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Article ; Online: Fluid migrations and volcanic earthquakes from depolarized ambient noise.

Petrosino, S / De Siena, L

2021 Volume 12, Issue 1, Page(s) 6656

Abstract: Ambient noise polarizes inside fault zones, yet the spatial and temporal resolution of polarized noise on gas-bearing fluids migrating through stressed volcanic systems is unknown. Here we show that high polarization marks a transfer structure connecting ...

Abstract	Ambient noise polarizes inside fault zones, yet the spatial and temporal resolution of polarized noise on gas-bearing fluids migrating through stressed volcanic systems is unknown. Here we show that high polarization marks a transfer structure connecting the deforming centre of the caldera to open hydrothermal vents and extensional caldera-bounding faults during periods of low seismic release at Campi Flegrei caldera (Southern Italy). Fluids pressurize the Campi Flegrei hydrothermal system, migrate, and increase stress before earthquakes. The loss of polarization (depolarization) of the transfer and extensional structures maps pressurized fluids, detecting fluid migrations after seismic sequences. After recent intense seismicity (December 2019-April 2020), the transfer structure appears sealed while fluids stored in the east caldera have moved further east. Our findings show that depolarized noise has the potential to monitor fluid migrations and earthquakes at stressed volcanoes quasi-instantaneously and with minimum processing.
Language	English
Publishing date	2021-11-17
Publishing country	England
Document type	Journal Article
ZDB-ID	2553671-0
ISSN	2041-1723 ; 2041-1723
ISSN (online)	2041-1723
ISSN	2041-1723
DOI	10.1038/s41467-021-26954-w
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: A record of seafloor methane seepage across the last 150 million years.

Oppo, D / De Siena, L / Kemp, D B

Scientific reports

2020 Volume 10, Issue 1, Page(s) 2562

Abstract: Seafloor methane seepage is a significant source of carbon in the marine environment. The processes and temporal patterns of seafloor methane seepage over multi-million-year time scales are still poorly understood. The microbial oxidation of methane can ... ...

Abstract	Seafloor methane seepage is a significant source of carbon in the marine environment. The processes and temporal patterns of seafloor methane seepage over multi-million-year time scales are still poorly understood. The microbial oxidation of methane can store carbon in sediments through precipitation of carbonate minerals, thus providing a record of past methane emission. In this study, we compiled data on methane-derived carbonates to build a proxy time series of methane emission over the last 150 My and statistically compared it with the main hypothesised geological controllers of methane emission. We quantitatively demonstrate that variations in sea level and organic carbon burial are the dominant controls on methane leakage since the Early Cretaceous. Sea level controls methane seepage variations by imposing smooth trends on timescales in the order of tens of My. Organic carbon burial is affected by the same cyclicities, and instantaneously controls methane release because of the geologically rapid generation of biogenic methane. Both the identified fundamental (26-27 My) and higher (12 My) cyclicities relate to global phenomena. Temporal correlation analysis supports the evidence that modern expansion of hypoxic areas and its effect on organic carbon burial may lead to higher seawater methane concentrations over the coming centuries.
Language	English
Publishing date	2020-02-13
Publishing country	England
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	2615211-3
ISSN	2045-2322 ; 2045-2322
ISSN (online)	2045-2322
ISSN	2045-2322
DOI	10.1038/s41598-020-59431-3
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Conference proceedings ; Online: Scattering and absorption imaging of a seismic gap, the Mt. Pollino area (Italy)

Napolitano, F. / Amoroso, O. / Gabrielli, S. / Capuano, P. / De Siena, L.

XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)

2023

Abstract: The Mt.Pollino area is the largest seismic gap in Italy, with faults capable of M6.5-7 but no historical and instrumental M6 events recorded. Between 2010 and 2014 this area has been affected by a seismic sequence of more than 10,000 small magnitude ... ...

