The analysis of seismicity in the Etna area allows us to know the structure of the earth's crust through which the magma rises and to investigate the migration of magmatic fluids along the volcano's feeding system
Analyze the natural seismicity of Etna to investigate the rise of magmatic fluids along the plumbing system of the volcano, i.e. along that sector of the earth's crust through which magma is transferred from the depths of the magma source to the surface. This is the main focus of the study “Frequency-magnitude distribution of earthquakes at Etna volcano unravels critical stress changes along magma pathways” conducted by a team of researchers from the National Institute of Geophysics and Volcanology (INGV) and just published in the scientific journal 'Communications Earth & Environment' by Nature.
Analyzing more than 13.700 earthquakes that occurred between 2005 and 2019, recorded by over 30 seismic stations of the INGV Observatory of Etna monitoring network, the researchers highlighted how the analysis of natural seismicity can be used to investigate the ascent of the magma, as well as to study the structure of the crust under Etna.
“The crustal sector that hosts Etna is characterized by high seismicity, with numerous earthquakes linked to fracturing processes and movements along pre-existing fault planes. These seismic events can be triggered both by the thrust of the rising magma and by the tectonic processes of deformation of the earth's crust", explains Marco Firetto Carlino, INGV researcher and author of the study. “However, the local stress conditions (such as, for example, the pressure exerted by the magma), the action of the magmatic gases present in the subsoil, the thermal gradients and the mechanical properties of the different crustal volumes capable of generating earthquakes condition the with which the seismic energy is released. In particular, by studying the relationship between the number of earthquakes that occur in a given region and the relative magnitude, through a parameter known as 'b-value', it is possible to define whether this region tends to release seismic energy preferentially through numerous earthquakes of relative low magnitude, or through less frequent higher energy events".
This study has allowed the researchers to identify an aseismic zone that extends from a depth of over 30 km to about 10 km below the entire Etna region, which corresponds to the deepest part of the plumbing system. More on the surface, however, an intermediate magmatic reservoir has been identified, located between 1 and 6 km below sea level, around which numerous low-magnitude earthquakes occur, favored by the high pressure of the magmatic fluids and by the conditions of widespread fracturing of the crust.
“The analysis of the temporal variations of the b-value along the 'plumbing system' of Etna has allowed us to investigate the movement of the magma in depth”, continues Firetto Carlino. "In particular, on 24 December 2018 the Etna activity was characterized by one of the major intrusive events ever recorded, i.e. linked to the ascent of approximately 30 million cubic meters of magma which arrested their ascent below the volcano, all 'at about sea level, triggering a modest eruption that lasted only 4 days. The time series show a pressurization around the intermediate reservoir by magmatic gases, traced by a marked increase in the b-value, which occurred about 19 days before the eruption. The latter was then anticipated by a collapse of the b-value 2 days before the event".
“The analysis of this seismological parameter has made it possible to hypothesize that the anomalous accumulation of magma inside the volcano may have been caused by an increased stress along the 'plumbing system', which can be traced back either to intrinsic dynamics linked to the transfer of magma itself, or to crustal deformations of tectonic origin. In the latter hypothesis, the tectonic processes would be able to locally produce such rapid and intense deformations as to temporarily inhibit the transfer of magma to the surface", concludes the researcher.
#ingv #nature #etna #eruption #seismicity #volcano
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Etna | Seismicity of the Etna area provides the chance to investigate magma uprising beneath the volcano
The analysis of seismicity in the Etna area allows us to outline the crustal structure through which magma uprises and to investigate the migration of magmatic fluids along the volcano's plumbing system
Analyzing the natural seismicity of Etna to investigate the ascent of magmatic fluids along the “plumbing system” of the volcano, or rather along that sector of the Earth's crust through which magma is transferred from the depths of the magma source to the surface. This is the main focus of the study "Frequency-magnitude distribution of earthquakes at Etna volcano unravels critical stress changes along magma pathways” conducted by a team of researchers from the National Institute of Geophysics and Volcanology (INGV) and just published in the scientific journal 'Communications Earth & Environment' by Nature.
By the analysis of more than 13,700 earthquakes that occurred between 2005 and 2019, recorded by the more than 30 seismic stations of the INGV's Etnean Observatory monitoring network, the researchers highlighted how the analysis of natural seismicity can be used to investigate magma ascent, as well as to study the structure of the crust beneath Etna.
“The crustal sector beneath Mt. Etna is characterized by high seismicity, with numerous earthquakes linked to fracturing processes and slip along pre-existing fault surfaces. Such seismic events can be triggered both by the push of the ascending magma and by tectonic processes deforming Earth's crust”, explains Marco Firetto Carlino, INGV researcher and author of the study. “However, the local stress conditions (such as, for example, the pressure exerted by the magma), the action of the magmatic gases in the subsurface, thermal gradients and the mechanical properties of the different crustal volumes capable of generating earthquakes affect the way in which seismic energy is released. In particular, by studying the relationship between the number of earthquakes occurring in a given region and related magnitude, through a parameter known as 'b-value', it is possible to define whether this region tends to release seismic energy preferentially through numerous earthquakes of relatively low magnitude, or through less frequent but more energetic events”.
