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  • AGU
  • 2020-2023  (9)
  • 2010-2014  (108)
  • 1980-1984  (24)
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  • 1
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    Velocity changes in the Charlevoix region, Quebec (1981)
    AGU
    In:  Professional Paper, Earthquake Prediction, Washington, D.C., AGU, vol. 4, no. 16, pp. 367-376, (ISBN 1-86239-165-3, vi + 330 pp.)
    Details
    Publication Date: 1981
    Keywords: Earthquake precursor: prediction research ; Earthquake precursor: Vp/Vs anomalies ; Dual Induction Latero logAT
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    The state of stress in the plates (1980)
    AGU
    In:  Professional Paper, Dynamics of Plate Interiors, Roma, AGU, vol. 1, no. 231, pp. 145-153, (ISBN: 3-540-23712-7)
    Details
    Publication Date: 1980
    Keywords: Review article ; Stress
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    BIBLIOGRAPHY SEISMOLOGY
  • 3
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    Seismicity in western Japan and long-term earthquake forecasting (1981)
    AGU
    In:  Bull., Polar Proj. OP-O3A4, Earthquake Prediction, Washington, D.C., AGU, vol. 4, no. Subvol. b, pp. 43-51, (ISBN 0080419208)
    Details
    Publication Date: 1981
    Keywords: Seismicity ; Earthquake precursor: prediction research
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    BIBLIOGRAPHY SEISMOLOGY
  • 4
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    Earthquake Prediction (1981)
    AGU
    In:  Washington, D.C., AGU, vol. 4, no. Publ. No. 12, pp. 9, (3-540-24165-5, XXVI + 228 p.)
    Details
    Publication Date: 1981
    Keywords: Handbook of geophysics ; Earthquake precursor: prediction research ; Earthquake precursor: deformation or strain ; Seismicity ; Seismology
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    BIBLIOGRAPHY SEISMOLOGY
  • 5
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    An asperity model of large earthquake sequences (1981)
    AGU
    In:  Bull., Polar Proj. OP-O3A4, Earthquake Prediction, Washington, D.C., AGU, vol. 4, no. 4, pp. 579-592, (ISBN 0080419208)
    Details
    Publication Date: 1981
    Keywords: Earthquake precursor: prediction research ; Earthquake asperities ; Recurrence of earthquakes ; Fault zone
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    BIBLIOGRAPHY SEISMOLOGY
  • 6
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    Possible precursors of the 1976 Tangshan earthquake (1982)
    AGU
    In:  Professional Paper, Open-File Rept., Chin. Geophys., Washington, D.C., AGU, vol. 2, no. 1, pp. 157-172, (ISBN 0080419208)
    Details
    Publication Date: 1982
    Keywords: Earthquake precursor: prediction research ; China
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    BIBLIOGRAPHY SEISMOLOGY
  • 7
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    A review of geological evidence for recurrence times of large earthquakes (1981)
    AGU
    In:  Bull., Open-File Rept., Earthquake Prediction, Washington, D.C., AGU, vol. 4, no. 16, pp. 181-207, (ISBN 1-86239-165-3, vi + 330 pp.)
    Details
    Publication Date: 1981
    Keywords: Earthquake precursor: prediction research ; Earthquake precursor: deformation or strain
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    BIBLIOGRAPHY SEISMOLOGY
  • 8
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    Cooperative earthquake research supported by the U.S. Geological Survey and the State Seismological Bureau of the People's Republic of China (1982)
    AGU
    In:  Bull., Open-File Rept., Chin. Geophys., Washington, D.C., AGU, vol. 2, no. 1, pp. 109-138, (ISBN 1-86239-165-3, vi + 330 pp.)
    Details
    Publication Date: 1982
    Keywords: Earthquake precursor: prediction research
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    BIBLIOGRAPHY SEISMOLOGY
  • 9
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    Plate Reconstruction from Paleozoic Paleomagnetism (1984)
    AGU
    In:  Washington, D.C., AGU, vol. 12, no. ALEX(01)-FR-77-01, AFTAC Contract F08606-76-C-0025, pp. 329, (ISBN: 0-444-50309-9)
    Details
    Publication Date: 1984
    Keywords: Plate tectonics ; Geomagnetics ; Handbook of geophysics
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    BIBLIOGRAPHY SEISMOLOGY
  • 10
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    A preliminary analysis of reported changes in groundwater and anomalous animal behavior before the 4 February 1975 Haicheng earthquake (1981)
    AGU
    In:  Professional Paper, Earthquake Prediction, Washington, D.C., AGU, vol. 4, no. 16, pp. 543-565, (ISBN 1-4020-1729-4)
    Details
    Publication Date: 1981
    Keywords: Earthquake precursor: chemical (Rn, water(-level,...) ; China ; Earthquake precursor: others (animal behav., wobble, tides) ; Earthquake precursor: prediction research
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    BIBLIOGRAPHY SEISMOLOGY
  • 11
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    Seismicity pattern in the South Iceland Seismic Zone (1981)
    AGU
    In:  Professional Paper, Earthquake Prediction, Washington, D.C., AGU, vol. 4, no. 16, pp. 141-151, (ISBN 1-4020-1729-4)
    Details
    Publication Date: 1981
    Keywords: Plate tectonics ; Seismicity ; Volcanology ; Earthquake precursor: prediction research ; Earthquake precursor: statistical anal. of seismicity ; Stefansson
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    BIBLIOGRAPHY SEISMOLOGY
  • 12
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    Epeirogeny and plate tectonics (1980)
    AGU
    In:  Bull., Polar Proj. OP-O3A4, Plate Tectonics. Selected Papers from Publications of the AGU, Washington, D.C., AGU, vol. 22, no. 4, pp. 444-455, (ISBN 0080419208)
    Details
    Publication Date: 1980
    Keywords: Crustal deformation (cf. Earthquake precursor: deformation or strain) ; Plate tectonics
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    BIBLIOGRAPHY SEISMOLOGY
  • 13
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    Induced earthquakes associated with large reservoirs in China (1983)
    AGU
    In:  Chinese Geophysics, Washington, D.C., AGU, vol. 2, no. 2, pp. 383-403, pp. L24604, (ISSN: 1340-4202)
    Details
    Publication Date: 1983
    Keywords: Earthquake ; Induced seismicity ; JAPAN
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    BIBLIOGRAPHY SEISMOLOGY
  • 14
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    Changes in the seismicity and focal mechanism of small earthquakes prior to an Ms-2dsus0 6.7 earthquake in the central Aleutian island arc (1981)
    AGU
    In:  Professional Paper, Earthquake Prediction, Washington, D.C., AGU, vol. 4, no. 16, pp. 348-356, (ISBN 0080419208)
    Details
    Publication Date: 1981
    Keywords: Earthquake precursor: prediction research ; Seismicity ; Earthquake precursor: stresses ; Fault plane solution, focal mechanism ; Source
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    BIBLIOGRAPHY SEISMOLOGY
  • 15
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    Height dependent errors in southern California leveling (1981)
    AGU
    In:  Bull., Polar Proj. OP-O3A4, Earthquake Prediction, Washington, D.C., AGU, vol. 4, no. XVI:, pp. 457-472, (ISBN: 3-540-23712-7)
    Details
    Publication Date: 1981
    Keywords: Earthquake precursor: prediction research ; Earthquake precursor: deformation or strain ; Geodesy
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    BIBLIOGRAPHY SEISMOLOGY
  • 16
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    The nature of seismicity patterns before large earthquakes (1981)
    AGU
    In:  Bull., Polar Proj. OP-O3A4, Earthquake Prediction, Washington, D.C., AGU, vol. 4, no. 1, pp. 1-19, (ISBN: 3-540-23712-7)
    Details
    Publication Date: 1981
    Keywords: Seismicity ; Earthquake precursor: prediction research ; FROTH ; (abstract)
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    BIBLIOGRAPHY SEISMOLOGY
  • 17
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    Seismic potential for the world's major plate boundaries: 1981 (1981)
    AGU
    In:  Bull., Polar Proj. OP-O3A4, Earthquake Prediction, Washington, D.C., AGU, vol. 4, no. Subvol. a, pp. 20-28, (ISBN 0080419208)
    Details
    Publication Date: 1981
    Keywords: Earthquake precursor: prediction research ; Earthquake precursor: statistical anal. of seismicity ; FROTH ; (book)
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    BIBLIOGRAPHY SEISMOLOGY
  • 18
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    Kinematics of the South American subduction zone from global plate reconstructions (1983)
    AGU
    In:  Bull., Open-File Rept., Geodynamics of the Eastern Pacific Region, Caribbean and Scotia Arcs, Washington, D.C., AGU, vol. 9, no. 1, pp. 113-125, (ISBN 0080419208)
    Details
    Publication Date: 1983
    Keywords: Plate tectonics ; Crustal deformation (cf. Earthquake precursor: deformation or strain) ; Subduction zone ; Review article ; Cabre
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    BIBLIOGRAPHY SEISMOLOGY
  • 19
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    Neotectonic deformation, near surface movements and systematic errors in U.S. releveling measurements: Implications for earthquake prediction (1981)
    AGU
    In:  Bull., Open-File Rept., Earthquake Prediction, Washington, D.C., AGU, vol. 4, no. 1, pp. 422-440, (ISBN 0080419208)
    Details
    Publication Date: 1981
    Keywords: Earthquake precursor: prediction research ; Geodesy ; Earthquake precursor: deformation or strain
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    BIBLIOGRAPHY SEISMOLOGY
  • 20
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    Active faults, paleoseismology, and earthquake hazards in the western United States (1981)
    AGU
    In:  Professional Paper, Open-File Rept., Earthquake Prediction, Washington, D.C., AGU, vol. 4, no. 16, pp. 209-216, (ISBN 0080419208)
    Details
    Publication Date: 1981
    Keywords: Earthquake precursor: prediction research ; Earthquake precursor: deformation or strain
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    BIBLIOGRAPHY SEISMOLOGY
  • 21
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    Role of elevation-dependent errors on the accuracy of geodetic leveling in the southern California uplift (1981)
    AGU
    In:  Bull., Open-File Rept., Earthquake Prediction, Washington, D.C., AGU, vol. 4, no. 16, pp. 441-456, (ISBN 1-86239-165-3, vi + 330 pp.)
    Details
    Publication Date: 1981
    Keywords: Tectonics ; Earthquake precursor: prediction research ; Earthquake precursor: deformation or strain ; Geodesy
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    BIBLIOGRAPHY SEISMOLOGY
  • 22
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    Repeat times of great earthquakes along simple plate boundaries (1981)
    AGU
    In:  Bull., Open-File Rept., Earthquake Prediction, Washington, D. C., AGU, vol. 65, no. 1, pp. 217-247, (ISBN 1-86239-165-3, vi + 330 pp.)
    Details
    Publication Date: 1981
    Keywords: Recurrence of earthquakes ; Fault zone ; Earthquake
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    BIBLIOGRAPHY SEISMOLOGY
  • 23
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    Seismicity patterns in China (1981)
    AGU
    In:  Professional Paper, Open-File Rept., Earthquake Prediction, Washington, D.C., AGU, vol. 4, no. 2, pp. 117-125, (ISBN 0080419208)
    Details
    Publication Date: 1981
    Keywords: Seismicity
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    BIBLIOGRAPHY SEISMOLOGY
  • 24
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    Crustal deformation studies and earthquake prediction research (1981)
    AGU
    In:  Professional Paper, Open-File Rept., Earthquake Prediction, Washington, D.C., AGU, vol. 4, no. 16, pp. 394-410, (ISBN 1-86239-165-3, vi + 330 pp.)
    Details
    Publication Date: 1981
    Keywords: Earthquake precursor: prediction research ; Earthquake precursor: deformation or strain
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    BIBLIOGRAPHY SEISMOLOGY
  • 25
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    Mechanical aspects of postglacial volcanism and tectonics of the Reykjanes Peninsula, southwest Iceland (2012)
    AGU
    In:  Journal of Geophysical Research: Solid Earth, 91 (B12). pp. 12711-12721.
    Details
    Publication Date: 2020-07-23
    Description: Four major NE trending postglacial volcanic and tectonic fissure swarms (volcanic systems) occur on the Reykjanes Peninsula, and the westernmost three are the main subject of this paper. Two main types of basaltic volcanoes are associated with these systems: shields of picrite and olivine tholeiite and tholeiite fissures. The average volume of 26 shields is 1.11 km3, and the total production is 29 km3, whereas the corresponding figures for lavas from 101 volcanic fissures are 0.11 km3 and 11 km3. The tectonic fractures are either tension fractures or normal faults of widths up to 20 m, throws up to 10 m, and lengths up to several kilometers. The volcanism and tectonics can be explained by magmatic pressure changes in ellipsoidal magma reservoirs located beneath the fissure swarms. A magmatic pressure increase of the order of 10 MPa is found to be sufficient for an excess uplift of the order of several meters, which is all that is needed to account for the fractures and measured dilation in the fissure swarms. It is concluded that most shield volcanoes, in particular the picrite shields and the large olivine tholeiite shields, formed during the early postglacial period and that their formation was facilitated by the stress field generated as a result of rapid uplift and bending of the crust above the reservoirs. Since that time the reservoirs have become independent systems, the volcanism has been confined to fissures, and the production rate has decreased significantly. During typical fissure eruptions (0.015 km3), only the uppermost several hundred meters of the source reservoir, depending on its magma content, supply magma to the eruption.