Abstract	The Mt.Pollino area is the largest seismic gap in Italy, with faults capable of M6.5-7 but no historical and instrumental M6 events recorded. Between 2010 and 2014 this area has been affected by a seismic sequence of more than 10,000 small magnitude earthquakes and two moderate main events occurred late in the sequence (ML 4.3 and ML 5.0). The goal of this work is to provide 3D scattering and absorption images of this area using the peak delay time and the coda-Q methods, respectively. Scattering anomalies suggest that the area involved in the sequence is highly fractured, with the strongest scattering contrast interpreted as the Pollino Fault. This large structure acted as a barrier, bounding migration of the seismicity southward, as suggested in recent structural geological works. Declustered high-absorption anomalies mark the area affected by the sequence, suggesting that fluids have played a key role in its development. This result is in good agreement with high VP/VS and high pore pressure anomalies highlighted by recent works on the area. This work was supported by the PRIN-2017 MATISSE project (no. 20177EPPN2), funded by the Italian Ministry of Education and Research.
Subject code	550
Language	English
Publishing country	de
Document type	Conference proceedings ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Conference proceedings ; Online: Imaging the deep petrophysical architecture of Toba caldera from seismic data

Magrini, F. / De Siena, L. / Kaus, B. / Riel, N. / Diaferia, G. / Forni, F.

XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)

2023

Abstract: The crustal feeding systems of Toba caldera (Indonesia) remain largely unknown due to (1) the lack of seismic images resolving magmatic sills and fluid reservoirs and (2) our inability to translate seismic parameters into meaningful petrophysical ... ...

Abstract	The crustal feeding systems of Toba caldera (Indonesia) remain largely unknown due to (1) the lack of seismic images resolving magmatic sills and fluid reservoirs and (2) our inability to translate seismic parameters into meaningful petrophysical quantities. Using data from available seismic arrays, we obtained thousands of dispersion curves sensitive to both the shallow crust and the upper mantle. The usual seismological approach is to invert them for phase-velocity maps at different periods and transform them into a shear-wave model. This model shows low-velocity sill-like structures at different depths under the northern and central Toba caldera; however, the uncertainty in their interpretation cannot be quantified just by looking at their shape, depths and correlation with surface features. Therefore, we used a Gibbs energy-minimization solver that computes seismic velocities from phase petrology for the compositions relevant to Toba to forward phase velocities directly. A Bayesian Monte Carlo Markov chain inversion then inverts for temperature, composition, background host rock damage and melt content. As a result, every velocity value from our calculations is petrologically feasible. The results identify the portions of the crust where mafic sills are located, quantitatively defining their melt content, chemical composition, rock damage, temperature and associated uncertainty. Due to the low sensitivity of shear waves to temperature, there are still fundamental challenges in defining the thermal structure of the volcano; yet, seismo-petrological inversions are feasible today within one of the most complex crustal systems, a result few expected to achieve a decade ago.
Subject code	550
Language	English
Publishing country	de
Document type	Conference proceedings ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Imaging overpressurised fracture networks and geological barriers hindering fluid migrations across a slow-deformation seismic gap.

Napolitano, Ferdinando / Gabrielli, Simona / De Siena, Luca / Amoroso, Ortensia / Capuano, Paolo

Scientific reports

2023 Volume 13, Issue 1, Page(s) 19680

Abstract: There is an ongoing debate on the processes producing background seismicity and deformation transients across seismic gaps, i.e., regions that lack historical large-magnitude earthquakes. Essential missing elements are geophysical images that resolve ... ...

