This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Mount Melbourne (74821? S, 164843? E) is a quiescent volcano located in northern Victoria Land, A... more Mount Melbourne (74821? S, 164843? E) is a quiescent volcano located in northern Victoria Land, Antarctica. Tilt signals have been recorded on Mount Melbourne since early 1989 by a permanent shallow borehole tiltmeter network comprising five stations. An overall picture of tilt, air and permafrost temperatures over 15 years of continuous recording data is reported. We focused our observations on long-term tilt trends that at the end of 1997 65
Il 9 gennaio 2001 uno sciame sismico localizzato sul fianco sud-orientale dell'Etna e caratte... more Il 9 gennaio 2001 uno sciame sismico localizzato sul fianco sud-orientale dell'Etna e caratterizzato da forme d'onda molto simili, ha prodotto diversi danni all'abitato di Zafferana Etnea, che dista circa 3 km dall'area epicentrale. Un'analisi della sismicità registrata a partire dal 1994, ha rivelato che altri terremoti con le stesse caratteristiche hanno interessato quest'area; alcuni hanno preceduto o seguito per alcuni mesi lo sciame del gennaio 2001, altri sono stati registrati ben cinque anni prima. L'utilizzo di tecniche di cross-correlazione, applicato su 3 famiglie di eventi, ha permesso di ottenere una precisa distribuzione spaziale degli ipocentri (errore medio 10-20 metri) e conseguentemente di descrivere la geometria di faglia. La direzione di tale discontinuità, coincidente con uno dei piani nodali ottenuti dai meccanismi focali (che prevede movimenti di tipo strike destro), risulta coerente con uno dei principali trend regionali che interes...
ABSTRACT On 9 of January 2001 the INGV seismic network of Catania (Italy) recorded a seismic swar... more ABSTRACT On 9 of January 2001 the INGV seismic network of Catania (Italy) recorded a seismic swarm of about 60 earthquakes with 1.0>Md>3.6, and nearly identical seismograms. The main shock caused damage to the town of Zafferana Etnea 2.5 km distant from the epicenter located on SE flank of the volcano. Some other events with similar waveform forecasted (up to 2 months before) and followed (for about one month) this swarm; moreover a check of Mt. Etna SE flank seismicity, starting from 1994, has permitted to identify a cluster of 6 multiplets recorded on August 1995 whose seismograms are strongly coherent with the January 9, 2001 ones. Thus we recognize for the first time the occurrence of seismic events on Mount Etna with nearly identical sources separated by years. We applied a cross-spectral technique that allows to obtain the relative relocation of events within a multiplet to at least an order of magnitude higher precision than is typically possible with traditional techniques. The results describe clearly the geometry of the seismogenetic structure; the events lie on planes oriented ENE-WSW that are coincident with one of the planes of the focal mechanism obtained by first-arrivals polarities. This alignment is coherent with one of the main regional tectonic trends that characterize the Mt. Etna area The multiplets analysis has allowed to recognize, on SE flank, a right-lateral strike seismic source along ENE-WSW fault plane, 4 km deep, time repeated and able to produce strong releases.
On October 27, 2002, after about 15 months of quiescence Mt. Etna started a new eruption, still i... more On October 27, 2002, after about 15 months of quiescence Mt. Etna started a new eruption, still in progress, that has involved the forming of eruptive fracture both on south and north flanks of the volcano. A permanent tilt network that comprises nine bi-axial instruments installed in shallow boreholes and a mercury long-base guarantees continuous tilt measurements on Mt. Etna
The Trecastagni Fault (TF) is a NNW-SSE tectonic structure inside Mt. Etna that is characterized ... more The Trecastagni Fault (TF) is a NNW-SSE tectonic structure inside Mt. Etna that is characterized by evident morphological scarps and normal and right-lateral type movements that directly affect roads and buildings. The TF has an important role in the instability that affects the southeastern flank of Mt. Etna, and it represents part of the southern boundary of the unstable sector. Starting from 2005, the TF has been monitored using continuous wire extensometers and by carrying out periodic direct measurements across the northern and central sectors. From 2005 to September 2009, the measurements show that the TF has undergone continuous extension of about 2-3 mm/yr. During the October 2009 to January 2010 period, the creep rate of the TF reached up to 5.5 to 7.0 mm/yr, and this was accompanied by several shallow, low magnitude earthquakes that were felt by local people. This episode appears to be linked to the increase in the sliding velocity of the eastern flank that occurred during 2009.