    Type: Article , PeerReviewed
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  • 26
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    Variability of the Denmark Strait overflow: Moored time series from 1996–2011 (2012)
    AGU
    In:  Journal of Geophysical Research: Oceans, 117 (C12). C12003.
    Details
    Publication Date: 2020-07-23
    Description: The Denmark Strait overflow provides about half of the total dense water overflow from the Nordic Seas into the North Atlantic Ocean. The velocity of the overflow has been monitored in the Strait with two moored Acoustic Doppler Current Profilers since 1996 with several interruptions due to mooring losses or instrument failure. So far, overflow transports were only calculated when data from both moorings were available. In this work, we introduce a linear model to fill gaps in the time series when data from only one instrument is available. The mean overflow transport is 3.4 Sv and exhibits a variance of 2.0 Sv2. No significant trend was detected in the time series. The highest variability in the transport is associated with the passage of mesoscale eddies with time scales of 2–10 days (associated with a variance of 1.5 Sv2). Seasonal variability is weak and explains less than 5% of the variance in all time series, which is in contrast to the strong seasonal cycle found in high resolution model simulations. Interannual variability is on the order of 10% of the mean. A relation to atmospheric forcing such as the local wind stress curl, as well as to larger scale phenomena, e.g. the North Atlantic Oscillation, is not detected. Since 2005 data from moored temperature, conductivity and pressure recorders have been available as well, monitoring the hydrographic variability at the bottom of Denmark Strait. In recent years the temperature time series of the Denmark Strait overflow revealed a cooling, while the salinity stayed nearly constant.
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  • 27
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    Structure and variability of the abyssal water masses in the Ionian Sea in the period 2003-2010 (2013)
    AGU
    In:  Journal of Geophysical Research: Oceans, 118 (2). pp. 931-943.
    Details
    Publication Date: 2020-07-23
    Description: This study presents aspects of the spatial and temporal variability of abyssal water masses in the Ionian Sea, as derived from recent temperature, salinity, dissolved oxygen and velocity observations and from comparisons between these and former observations. Previous studies showed how in the Southern Adriatic Sea the Adriatic Deep Water (AdDW) became fresher (ΔS ≈ −0.08) and colder (ΔT ≈ −0.1°C) after experiencing warming and salinification between 2003 and 2007. Our data, collected from October 2009 to July 2010 from two bottom moorings, one within the Strait of Otranto and the other in the northern Ionian, confirm this tendency: a bottom vein of southward-flowing AdDW, whose temperature and salinity continuously decreased during the observation time, was detected there. Typically, the vein travel time between the two stations ranged between 45 and 50 days. This gave us a temporal estimate for AdDW anomaly propagation towards the Ionian abyss from their Adriatic generation region. The density excess of the observed vein was always enough to enable its existence as a bottom-arrested current. This evidence confirms that, at that time (2009 and 2010), the Adriatic Sea was greatly contributing to the formation of Eastern Mediterranean Deep Water (EMDW), the bottom water of the Eastern Mediterranean. Hence, based on these results and on the evidence that, from 2003 to 2009, abyssal Ionian waters became saltier and warmer under the time-lagged influence of AdDW, possible future changes in the EMDW characteristics, as a response to Adriatic variability, are discussed.
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  • 28
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    Constraints on fluid flow processes in the Hellenic Accretionary Complex (eastern Mediterranean Sea) from numerical modeling (2014)
    AGU
    In:  Journal of Geophysical Research: Solid Earth, 119 (4). pp. 3601-3626.
    Details
    Publication Date: 2020-07-23
    Description: The dynamics of accretionary convergent margins are severely influenced by intense deformation and fluid expulsion. To quantify the fluid pressure and fluid flow velocities in the Hellenic subduction system, we set up 2-D hydrogeological numerical models following two seismic reflection lines across the Mediterranean Ridge. These profiles bracket the along-strike variation in wedge geometry: moderate compression and a 〉4 km thick underthrust sequence in the west versus enhanced compression and 〈1 km of downgoing sediment in the center. Input parameters were obtained from preexisting geophysical data, drill cores, and new geotechnical laboratory experiments. A permeability-porosity relationship was determined by a sensitivity analysis, indicating that porosity and intrinsic permeability are small. This hampers the expulsion of fluids and leads to the build up of fluid overpressure in the deeper portion of the wedge and in the underthrust sediment. The loci of maximum fluid pressure are mainly controlled by the compactional fluid source, which generally decreases toward the backstop. However, pore pressure is still high at the decollement level at distances 〈100 km from the deformation front, either by the incorporation of low permeability evaporites or additional compaction of the wedge sediments in the two profiles. In the west, however, formation of a wide accretionary complex is facilitated by high pore pressure zones. When compared to other large accretionary complexes such as Nankai or Barbados, our results not only show broad similarities but also that near-lithostatic pore pressures may be easier to maintain in the Hellenic Arc because of accentuated collision, some underthrust evaporates, and a thicker underthrust sequence.
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  • 29
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    Observed and modeled surface eddy heat fluxes in the eastern Nordic Seas (2012)
    AGU
    In:  Journal of Geophysical Research: Oceans, 117 (C8).
    Details
    Publication Date: 2020-07-23
    Description: Large-scale budget calculations and numerical model process studies suggest that lateral eddy heat fluxes have an important cooling effect on the Norwegian Atlantic Current (NwAC) as it flows through the Nordic Seas. But observational estimates of such fluxes have been lacking. Here, wintertime surface eddy heat fluxes in the eastern Nordic Seas are estimated from surface drifter data, satellite data and an eddy-permitting numerical model. Maps of the eddy heat flux divergence suggest advective cooling along the path of the NwAC. Integrating the flux divergence over temperature classes yields consistent estimates for the three data sets; the waters warmer than about 6°C are cooled while the cooler waters are warmed. Similar integrations over bottom depth classes show that regions shallower than about 2000 m are cooled while deeper regions are warmed. Finally, integrating the flux divergence along the core of the NwAC suggests that the highest eddy-induced heat loss at the surface is along the steepest part of the continental slope, east of the Lofoten Basin. The model fields indicate that cooling of the current by lateral eddy fluxes is comparable to or larger than the local heat loss to the atmosphere.
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  • 30
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    Precipitation downscaling under climate change: Recent developments to bridge the gap between dynamical models and the end user (2010)
    AGU
    In:  Reviews of Geophysics, 48 (3). RG3003.
    Details
    Publication Date: 2020-06-03
    Description: Precipitation downscaling improves the coarse resolution and poor representation of precipitation in global climate models and helps end users to assess the likely hydrological impacts of climate change. This paper integrates perspectives from meteorologists, climatologists, statisticians, and hydrologists to identify generic end user (in particular, impact modeler) needs and to discuss downscaling capabilities and gaps. End users need a reliable representation of precipitation intensities and temporal and spatial variability, as well as physical consistency, independent of region and season. In addition to presenting dynamical downscaling, we review perfect prognosis statistical downscaling, model output statistics, and weather generators, focusing on recent developments to improve the representation of space-time variability. Furthermore, evaluation techniques to assess downscaling skill are presented. Downscaling adds considerable value to projections from global climate models. Remaining gaps are uncertainties arising from sparse data; representation of extreme summer precipitation, subdaily precipitation, and full precipitation fields on fine scales; capturing changes in small-scale processes and their feedback on large scales; and errors inherited from the driving global climate model.
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  • 31
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    Response of the eastern subtropical Atlantic SST to Saharan dust: A modeling and observational study (2010)
    AGU
    In:  Journal of Geophysical Research: Oceans, 115 (C8).
    Details
    Publication Date: 2020-07-23
    Description: Retrievals of aerosol optical depth (AOD) from MODIS, and of sea surface temperature (SST) from TMI are analyzed jointly with the output of a numerical model for the period 2000-2006 to determine the impact of Saharan dust on the eastern subtropical North Atlantic SST. Simultaneously with, or shortly after strong dust outbreaks, a decrease in SST of 0.2 degrees to 0.4 degrees C can be observed in the microwave SST data set, which is consistent with an independent estimate of SST decrease simulated here by a local mixed layer model. However, low wind conditions and a shallow mixed layer are required to reach this response, and it is therefore unlikely that a clear response of SST to dust lasting more than a few days can be seen in the microwave SST observations. An inspection of microwave SST observations suggests that about 30% of SST variance could be explained by dust-induced cooling in our study region that is not represented in existing AVHRR SST fields nor represented in reanalysis centers-provided surface heat fluxes. On longer time scales, a comparison between observed SST fields and simulated SST, using an eddy-permitting model of the North Atlantic, suggests a cooling of about 0.5 degrees C on the local SST on sub-seasonal to interannual time scales which is significantly correlated and consistent with a dust-induced cooling. However, while supportive of the hypothesis that Saharan dust lead to a reduction in SST, the eddy-resolving model results are not by themselves conclusive. Moreover, the effects of dust-induced cooling on simulations of the ocean circulation, on atmospheric forecasts and on climate simulations remains to be investigated in future studies.
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  • 32
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    Structure and seismogenic properties of the Mentawai segment of the Sumatra subduction zone revealed by local earthquake traveltime tomography (2012)
    AGU
    In:  Journal of Geophysical Research: Oceans, 117 (B1). B01312.
    Details
    Publication Date: 2020-07-23
    Description: On 12 September 2007, an Mw8.4 earthquake occurred within the southern section of the Mentawai segment of the Sumatra subduction zone, where the subduction thrust had previously ruptured in 1833 and 1797. Traveltime data obtained from a temporary local seismic network, deployed between December 2007 and October 2008 to record the aftershocks of the 2007 event, was used to determine two-dimensional (2-D) and three-dimensional (3-D) velocity models of the Mentawai segment. The seismicity distribution reveals significant activity along the subduction interface and within two clusters in the overriding plate either side of the forearc basin. The downgoing slab is clearly distinguished by a dipping region of highVp (8.0 km/s), which can be a traced to ∼50 km depth, with an increased Vp/Vs ratio (1.75 to 1.90) beneath the islands and the western side of the forearc basin, suggesting hydrated oceanic crust. Above the slab, a shallow continental Moho of less than 30 km depth can be inferred, suggesting that the intersection of the continental mantle with the subducting slab is much shallower than the downdip limit of the seismogenic zone despite localized serpentinization being present at the toe of the mantle wedge. The outer arc islands are characterized by low Vp (4.5–5.8 km/s) and high Vp/Vs (greater than 2.0), suggesting that they consist of fluid saturated sediments. The very low rigidity of the outer forearc contributed to the slow rupture of the Mw 7.7 Mentawai tsunami earthquake on 25 October 2010.
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  • 33
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    Young mafic back arc volcanic rocks as indicators of continental lithospheric delamination beneath the Argentine Puna Plateau, central Andes (2012)
    AGU
    In:  Journal of Geophysical Research: Oceans, 99 (B12). pp. 24323-24339.
    Details
    Publication Date: 2020-07-23
    Description: The spatial distribution of some major and trace element and isotopic characteristics of backarc Plio-Quaternary basaltic to high-Mg andesitic (51% to 58% SiO2) lavas in the southern Puna (24°S to 27°S) of the Central Andean Volcanic Zone (CVZ) reflect varying continental lithospheric thickness and the thermal state of the underlying mantle wedge and subducting plate. These lavas erupted from small cones and fissures associated with faults related to a change in the regional stress system in the southern Puna at ≈ 2 to 3 Ma. Three geochemical groups are recognized: (1) a relatively high volume intraplate group (high K; La/Ta ratio 〈25) that occurs over a thin continental lithosphere above a gap in the modern seismic zone and represents the highest percentage of mantle partial melt, (2) an intermediate volume, high-K calc-alkaline group ( La/Ta ratio 〉25) that occurs over intermediate thickness lithosphere on the margins of the seismic gap and behind the main CVZ and represents an intermediate percentage of mantle partial melt, and (3) a small-volume shoshonitic group (very high K) that occurs over relatively thick continental lithosphere in the northeast Puna and Altiplano and represents a very small percentage of mantle partial melt. Mantle-generated characteristics of these lavas are partially overprinted by mixing with melts of the overlying thickened crust as shown by the presence of quartz and feldspar xenocrysts, negative Eu anomalies (Eu/Eu 〈 0.90; most 〈 0.80), and radiogenic Sr (〉 0.7055) and Pb and nonradiogenic Nd ( εNd 〈 −0.4) isotopic ratios. Mixing calculations show that the lavas generally contain more than 20% to 25% crustal melt. The eruption of the intraplate group mafic lavas, the change in regional stress orientation, and the high elevation of the southern Puna are suggested to be the result of the late Pliocene mechanical delamination of a block (or blocks) of continental lithosphere (mantle and possibly lowermost crust). The loss of this lithosphere resulted in an influx of asthenosphere that caused heating of the subducting slab and yielded intraplate basic magmas that produced extensive melting at the base of the thickened crust. Heating of the subducting slab led to formation of the seismic gap and trenchward depletion of the slab component. Backarc calc-alkaline group lavas erupted on the margins of this delaminated block, whereas shoshonitic group lavas erupted over a zone of relatively thick nondelaminated lithosphere to the north.
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  • 34
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    Marine geology of the Hess Rise: 1. Bathymetry, surface sediment distribution, and environment of deposition (2012)
    AGU
    In:  Journal of Geophysical Research: Solid Earth, 86 (B11). pp. 10734-10752.