This study allowed the researchers to identify an aseismic area that extends from over 30 to about 10 km of depth below the entire Etna region, which corresponds to the deepest part of the plumbing system. At shallower depths, an intermediate magma storage has been identified between 1 and 6 km below sea level, around which many low-magnitude earthquakes occur, favored by the high magmatic gas pressure and by the intense fracturing condition of the crust.
“The analysis of the temporal variations of the b-value along the Etna 'plumbing system' made it possible to investigate magma movements in depth”, continues Firetto Carlino. “In particular, on 24 December 2018 Mt. Etna experienced one of the strongest known intrusive episodes, related to the ascent of about 30 million cubic meters of magma that aborted, rather oddly, its ascent inside the volcano at about sea level. Nevertheless, this major intrusive event resulted in a relatively modest eruption that lasted only 4 days. The time series show a pressurization by magmatic gases around the intermediate storage, marked by a strong increase in the b-value that occurred about 19 days before the eruption. This eruption was then preceded by a drop of the b-value 2 days before the event”.
“The analysis of this seismological parameter has allowed us to speculate that the anomalous accumulation of magma inside the volcano may have been linked to increased stress along the 'plumbing system', which can be traced back to magma dynamics or to crustal deformation of tectonic origin . In the latter hypothesis, tectonic processes might locally result in small-scale deformation that can be so rapid and strong as to severely perturb the isostatic uprising of magma within the crust”, concludes the researcher.
#ingv #nature #etna #eruption #volcano #plumbingsystem
Link to the article
Analyze the natural seismicity of Etna to investigate the rise of magmatic fluids along the plumbing system of the volcano, i.e. along that sector of the earth's crust through which magma is transferred from the depths of the magma source to the surface. This is the main focus of the study “Frequency-magnitude distribution of earthquakes at Etna volcano unravels critical stress changes along magma pathways” conducted by a team of researchers from the National Institute of Geophysics and Volcanology (INGV) and just published in the scientific journal 'Communications Earth & Environment' by Nature.
Analyzing more than 13.700 earthquakes that occurred between 2005 and 2019, recorded by over 30 seismic stations of the INGV Observatory of Etna monitoring network, the researchers highlighted how the analysis of natural seismicity can be used to investigate the ascent of the magma, as well as to study the structure of the crust under Etna.
“The crustal sector that hosts Etna is characterized by high seismicity, with numerous earthquakes linked to fracturing processes and movements along pre-existing fault planes. These seismic events can be triggered both by the thrust of the rising magma and by the tectonic processes of deformation of the earth's crust", explains Marco Firetto Carlino, INGV researcher and author of the study. “However, the local stress conditions (such as, for example, the pressure exerted by the magma), the action of the magmatic gases present in the subsoil, the thermal gradients and the mechanical properties of the different crustal volumes capable of generating earthquakes condition the with which the seismic energy is released. In particular, by studying the relationship between the number of earthquakes that occur in a given region and the relative magnitude, through a parameter known as 'b-value', it is possible to define whether this region tends to release seismic energy preferentially through numerous earthquakes of relative low magnitude, or through less frequent higher energy events".
This study has allowed the researchers to identify an aseismic zone that extends from a depth of over 30 km to about 10 km below the entire Etna region, which corresponds to the deepest part of the plumbing system. More on the surface, however, an intermediate magmatic reservoir has been identified, located between 1 and 6 km below sea level, around which numerous low-magnitude earthquakes occur, favored by the high pressure of the magmatic fluids and by the conditions of widespread fracturing of the crust.
“The analysis of the temporal variations of the b-value along the 'plumbing system' of Etna has allowed us to investigate the movement of the magma in depth”, continues Firetto Carlino. "In particular, on 24 December 2018 the Etna activity was characterized by one of the major intrusive events ever recorded, i.e. linked to the ascent of approximately 30 million cubic meters of magma which arrested their ascent below the volcano, all 'at about sea level, triggering a modest eruption that lasted only 4 days. The time series show a pressurization around the intermediate reservoir by magmatic gases, traced by a marked increase in the b-value, which occurred about 19 days before the eruption. The latter was then anticipated by a collapse of the b-value 2 days before the event".
“The analysis of this seismological parameter has made it possible to hypothesize that the anomalous accumulation of magma inside the volcano may have been caused by an increased stress along the 'plumbing system', which can be traced back either to intrinsic dynamics linked to the transfer of magma itself, or to crustal deformations of tectonic origin. In the latter hypothesis, the tectonic processes would be able to locally produce such rapid and intense deformations as to temporarily inhibit the transfer of magma to the surface", concludes the researcher.