Advances in volcano monitoring and forecasting need a multidisciplinary collaborative framework. ... more Advances in volcano monitoring and forecasting need a multidisciplinary collaborative framework. In light of this, a Bayesian Event Tree (BET) approach was performed by the application of the BET for Eruption Forecasting (BET_EF) code to analyze the space-time distribution of the volcanic activity of Mount Etna from 2001-2005. First, a reliable monitoring dataset was set up after some sessions to elicit geophysical, volcanological and geochemical 'precursor' parameters. A constant unrest probability of 100%, with a magma involvement usually greater than 95%, was computed throughout the time period analyzed. Eruption probabilities higher than 90% were estimated a few days before the onsets of the 2001 and 2002-2003 flank eruptions. Values slightly higher than 75% were observed during the lava fountaining period in June-July 2001. However, the probabilities flattened to around 30% for the 2004-2005 flank eruption. With suitable data, a good depiction of the actual location of the eruptive scenario for the 2001 and 2002-2003 events was provided. Conversely, the size of the eruptions was not indicated.
In the last ten years (1990-1999), 21 discrete variations of continuous tilt signal have been rec... more In the last ten years (1990-1999), 21 discrete variations of continuous tilt signal have been recorded on Mount Etna, among which one episode was caused by the opening of the eruptive fracture. The remaining 20 anomalies can be classified into two categories: the first comprises 5 ''instantaneous'' tilt variations recorded in correspondence to the most energetic seismic events (M L ‡ 3.3) localized on the high western part of the volcano; the second consists of 15 transient anomalies ranging from some hours to 1-2 days, observed at different times at the various tilt stations, with no correlation to seismic events or other evident volcanic episodes. The aseismic variations propagate through the volcanic edifice with a velocity between 4.5-6.0 km/day. Modeling studies suggest that the deformation is generated by a tensile source located 3-6 km SW from Etna volcano summit and 5-10 km depth.
Journal of Volcanology and Geothermal Research, 2009
The multi-parametric permanent system (tilt and GPS networks, robotized geodetic station) for mon... more The multi-parametric permanent system (tilt and GPS networks, robotized geodetic station) for monitoring ground deformation at Stromboli volcano was set up in the 1990s and later greatly improved during the effusive event of 2002–2003. Unlike other volcanoes, e.g. Mt. Etna, the magnitude of ground deformation signals of Stromboli is very small and through the entire period of operation of the
ABSTRACT Ground deformations measured during the last two GPS surveys carried out in March 2006 a... more ABSTRACT Ground deformations measured during the last two GPS surveys carried out in March 2006 and September 2007 on the Lipari-Vulcano network are analyzed. Through this period, the monitoring seismic network measured an increase of seismic strain release around the Lipari-Vulcano complex with respect to the previous years. GPS surveys measured a significant N-ward motion of Vulcano island with respect to the ITRF05. This motion abruptly decreases in the N part of Vulcano, suggesting a decoupling of the main Vulcano island from the rest of the volcanic complex. By assuming a local reference frame, we observed that the Lipari island and the northernmost part of the Vulcano island are moving SSE-ward with respect to the central and southernmost part of the Vulcano island. GPS data also highlighted a local uplift of the ``La Fossa'' cone superimposed on the general subsidence of the island, increasing towards N. The vertical movements measured by GPS are compared with the results of the leveling surveys carried out on the network installed and managed by the INGV - Osservatorio Vesuviano for monitoring vertical ground movements on Volcano island. Height variations are computed with respect to a reference benchmark located on the southern part of the island, which is a relatively stable area compared to the northern part. The comparison between the two most recent surveys (October 2003 and October 2008) indicates a significant subsidence of the centre-northern area of the island (bottom Fossa Crater and Vulcanello). We also analyzed the long-term tilt observations through the same period. The tilt network at Vulcano Island currently has five borehole stations, four of which are installed at depth of 8-10 m, allowing recording stable and highly accurate signals with low noise. Tilt vectors concur well with leveling and GPS data, highlighting a deflection towards the central-northern part of the island. Geodetic strain tensor analysis derived by GPS data was performed over the area covered by the Lipari-Vulcano network. Transpressive kinematics of the Lipari-Vulcano volcanic complex, with a main N-S contraction and a minor E-W extension only on the Southern part of Vulcano is revealed. In addition, data inversion was performed using a simple Okada model, inverting the horizontal strain measured on 258 GPS baselines. We prefer using baselines rather than displacement vectors to avoid bias due to the ambiguity in fixing the reference system. The final structural framework defines a main compression with a dextral component of displacement on a NW-SE striking structure. This kinematics agrees with focal mechanisms of the strongest seismic events recorded in this area over the same time span as the GPS surveys. Furthermore, a preliminary analysis shows that the observed tilt fits well with the expected one from the model.