    Details
    Publication Date: 2020-07-23
    Description: New charts of bathymetry, acoustic character, and sediment distribution describe the Hess Rise, a large oceanic plateau in the central north Pacific. Discrete physiographic provinces on the Hess Rise are the High Plateau, shallower than 3900 m, trending N30°W; the Northeastern Flank, a smooth, gentle slope gradually increasing in depth to the northeast; the Woollard Abyssal Plain, extending farther to the northeast; the Volcanic Province with its high peaks and ridges along the southern margin of the Hess Rise; the Mendocino Fracture Zone to the south, expressed by broad, planar seafloor regions bordered by ridges and scarps; the Western Steps, formed by structural benches on the western side of the Rise; and the Emperor Deep, between the rise and the Emperor Seamounts. Five types of acoustic units have been mapped and interpreted: a transparent layer, predominantly of biosiliceous pelagic clay; a stratified layer, predominantly of nannofossil ooze; a diffuse layer of debris flows that seem to have originated mostly in the Volcanic Province; an opaque horizon commonly formed of volcaniclastic sediments that are usually found on the seafloor of the Mendocino Fracture Zone; and a hyperbolic horizon, indicating outcrops of igneous rock. The pronounced effect of bottom currents on the present-day environment of deposition in the Hess Rise is evidenced by the presence of the opaque horizon, which is interpreted as an erosion surface, and by current moating, abrupt thinning of surface layers and truncation of subbottom reflectors. The widespread erosion on the seafloor of the Mendocino Fracture Zone is attributed to the flow of Antarctic bottom water.
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  • 35
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    MIMOC: A global monthly isopycnal upper-ocean climatology with mixed layers (2013)
    AGU
    In:  Journal of Geophysical Research: Oceans, 118 (4). pp. 1658-1672.
    Details
    Publication Date: 2020-07-23
    Description: A monthly, isopycnal/mixed-layer ocean climatology (MIMOC), global from 0 to 1950 dbar, is compared with other monthly ocean climatologies. All available quality-controlled profiles of temperature (T) and salinity (S) versus pressure (P) collected by conductivity-temperature-depth (CTD) instruments from the Argo Program, Ice-Tethered Profilers, and archived in the World Ocean Database are used. MIMOC provides maps of mixed layer properties (conservative temperature, Θ, absolute salinity, SA, and maximum P) as well as maps of interior ocean properties (Θ, SA, and P) to 1950 dbar on isopycnal surfaces. A third product merges the two onto a pressure grid spanning the upper 1950 dbar, adding more familiar potential temperature (θ) and practical salinity (S) maps. All maps are at monthly 0.5° × 0.5° resolution, spanning from 80°S to 90°N. Objective mapping routines used and described here incorporate an isobath-following component using a “Fast Marching” algorithm, as well as front-sharpening components in both the mixed layer and on interior isopycnals. Recent data are emphasized in the mapping. The goal is to compute a climatology that looks as much as possible like synoptic surveys sampled circa 2007–2011 during all phases of the seasonal cycle, minimizing transient eddy and wave signatures. MIMOC preserves a surface mixed layer, minimizes both diapycnal and isopycnal smoothing of θ-S, as well as preserves density structure in the vertical (pycnoclines and pycnostads) and the horizontal (fronts and their associated currents). It is statically stable and resolves water mass features, fronts, and currents with a high level of detail and fidelity.
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  • 36
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    Mapping the fluid flow of the Mariana Mounds ridge flank hydrothermal system: Pore water chemical tracers (2012)
    AGU
    In:  Journal of Geophysical Research: Solid Earth, 100 (B5). pp. 8115-8131.
    Details
    Publication Date: 2020-07-23
    Description: We present a conceptual model of fluid circulation in a ridge flank hydrothermal system, the Mariana Mounds. The model is based on chemical data from pore waters extracted from piston cores and from push cores collected by deep‐sea research vessel Alvin in small, meter‐sized mounds situated on a local topographic high. These mounds are located within a region of heat flow exceeding that calculated from a conductive model and are zones of strong pore water upflow. We have interpreted the chemical data with time‐dependent transport‐reaction models to estimate pore water velocities. In the mounds themselves pore water velocities reach several meters per year to kilometers per year. Within about 100 m from these zones of focused upflow velocities decrease to several centimeters per year up to tens of centimeters per year. A larger area of low heat flow surrounds these heat flow and topographic highs, with upwelling pore water velocities less than 2 cm/yr. In some nearby cores, downwelling of bottom seawater is evident but at speeds less than 2 cm/yr. Downwelling through the sediments appears to be a minor source of seawater recharge to the basaltic basement. We conclude that the principal source of seawater recharge to basement is where basement outcrops exist, most likely a scarp about 2–4 km to the east and southeast of the study area.
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  • 37
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    Statistical analysis of the volcano seismicity during the 2007 crisis of Stromboli, Italy: a 3-day oscillatory signal as onset of the activity (2010)
    AGU
    Details
    Publication Date: 2020-11-17
    Description: We analyze the volcano seismicity recorded during the 2007 eruption of Stromboli. Data-set is composed of the continuous recordings of a three-component broad-band seismometer and of a strainmeter. Starting from the characterization of the standard activity as a stationary phase of equilibrium, we investigate the non-equilibrium phase of the effusive process. A statistical analysis of the explosions reveals that the occurrence is always driven by a Poisson process as for the standard activity, even approaching the effusion phase, with the only difference in shortening the inter-times just during the effusion. A slightly different process can be advocated for the swarms of the explosions, because a maximum in the distribution of inter-times can be evidenced. Regarding the amplitudes of the explosion-quakes, they have a log-normal distribution until the effusion onset as in the standard Strombolian activity. The actual departure from that stationarity seems to be traced by an early deformative response at very long period. It appears as a transient oscillating signal characterized by a period of about three days that modulates the explosion amplitudes. In a conceptual organ pipe-like model it is related to the chocking of the pipe. The successive activity can be interpreted as the response of volcano to restore the equilibrium condition.
    Description: Published
    Description: B09312
    Description: 1V. Storia eruttiva
    Description: JCR Journal
    Description: open
    Keywords: Stromboli ; eruption ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
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  • 38
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    Soil CO2 emissions at Furnas volcano (São Miguel Island, Azores archipelago) - volcano monitoring perspectives, geomorphologic studies and land-use planning application (2011)
    AGU
    Details
    Publication Date: 2020-11-12
    Description: Accepted for publication in Journal of Geophysical Research. Copyright (2010) American Geophysical Union.
    Description: Carbon dioxide (CO2) diffuse degassing structures (DDS) at Furnas Volcano (São Miguel Island, Azores) are mostly associated with the main fumarolic fields, evidence that CO2 soil degassing is the surface expression of rising steam from the hydrothermal system. Locations with anomalous CO2 flux are mainly controlled by tectonic structures oriented WNW-ESE and NW-SE and by the geomorphology of the volcano, as evidenced by several DDS located in depressed areas associated with crater margins. Hydrothermal soil CO2 emissions in Furnas volcano are estimated to be ~ 968 t d-1. Discrimination between biogenic and hydrothermal CO2 was determined using a 1 statistical approach and the carbon isotope composition of the CO2 efflux. Different sampling densities were used to evaluate uncertainty in the estimation of the total CO2 flux, and showed that a low density of points may not be adequate to quantify soil emanations from a relatively small DDS. Thermal energy release associated to diffuse degassing at Furnas caldera is about 118 MW (from an area of ~ 4.8 km2) based on the H2O/CO2 ratio in fumarolic gas. The DDS affect also Furnas and Ribeira Quente villages, which are located inside the caldera and in the south flank of the volcano, respectively. At these sites, 58% and 98% of the houses are built over hydrothermal CO2 emanations, and the populations are at risk due to potential high concentrations of CO2 accumulating inside the dwellings. Keywords: Soil diffuse degassing; soil CO2 flux; emission rates; Azores archipelago 2
    Description: Published
    Description: B12208
    Description: 3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici
    Description: JCR Journal
    Description: open
    Keywords: Soil CO2 emissions ; Furnas volcano ; volcano monitoring. ; 04. Solid Earth::04.04. Geology::04.04.11. Instruments and techniques ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
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  • 39
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    Unusual nighttime impulsive foF2 enhancement below the southern anomaly crest under geomagnetically quiet conditions (2011)
    AGU
    Details
    Publication Date: 2020-12-14
    Description: An unusual nighttime impulsive electron density enhancement was observed on 6 March 2010 over a wide region of South America, below the southern crest of the equatorial anomaly, under low solar activity and quiet geomagnetic conditions. The phenomenon was observed almost simultaneously by the F2 layer critical frequency ( foF2) recorded at three ionospheric stations which are widely distributed in space, namely Cachoeira Paulista (22.4°S, 44.6°W, magnetic latitude 13.4°S), São José dos Campos (23.2°S, 45.9°W, magnetic latitude 14.1°S), Brazil, and Tucumán (26.9°S, 65.4°W, magnetic latitude 16.8°S), Argentina. Although in a more restricted region over Tucumán, the phenomenon was also observed by the total electron content (TEC) maps computed by usingmeasurements from 12 GPS receivers. The investigated phenomenon is very particular because besides being of brief duration, it is characterized by a pronounced compression of the ionosphere. This compression was clearly visible both by the virtual height of the base of the F region (h′F) recorded at the aforementioned ionospheric stations, and by both the vertical electron density profiles and the slab thickness computed over Tucumán. Consequently, neither an enhanced fountain effect nor plasma diffusion from the plasmasphere can be considered as the single cause of this unusual event. A thorough analysis of isoheight and isofrequency ionosonde plots suggest that traveling ionospheric disturbances (TIDs) caused by gravity wave (GW) propagation could have likely played a significant role in causing the phenomenon.
    Description: Published
    Description: A12314
    Description: 1.6. Osservazioni di geomagnetismo
    Description: 1.7. Osservazioni di alta e media atmosfera
    Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale
    Description: 5.4. Banche dati di geomagnetismo, aeronomia, clima e ambiente
    Description: JCR Journal
    Description: open
    Keywords: equatorial ionosphere ; travelling ionospheric disturbance ; ionosphere-atmosphere interactions ; instrument and techniques ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous ; 01. Atmosphere::01.02. Ionosphere::01.02.02. Dynamics ; 01. Atmosphere::01.02. Ionosphere::01.02.04. Plasma Physics ; 01. Atmosphere::01.02. Ionosphere::01.02.05. Wave propagation ; 01. Atmosphere::01.02. Ionosphere::01.02.06. Instruments and techniques ; 05. General::05.07. Space and Planetary sciences::05.07.99. General or miscellaneous ; 05. General::05.07. Space and Planetary sciences::05.07.01. Solar-terrestrial interaction ; 05. General::05.07. Space and Planetary sciences::05.07.02. Space weather
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  • 40
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    Automatic detection of long-period events at Campi Flegrei Caldera (Italy) (2011)
    AGU
    Details
    Publication Date: 2020-12-15
    Description: We propose a novel approach to analyze continuous seismic signal and separate the sources from background noise. A specific application to the seismicity recorded at Campi Flegrei Caldera during the 2006 ground uplift is presented. The fundamental objective is to improve the standard procedures of picking the emergent onset arrivals of the seismic signals, often buried in the high-level ambient noise, in order to obtain an appropriate catalogue for monitoring the activity of this densely populated volcanic area. This is particularly useful in order to estimate the release of the seismic energy and to put constraints on the source dynamics. An Independent Component Analysis based approach for the Blind Source Separation of convolutive mixtures is adopted to obtain a clear separation of Long Period events from the ambient noise. The approach presents good performance and it is suitable for real time implementation in seismic monitoring. Its application to the continuous seismic signal recorded at Campi Flegrei has allowed the extraction of high-quality waveforms, considerably improving the detection of low-energy events.
    Description: Published
    Description: 5
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: Campi Flegrei ; convolutive independent component analysis ; long-period detection ; 05. General::05.01. Computational geophysics::05.01.05. Algorithms and implementation
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  • 41
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    Coherence of Mach fronts during heterogeneous supershear earthquake rupture propagation: Simulations and comparison with observations (2010)
    AGU
    Details
    Publication Date: 2021-02-17
    Description: An edited version of this paper was published by AGU. Copyright (2010) American Geophysical Union.
    Description: We study how heterogeneous rupture propagation affects the coherence of shear– and Rayleigh–Mach wave fronts radiated by supershear earthquakes. We address this question using numerical simulations of ruptures on a planar, vertical strike–slip fault embedded in a three–dimensional, homogeneous, linear elastic half–space. Ruptures propagate spontaneously in accordance with a linear slip–weakening friction law through both homogeneous and heterogeneous initial shear stress fields. In the 3–D homogeneous case, rupture fronts are curved due to interactions with the free surface and the finite fault width; however, this curvature does not greatly diminish the coherence of Mach fronts relative to cases in which the rupture front is constrained to be straight, as studied by Dunham and Bhat (2008). Introducing heterogeneity in the initial shear stress distribution causes ruptures to propagate at speeds that locally fluctuate above and below the shear–wave speed. Calculations of the Fourier amplitude spectra (FAS) of ground velocity time histories corroborate the kinematic results of Bizzarri and Spudich (2008): 1) The ground motion of a supershear rupture is richer in high frequency with respect to a subshear one. 2) When a Mach pulse is present, its high frequency content overwhelms that arising from stress heterogeneity. Present numerical experiments indicate that a Mach pulse causes approximately an –1.7 high frequency falloff in the FAS of ground displacement. Moreover, within the context of the employed representation of heterogeneities and over the range of parameter space that is accessible with current computational resources, our simulations suggest that while heterogeneities reduce peak ground velocity and diminish the coherence of the Mach fronts, ground motion at stations experiencing Mach pulses should be richer in high frequencies compared to stations without Mach pulses. In contrast to the foregoing theoretical results, we find no average elevation of 5%–damped absolute response spectral accelerations (SA) in the period band 0.05–0.4 s observed at stations that presumably experienced Mach pulses during the 1979 Imperial Valley, 1999 Kocaeli, and 2002 Denali Fault earthquakes compared to SA observed at non–Mach pulse stations in the same earthquakes. A 20% amplification of short period SA is seen only at a few of the Imperial Valley stations closest to the fault. This lack of elevated SA suggests that either Mach pulses in real earthquakes are even more incoherent that in our simulations, or that Mach pulses are vulnerable to attenuation through nonlinear soil response. In any case, this result might imply that current engineering models of high frequency earthquake ground motions do not need to be modified by more than 20% close to the fault to account for Mach pulses, provided that the existing data are adequately representative of ground motions from supershear earthquakes.
