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  • Physics - Geophysics; Physics - Geophysics  (3)
  • 3D geological model  (2)
  • Elsevier  (5)
  • American Institute of Physics (AIP)
  • 2020-2023  (5)
  • 1
    Publication Date: 2022-02-03
    Description: This work presents the first 3D geological model of the Rome coastal area that integrates available subsurface geological, stratigraphic and geophysical data with surface geochemical data obtained both from the literature and new surveys. The model provides new insights into the stratigraphic and tectonic setting of the area and the geological factors controlling both natural and human-induced gas emissions. This sector of the Italian Tyrrhenian margin has been historically affected by natural emissions of deep CO2 and thermogenic CH4, stored in permeable layers but with local migration to the surface along buried normal faults. In addition to natural processes, human activities can also cause leakage and serious health risks, such as the abrupt gas release in August 2013, that was triggered by borehole drillings near the Rome international airport. The presented 3D reconstruction unveils the link between faults, stratigraphy, lithology and the distribution of the soil gas anomalies. It provides information about the depth of the reservoir that can potentially trap endogenous gases, and the location and geometry of the main faults along which the gas migrates towards the surface. Furthermore, reconstruction of the distribution and thickness of important clay layers better constrains the low permeable areas that prevent gas escape. The 3D model, coupled with the geochemical information, can serve as a useful tool for the local administration to perform land-use planning and manage the local geological and degassing hazards that affect this highly urbanized area near Rome. Furthermore, we estimate that the large amount of CO2 broadly released in the area also provides a contribution to the budget of natural greenhouse gases in the atmosphere.
    Description: Published
    Description: 106527
    Description: 6A. Geochimica per l'ambiente e geologia medica
    Description: JCR Journal
    Keywords: 3D geological model ; Soil gas ; Active faults ; Surface degassing ; Geological hazards ; Tiber delta ; 04.04. Geology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Publication Date: 2022-10-28
    Description: Katla is a threatening volcano in Iceland, partly covered by the M\'yrdalsj\"okull ice cap. The volcano has a large caldera with several active geothermal areas. A peculiar cluster of long-period seismic events started on Katla's south flank in July 2011, during an unrest episode in the caldera that culminated in a glacier outburst. The seismic events were tightly clustered at shallow depth in the Gvendarfell area, 4 km south of the caldera, under a small glacier stream on the southern margin of M\'yrdalsj\"okull. No seismic events were known to have occurred in this area before. The most striking feature of this seismic cluster is its temporal pattern, characterized by regular intervals between repeating seismic events, modulated by a seasonal variation. Remarkable is also the stability of both the time and waveform features over a long time period, around 3.5 years. No comparable examples have been found in the literature. Both volcanic and glacial processes can produce similar waveforms and therefore have to be considered as potential seismic sources. Discerning between these two causes is critical for monitoring glacier-clad volcanoes and has been controversial at Katla. For this new seismic cluster on the south flank we regard volcano-related processes as more likely than glacial ones for the following reasons: 1) the seismic activity started during an unrest episode involving sudden melting of the glacier and a j\"okulhlaup; 2) the glacier stream is small and stagnant; 3) the seismicity remains regular and stable for years; 4) there is no apparent correlation with short-term weather changes, such as rain storms. We suggest that a small, shallow hydrothermal system was activated on Katla's south flank in 2011, either by a minor magmatic injection or by changes of permeability in a local crack system.
    Description: Published
    Description: 28-40
    Description: 3T. Fisica dei terremoti e Sorgente Sismica
    Description: JCR Journal
    Keywords: Physics - Geophysics; Physics - Geophysics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Publication Date: 2022-10-28
    Description: A 23 hour tremor burst was recorded on July 8-9th 2011 at the Katla subglacial volcano, one of the most active and hazardous volcanoes in Iceland. This was associated with deepening of cauldrons on the ice cap and a glacial flood that caused damage to infrastructure. Increased earthquake activity within the caldera started a few days before and lasted for months afterwards and new seismic activity started on the south flank. No visible eruption broke the ice and the question arose as to whether this episode relates to a minor subglacial eruption with the tremor being generated by volcanic processes, or by the flood. The tremor signal consisted of bursts with varying amplitude and duration. We have identified and described three different tremor phases, based on amplitude and frequency features. A tremor phase associated with the flood was recorded only at stations closest to the river that flooded, correlating in time with rising water level observed at gauging stations. Using back-projection of double cross-correlations, two other phases have been located near the active ice cauldrons and are interpreted to be caused by volcanic or hydrothermal processes. The greatly increased seismicity and evidence of rapid melting of the glacier may be explained by a minor sub-glacial eruption. It is also plausible that the tremor was generated by hydrothermal boiling and/or explosions with no magma involved. This may have been induced by pressure drop triggered by the release of water when the glacial flood started. All interpretations require an increase of heat released by the volcano.