Abstract	There is an ongoing debate on the processes producing background seismicity and deformation transients across seismic gaps, i.e., regions that lack historical large-magnitude earthquakes. Essential missing elements are geophysical images that resolve sources of geophysical unrest. Here, we apply seismic scattering and absorption tomography to data recorded during the 2010-2014 seismic sequence within the Mt. Pollino seismic gap region (Southern Italy). The tomographic models show high sensitivity to fluid content, deformed fractured structures, and impermeable layers stopping fluid migrations. They bridge the gaps between geological and geophysical models and provide a highly-resolved image of the source of seismic and deformation unrest within this seismic gap. High absorption topping the western Pollino seismic volume appears pressurized between the low-Vp/Vs and low-scattering San Donato metamorphic core and a deep basement. Absorbing fluids can only migrate laterally to the east, blocked in the west and southwest by deep low-scattering barriers associated with east-dipping faults and to the north and southeast by saturated overpressurized low-scattering basins. This eastern migration is only partially effective, producing seismicity across the lowest boundary of the high-absorption volume. Our results showcase the potential of seismic scattering and absorption when imaging structures causing geophysical unrest processes across fault networks.
Language	English
Publishing date	2023-11-11
Publishing country	England
Document type	Journal Article
ZDB-ID	2615211-3
ISSN	2045-2322 ; 2045-2322
ISSN (online)	2045-2322
ISSN	2045-2322
DOI	10.1038/s41598-023-47104-w
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: P and S wave travel time tomography of the SE Asia-Australia collision zone

Zenonos, Aristides / De Siena, Luca / Widiyantoro, Sri / Rawlinson, Nicholas

2019

Abstract: The southeast (SE) Asia - Australia collision zone is one of the most tectonically active and seismogenic regions in the world. Here, we present new 3-D P- and S-wave velocity models of the crust and upper mantle by applying regional earthquake travel- ... ...

Abstract	The southeast (SE) Asia - Australia collision zone is one of the most tectonically active and seismogenic regions in the world. Here, we present new 3-D P- and S-wave velocity models of the crust and upper mantle by applying regional earthquake travel-time tomography to global catalogue data. We first re-locate earthquakes provided by the standard ISC-Reviewed and ISC-EHB catalogues using a non-linear oct-tree scheme. A machine learning algorithm that clusters earthquakes depending on their spatiotemporal density was then applied to significantly improve the consistency of travel-time picks. We used the Fast Marching Tomography software package to retrieve 3-D velocity and interface structures from starting 1-D velocity and Moho models. Synthetic resolution and sensitivity tests demonstrate that the final models are robust, with P-wave speed variations (~130 km horizontal resolution) generally recovered more robustly than S-wave speed variations (~220 km horizontal resolution). The retrieved crust and mantle anomalies offer a new perspective on the broad-scale tectonic setting and underlying mantle architecture of SE Asia. While we observe clear evidence of subducted slabs as high velocity anomalies penetrating into the mantle along the Sunda arc, Banda arc and Halmahera arc, we also see evidence for slab gaps or holes in the vicinity of east Java. Furthermore, a high-velocity region in the mantle lithosphere connects northern Australia with Timor and West Papua. The S-wave model shows broad-scale features similar to those of the P-wave model, with mantle earthquakes generally distributed within high-velocity slabs. The high velocity mantle connection between northern Australia and the eastern margin of the Sunda arc is also present in the S-wave model. While the S-wave model has a lower resolution than the P-wave model due to the availability of fewer paths, it nonetheless provides new and complementary insights into the structure of the upper mantle beneath southeast Asia.
Subject code	550
Language	English
Publisher	Elsevier
Publishing country	de
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: P and S wave travel time tomography of the SE Asia-Australia collision zone