    Description: Published
    Description: B08301
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: Numerical modeling ; Supershear ruptures ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
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  • 42
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    Rheology of magmas with bimodal crystal size and shape distributions: Insights from analog experiments (2012)
    AGU
    Details
    Publication Date: 2020-12-14
    Description: Magmas in volcanic conduits commonly contain microlites in association with preexisting phenocrysts, as often indicated by volcanic rock textures. In this study, we present two different experiments that investigate the flow behavior of these bidisperse systems. In the first experiments, rotational rheometric methods are used to determine the rheology of monodisperse and polydisperse suspensions consisting of smaller, prolate particles (microlites) and larger, equant particles (phenocrysts) in a bubble‐free Newtonian liquid (silicate melt). Our data show that increasing the relative proportion of prolate microlites to equant phenocrysts in a magma at constant total particle content can increase the relative viscosity by up to three orders of magnitude. Consequently, the rheological effect of particles in magmas cannot be modeled by assuming a monodisperse population of particles. We propose a new model that uses interpolated parameters based on the relative proportions of small and large particles and produces a considerably improved fit to the data than earlier models. In a second series of experiments we investigate the textures produced by shearing bimodal suspensions in gradually solidifying epoxy resin in a concentric cylinder setup. The resulting textures show the prolate particles are aligned with the flow lines and spherical particles are found in well‐organized strings, with sphere‐depleted shear bands in high‐shear regions. These observations may explain the measured variation in the shear thinning and yield stress behavior with increasing solid fraction and particle aspect ratio. The implications for magma flow are discussed, and rheological results and textural observations are compared with observations on natural samples.
    Description: Published
    Description: Q07024
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: restricted
    Keywords: analog experiments ; crystal bearing ; polydisperse suspensions ; rheology ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous
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  • 43
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    The 1974 flank eruption of Mount Etna: An archetype for deep dike-fed eruptions at basaltic volcanoes and a milestone in Etna's recent history (2010)
    AGU
    Details
    Publication Date: 2021-05-25
    Description: The 1974 western flank eruption of Mount Etna produced a rare, nearly aphyric and plagioclase-free trachybasalt that could not be derived from the central volcano conduits and was more alkaline and more radiogenic than all previous historical lavas. New results for the petrochemistry and volatile content of its products, combined with contemporaneous seismic and volcanological observations, allow us to reinterpret the origin and significance of this event. We show that the eruption was most likely triggered by deep tectonic fracturing that allowed a dike-like intrusion to propagate in 9 days from 11 km depth up to the surface, bypassing the central conduits. Relatively fast, closed system decompression of the volatile-rich magma initially led to lava fountaining and the rapid growth of two pyroclastic cones (Mounts De Fiore), followed by Strombolian activity and the extrusion of viscous lava flows when gas-melt separation developed in the upper portion of the feeding fracture. The 1974 trachybasalt geochemistry indicates its derivation by mixing 25% of preexisting K-poor magma (best represented by 1763 La Montagnola eruption’s products) and 75% of a new K-rich feeding magma that was gradually invading Mount Etna’s plumbing system and became directly extruded during two violent flank eruptions in 2001–2003. We propose to classify 1974-type so-called ‘‘eccentric’’ eruptions on Etna as deep dike-fed (DDF) eruptions, as opposed to more common central conduit-fed flank eruptions, in order to highlight their actual origin rather than their topographic location. We ultimately discuss the possible precursors of such DDF eruptions.
    Description: Published
    Description: B07204
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: reserved
    Keywords: 1974 deep dike-fed eruption ; Mt. Etna ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas
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  • 44
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    Physical characteristics of subduction interface type seismogenic zones revisited (2012)
    AGU
    Details
    Publication Date: 2021-06-16
    Description: Based on global earthquake catalogs, the hypocenters, nodal planes, and seismic moments of worldwide subduction plate interface earthquakes were extracted for the period between 1900 and 2007. Assuming that the seismogenic zone coincides with the distribution of 5.5 ≤ M 〈 7 earthquakes, the subduction interface seismogenic zones were mapped for 80% of the trench systems and characterized with geometrical and mechanical parameters. Using this database, correlations were isolated between significant parameters to identify cause-effect relationships. Empirical laws obtained in previous studies were revisited in light of this more complete, accurate, and uniform description of the subduction interface seismogenic zone. The seismogenic zone was usually found to end in a fore-arc mantle, rather than at a Moho depth. The subduction velocity was the first-order controlling parameter for variations in the physical characteristics of plate interfaces, determining both the geometry and mechanical behavior. As such, the fast subduction zones and cold slabs were associated with large and steep plate interfaces, which, in turn, had large seismic rates. The subduction velocity could not account for the potential earthquake magnitude diversity that was observed along the trenches. Events with Mw ≥ 8.5 preferentially occurred in the vicinity of slab edges, where the upper plate was continental and the back-arc strain was neutral. This observation was interpreted in terms of compressive normal stresses along the plate interface. Large lateral ruptures should be promoted in neutral subduction zones due to moderate compressive stresses along the plate interface that allow the rupture to propagate laterally.
    Description: Published
    Description: Q01004
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: subduction zones ; seismicity ; statistics ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
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  • 45
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    Potential Field modeling of collapse-prone submarine volcanoes in the southern Tyrrhenian Sea (Italy) (2010)
    AGU
    Details
    Publication Date: 2021-07-14
    Description: Hydrothermal alteration may weaken volcanic rocks, causing the gravitational instability of portions of active volcanoes with potentially hazardous collapses. Here we show high‐resolution multibeam, magnetic and gravity surveys of the Marsili seamount, the largest active volcano of Europe located in the southern Tyrrhenian back‐arc basin. These surveys reveal zones with exceptionally low densities and with vanishing magnetizations, due probably to the comminution of basalts during hyaloclastic submarine eruptions and to their post‐eruptive hydrothermal alteration. The location of these regions correlates with morphological data showing the occurrence of past collapses. Similar evidence has been obtained from pre existing data at Vavilov Seamount, another older volcanic system in the Tyrrhenian back‐arc basin. Here a large volume of at least 50 km3 may have collapsed in a single event from its 40 km long western flank. Given the similarities between these volcanoes, a large collapse event may also be expected at Marsili.
    Description: Published
    Description: L03305
    Description: 2.6. TTC - Laboratorio di gravimetria, magnetismo ed elettromagnetismo in aree attive
    Description: 3.4. Geomagnetismo
    Description: JCR Journal
    Description: reserved
    Keywords: Marsili Seamount ; Gravity anomalies ; Magnetic anomalies ; Tyrrhenian Sea ; 04. Solid Earth::04.02. Exploration geophysics::04.02.02. Gravity methods ; 04. Solid Earth::04.04. Geology::04.04.04. Marine geology ; 04. Solid Earth::04.05. Geomagnetism::04.05.04. Magnetic anomalies ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
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  • 46
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    Movements of the Sciara del Fuoco (2012)
    AGU
    Details
    Publication Date: 2021-01-27
    Description: The Sciara del Fuoco (SdF) landslides that occurred at the end of December 2002 prompted researchers to install geodetic networks to monitor deformations related to potential new slope failures. With this aim, an integrated multiparametric monitoring system was designed and deployed. In particular, this complex monitoring system is composed of four single systems: an electronic distance measurement network, installed immediately after the landslide events, a realtime GPS network, a ground-based interferometric linear synthetic aperture radar (GB-InSAR), and an automated topographic monitoring system (named Theodolite Robotic Observatory of Stromboli, or THEODOROS); the three last systems provided a continuous monitoring of selected points or sectors of the SdF. Data acquired from different systems have been jointly analyzed to reach a better understanding of the SdF dynamics. Displacement data obtained from the topographic systems are compared with those obtained from GB-InSAR, and the results of the comparison are analyzed and discussed. Furthermore, in this chapter, an example of a warning system that can detect slope instability precursors on the SdF based on a statistical analysis of the data collected by the THEODOROS system is reported.
    Description: Published
    Description: 183-199
    Description: 1.3. TTC - Sorveglianza geodetica delle aree vulcaniche attive
    Description: reserved
    Keywords: Flank instability ; Slope failure ; Terrestrial geodesy ; Ground Based InSAR ; Continuous GPS ; Landslide monitoring ; 04. Solid Earth::04.03. Geodesy::04.03.06. Measurements and monitoring ; 04. Solid Earth::04.03. Geodesy::04.03.07. Satellite geodesy ; 04. Solid Earth::04.03. Geodesy::04.03.09. Instruments and techniques ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 47
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    Excess volatiles supplied by mingling of mafic magma at an andesite arc volcano (2010)
    AGU
    Details
    Publication Date: 2021-04-07
    Description: We present the results of a study of volcanic gases at Soufrière Hills Volcano, Montserrat, which includes the first spectroscopic measurements of the major gas species CO2 and H2S at this volcano using a Multisensor Gas Analyzer System (MultiGAS) sensor. The fluxes of CO2 and H2S were 640–2750 t/d and 84–266 t/d, respectively, during July 2008, during a prolonged eruptive pause. The flux of CO2 is similar to estimates for the entire arc from previous geochemical studies, while the measured H2S flux significantly alters our interpretation of the sulphur budget for this volcano. The fluxes of both sulphur and carbon show considerable excesses over that which can be supplied by degassing of erupted magma. We demonstrate, using thermodynamic models and published constraints on preeruptive volatile concentrations, that the gas composition and fluxes are best modeled by mixing between (1) gases derived from isobaric quenching of mafic magma against cooler andesite magma at depth and (2) gases derived from shallower rhyolitic interstitial melt within the porpyritic andesite. The escape of deep‐derived gases requires pervasive permeability or vapor advection extending to several kilometers depth in the conduit and magma storage system. These results provide more compelling evidence for both the contribution of unerupted mafic magma to the volatile budget of this andesitic arc volcano and the importance of the intruding mafic magma in sustaining the eruption. From a broader perspective, this study illustrates the importance and role of underplating mafic magmas in arc settings. These magmas play an important role in triggering and sustaining eruptions and contribute in a highly significant way to the volatile budget of arc volcanoes.
    Description: Published
    Description: Q04005
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: JCR Journal
    Description: restricted
    Keywords: magma degassing ; thermodynamics ; volcanic gases ; Soufriere Hills ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 48
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    Analysis of vanillic acid in polar ice cores as a biomass burning proxy – preliminary results from the Akademii Nauk Ice Cap in Siberia (2013)
    AGU
    In:  EPIC3AGU Fall meeting, San Francisco, US, 2013-12-09-2013-12-13AGU
    Details
    Publication Date: 2019-07-16
    Description: Biomass burning influences global climate change and the composition of the atmosphere. The drivers, effects, and climate feedbacks related to fire are poorly understood. Many different proxies have been used to reconstruct past fire frequency from lake sediments and polar ice cores. Reconstruction of historical trends in biomass burning is challenging because of regional variability and the qualitative nature of various proxies. Vanillic acid (4-hydroxy-3-methoxybenzoic acid) is a product of the combustion of conifer lignin that is known to occur in biomass burning aerosols. Biomass burning is likely the only significant source of vanillic acid in polar ice. In this study we describe an analytical method for quantifying vanillic acid in polar ice using HPLC with electrospray ionization and tandem mass spectrometric detection. The method has a detection limit of 100 pM and a precision of ± 10% at the 100 pM level for analysis of 100 μl of ice melt water. The method was used to analyze more than 1000 discrete samples from the Akademii Nauk ice cap on Severnaya Zemlya in the high Russia Arctic (79°30’N, 97°45’E) (Fritzsche et al., 2002; Fritzsche et al., 2005; Weiler et al., 2005). The samples range in age over the past 2,000 years. The results show a mean vanillic acid concentration of 440 ± 710 pM (1σ), with elevated levels during the periods from 300-600 and 1450-1550 C.E.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 49
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    On the relations between fracture energy and physical observables in dynamic earthquake models (2010)
    AGU
    Details
    Publication Date: 2012-02-03
    Description: We explore the relationships between the fracture energy density (E_G) and the key parameters characterizing earthquake sources, such as the rupture velocity (v_r), the total fault slip (u_tot), and the dynamic stress drop (Dt_d). We perform several numerical experiments of three‐dimensional, spontaneous, fully dynamic ruptures developing on planar faults of finite width, obeying different governing laws and accounting for both homogeneous and heterogeneous friction. Our results indicate that E_G behaves differently, depending on the adopted governing law and mainly on the rupture mode (pulselike or cracklike, sub‐ or supershear regime). Subshear, homogeneous ruptures show a general agreement with the theoretical prediction of E_G *proportional to* (1 - (v_r/v_S)^2)^(1/2), but for ruptures that accelerate up to supershear speeds it is difficult to infer a clear dependence of fracture energy density on rupture speed, especially in heterogeneous configurations. We see that slip pulses noticeably agree with the theoretical prediction of E_G *proportional to* u_tot^2 , contrarily to cracklike solutions, both sub‐ and supershear and both homogeneous and heterogeneous, which is in agreement with seismological inferences, showing a scaling exponent roughly equal to 1. We also found that the proportionality between E_G and Dt_d^2, expected from theoretical predictions, is somehow verified only in the case of subshear, homogeneous ruptures with RD law. Our spontaneous rupture models confirm that the total fracture energy (the integral of EG over the whole fault surface) has a power law dependence on the seismic moment, with an exponent nearly equal to 1.13, in general agreement with kinematic inferences of previous studies. Overall, our results support the idea that E_G should not be regarded as an intrinsic material property.