    Description: Published
    Description: 63-78
    Description: 3T. Fisica dei terremoti e Sorgente Sismica
    Description: 2V. Struttura e sistema di alimentazione dei vulcani
    Description: JCR Journal
    Keywords: Physics - Geophysics; Physics - Geophysics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
    Publication Date: 2021-12-23
    Description: Machine learning is becoming increasingly important in scientific and technological progress, due to its ability to create models that describe complex data and generalize well. The wealth of publicly-available seismic data nowadays requires automated, fast, and reliable tools to carry out a multitude of tasks, such as the detection of small, local earthquakes in areas characterized by sparsity of receivers. A similar application of machine learning, however, should be built on a large amount of labeled seismograms, which is neither immediate to obtain nor to compile. In this study we present a large dataset of seismograms recorded along the vertical, north, and east components of 1487 broad-band or very broad-band receivers distributed worldwide; this includes 629,095 3-component seismograms generated by 304,878 local earthquakes and labeled as EQ, and 615,847 ones labeled as noise (AN). Application of machine learning to this dataset shows that a simple Convolutional Neural Network of 67,939 parameters allows discriminating between earthquakes and noise single-station recordings, even if applied in regions not represented in the training set. Achieving an accuracy of 96.7, 95.3, and 93.2% on training, validation, and test set, respectively, we prove that the large variety of geological and tectonic settings covered by our data supports the generalization capabilities of the algorithm, and makes it applicable to real-time detection of local events. We make the database publicly available, intending to provide the seismological and broader scientific community with a benchmark for time-series to be used as a testing ground in signal processing.
    Description: Published
    Description: 1-10
    Description: 1SR TERREMOTI - Sorveglianza Sismica e Allerta Tsunami
    Description: N/A or not JCR
    Keywords: Physics - Geophysics; Physics - Geophysics ; dataset for machine learning in seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
    Publication Date: 2022-06-09
    Description: Young and tectonically active chains like the Central Apennines (Italy) are featured by high structural complexity as a result of the overprint of subsequent deformational stages, making interpretation of seismotectonics challenging. The Central Apennines are characterized by the stacking of tectono-sedimentary units organized in thrust sheets. However, extensional tectonics is currently affecting the axial sector of the thrust belt, mostly expressing in extensional earthquakes. Using a large subsurface dataset acquired for hydrocarbon exploration in the region struck by the 2016–2017 Central Italy seismic sequence, we built a comprehensive 3D geological model and compared it with the seismicity. The model primarily shows a series of thrusts developed during the Miocene-Pliocene Apennines orogenesis and inherited normal faults developed during the Mesozoic extensional phase and the Miocene foreland flexural process. These normal faults were segmented and transported within the thrust sheets, and sometimes they still show a clear surface expression. The succession of tectonic stages resulted in a widespread reactivation of inherited structures, sometimes inverting their kinematics with different styles and rates, and disarticulating pre-existing configurations. Such evolution has a strong impact on the seismicity observed in the area, as demonstrated by some examples that show how the seismicity is aligned on segments of inherited faults, both compressional and extensional. Their reactivation can be explained by their favorable orientation within the current extensional stress field. Results feed the debate about the seismogenic potential of faults identified both at depth and surface, which can impact the seismic hazard of the Apennines.
    Description: Published
    Description: 228861
    Description: 1T. Struttura della Terra
    Description: 2T. Deformazione crostale attiva
    Description: 4T. Sismicità dell'Italia
    Description: JCR Journal
    Keywords: Normal faults ; Thrust sheets ; Inherited faults ; Earthquakes ; Central Apennines ; 3D geological model ; 04.07. Tectonophysics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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