A multidisciplinary approach integrating a wide data set ranging from bulk rock compositions of t... more A multidisciplinary approach integrating a wide data set ranging from bulk rock compositions of the erupted products to volcanic tremor, long-period events, and tilt and gravity signals is used to investigate the source depth and magma dynamics of the 10 May 2008 lava fountain at Southeast crater (SEC) of Mount Etna. The investigation was undertaken in the framework of the previous 2007 explosive activity as well as the subsequent effusive eruption beginning 13 May 2008 and lasting up to July 2009. All the data concur in indicating that the 10 May lava fountain was generated by the fragmentation of a foam layer trapped at the top of a shallow reservoir, about 1500-1700 m below the summit of SEC. The shift from the episodic strombolian/lava fountain activity occurring in 2007 at SEC to the more powerful 10 May 2008 lava fountain is explained by the intrusion of a new more primitive magma into the shallow reservoir. Data also indicate that an attempted magma intrusion east of the summit area occurred during the 10 May fire fountain. This event caused the fracturing and weakening of the surrounding rocks and created a preferential pathway for the penetration of the magma that, only 3 days later, started to feed the 2008-2009 effusive eruption.
We report a 25 year-long data set (1990-2014) of combined continuous tilt and GPS vertical displa... more We report a 25 year-long data set (1990-2014) of combined continuous tilt and GPS vertical displacement series recorded at Etna volcano. To our knowledge, this is the first time that such a data set on an active volcano has been presented. We show the coherence of the two series, which help draw new insights on how the volcano, characterized by frequent flank eruptions, works in the long-term (tens of years). This data set provides evidence that after the 1992-1993 flank eruption (the biggest in the last three centuries) and the following major recharging phase (1994-2001), all the ensuing eruptions fall within a single long-term reequilibrium phase (2001-2014).
The island of Vulcano is a composite volcanic edifice located in the south-central sector of the ... more The island of Vulcano is a composite volcanic edifice located in the south-central sector of the Aeolian Archipelago (Tyrrhenian Sea, Italy). The island, together with Lipari and Salina islands (fig. 1), represents the emerged part of the Tin-dari-Letojanni system (TL), a NW-SE ...
In 2007-2008, we installed on Mt. Etna two deep tilt stations using high resolution, self-levelin... more In 2007-2008, we installed on Mt. Etna two deep tilt stations using high resolution, self-leveling instruments. These installations are the result of accurate instrument tests, site selection, drilling and sensor positioning that has allowed detecting variations related to the principal diurnal and semidiurnal tides for first time on Mt. Etna using tilt data.