    Description: Published
    Description: B10307
    Description: 2.3. TTC - Laboratori di chimica e fisica delle rocce
    Description: JCR Journal
    Description: reserved
    Keywords: Fracture energy ; Dynamic models ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 50
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    On the recurrence of earthquakes: Role of wear in brittle faulting (2010)
    AGU
    Details
    Publication Date: 2012-02-03
    Description: An edited version of this paper was published by AGU. Copyright (2010) American Geophysical Union.
    Description: The time of occurrence of an earthquake is related to the state of the fault, tectonic loading, and possible triggering mechanisms, and it plays a prominent role in hazard assessment. In this paper we incorporate the effects of wear generation into a seismogenic model. We show that without wear the recurrence time of repeated earthquakes is constant through time and it is controlled by the initial conditions, tectonic loading and constitutive properties, including the presence of pore fluids. Our results indicate that considering the wear development into the fault model dramatically affects the temperature evolution of the fault, the stress release, the developed cosesimic slip and ultimately the duration of the seismic cycle. Moreover, we find that as long as the slipping zone thickness increases, the recurrence time continuously decreases through time. This further complicates the predictability of a subsequent earthquake, even in the simple case of an isolated fault.
    Description: Published
    Description: L20315
    Description: 4.4. Scenari e mitigazione del rischio ambientale
    Description: JCR Journal
    Description: reserved
    Keywords: Earthquake recurrence ; Dynamic models ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk
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  • 51
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    Seismic attenuation and mantle wedge temperature in the northern Apennine subtuction zone (Italy) from teleseismic body wave spectra. (2010)
    AGU
    Details
    Publication Date: 2012-02-03
    Description: An edited version of this paper was published by AGU. Copyright (2010) American Geophysical Union.
    Description: We analyze P and S wave spectra from moderate‐ to deep‐focus teleseisms recorded at the Retreating‐Trench, Extension, and Accretion Tectonics (RETREAT) temporary broadband seismic network to assess the variations of the Earth mantle attenuation in the northern Apennines region (Italy). For each earthquake, we compute the ratio between the spectrum at each station and the average spectrum, in order to estimate t* residuals (Δt*) from the spectral ratio decay. The number and distribution of the teleseisms useable for the P wave t* calculation allow for a gross azimuthal analysis; although the (Δt*) values at single station display, in most cases, azimuthal‐dependent fluctuations, their overall distribution shows a partition of the study region into two main areas, whose gross features remain almost unchanged over the whole azimuthal range. This partition is confirmed by the S wave t* mean values, computed for each station over the set of useable events. We distinguish a relatively high attenuation area on the western, Tyrrhenian side and a relatively low attenuation area on the eastern, Adriatic side. By correlating our Δt* estimates and the velocity structure derived from the existing tomographic models, we compute the ranges of possible P and S wave Q values in the mantle wedge above the Apennines slab (on the Tyrrhenian side) and in the asthenosphere below the Adriatic region. Furthermore, the determined attenuation properties are used to draw some inferences on the thermal state of the uppermost mantle and on the physical properties of the tectonic elements, which constitute the subduction system in the region.
    Description: Published
    Description: B09309
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: Northern Apennine ; Slab ; RETREAT ; attenuation ; mantle ; 04. Solid Earth::04.01. Earth Interior::04.01.03. Mantle and Core dynamics ; 04. Solid Earth::04.01. Earth Interior::04.01.05. Rheology ; 04. Solid Earth::04.02. Exploration geophysics::04.02.06. Seismic methods ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
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  • 52
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    Turbulent Times in the Northern Polar Ionosphere? (2010)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: A model is presented of the growth rate of turbulently generated irregularities in the electron concentration of northern polar cap plasma patches. The turbulence is generated by the short-term fluctuations in the electric field imposed on the polar-cap ionosphere by electric field mapping from the magnetosphere. The model uses an ionospheric imaging algorithm to specify the state of the ionosphere, throughout. The growth rates are used to estimate mean amplitudes for the irregularities and these mean amplitudes are compared with observations of the scintillation indices, S4 and бø, by calculating the linear correlation co-efficients between them. The scintillation data are recorded by GPS L1 band receivers stationed at high northern latitudes. A total of 13 days are analysed, covering four separate magnetic storm periods. These results are compared with those from a similar model of the Gradient Drift Instability (GDI) growth rate. Over-all, the results show better correlation between the GDI process and the scintillation indices than for the turbulence process and the scintillation indices. Two storms, however, show approximately equally good correlations for both processes, indicating that there might be times when the turbulence process of irregularity formation on plasma patches may be the controlling one.
    Description: In press
    Description: 1.7. Osservazioni di alta e media atmosfera
    Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale
    Description: JCR Journal
    Description: open
    Keywords: polar cap patches ; turbulence ; scintillations ; 01. Atmosphere::01.02. Ionosphere::01.02.04. Plasma Physics ; 05. General::05.07. Space and Planetary sciences::05.07.02. Space weather
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  • 53
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    Coseismic deformation of the destructive April 6, 2009 L’Aquila earthquake (central Italy) from GPS data (2010)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: On April 6, 2009, 01:32:39 GMT, the city of L’Aquila was struck by a Mw 6.3 earthquake that killed 307 people, causing severe destruction and ground cracks in a wide area around the epicenter. Four days before the main shock we augmented the existing permanent GPS network with five GPS stations of the Central Apennine Geodetic Network (CaGeoNet) bordering the L’Aquila basin. The maximum horizontal and vertical coseismic surface displacements detected at these stations was 10.39 ± 0.45 cm and 15.64 ± 1.55 cm, respectively. Fixing the strike direction according to focal mechanism estimates, we estimated the source geometry with a non linear inversion of the geodetic data.Our best fitting fault model is a 13 15.7 km2 rectangular fault,SW-dipping at 55.3 ± 1.8 , consistent with the position of observed surface ruptures. The estimated slip (495 ± 29 mm) corresponds to a 6.3 moment magnitude, in excellent agreement with seismological data.
    Description: Published
    Description: L17307
    Description: 1.9. Rete GPS nazionale
    Description: JCR Journal
    Description: reserved
    Keywords: L'Aquila Earthquake ; GPS ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
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  • 54
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    Static stress drop associated with brittle slip events on exhumed faults. (2010)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: We estimate the static stress drop on small exhumed strike-slip faults in the Lake Edison granodiorite of the central Sierra Nevada (California). The subvertical strike-slip faults were exhumed from 4 to 15 km depth and were chosen because they are exposed in outcrop along their entire tip-to-tip lengths of 8–12 m. Slip nucleated on joints and accumulated by crystal-plastic shearing (forming quartz mylonites from early quartz vein filling in joints) and successive brittle faulting (forming epidote-bearing cataclasites). The occurrence of thin, 300 mm wide, pseudotachylytes along some small faults throughout the study area suggests that some, if not all, of the brittle slip on the study area faults may have been seismic. We suggest that the contribution of brittle, cataclastic slip to the total slip along the studied cataclasite-bearing small faults may be estimated by the length of epidote-filled, rhombohedral dilatational jogs (rhombochasms) distributed quasi-periodically along the length of the faults. The interpretation that slip recorded by rhombochasms occurred in single events is based on evidence that (1) epidote crystals are randomly oriented and undeformed within the rhombochasm; (2) cataclasite in principal slip zones does not include clasts of previous cataclasite, and (3) rhombochasm lengths vary systematically along the length of the faults with slip maximum occurring near the fault center, tapering to the fault tips. We thereby constrain both the rupture length and slip. On the basis of these measurements, we calculate stress drops ranging over 90–250 MPa, i.e., one to two orders of magnitude larger than typical seismological estimates for earthquakes, but similar in magnitude to seismological estimates of small (〈M2) earthquakes from the San Andreas Fault Observatory at Depth (SAFOD). The slip events described in the present study occurred along small, deep-seated faults, and, given the calculated stress drops and observations that brittle faults exploited joints sealed by quartz-bearing mylonite, we conclude that these were ‘‘strong’’ faults.
    Description: Published
    Description: B02402
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: earthquakes ; stress drops ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous
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  • 55
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    Effects of the 1989 fracture system in the dynamics of the upper SE flank of Etna revealed by volcanic tremor data: The missing link? (2010)
    AGU
    Details
    Publication Date: 2012-02-03
    Description: An edited version of this paper was published by AGU. Copyright (2010) American Geophysical Union.
    Description: Fracture reactivation is a widespread process in nature even though evidence of magma-induced reactivation is less documented. Here we provide evidence of the reactivation of a fracture system on the upper flank of the Mt. Etna volcano and consider its possible implications in understanding the recent volcanic and tectonic activity. A NNW–SSE trending fracture, partly accompanied by magma emplacement in the form of a laterally propagating dike, formed in 1989 on the upper SE flank of Etna. Lava effusions in 1991–1993, 2001, and 2006 were associated with volcano-tectonic (VT) seismicity and ground deformations on the upper part of the volcano, which document the seismogenetic involvement of the 1989 fractures, although without eruptive phenomena along the discontinuity. In addition to the aforementioned episodes of VT seismicity, differences in the characteristics of the background seismic radiation (volcanic tremor) were measured at stations close to these fractures during the eruptive activity on 24 November 2006, for which more detailed volcanological and seismological time histories are available. Moving on from these findings, we analyze volcanic tremor data recorded close to the summit and along the S flank of the volcano to highlight the interactions between seismic radiation and the 1989 fracture system. Centroid location of volcanic tremor and wave field characteristics at stations of the permanent local seismic network of Etna highlight the guidance role played by the 1989 fractures during the eruptive activity on 24 November 2006. In addition, the collected data shed light on hitherto unknown structural features, which appear to connect the volcano summit to the lower SE slope and also play an important role in controlling the instability of the E flank. More generally, this study shows how (1) using an integrated approach, it is possible to link apparently different features to a common structure, showing uniform and distinct dynamics relevant at the volcano scale, and (2) fracture reactivation can also occur by means of magma intrusion, playing an important role in the transfer of magma within a volcanic edifice.
    Description: Published
    Description: B11306
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: Mount Etna ; fracture system ; volcanic tremor ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
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  • 56
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    Unusually large magmatic CO2 gas emissions prior to a basaltic paroxysm (2010)
    AGU
    Details
    Publication Date: 2012-02-03
    Description: An edited version of this paper was published by AGU. Copyright (2010) American Geophysical Union.
    Description: The low‐intensity activity of basaltic volcanoes is occasionally interrupted by short‐lived but energetic explosions which, whilst frequently observed, are amongst the most enigmatic volcanic events in Nature. The combination of poorly understood and deep, challenging to measure, source processes make such events currently impossible to forecast. Here we report increases in quiescent degassing CO2 emissions (〉10,000 t/day) prior to a powerful explosive event on Stromboli volcano on 15 March 2007. We interpret such large CO2 flux as being sourced by passive gas leakage from a deeply (〉4 km) stored magma, whose depressurization, possibly caused by the onset of an effusive eruption on 28 February 2007, was the explosion trigger. Our observations suggest that continuous CO2 flux monitoring may allow anomalously large explosions to be accurately forecast at basaltic volcanoes.
    Description: Funding from INGV‐DPC project Paroxysm
    Description: Published
    Description: L17303
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: CO2, UV scanner, Stromboli ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases
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  • 57
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    Volcanic ash and SO2 in the 2008 Kasatochi eruption: Retrievals comparison from different IR satellite sensors (2011)
    AGU
    Details
    Publication Date: 2012-02-03
    Description: The Kasatochi 2008 eruption was detected by several infrared satellite sensors including Moderate Resolution Imaging Spectroradiometer (MODIS), Advanced Very High Resolution Radiometer (AVHRR), and Atmospheric Infrared Sounder (AIRS). In this work a comparison between the volcanic cloud SO2 and ash retrievals derived from these instruments has been undertaken. The SO2 retrieval is carried out by using both the 7.3 and 8.7 micron absorption features while ash retrieval exploits the 10–12 micron atmospheric window. A radiative transfer scheme is also used to correct the volcanic ash effect on the 8.7 micron SO2 signature. As test cases, three near‐contemporary images for each sensor, collected during the first days of the eruption, have been analyzed. The results show that the volcanic SO2 and ash are simultaneously present and generally collocated. The MODIS and AVHRR total ash mass loadings are in good agreement and estimated to be about 0.5 Tg, while the AIRS retrievals are slightly lower and equal to about 0.3 Tg. The AIRS and MODIS 7.3 micron SO2 mass loadings are also in good agreement and vary between 0.3 and 1.2 Tg, while the MODIS ash corrected 8.7 micron SO2 masses vary between 0.4 and 2.7 Tg. The mass increase with time confirms the continuous SO2 injection in the atmosphere after the main explosive episodes. Moreover the difference between the 7.3 and 8.7 micron retrievals suggests a vertical stratification of the volcanic cloud. The results also confirm the importance of the ash correction; the corrected 8.7 micron SO2 total masses are less than 30–40% of the uncorrected values.
