the days before the collapses in July 2003 and February 2010 suggested that neither were stable, and should have already collapsed. The errors involved in such a calculation are large due to the large uncertainties associated with the mechanical properties of the rock masses involved which act as an input to the model. Therefore, in order to develop more accurate dome stability models, it is essential that these uncertainties in mechanical properties are reduced. Application of this combined methodology of the FFM and a cross correlation technique as a forecasting tool was also applied for the first time to the onset of an unrest scenario at Chiles-Cerro Negro (Ecuador/Colombia) in October 2014, which had previously been assumed to be dormant. At the time of investigation (February 2015) unrest was still ongoing, and there was very little geological or geophysical information regarding this volcano in the past. The number of similar seismic events accelerated and became distinctly organised into separate temporal clusters on 20 October 2014, prior to a Magnitude 5.8 earthquake directly beneath the volcano. Each temporal cluster displayed a distinctly different waveform shape, indicating the activation of a number of different sources (either in mechanism or location) at depth. Application of the FFM to the acceleration in similar seismicity allowed an accurate forecast of the Magnitude 5.8 earthquake beneath the volcano, suggesting a direct relationship. Similar seismicity has not been identified at any of the Ecuadorian volcanoes before, and consequently the computer codes for identifying similar seismicity, and using it as a forecasting tool are currently being tested at the Instituto-Geofisico, Ecuador, for their real time application potential

InSAR-Based Mapping to Support Decision-Making after an Earthquake

It has long been recognized that earthquakes change the stress in the upper crust around the fault rupture and can influence the behaviour of neighbouring faults and volcanoes. Rapid estimates of these stress changes can provide the authorities managing the post-disaster situation with valuable data to identify and monitor potential threads and to update the estimates of seismic and volcanic hazard in a region. Here we propose a methodology to evaluate the potential influence of an earthquake on nearby faults and volcanoes and create easy-to-understand maps for decision-making support after large earthquakes. We apply this methodology to the Mw 7.8, 2016 Ecuador earthquake. Using Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR) and continuous GPS data, we measure the coseismic ground deformation and estimate the distribution of slip over the fault rupture. We also build an alternative source model using the Global Centroid Moment Tensor (CMT) solution. Then we use these models to evaluate changes of static stress on the surrounding faults and volcanoes and produce maps of potentially activated faults and volcanoes. We found, in general, good agreement between our maps and the seismic and volcanic events that occurred after the Pedernales earthquake. We discuss the potential and limitations of the methodology.This work is supported by the European Commission, Directorate-General Humanitarian Aid and Civil Protection (ECHO) under the SAFETY (Sentinel for Geohazards regional monitoring and forecasting) project (ECHO/SUB/2015/718679/Prev02) and by the Spanish Ministry of Economy and Competitiveness under INTERGEOSIMA (CGL2013-47412) and ACTIVESTEP (CGL2017-83931-C3), QUAKESTEP (1-P) + 3GEO(2-P) + GEOACTIVA (3-P) projects

Volcanic Processes Monitoring and Hazard Assessment Using Integration of Remote Sensing and Ground-Based Techniques

The monitoring of active volcanoes is a complex task based on multidisciplinary and integrated analyses that use ground, drones and satellite monitoring devices. Over time, and with the development of new technologies and increasing frequency of acquisition, the use of remote sensing to accomplish this important task has grown enormously. This is especially so with the use of drones and satellites for classifying eruptive events and detecting the opening of new vents, the spreading of lava flows on the surface or ash plumes in the atmosphere, the fallout of tephra on the ground, the intrusion of new magma within the volcano edifice, and the deformation preceding impending eruptions, and many other factors. The main challenge in using remote sensing techniques is to develop automated and reliable systems that may assist the decision maker in volcano monitoring, hazard assessment and risk reduction. The integration with ground-based techniques represents a valuable additional aspect that makes the proposed methods more robust and reinforces the results obtained. This collection of papers is focused on several active volcanoes, such as Stromboli, Etna, and Volcano in Italy; the Long Valley caldera and Kilauea volcano in the USA; and Cotopaxi in Ecuador