We investigated the relationship between volcano-seismic events, recorded at La Fossa crater of V... more We investigated the relationship between volcano-seismic events, recorded at La Fossa crater of Vulcano (Aeolian Islands, Italy) during 2004-2006, and the dynamics of the hydrothermal system. During the period of study, three episodes of increasing numbers of volcano-seismic events took place at the same time as geothermal and geochemical anomalies were observed. These geothermal and geochemical anomalies have been interpreted
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Mount Melbourne (74821? S, 164843? E) is a quiescent volcano located in northern Victoria Land, A... more Mount Melbourne (74821? S, 164843? E) is a quiescent volcano located in northern Victoria Land, Antarctica. Tilt signals have been recorded on Mount Melbourne since early 1989 by a permanent shallow borehole tiltmeter network comprising five stations. An overall picture of tilt, air and permafrost temperatures over 15 years of continuous recording data is reported. We focused our observations on long-term tilt trends that at the end of 1997 65
Il 9 gennaio 2001 uno sciame sismico localizzato sul fianco sud-orientale dell'Etna e caratte... more Il 9 gennaio 2001 uno sciame sismico localizzato sul fianco sud-orientale dell'Etna e caratterizzato da forme d'onda molto simili, ha prodotto diversi danni all'abitato di Zafferana Etnea, che dista circa 3 km dall'area epicentrale. Un'analisi della sismicità registrata a partire dal 1994, ha rivelato che altri terremoti con le stesse caratteristiche hanno interessato quest'area; alcuni hanno preceduto o seguito per alcuni mesi lo sciame del gennaio 2001, altri sono stati registrati ben cinque anni prima. L'utilizzo di tecniche di cross-correlazione, applicato su 3 famiglie di eventi, ha permesso di ottenere una precisa distribuzione spaziale degli ipocentri (errore medio 10-20 metri) e conseguentemente di descrivere la geometria di faglia. La direzione di tale discontinuità, coincidente con uno dei piani nodali ottenuti dai meccanismi focali (che prevede movimenti di tipo strike destro), risulta coerente con uno dei principali trend regionali che interes...
ABSTRACT On 9 of January 2001 the INGV seismic network of Catania (Italy) recorded a seismic swar... more ABSTRACT On 9 of January 2001 the INGV seismic network of Catania (Italy) recorded a seismic swarm of about 60 earthquakes with 1.0>Md>3.6, and nearly identical seismograms. The main shock caused damage to the town of Zafferana Etnea 2.5 km distant from the epicenter located on SE flank of the volcano. Some other events with similar waveform forecasted (up to 2 months before) and followed (for about one month) this swarm; moreover a check of Mt. Etna SE flank seismicity, starting from 1994, has permitted to identify a cluster of 6 multiplets recorded on August 1995 whose seismograms are strongly coherent with the January 9, 2001 ones. Thus we recognize for the first time the occurrence of seismic events on Mount Etna with nearly identical sources separated by years. We applied a cross-spectral technique that allows to obtain the relative relocation of events within a multiplet to at least an order of magnitude higher precision than is typically possible with traditional techniques. The results describe clearly the geometry of the seismogenetic structure; the events lie on planes oriented ENE-WSW that are coincident with one of the planes of the focal mechanism obtained by first-arrivals polarities. This alignment is coherent with one of the main regional tectonic trends that characterize the Mt. Etna area The multiplets analysis has allowed to recognize, on SE flank, a right-lateral strike seismic source along ENE-WSW fault plane, 4 km deep, time repeated and able to produce strong releases.
On October 27, 2002, after about 15 months of quiescence Mt. Etna started a new eruption, still i... more On October 27, 2002, after about 15 months of quiescence Mt. Etna started a new eruption, still in progress, that has involved the forming of eruptive fracture both on south and north flanks of the volcano. A permanent tilt network that comprises nine bi-axial instruments installed in shallow boreholes and a mercury long-base guarantees continuous tilt measurements on Mt. Etna
The Trecastagni Fault (TF) is a NNW-SSE tectonic structure inside Mt. Etna that is characterized ... more The Trecastagni Fault (TF) is a NNW-SSE tectonic structure inside Mt. Etna that is characterized by evident morphological scarps and normal and right-lateral type movements that directly affect roads and buildings. The TF has an important role in the instability that affects the southeastern flank of Mt. Etna, and it represents part of the southern boundary of the unstable sector. Starting from 2005, the TF has been monitored using continuous wire extensometers and by carrying out periodic direct measurements across the northern and central sectors. From 2005 to September 2009, the measurements show that the TF has undergone continuous extension of about 2-3 mm/yr. During the October 2009 to January 2010 period, the creep rate of the TF reached up to 5.5 to 7.0 mm/yr, and this was accompanied by several shallow, low magnitude earthquakes that were felt by local people. This episode appears to be linked to the increase in the sliding velocity of the eastern flank that occurred during 2009.