    Description: Published
    Description: D00L21
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 1.10. TTC - Telerilevamento
    Description: JCR Journal
    Description: reserved
    Keywords: Remote sensing ; ash retrieval ; SO2 retrieval ; multispectral satellite instruments ; MODIS ; AVHRR ; AIRS ; hyperspectral satellite instruments ; 01. Atmosphere::01.01. Atmosphere::01.01.07. Volcanic effects ; 01. Atmosphere::01.01. Atmosphere::01.01.08. Instruments and techniques ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
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  • 58
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    Large amplitude variations recorded by an on‐fault seismological station during the L’Aquila earthquakes: Evidence for a complex fault‐induced site effect (2011)
    AGU
    Details
    Publication Date: 2012-02-03
    Description: A station (FAGN) installed on a segment of the fault system that generated the April 2009 L’Aquila earthquakes shows larger ground motions compared to nearby stations. Spectral ratios using 304 earthquakes result in a station amplification significantly varying event by event in the frequency band 1–8 Hz. The resulting pattern of amplitude dependence on causative earthquake location reveals that the strongest (up to a factor of 10) amplifications occur for tightly clustered aftershocks aligned with the fault dip beneath FAGN thus indicating a fault‐guided effect. Fault models are investigated in a grid‐search approach by varying velocity, Q, width and depth of the fault zone. Although the problem solution is not unique and there are strong trade‐offs among the model parameters, constraints from observations yield a deep trapping structure model where the most likely values of velocity reduction, Q and damage zone width are 25%, 20, and 280 m, respectively.
    Description: Published
    Description: L24305
    Description: 3.1. Fisica dei terremoti
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: reserved
    Keywords: L'Aquila earthquake ; fault zone ; trapped waves ; site amplification ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
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  • 59
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    Normal faults and thrusts re-activated by deep fluids: the 6 April 2009 Mw 6.3 L’Aquila earthquake, central Italy. (2010)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: On April 6 2009, a Mw=6.3 earthquake occurred in the central Apennines (Italy) damaging L’Aquila city and the surrounding country. We relocate the October 2008-April 6 2009 foreshocks and about 2000 aftershocks occurred between April 6 and April 30 2009, by applying a double-difference technique and determine the stress field from focal mechanisms. The events concentrate in the upper 15 km of the crust. Three main NW-SE to NNW-SSE striking, 30°-45° and 80°-90° dipping faults activate during the seismic sequence. Among these, a normal fault and a thrust were re-activated with dip-slip movements in response to NE-SW extension. The structural maturity of the seismogenic fault system is lower than that displayed by other systems in southern Apennines, because of the lower strain rate of the central sector of the chain with respect to the southern one. VP/VS increases progressively from October 2008 to the April 6 2009 mainshock occurrence along a NW-SE strike due to an increment in pore fluid pressure along the fault planes. Pore pressure diffusion controls the space-time evolution of aftershocks. A hydraulic diffusivity of 80 m2/s and a seismogenic permeability of about 10-12 m2 suggest the involvement of gas-rich (CO2) fluids within a highly fractured medium. Suprahydrostatic, high fluid pressure (about 200 MPa at 10 km of depth) within overpressurized traps, bounded by pre-existing structural and/or lithological discontinuities at the lower-upper crust boundary, are required to activate the April 2009 sequence. Traps are the storage zone of CO2-rich fluids uprising from the underlying, about 20 km deep, metasomatized mantle wedge. These traps easily occur in extensional regimes like in the axial sector of Apennines, but are difficult to form in strike-slip regimes, where sub-vertical faults may cross the entire crust. In the Apennines, fluids may activate faults responsible for earthquakes up to Mw=5-6. Deep fluids more than tectonic stress may control the seismotectogenesis of accretionary wedges.
    Description: Published
    Description: B06315
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: open
    Keywords: L'Aquila 2009 earthquake ; fault kinematics and reactivation ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous
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  • 60
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    Seismic tremor in subduction zones: the rock-physics evidence (2010)
    AGU
    Details
    Publication Date: 2017-04-03
    Description: Episodic tremor and slip (ETS) have been correlated with rupture phenomena in subducting oceanic lithosphere at 30–45 km depth, where high VP/VS ratios, which suggest high-fluid pressures, have been observed. ETS, by accommodating slip in the down-dip portion of the subduction zone, may trigger megathrust earthquakes up-dip in the locked section. During dehydration experiments on serpentinite (typical rock of the oceanic lithosphere) at temperatures found in nature at 30–45 km depth (400– 550 C), we observe seismic signals in the form of acoustic emissions that closely resemble low frequency earthquakes, seismic tremor and regular earthquakes. Our findings support the concept that water released during dehydration reactions increases the pore pressures and can trigger ETS and regular earthquakes by reducing slip resistance. Citation: Burlini, L., G. Di Toro, and P. Meredith (2009), Seismic tremor in subduction zones: Rock physics evidence, Geophys. Res. Lett., 36, L08305, doi:10.1029/2009GL037735.
    Description: Published
    Description: L08305
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: Non volcanic tremor ; dehydration reactions ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous
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  • 61
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    Rough Faults, Distributed Weakening, and Off-Fault Deformation (2010)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: We report systematic spatial variations of fault rocks along non-planar strike-slip faults 11 cross-cutting the Lake Edison Granodiorite, Sierra Nevada, California (Sierran wavy fault) and 12 Lobbia outcrops of the Adamello Batholith in the Italian Alps (Lobbia wavy fault). In the case of 13 the Sierran fault, pseudotachylyte formed at contractional fault bends, where it is found as thin 14 (1-2 mm) fault-parallel veins. Epidote and chlorite developed in the same seismic context as the 15 pseudotachylyte and are especially abundant in extensional fault bends. We argue that the 16 presence of fluids, as illustrated by this example, does not necessarily preclude the development 17 of frictional melt. In the case of the Lobbia fault, pseudotachylyte thickness varies along the 18 length of the fault, but the pseudotachylyte veins thicken and pool in extensional bends. We 19 conduct a quantitative analysis of fault roughness, microcrack distribution, stress, and friction 20 along the Lobbia fault. 21 Numerical modeling results show that opening in extensional bends and localized thermal 22 weakening in contractional bends counteract resistance encountered by fault waviness, resulting 23 in an overall weaker fault than suggested by the corresponding static friction coefficient. The 24 models also predict static stress redistribution around bends in the faults which are consistent 25 with distributions of microcracks, indicating significant elastic and inelastic strain energy is 26 dissipated into the wall rocks due to non-planar fault geometry. Together these observations suggest that damage and energy dissipation occurs along the entire non-planar fault during slip, 28 rather than being confined to the region close to the dynamically propagating crack tip.
    Description: Published
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: open
    Keywords: earthquakes ; rutpure ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous
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    Tsunami early warning using earthquake rupture duration (2010)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: Effective tsunami early warning for coastlines near a tsunamigenic earthquake requires notification within 5-15 minutes. We have shown recently that tsunamigenic earthquakes have an apparent rupture duration, T0, greater than about 50 s. Here we show that T0 gives more information on tsunami importance than moment magnitude, Mw, and we introduce a procedure using seismograms recorded near an earthquake to rapidly determine if T0 is likely to exceed T=50 or 100 s. We show that this “duration-exceedance” procedure can be completed within 3-10 min after the earthquake occurs, depending on station density, and that it correctly identifies most recent earthquakes which produced large or devastating tsunamis. This identification forms a complement to initial estimates of the location, depth and magnitude of an earthquake to improve the reliability of tsunami early warning, and, in some cases, may make possible such warning.
    Description: DPC-S3 2007-2009
    Description: Published
    Description: L09306
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: JCR Journal
    Description: open
    Keywords: tsunami ; fault rupture ; early warning ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous
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  • 63
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    A total volatile inventory for Masaya Volcano, Nicaragua (2010)
    AGU
    Details
    Publication Date: 2012-02-03
    Description: We present results from a campaign in March 2009 to assess the current state of emissions from Masaya Volcano, Nicaragua. These results constitute one of the most comprehensive inventories to date of emissions from an active volcano and update the exceptional record of emissions from Masaya. Results from open‐path Fourier transform infrared spectroscopy and filter packs demonstrate that, in terms of H2O, SO2,CO2, HCl,and HF (molar H2O/SO2 = 63, CO2/SO2 = 2.7, SO2/HCl = 1.7, SO2/HF = 8.8), the 2009 gas composition was highly comparable to that from the 1998 to 2000 period,indicating stability of the shallow magma system. This continuity extends to certain aerosol species (molar SO2/SO42−= 190, Na+ /SO4 2−= 0.68, K+/SO4 2−= 0.71, Ca 2+/SO4 2−= 1.6 × 10−2,Mg2+/SO4 2− = 3.6 × 10−3) and, to a lesser extent, the heavy halogens (i.e., molar HCl/HBr = 2.4 × 103 , HCl/HI = 5.0 × 104). In contrast to an arlier study at Masaya, we did not detect HNO3.SO2 fluxes were low (690 Mg d−1 ), suggesting that Masaya was close to the minimum of its degassing cycle. By combining compositional results with the SO2 flux, we estimate a total volatile flux of 14,000 Mg d−1. This rate is consistent with 1−4 wt% volatile loss from a convective magma flux of 17,000–4000 kg s−1. These results will allow for a better understanding of degassing processes at Masaya and other basaltic volcanoes
    Description: NERC project “Magma dynamics at persistently degassing basaltic volcanoes: A novel approach to linking volcanic gases and magmatic volatiles within a physical model” (NE/F004222/1 and NE/F005342/1).
    Description: Published
    Description: B09215
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: JCR Journal
    Description: reserved
    Keywords: Masaya Volcano ; Degassing regime ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
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  • 64
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    Pulse‐like dynamic earthquake rupture propagation under rate‐, state‐ and temperature‐dependent friction (2010)
    AGU
    Details
    Publication Date: 2012-02-03
    Description: An edited version of this paper was published by AGU. Copyright (2010) American Geophysical Union.
    Description: Healing of faults is an important process in earthquake source physics since it accounts for a rapid restrengthening of the fault traction and for a consequent short slip duration, as indicated by slip inversions of seismic data. In this paper we show that a laboratory‐derived constitutive model, with an explicit dependence on the temperature developed by frictional heat, can provide a suitable explanation for the generation of self‐healing slip pulses. The model requires neither special modifications at low or high speeds nor the introduction of heterogeneities in the material properties, as previously proposed. We also demonstrate through numerical experiments of 3‐D ruptures that the temperature evolution can discriminate between crack‐like and slip pulses mode of propagation. In particular, we find that for a moderate level of strain localization (slipping zone width larger than 20 mm) ruptures behave as classical enlarging cracks.
    Description: Published
    Description: L18307
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: Temperature ; Numerical models ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
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  • 65
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    Ultrashallow seismic imaging of the causative fault of the 1980, M6.9, southern Italy earthquake by pre‐stack depth migration of dense wide‐aperture data (2010)
    AGU
    Details
    Publication Date: 2012-02-03
    Description: An edited version of this paper was published by AGU. Copyright (2010) American Geophysical Union.
    Description: Pre-Stack Depth Migration (PSDM) is an effective tool to improve seismic reflection imaging of laterally heterogeneous media. However, migration performance strongly depends on the accuracy of the velocity model, therefore, PSDM is often ineffective for ultrashallow imaging (100 m and less) of complex structures. In this study, we applied non-linear multiscale refraction tomography and PSDM on dense wide-aperture data to image the causative fault of the 1980, M6.9, Irpinia normal faulting earthquake in a very complex geologic environment. Dense wide-aperture profiling allowed us to build accurate velocity models by multi-scale non linear refraction tomography and to record wide-angle reflections from steep reflectors. PSDM provided superior imaging with respect to conventional post-stack depth migration, and a better definition of fault geometry and apparent cumulative displacement. The estimated throw of Irpinia fault is only 29-38 m. This value, combined with the vertical slip rate estimated by nearby trenches, suggests a young age (97-127 kyr) of fault inception. Our outcomes are in agreement with paleoseismic data and indicate that this imaging strategy can be very effective for near-surface fault detection and characterization.