InSAR-Based Mapping to Support Decision-Making after an Earthquake

It has long been recognized that earthquakes change the stress in the upper crust around the fault rupture and can influence the behaviour of neighbouring faults and volcanoes. Rapid estimates of these stress changes can provide the authorities managing the post-disaster situation with valuable data to identify and monitor potential threads and to update the estimates of seismic and volcanic hazard in a region. Here we propose a methodology to evaluate the potential influence of an earthquake on nearby faults and volcanoes and create easy-to-understand maps for decision-making support after large earthquakes. We apply this methodology to the Mw 7.8, 2016 Ecuador earthquake. Using Sentinel-1 Interferometric Synthetic Aperture Radar (InSAR) and continuous GPS data, we measure the coseismic ground deformation and estimate the distribution of slip over the fault rupture. We also build an alternative source model using the Global Centroid Moment Tensor (CMT) solution. Then we use these models to evaluate changes of static stress on the surrounding faults and volcanoes and produce maps of potentially activated faults and volcanoes. We found, in general, good agreement between our maps and the seismic and volcanic events that occurred after the Pedernales earthquake. We discuss the potential and limitations of the methodology

Updates in Volcanology

Updates in Volcanology - From Volcano Modeling to Volcano Geology is a new book that is based on book chapters offered by various authors to provide a snapshot of current trends in volcanological researches. Following a short Introduction, the book consists of three sections, namely, ''Understanding the Volcano System from Petrology, Geophysics to Large Scale Experiments,'' ''Volcanic Eruptions and Their Impact to the Environment,' and ''Volcanism in the Geological Record.'' These sections collect a total of 13 book chapters demonstrating clearly the research activity in volcanology from geophysical aspects of volcanic systems to their geological framework. Each chapter provides a comprehensive summary of their subject's current research directions. This book hence can equally be useful for students and researchers

Impact of Etna’s volcanic emission on major ions and trace elements composition of the atmospheric deposition

Mt. Etna, on the eastern coast of Sicily (Italy), is one of the most active volcanoes on the planet and it is widely recognized as a big source of volcanic gases (e.g., CO2 and SO2), halogens, and a lot of trace elements, to the atmosphere in the Mediterranean region. Especially during eruptive periods, Etna’s emissions can be dispersed over long distances and cover wide areas. A group of trace elements has been recently brought to attention for their possible environmental and human health impacts, the Technology-critical elements. The current knowledge about their geochemical cycles is still scarce, nevertheless, recent studies (Brugnone et al., 2020) evidenced a contribution from the volcanic activity for some of them (Te, Tl, and REE). In 2021, in the framework of the research project “Pianeta Dinamico”, by INGV, a network of 10 bulk collectors was implemented to collect, monthly, atmospheric deposition samples. Four of these collectors are located on the flanks of Mt. Etna, other two are in the urban area of Catania and three are in the industrial area of Priolo, all most of the time downwind of the main craters. The last one, close to Cesarò (Nebrodi Regional Park), represents the regional background. The research aims to produce a database on major ions and trace element compositions of the bulk deposition and here we report the values of the main physical-chemical parameters and the deposition fluxes of major ions and trace elements from the first year of research. The pH ranged from 3.1 to 7.7, with a mean value of 5.6, in samples from the Etna area, while it ranged between 5.2 and 7.6, with a mean value of 6.4, in samples from the other study areas. The EC showed values ranging from 5 to 1032 μS cm-1, with a mean value of 65 μS cm-1. The most abundant ions were Cl- and SO42- for anions, Na+ and Ca+ for cations, whose mean deposition fluxes, considering all sampling sites, were 16.6, 6.8, 8.4, and 6.0 mg m-2 d, respectively. The highest deposition fluxes of volcanic refractory elements, such as Al, Fe, and Ti, were measured in the Etna’s sites, with mean values of 948, 464, and 34.3 μg m-2 d-1, respectively, higher than those detected in the other sampling sites, further away from the volcanic source (26.2, 12.4, 0.5 μg m-2 d-1, respectively). The same trend was also observed for volatile elements of prevailing volcanic origin, such as Tl (0.49 μg m-2 d-1), Te (0.07 μg m-2 d-1), As (0.95 μg m-2 d-1), Se (1.92 μg m-2 d-1), and Cd (0.39 μg m-2 d-1). Our preliminary results show that, close to a volcanic area, volcanic emissions must be considered among the major contributors of ions and trace elements to the atmosphere. Their deposition may significantly impact the pedosphere, hydrosphere, and biosphere and directly or indirectly human health