Zenonos, Aristides / De Siena, Luca / Widiyantoro, Sri / Rawlinson, Nicholas

2019

Abstract	The southeast (SE) Asia - Australia collision zone is one of the most tectonically active and seismogenic regions in the world. Here, we present new 3-D P- and S-wave velocity models of the crust and upper mantle by applying regional earthquake travel-time tomography to global catalogue data. We first re-locate earthquakes provided by the standard ISC-Reviewed and ISC-EHB catalogues using a non-linear oct-tree scheme. A machine learning algorithm that clusters earthquakes depending on their spatiotemporal density was then applied to significantly improve the consistency of travel-time picks. We used the Fast Marching Tomography software package to retrieve 3-D velocity and interface structures from starting 1-D velocity and Moho models. Synthetic resolution and sensitivity tests demonstrate that the final models are robust, with P-wave speed variations (~130 km horizontal resolution) generally recovered more robustly than S-wave speed variations (~220 km horizontal resolution). The retrieved crust and mantle anomalies offer a new perspective on the broad-scale tectonic setting and underlying mantle architecture of SE Asia. While we observe clear evidence of subducted slabs as high velocity anomalies penetrating into the mantle along the Sunda arc, Banda arc and Halmahera arc, we also see evidence for slab gaps or holes in the vicinity of east Java. In the Banda arc, we image the slab as a single curved subduction zone. Furthermore, a high-velocity region in the mantle lithosphere connects northern Australia with Timor and West Papua. The S-wave model shows broad-scale features similar to those of the P-wave model, with mantle earthquakes generally distributed within high-velocity slabs. The high velocity mantle connection between northern Australia and the eastern margin of the Sunda arc is also present in the S-wave model. While the S-wave model has a lower resolution than the P-wave model due to the availability of fewer paths, it nonetheless provides new and complementary insights into the structure of the ...
Subject code	550
Language	English
Publisher	Elsevier
Publishing country	de
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article: Volcanic structures investigation through SAR and seismic interferometric methods: The 2011–2013 Campi Flegrei unrest episode

Pepe, S / De Siena, L / Barone, A / Castaldo, R / D'Auria, L / Manzo, M / Casu, F / Fedi, M / Lanari, R / Bianco, F / Tizzani, P

Remote sensing of environment. 2019 Dec. 01, v. 234

2019

Abstract: Observations from satellites provide high-resolution images of ground deformation allowing to infer deformation sources by developing advanced modeling of magma ascent and intrusion processes. Nevertheless, such models can be strongly biased without a ... ...

Abstract	Observations from satellites provide high-resolution images of ground deformation allowing to infer deformation sources by developing advanced modeling of magma ascent and intrusion processes. Nevertheless, such models can be strongly biased without a precise model of the internal structure of the volcano. In this study, we jointly exploited two interferometric techniques to interpret the 2011–2013 unrest at Campi Flegrei caldera (CFc). The first is the Interferometric Synthetic Aperture Radar (InSAR) technique, which provides highly-resolved spatial and temporal images of ground deformation. The second is the Ambient Noise Tomography (ANT), which images subsurface structures, providing the constraints necessary to infer the depth of the shallow source at CFc (between 0.8 and 1.2 km). We applied for the first time a tool to delineate the deformation source boundaries from the observed deformation maps: the Total Horizontal Derivative (THD) technique. The THD processes the vertical component of the ground deformation field detected through InSAR applied to COSMO-SkyMed data. The patterns retrieved by applying the THD technique show consistent spatial correlations with (1) the seismic group-velocity maps achieved through the ANT and (2) the distribution of the earthquakes nucleated during the unrest at ~1 km. High-velocity anomalies, the retrieved geometrical features of the deformation field, and the spatial distribution of seismicity coincide with extinct volcanic vents in the eastern part of the caldera (Solfatara/Pisciarelli and Astroni). Such a coincidence hints at a significant role of the extinct plumbing system in either constraining or channeling the eastward propagation of magmatic fluids. Here, we demonstrated that a joint analysis of the InSAR patterns, seismic structures, and seismicity allows us to model in space and time the characteristics and nature of the shallow deformation source at CFc. Using published literature, we show that the effects of structural heterogeneities at shallow depths may have a more significant early-stage impact on the evolution of the surface displacement signals than deeper magmatic sources: these secondary structural effects may produce local amplification in the deformation records which can be mistakenly interpreted as early signals of impending eruptions. The achieved results are particularly relevant for the understanding of the origin of deformation signal at volcanoes where magma propagation within sills is expected, as at CFc.
Keywords	deformation ; earthquakes ; geophysics ; image analysis ; interferometry ; models ; remote sensing ; satellites ; space and time ; synthetic aperture radar ; tomography ; volcanoes
Language	English
Dates of publication	2019-1201
Publishing place	Elsevier Inc.
Document type	Article
ZDB-ID	431483-9
ISSN	0034-4257
ISSN	0034-4257
DOI	10.1016/j.rse.2019.111440
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Clues on the origin of post-2000 earthquakes at Campi Flegrei caldera (Italy).