    Description: Grant L.R. n. 5/2002 - Annuity 2003 - to Pier Paolo Bruno
    Description: Published
    Description: L19302
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: reserved
    Keywords: pre-stack migration, seismic reflection, seismic tomography, irpinia fault ; 04. Solid Earth::04.02. Exploration geophysics::04.02.99. General or miscellaneous
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  • 66
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    Challenges of modeling depth-integrated marine primary productivity over multiple decades: A case study at BATS and HOT (2011)
    AGU
    Details
    Publication Date: 2012-02-03
    Description: The performance of 36 models (22 ocean color models and 14 biogeochemical ocean circulation models (BOGCMs)) that estimate depth-integrated marine net primary productivity (NPP) was assessed by comparing their output to in situ 14C data at the Bermuda Atlantic Time series Study (BATS) and the Hawaii Ocean Time series (HOT) over nearly two decades. Specifically, skill was assessed based on the models' ability to estimate the observed mean, variability, and trends of NPP. At both sites, more than 90% of the models underestimated mean NPP, with the average bias of the BOGCMs being nearly twice that of the ocean color models. However, the difference in overall skill between the best BOGCM and the best ocean color model at each site was not significant. Between 1989 and 2007, in situ NPP at BATS and HOT increased by an average of nearly 2% per year and was positively correlated to the North Pacific Gyre Oscillation index. The majority of ocean color models produced in situ NPP trends that were closer to the observed trends when chlorophyll-a was derived from high-performance liquid chromatography (HPLC), rather than fluorometric or SeaWiFS data. However, this was a function of time such that average trend magnitude was more accurately estimated over longer time periods. Among BOGCMs, only two individual models successfully produced an increasing NPP trend (one model at each site). We caution against the use of models to assess multiannual changes in NPP over short time periods. Ocean color model estimates of NPP trends could improve if more high quality HPLC chlorophyll-a time series were available
    Description: Published
    Description: GB3020
    Description: 3.7. Dinamica del clima e dell'oceano
    Description: JCR Journal
    Description: restricted
    Keywords: marine primary productivity models ; BATS HOT trends ; multidecadal climate forcing ; 03. Hydrosphere::03.01. General::03.01.01. Analytical and numerical modeling ; 03. Hydrosphere::03.01. General::03.01.07. Physical and biogeochemical interactions ; 03. Hydrosphere::03.04. Chemical and biological::03.04.01. Biogeochemical cycles ; 03. Hydrosphere::03.04. Chemical and biological::03.04.04. Ecosystems
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  • 67
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    The influence of tectonic regimes on the earthquake size distribution: A case study for Italy (2010)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: An edited version of this paper was published by AGU. Copyright (2010) American Geophysical Union
    Description: We explore the hypothesis that the relative size distribution of earthquakes, or b‐value, systematically depends on the style‐of‐faulting of seismotectonic zones. Because the b‐value has been shown to be inversely proportional to stress, we expect to find b(thrust) 〈 b (strike‐slip) 〈 b(normal). We test this expectation for the case of Italy. We first of all build a seismotectonic zonation model, consisting of 10 distinct tectonic zones. The faulting style of each zone is then characterized by the summed moment tensor of first‐motion and full‐waveform based focal mechanism. We calculate the b‐value for each zone: the lowest values are obtained for reverse zones (0.75– 0.81), highest for the normal (1.09), followed by the strikeslips (0.9–0.92). Our results suggest that b‐values, which are a critical parameter in all seismic hazard assessments, should be set according to the local faulting regimes. In addition, seismotectonic zonation models should take b‐value variations as one input.
    Description: Published
    Description: L10305
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: b-value ; stress regime ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
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  • 68
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    Geochemical Evidence of Melt Intrusions Along Lithospheric Faults of the Southern Apennines (Italy): Geodynamic and Seismogenic Implications (2010)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: Several gas emissions, distributed along 200 km of the Southern Apennine axial zone, have been investigated. This portion of the sedimentary chain, which constitutes the accretionary prism of the westward subduction of the Adriatic plate, is subjected to a tensile stress field responsible of high-magnitude earthquakes. The studied emissions are generally CO2-dominated, have 3He/4He ratios in the range of 0.09-2.84 Ra, and display both 3He and 4He outputs in the range of those reported for the Italian active volcanoes Phlegrean Fields and Vulcano. The helium isotope ratios, together with the amount of released gas, indicate that a huge amount of mantle-derived helium is released over all the investigated area. Our geochemical data and the geophysical peculiarities of the region, such as the high heat flow and the low resistivity of rocks below a depth of 15 km, coherently indicate the presence of melt intruded into the crust along lithospheric faults. Magma intrusions along the axial part of the Southern Apennine sedimentary chain are certainly unusual, since volcanism in Central and Southern Italy is concentrated along the perityrrhenian margin of the peninsula. We suggest that melt is promoted by adiabatic uprise of the asthenosphere in the mantle wedge beneath the Apennines and it is subsequently intruded along tensile lithospheric faults, strongly affecting the thermal state of the lower crust. An inter-relation between the geodynamics, the melt intrusions and the genesis of the large earthquakes (up to M = 7.1) in the region is suggested.
    Description: Published
    Description: 13569-13578
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: reserved
    Keywords: melt intrusions ; gas geochemistry ; tectonic structures ; seismicity ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
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  • 69
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    CO2 degassing system of Stromboli volcano inferred by summit, peripheral and hydrothermal continuous measurements. (2010)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: Stromboli is an open conduct volcano characterized by “Strombolian” activity. This activity is the result of a “delicate” dynamic equilibrium between continuous refilling of deep volatiles exsolved from the magma batch and superficial degassing. The volatiles, reaching the surface, interact with superficial fluids modifying peripheral and summit degassing processes. In particular, the main peripheral manifestations are represented by dissolved volatiles in the basal hydrothermal aquifer, as well as structurally controlled soil degassing at the lower parts of the volcanic edifice. Summit degassing is manifested by active (explosions from the conduct) and passive degassing (plume degassing from the conduct and diffuse soil degassing). During “normal” Strombolian activity this dynamic equilibrium allows the discharge of the volatiles in the atmosphere arriving from the depth. When the deep volatile flux increases, we observe that the system reacts by first increasing the diffuse volatile discharge from the superficial system. In fact, the result is the increase of Strombolian activity (frequency and energy of explosions due to the increase of the total volatiles pressure) and the increase of the total dissolved volatiles in the hydrothermal aquifer and soils anomalous flux. During overpressure of the plumbing system paroxistic activity is necessary to maintain the dynamic pressure equilibrium, allows to maintain the dynamic equilibrium between deep and superficial volatiles. In fact, through the opening of new fractures and consecutive lava flow or by major explosions and paroxysms the system decreases the total pressure of volatiles and restores the dynamic equilibrium of the Stromboli plumbing system. On the basis of the experiences acquired during the last two eruptions (2002-2003 and 2007) we improved our geochemical monitoring network by installing new equipments for monitoring, continuously, selected fluid manifestations located on the peripheral areas. In particular, we installed two automatic equipments for measuring dissolved CO2 in the thermal wells located in the N-E side of Stromboli (Stromboli village). In this way we covered wider area of fluid degassing of Stromboli volcano to better understand the relationships between the degassing regimes of the summit and basal hydrothermal systems.
    Description: Published
    Description: San Francisco CA, USA
    Description: 2.4. TTC - Laboratori di geochimica dei fluidi
    Description: open
    Keywords: CO2 flux ; Volcano monitoring ; Stromboli ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.02. Experimental volcanism ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
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  • 70
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    Source Complexity of the 6 April 2009 L'Aquila (Central Italy) Earthquake and Its Strongest Aftershock Revealed by Elementary Seismological Analysis (2010)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: Seismic recordings are immediately available when an earthquake occurs. Their analysis allows the reconstruction of the rupture dynamics by means of sophisticated techniques, which usually need some tests to provide robust results. However, immediate information on the source kinematics is required in order to imagine the fault location and extent and quickly reconstruct the areas of stress release and subsequent accumulation. Very simple analysis may provide useful information, giving insight in source complexity. Right after the 6 April 2009 L'Aquila earthquake (MW = 6.3), we analyzed the seismograms recorded at broadband and strong motion stations and provided firm constraints on rupture kinematics, slip distribution, and static surface deformation, also discriminating the actual fault plane. The fracture occurred in two stages, with initial updip propagation, successively proceeding toward SE, possibly on a different plane. We also analyzed the strongest aftershock (MW = 5.6), showing that useful indications could be retrieved for lower magnitude events.
    Description: Published
    Description: L23305
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: JCR Journal
    Description: open
    Keywords: L'Aquila 2009 earthquake ; directivity ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous
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    A model for wet aggregation of ash particles in volcanic plumes and clouds: 2. Model application (2011)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: The occurrence of particle aggregation has a dramatic effect on the transport and sedimentation of volcanic ash. The aggregation process is complex and can occur under different conditions and in multiple regions of the plume and in the ash cloud. In the companion paper, Costa et al. develop an aggregation model based on a fractal relationship to describe the rate particles are incorporated into ash aggregates. The model includes the effects of both magmatic and atmospheric water present in the volcanic cloud and demonstrates that the rate of aggregation depends on the characteristics of the initial particle size distribution. The aggregation model includes two parameters, the fractal exponent Df, which describes the efficiency of the aggregation process, and the aggregate settling velocity correction factor ye, which influences the distance at which distal mass deposition maxima form. Both parameters are adjusted using features of the observed deposits. Here this aggregation model is implemented in the FALL3D volcanic ash transport model and applied to the 18 May 1980 Mount St. Helens and the 17–18 September 1992 Crater Peak eruptions. For both eruptions, the optimized values for Df (2.96–3.00) and ye (0.27–0.33) indicate that the ash aggregates had a bulk density of 700–800 kg m−3. The model provides a higher degree of agreement than previous fully empirical aggregation models and successfully reproduces the depositional characteristics of the deposits investigated over a large range of scales, including the position and thickness of the secondary maxima.
    Description: Published
    Description: B09202
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: JCR Journal
    Description: restricted
    Keywords: volcanic ash ; particle aggregation ; 01. Atmosphere::01.01. Atmosphere::01.01.04. Processes and Dynamics ; 01. Atmosphere::01.01. Atmosphere::01.01.07. Volcanic effects ; 05. General::05.01. Computational geophysics::05.01.99. General or miscellaneous
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  • 72
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    Dynamic seismic ruptures on melting fault zones (2011)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: We present a physical model that describes the behavior of spontaneous earthquake ruptures dynamically propagating on a fault zone and that accounts for the presence of frictional melt produced by the sliding surfaces. First, we analytically derive the solution for the temperature evolution inside the melt layer, which generalizes previous approximations. Then we incorporate such a solution into a numerical code for the solution of the elastodynamic problem. When a melt layer is formed, the linear slip‐weakening law (initially governing the fault and relying on the Coulomb friction) is no longer valid. Therefore we introduce on the fault a linearly viscous rheology, with a temperature‐dependent dynamic viscosity. We explore through numerical simulations the resulting behavior of the traction evolution in the cohesive zone before and after the transition from Coulomb friction and viscous rheology. The predictions of our model are in general agreement with the data from exhumed faults.We also find that the fault, after undergoing the breakdown stress drop controlled by the slip‐weakening constitutive equation, experiences a second traction drop controlled by the exponential weakening of fault resistance due to the viscous rheology. This further drop enhances the instability of the fault, increasing the rupture speeds, the peaks in fault slip velocity, and the fracture energy density.
    Description: Published
    Description: B02310
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: Melting ; theoretical seismology ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
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  • 73
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    On the deterministic description of earthquakes (2011)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: The quantitative estimate of earthquake damage due to ground shaking is of pivotal importance in geosciences, and its knowledge should hopefully lead to the formulation of improved strategies for seismic hazard assessment. Numericalmodels of the processes occurring during seismogenic faulting represent a powerful tool to explore realistic scenarios that are often far from being fully reproduced in laboratory experiments because of intrinsic, technical limitations. In this paper we discuss the prominent role of the fault governing model, which describes the behavior of the fault traction during a dynamic slip failure and accounts for the different, and potentially competing, chemical and physical dissipative mechanisms. We show in a comprehensive sketch the large number of constitutive models adopted in dynamic modeling of seismic events, and we emphasize their prominent features, limitations, and specific advantages. In a quantitative comparison, we show through numerical simulations that spontaneous dynamic ruptures obeying the idealized, linear slip‐weakening (SW) equation and a more elaborated rate‐ and state‐dependent friction law produce very similar results (in terms of rupture times, peaks slip velocity, developed slip, and stress drops), provided that the frictional parameters are adequately comparable and, more importantly, that the fracture energy density is the same. Our numerical experiments also illustrate that the different models predict fault slip velocity time histories characterized by a similar frequency content; a feeble predominance of high frequencies in the SW case emerges in the frequency ranges [0.3, 1] and [11, 50] Hz. These simulations clearly indicate that, even forgiving the frequency band limitation, it would be very difficult (virtually impossible) to discriminate between two different, but energetically identical, constitutive models, on the basis of the seismograms recorded after a natural earthquake.
    Description: Published
    Description: RG3002
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: Earthquake mechanics ; constitutive equations ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution
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  • 74
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    Assimilation of autoscaled data and regional and local ionospheric models as input source for a real-time 3-D IRI modeling (2011)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: This paper describes how the joint utilization of autoscaled data such as the F2 peak critical frequency foF2, the propagation factor M(3000)F2 and the electron density profile, coming from two reference ionospheric stations (Rome and Gibilmanna), the regional (SIRMUP) and global (IRI) ionospheric models, can provide a valid tool for obtaining a real-time three-dimensional (3-D) electron density mapping of the ionosphere. Preliminary results of the proposed 3-D model are shown by comparing the electron density profiles given by the model with the ones measured at three testing ionospheric stations (Athens, Roquetes and S.Vito).