Advances in volcano monitoring and forecasting need a multidisciplinary collaborative framework. ... more Advances in volcano monitoring and forecasting need a multidisciplinary collaborative framework. In light of this, a Bayesian Event Tree (BET) approach was performed by the application of the BET for Eruption Forecasting (BET_EF) code to analyze the space-time distribution of the volcanic activity of Mount Etna from 2001-2005. First, a reliable monitoring dataset was set up after some sessions to elicit geophysical, volcanological and geochemical 'precursor' parameters. A constant unrest probability of 100%, with a magma involvement usually greater than 95%, was computed throughout the time period analyzed. Eruption probabilities higher than 90% were estimated a few days before the onsets of the 2001 and 2002-2003 flank eruptions. Values slightly higher than 75% were observed during the lava fountaining period in June-July 2001. However, the probabilities flattened to around 30% for the 2004-2005 flank eruption. With suitable data, a good depiction of the actual location of the eruptive scenario for the 2001 and 2002-2003 events was provided. Conversely, the size of the eruptions was not indicated.
In the last ten years (1990-1999), 21 discrete variations of continuous tilt signal have been rec... more In the last ten years (1990-1999), 21 discrete variations of continuous tilt signal have been recorded on Mount Etna, among which one episode was caused by the opening of the eruptive fracture. The remaining 20 anomalies can be classified into two categories: the first comprises 5 ''instantaneous'' tilt variations recorded in correspondence to the most energetic seismic events (M L ‡ 3.3) localized on the high western part of the volcano; the second consists of 15 transient anomalies ranging from some hours to 1-2 days, observed at different times at the various tilt stations, with no correlation to seismic events or other evident volcanic episodes. The aseismic variations propagate through the volcanic edifice with a velocity between 4.5-6.0 km/day. Modeling studies suggest that the deformation is generated by a tensile source located 3-6 km SW from Etna volcano summit and 5-10 km depth.
Journal of Volcanology and Geothermal Research, 2009
The multi-parametric permanent system (tilt and GPS networks, robotized geodetic station) for mon... more The multi-parametric permanent system (tilt and GPS networks, robotized geodetic station) for monitoring ground deformation at Stromboli volcano was set up in the 1990s and later greatly improved during the effusive event of 2002–2003. Unlike other volcanoes, e.g. Mt. Etna, the magnitude of ground deformation signals of Stromboli is very small and through the entire period of operation of the
ABSTRACT Ground deformations measured during the last two GPS surveys carried out in March 2006 a... more ABSTRACT Ground deformations measured during the last two GPS surveys carried out in March 2006 and September 2007 on the Lipari-Vulcano network are analyzed. Through this period, the monitoring seismic network measured an increase of seismic strain release around the Lipari-Vulcano complex with respect to the previous years. GPS surveys measured a significant N-ward motion of Vulcano island with respect to the ITRF05. This motion abruptly decreases in the N part of Vulcano, suggesting a decoupling of the main Vulcano island from the rest of the volcanic complex. By assuming a local reference frame, we observed that the Lipari island and the northernmost part of the Vulcano island are moving SSE-ward with respect to the central and southernmost part of the Vulcano island. GPS data also highlighted a local uplift of the ``La Fossa'' cone superimposed on the general subsidence of the island, increasing towards N. The vertical movements measured by GPS are compared with the results of the leveling surveys carried out on the network installed and managed by the INGV - Osservatorio Vesuviano for monitoring vertical ground movements on Volcano island. Height variations are computed with respect to a reference benchmark located on the southern part of the island, which is a relatively stable area compared to the northern part. The comparison between the two most recent surveys (October 2003 and October 2008) indicates a significant subsidence of the centre-northern area of the island (bottom Fossa Crater and Vulcanello). We also analyzed the long-term tilt observations through the same period. The tilt network at Vulcano Island currently has five borehole stations, four of which are installed at depth of 8-10 m, allowing recording stable and highly accurate signals with low noise. Tilt vectors concur well with leveling and GPS data, highlighting a deflection towards the central-northern part of the island. Geodetic strain tensor analysis derived by GPS data was performed over the area covered by the Lipari-Vulcano network. Transpressive kinematics of the Lipari-Vulcano volcanic complex, with a main N-S contraction and a minor E-W extension only on the Southern part of Vulcano is revealed. In addition, data inversion was performed using a simple Okada model, inverting the horizontal strain measured on 258 GPS baselines. We prefer using baselines rather than displacement vectors to avoid bias due to the ambiguity in fixing the reference system. The final structural framework defines a main compression with a dextral component of displacement on a NW-SE striking structure. This kinematics agrees with focal mechanisms of the strongest seismic events recorded in this area over the same time span as the GPS surveys. Furthermore, a preliminary analysis shows that the observed tilt fits well with the expected one from the model.