Chiodini, G / Selva, J / Del Pezzo, E / Marsan, D / De Siena, L / D'Auria, L / Bianco, F / Caliro, S / De Martino, P / Ricciolino, P / Petrillo, Z

Scientific reports

2017 Volume 7, Issue 1, Page(s) 4472

Abstract: The inter-arrival times of the post 2000 seismicity at Campi Flegrei caldera are statistically distributed into different populations. The low inter-arrival times population represents swarm events, while the high inter-arrival times population marks ... ...

Abstract	The inter-arrival times of the post 2000 seismicity at Campi Flegrei caldera are statistically distributed into different populations. The low inter-arrival times population represents swarm events, while the high inter-arrival times population marks background seismicity. Here, we show that the background seismicity is increasing at the same rate of (1) the ground uplift and (2) the concentration of the fumarolic gas specie more sensitive to temperature. The seismic temporal increase is strongly correlated with the results of recent simulations, modelling injection of magmatic fluids in the Campi Flegrei hydrothermal system. These concurrent variations point to a unique process of temperature-pressure increase of the hydrothermal system controlling geophysical and geochemical signals at the caldera. Our results thus show that the occurrence of background seismicity is an excellent parameter to monitor the current unrest of the caldera.
Language	English
Publishing date	2017-06-30
Publishing country	England
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	2615211-3
ISSN	2045-2322 ; 2045-2322
ISSN (online)	2045-2322
ISSN	2045-2322
DOI	10.1038/s41598-017-04845-9
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Source and dynamics of a volcanic caldera unrest: Campi Flegrei, 1983-84.

De Siena, Luca / Chiodini, Giovanni / Vilardo, Giuseppe / Del Pezzo, Edoardo / Castellano, Mario / Colombelli, Simona / Tisato, Nicola / Ventura, Guido

Scientific reports

2017 Volume 7, Issue 1, Page(s) 8099

Abstract: Despite their importance for eruption forecasting the causes of seismic rupture processes during caldera unrest are still poorly reconstructed from seismic images. Seismic source locations and waveform attenuation analyses of earthquakes in the Campi ... ...

Abstract	Despite their importance for eruption forecasting the causes of seismic rupture processes during caldera unrest are still poorly reconstructed from seismic images. Seismic source locations and waveform attenuation analyses of earthquakes in the Campi Flegrei area (Southern Italy) during the 1983-1984 unrest have revealed a 4-4.5 km deep NW-SE striking aseismic zone of high attenuation offshore Pozzuoli. The lateral features and the principal axis of the attenuation anomaly correspond to the main source of ground uplift during the unrest. Seismic swarms correlate in space and time with fluid injections from a deep hot source, inferred to represent geochemical and temperature variations at Solfatara. These swarms struck a high-attenuation 3-4 km deep reservoir of supercritical fluids under Pozzuoli and migrated towards a shallower aseismic deformation source under Solfatara. The reservoir became aseismic for two months just after the main seismic swarm (April 1, 1984) due to a SE-to-NW directed input from the high-attenuation domain, possibly a dyke emplacement. The unrest ended after fluids migrated from Pozzuoli to the location of the last caldera eruption (Mt. Nuovo, 1538 AD). The results show that the high attenuation domain controls the largest monitored seismic, deformation, and geochemical unrest at the caldera.
Language	English
Publishing date	2017-08-14
Publishing country	England
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	2615211-3
ISSN	2045-2322 ; 2045-2322
ISSN (online)	2045-2322
ISSN	2045-2322
DOI	10.1038/s41598-017-08192-7
Database	MEDical Literature Analysis and Retrieval System OnLINE

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