EVOLUTION OF THE SUBCONTINENTAL LITHOSPHERE DURING MESOZOIC TETHYAN RIFTING: CONSTRAINTS FROM THE EXTERNAL LIGURIAN MANTLE SECTION (NORTHERN APENNINE, ITALY)

Our study is focussed on mantle bodies from the External Ligurian ophiolites, within the Monte Gavi and Monte Sant'Agostino areas. Here, two distinct pyroxenite-bearing mantle sections were recognized, mainly based on their plagioclase-facies evolution. The Monte Gavi mantle section is nearly undeformed and records reactive melt infiltration under plagioclase-facies conditions. This process involved both peridotites (clinopyroxene-poor lherzolites) and enclosed spinel pyroxenite layers, and occurred at 0.7–0.8 GPa. In the Monte Gavi peridotites and pyroxenites, the spinel-facies clinopyroxene was replaced by Ca-rich plagioclase and new orthopyroxene, typically associated with secondary clinopyroxene. The reactive melt migration caused increase of TiO2 contents in relict clinopyroxene and spinel, with the latter also recording a Cr2O3 increase. In the Monte Gavi peridotites and pyroxenites, geothermometers based on slowly diffusing elements (REE and Y) record high temperature conditions (1200-1250 °C) related to the melt infiltration event, followed by subsolidus cooling until ca. 900°C. The Monte Sant'Agostino mantle section is characterized by widespread ductile shearing with no evidence of melt infiltration. The deformation recorded by the Monte Sant'Agostino peridotites (clinopyroxene-rich lherzolites) occurred at 750–800 °C and 0.3–0.6 GPa, leading to protomylonitic to ultramylonitic textures with extreme grain size reduction (10–50 μm). Compared to the peridotites, the enclosed pyroxenite layers gave higher temperature-pressure estimates for the plagioclase-facies re-equilibration (870–930 °C and 0.8–0.9 GPa). We propose that the earlier plagioclase crystallization in the pyroxenites enhanced strain localization and formation of mylonite shear zones in the entire mantle section. We subdivide the subcontinental mantle section from the External Ligurian ophiolites into three distinct domains, developed in response to the rifting evolution that ultimately formed a Middle Jurassic ocean-continent transition: (1) a spinel tectonite domain, characterized by subsolidus static formation of plagioclase, i.e. the Suvero mantle section (Hidas et al., 2020), (2) a plagioclase mylonite domain experiencing melt-absent deformation and (3) a nearly undeformed domain that underwent reactive melt infiltration under plagioclase-facies conditions, exemplified by the the Monte Sant'Agostino and the Monte Gavi mantle sections, respectively. We relate mantle domains (1) and (2) to a rifting-driven uplift in the late Triassic accommodated by large-scale shear zones consisting of anhydrous plagioclase mylonites. Hidas K., Borghini G., Tommasi A., Zanetti A. &amp; Rampone E. 2021. Interplay between melt infiltration and deformation in the deep lithospheric mantle (External Liguride ophiolite, North Italy). Lithos 380-381, 105855