#ingv #nature #etna #eruption #seismicity #volcano
Link to the article
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Etna | Seismicity of the Etna area provides the chance to investigate magma uprising beneath the volcano
The analysis of seismicity in the Etna area allows us to outline the crustal structure through which magma uprises and to investigate the migration of magmatic fluids along the volcano's plumbing system
Analyzing the natural seismicity of Etna to investigate the ascent of magmatic fluids along the “plumbing system” of the volcano, or rather along that sector of the Earth's crust through which magma is transferred from the depths of the magma source to the surface. This is the main focus of the study "Frequency-magnitude distribution of earthquakes at Etna volcano unravels critical stress changes along magma pathways” conducted by a team of researchers from the National Institute of Geophysics and Volcanology (INGV) and just published in the scientific journal 'Communications Earth & Environment' by Nature.
By the analysis of more than 13,700 earthquakes that occurred between 2005 and 2019, recorded by the more than 30 seismic stations of the INGV's Etnean Observatory monitoring network, the researchers highlighted how the analysis of natural seismicity can be used to investigate magma ascent, as well as to study the structure of the crust beneath Etna.
“The crustal sector beneath Mt. Etna is characterized by high seismicity, with numerous earthquakes linked to fracturing processes and slip along pre-existing fault surfaces. Such seismic events can be triggered both by the push of the ascending magma and by tectonic processes deforming Earth's crust”, explains Marco Firetto Carlino, INGV researcher and author of the study. “However, the local stress conditions (such as, for example, the pressure exerted by the magma), the action of the magmatic gases in the subsurface, thermal gradients and the mechanical properties of the different crustal volumes capable of generating earthquakes affect the way in which seismic energy is released. In particular, by studying the relationship between the number of earthquakes occurring in a given region and related magnitude, through a parameter known as 'b-value', it is possible to define whether this region tends to release seismic energy preferentially through numerous earthquakes of relatively low magnitude, or through less frequent but more energetic events”.
This study allowed the researchers to identify an aseismic area that extends from over 30 to about 10 km of depth below the entire Etna region, which corresponds to the deepest part of the plumbing system. At shallower depths, an intermediate magma storage has been identified between 1 and 6 km below sea level, around which many low-magnitude earthquakes occur, favored by the high magmatic gas pressure and by the intense fracturing condition of the crust.
“The analysis of the temporal variations of the b-value along the Etna 'plumbing system' made it possible to investigate magma movements in depth”, continues Firetto Carlino. “In particular, on 24 December 2018 Mt. Etna experienced one of the strongest known intrusive episodes, related to the ascent of about 30 million cubic meters of magma that aborted, rather oddly, its ascent inside the volcano at about sea level. Nevertheless, this major intrusive event resulted in a relatively modest eruption that lasted only 4 days. The time series show a pressurization by magmatic gases around the intermediate storage, marked by a strong increase in the b-value that occurred about 19 days before the eruption. This eruption was then preceded by a drop of the b-value 2 days before the event”.
“The analysis of this seismological parameter has allowed us to speculate that the anomalous accumulation of magma inside the volcano may have been linked to increased stress along the 'plumbing system', which can be traced back to magma dynamics or to crustal deformation of tectonic origin . In the latter hypothesis, tectonic processes might locally result in small-scale deformation that can be so rapid and strong as to severely perturb the isostatic uprising of magma within the crust”, concludes the researcher.
#ingv #nature #etna #eruption #volcano #plumbingsystem
Link to the article
figure 1 - Distribution of seismicity (black dots, whose size is a function of the magnitude) and of the relative b-value (colored dots) in the crustal region of Mount Etna. The deep plumbing system of the volcano corresponds to an almost aseismic zone, while the surroundings of the intermediate magma reservoir are characterized by high b-values.
Figure 2 - Time series showing the variation of b-value around the intermediate magma reservoir (in yellow) and in the more superficial portion of the plumbing system (in blue). It can be seen how the values of b grow markedly only around the magma reservoir about 19 days before the eruption of 24/12/2018, due to a pressurization of the system by the magmatic gases. The eruption is anticipated by a collapse of the b-value that started on 22/12/2018 only around the magma reservoir, and continued until the day of the eruption in both time series.
(Figure 1 – Volumetric view of seismicity (dark dots whose dimension is plotted as a function of magnitude) and related b-values (coloured dots) in the crustal region beneath Mt. Etna. The deeper “plumbing system” is highlighted by an aseismic zone, while the surrounding of the intermediate magma storage is characterized by high b-values.
(Figure 2 - Time series showing b-value variations in the surrounding of the intermediate magma storage (yellow) and within the shallower portion of the "plumbing system" (blue). The b-values notably increase only around the magma storage about 19 days before the 24/12/2018 eruption, due to a pressurization of the system by magmatic gases. The eruption was preceded by a fall of the b-value started on 22/12/2018 only in the surrounding of the magma storage, and continued until the day of the eruption in both time series.