A multidisciplinary approach integrating a wide data set ranging from bulk rock compositions of t... more A multidisciplinary approach integrating a wide data set ranging from bulk rock compositions of the erupted products to volcanic tremor, long-period events, and tilt and gravity signals is used to investigate the source depth and magma dynamics of the 10 May 2008 lava fountain at Southeast crater (SEC) of Mount Etna. The investigation was undertaken in the framework of the previous 2007 explosive activity as well as the subsequent effusive eruption beginning 13 May 2008 and lasting up to July 2009. All the data concur in indicating that the 10 May lava fountain was generated by the fragmentation of a foam layer trapped at the top of a shallow reservoir, about 1500-1700 m below the summit of SEC. The shift from the episodic strombolian/lava fountain activity occurring in 2007 at SEC to the more powerful 10 May 2008 lava fountain is explained by the intrusion of a new more primitive magma into the shallow reservoir. Data also indicate that an attempted magma intrusion east of the summit area occurred during the 10 May fire fountain. This event caused the fracturing and weakening of the surrounding rocks and created a preferential pathway for the penetration of the magma that, only 3 days later, started to feed the 2008-2009 effusive eruption.
We report a 25 year-long data set (1990-2014) of combined continuous tilt and GPS vertical displa... more We report a 25 year-long data set (1990-2014) of combined continuous tilt and GPS vertical displacement series recorded at Etna volcano. To our knowledge, this is the first time that such a data set on an active volcano has been presented. We show the coherence of the two series, which help draw new insights on how the volcano, characterized by frequent flank eruptions, works in the long-term (tens of years). This data set provides evidence that after the 1992-1993 flank eruption (the biggest in the last three centuries) and the following major recharging phase (1994-2001), all the ensuing eruptions fall within a single long-term reequilibrium phase (2001-2014).
The island of Vulcano is a composite volcanic edifice located in the south-central sector of the ... more The island of Vulcano is a composite volcanic edifice located in the south-central sector of the Aeolian Archipelago (Tyrrhenian Sea, Italy). The island, together with Lipari and Salina islands (fig. 1), represents the emerged part of the Tin-dari-Letojanni system (TL), a NW-SE ...
In 2007-2008, we installed on Mt. Etna two deep tilt stations using high resolution, self-levelin... more In 2007-2008, we installed on Mt. Etna two deep tilt stations using high resolution, self-leveling instruments. These installations are the result of accurate instrument tests, site selection, drilling and sensor positioning that has allowed detecting variations related to the principal diurnal and semidiurnal tides for first time on Mt. Etna using tilt data.
We investigated the relationship between volcano-seismic events, recorded at La Fossa crater of V... more We investigated the relationship between volcano-seismic events, recorded at La Fossa crater of Vulcano (Aeolian Islands, Italy) during 2004-2006, and the dynamics of the hydrothermal system. During the period of study, three episodes of increasing numbers of volcano-seismic events took place at the same time as geothermal and geochemical anomalies were observed. These geothermal and geochemical anomalies have been interpreted
Uploads
Papers by S. Gambino