    Description: Published
    Description: RS5009
    Description: 1.7. Osservazioni di alta e media atmosfera
    Description: 3.9. Fisica della magnetosfera, ionosfera e meteorologia spaziale
    Description: JCR Journal
    Description: open
    Keywords: IRI ; modeling ; ionogram ; electron density ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous ; 01. Atmosphere::01.02. Ionosphere::01.02.03. Forecasts ; 01. Atmosphere::01.02. Ionosphere::01.02.06. Instruments and techniques
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    The emergence of ocean biogeochemical provinces: a quantitative assessment and a diagnostic for model evaluation. (2012)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: The concept of ocean biogeochemical provinces is based on the observation that large ocean regions are characterized by coherent physical forcing and environmental conditions, which are eventually representative of macroscale ocean ecosystems. Biogeochemical models of the global ocean focus on simulating the coupling between prevalent physical conditions and the biogeochemical processes with the assumption that biological properties respond coherently to physics and therefore should produce such provinces as an emergent property. In this paper, we quantitatively assess the emergence of a reference set of predefined biogeochemical provinces in the available global data sets and propose a province‐based approach to the evaluation of one of the most comprehensive models of ocean biogeochemistry. Multivariate statistical tools were applied to model and observation data, verifying the existence, distinctiveness and reliability of the predefined provinces and quantifying the correlation of model results with observations at the global scale. The analysis of similarity between provinces shows that they are statistically separable in data and model output and therefore can be used as reliable metrics. The analyses indicate that provinces can be more easily distinguished in terms of their environmental features rather than using chlorophyll concentration. The characterization of provinces by means of chlorophyll values shows a significant overlap in both the Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS) data and the model. It is likely this is related to the choice of province boundaries based on coarse‐resolution mapped data, which are not necessarily the same as those derivable from high‐resolution satellite data. We also demonstrated through cluster analysis that the long‐term time series data collected at Joint Global Ocean Flux Study (JGOFS) stations are representative of environmental conditions of the respective province and can thus be used to evaluate model results extracted from that province. The method shows promise for helping to overcome problems with model verification due to under sampling of most ocean biogeochemical variables but also gives indications that unsupervised clustering may be required when more spatially resolved data and models are available.
    Description: Published
    Description: GB2005
    Description: 3.7. Dinamica del clima e dell'oceano
    Description: JCR Journal
    Description: restricted
    Keywords: PELAGOS ; ocean modelling ; 03. Hydrosphere::03.04. Chemical and biological::03.04.99. General or miscellaneous ; 03. Hydrosphere::03.04. Chemical and biological::03.04.01. Biogeochemical cycles ; 03. Hydrosphere::03.04. Chemical and biological::03.04.02. Carbon cycling ; 03. Hydrosphere::03.04. Chemical and biological::03.04.03. Chemistry of waters ; 03. Hydrosphere::03.04. Chemical and biological::03.04.04. Ecosystems
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    Modeling of the hydro-acoustic signal and tsunami wave generated by sea floor motion including a porous seabed (2010)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: Within the framework of a 2-D compressible tsunami generation model with a flat porous seabed, acoustic waves are generated and travel outwards from the source area. The effects of the porous seabed during tsunami generation and propagation processes include wave amplitude attenuation and low pass filtering of both the hydro-acoustic signal and tsunami wave. The period of the acoustic wave generated by the seafloor motion depends on water depth over the source area and is given by four times the period of time required for sound to travel from the sea bed to the surface: these waves carry information about seafloor motion. The semi-analytical solution of the 2-D compressible water layer model overlying a porous seabed is presented and discussed. Furthermore, to include the effects generated by the coupling between compressible porous sedimentary and water layers, a simplified two layer model with the sediment modelled as a compressible viscous fluid is presented.
    Description: Published
    Description: C03015
    Description: 1.8. Osservazioni di geofisica ambientale
    Description: JCR Journal
    Description: restricted
    Keywords: tsunami generation ; seafloor motion ; fluidodynamics ; 05. General::05.05. Mathematical geophysics::05.05.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 77
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    High‐resolution seismic imaging of the Mw5.7, 2002 Molise, southern Italy, earthquake area: Evidence of deep fault reactivation (2010)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: An edited version of this paper was published by AGU. Copyright (2010) American Geophysical Union.
    Description: We investigate the seismic structure of the Mw5.7, 2002 Molise earthquake area in order to understand the role of E–W trending strike‐slip faults in the tectonics of the southern Apennines. We apply an innovative seismic migration technique to a high quality data set of earthquakes recorded at a dense local network. SP‐converted waves are migrated in depth to image the high impedance contrast of the Apulian Platform top buried under the Apennines allochthonous cover. The continuity of the migrated seismic horizon is broken by vertical steps that we systematically picked along 200 cross sections. The best location points of these structures define two main tectonic features. The first one is related to NW–SE oriented normal faults and is consistent with the SW flexure of the foreland lithosphere beneath the orogenic belt. The second one indicates that shallow E–Woriented trans‐tensional faults are concentrated directly above the deeper (10– 20 km) strike‐slip fault, delineating the geometry of a negative flower‐type structure. This fault system delimits a depressed sector of the Apulian Platform, whose geometry is consistent with a pull‐apart basin inherited from a previous left‐lateral strike‐slip tectonic regime. The buried structure is analogous to those outcropping in the Apulian foreland and in the Adriatic offshore, to the east. This correlation brings new support to the hypothesis of a regional E–W trending shear zone cutting the Adria plate and suggests that other earthquakes could occur on this or on parallel E–W trending strike‐slip faults.
    Description: Project MIUR “Airplane” (contract RBPR05B2ZJ, UR 3)
    Description: Published
    Description: TC4014
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: reserved
    Keywords: seismic imaging ; Molise earthquake ; strike-slip faults ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
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  • 78
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    The 2007 Stromboli eruption: Event chronology and effusion rates using thermal infrared data (2010)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: Using thermal infrared images recorded by a permanent thermal camera network maintained on Stromboli volcano (Italy), together with satellite and helicopter‐based thermal image surveys, we have compiled a chronology of the events and processes occurring before and during Stromboli’s 2007 effusive eruption. These digital data also allow us to calculate the effusion rates and lava volumes erupted during the effusive episode. At the onset of the 2007 eruption, two parallel eruptive fissures developed within the northeast crater, eventually breaching the NE flank of the summit cone and extending along the easternmargin of the Sciara del Fuoco. These fed amain effusive vent at 400m above sea level to feed lava flows that extended to the sea. The effusive eruption was punctuated,on 15 March, by a paroxysm with features similar to those of the 5 April paroxysm that occurred during the 2002–2003 effusive eruption. A total of between 3.2 × 106 and 11 × 106 m3 of lava was erupted during the 2007 eruption, over 34 days of effusive activity. More than half of this volume was emplaced during the first 5.5 days of the eruption. Although the 2007 effusive eruption had an erupted volume comparable to that of the previous (2002–2003) effusive eruption, it had a shorter duration and thus a mean output rate (=total volume divided by eruption duration) that was 1 order of magnitude higher than that of the 2002– 2003 event (∼2.4 versus 0.32 ± 0.28 m3 s−1). In this paper, we discuss similarities and differences between these two effusive events and interpret the processes occurring in 2007 in terms of the recent dynamics witnessed at Stromboli.
    Description: Published
    Description: B04201
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: JCR Journal
    Description: restricted
    Keywords: Thermal mapping ; Stromboli ; 01. Atmosphere::01.01. Atmosphere::01.01.04. Processes and Dynamics
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  • 79
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    Active hydrothermal discharge on the submarine Aeolian Arc (2011)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: In November 2007 we conducted a water column and seafloor mapping study of the submarine volcanoes of the Aeolian Arc in the southern Tyrrhenian Sea aboard the R/V Urania. On 26 conductivity‐temperature‐depth casts and tows we measured temperature, conductivity, pressure, and light scattering and also collected discrete samples for helium isotopes, methane, and pH. The 3He/4He isotope ratio, an unambiguous indicator of hydrothermal input, showed a clear excess above background at 6 of the 10 submarine volcanoes surveyed. Marsili seamount had the highest anomaly, where the 3He/4He ratio reached a d3He value of 23% at 610 m depth compared with background values of ∼5%. Smaller but distinct d3He anomalies occurred over Palinuro, Enarete, Eolo, Sisifo, and Secca del Capo. Although hydrothermal emissions are known to occur offshore of some Aeolian subaerial volcanoes, and hydrothermal deposits have been sampled throughout the arc, our results are the first to confirm active discharge on Marsili, Enarete, Eolo, Sisifo, and Secca del Capo. Samples collected over Lametini, Filicudi North, Alicudi North, and Alcione had d3He near the regional background values, suggesting either absence of, or very weak, hydrothermal activity on these seamounts. Hydrocasts between the volcanoes revealed a consistent d3He maximum between 11% and 13% at 2000mdepth throughout the SE Tyrrhenian Sea. The volcanoes of the Aeolian arc and the Marsili back arc, all 〈1000 m deep, cannot contribute directly to this maximum. This deep 3He excess may be a remnant of tritium decay or may have been produced by an unknown deep hydrothermal source.
    Description: Published
    Description: B02102
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: hydrothermal systems ; helium ; Tyrrhenian sea ; seamounts ; 03. Hydrosphere::03.04. Chemical and biological::03.04.06. Hydrothermal systems
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  • 80
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    Hydrogen in the gas plume of an open‐vent volcano, Mount Etna, Italy (2011)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: We report here on the first hydrogen determinations in the volcanic gas plume of Mount Etna, in Italy, which we obtained during periodic field surveys on the volcano’s summit area with an upgraded MultiGAS. Using a specific (EZT3HYT) electrochemical sensor, we resolved H2 concentrations in the plume of 1–3 ppm above ambient (background) atmosphere and derived H2‐SO2 and H2‐H2O plume molar ratios of 0.002–0.044 (mean 0.013) and 0.0001–0.0042 (mean 0.0018), respectively. Taking the above H2‐SO2 ratios in combination with a time‐averaged SO2 flux of 1600 Gg yr−1, we evaluate that Etna contributes a time‐averaged H2 flux of ∼0.65 Gg yr−1, suggesting that the volcanogenic contribution to the global atmospheric H2 budget (70,000–100,000 Gg yr−1) is marginal. We also use our observed H2‐H2O ratios to propose that Etna’s passive plume composition is (at least partially) representative of a quenched (temperatures between 750°C and 950°C) equilibrium in the gas‐magma system, at redox conditions close to the nickel‐nickel oxide (NNO) mineral buffer. The positive dependence between H2‐SO2, H2‐H2O, and CO2‐SO2 ratios suggests that H2 is likely supplied (at least in part) by deeply rising CO2‐rich gas bubbles, fluxing through a CO2‐depleted shallow conduit magma.
    Description: Published
    Description: B10204
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: 2.4. TTC - Laboratori di geochimica dei fluidi
    Description: JCR Journal
    Description: restricted
    Keywords: Hydrogen ; Mount Etna ; Open-vent volcano ; plume ; 01. Atmosphere::01.01. Atmosphere::01.01.07. Volcanic effects ; 04. Solid Earth::04.02. Exploration geophysics::04.02.01. Geochemical exploration ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
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  • 81
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    Source radiation invariant property of local and near!regional shear wave coda: Application to source scaling for the Mw 5.9 Wells, Nevada sequence (2011)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: This study documents another unique property of local and regional shear!wave coda: that scattering in the Earth’s crust averages out source heterogeneities such as focal mechanism and directivity. We consider two recent events which exhibited significant source directivity. The first, an Mw 4.2 Oakland hills, California strike!slip event on July 20, 2007, resulted in uncharacteristically large amounts of damage in the Montclair and south Berkeley neighborhoods, along strike and north!west of the hypocenter, but almost no damage to the south!east. The second event, the Mw 5.9 Wells, Nevada dip!slip event of February 21, 2008, was well!recorded by the Earthscope Transportable Array (USArray) and determined to exhibit south!west directivity. We conclude with an example of corner!frequency ( fc) estimates from the Wells sequence, which showcase the coda’s low variance, and find that scaling is non!self!similar, suggesting a change in dynamics between the mainshock and aftershocks.
    Description: Published
    Description: L07306
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: JCR Journal
    Description: reserved
    Keywords: Source Scaling ; Radiated Energy ; 04. Solid Earth::04.04. Geology::04.04.06. Rheology, friction, and structure of fault zones
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  • 82
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    Leachate analyses of volcanic ashes from Stromboli volcano: A proxy for the volcanic gas plume composition? (2011)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: Many volcanoes show a change in chemical composition of the gas phase prior to periods of eruptive activity. Fine‐grained tephra erupted from active vents and transported through volcanic plumes can adsorb, and therefore rapidly scavenge, volatile elements such as sulfur, halogens, and metal species in the form of soluble salts adhering to ash surfaces. Analysis of such water‐soluble surface materials is a suitable supplement for remote monitoring of volcanic gases at inaccessible volcanoes. In this work, ash samples of the 2004 to 2009 eruptive activity of Stromboli volcano were sampled, leached, and analyzed for major and trace elements. Data analysis and interpretation was focused on determining the relationship between chemical composition of water‐soluble components adhering to volcanic ash and the volcano’s activity state. First results show significant temporal variations in ash leachate compositions, reflecting changes in the eruptive style of the volcano. In particular, we reveal that ash leachates S/F and Mg/Na ratios showed marked increases prior to a large‐scale explosion on 15 March 2007.
    Description: Published
    Description: D17204
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: Leachate analyses of volcanic ashes ; 01. Atmosphere::01.01. Atmosphere::01.01.07. Volcanic effects
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  • 83
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    Twelve Years of Ground Deformation Studies on Mt. Etna Volcano Based on GPS Surveys (2012)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: GPS (Global Positioning System) monitoring has been performed on Etna volcano since 1988, making this volcano one of those with the longest records of GPS data. The first order network, measured at least once every year in accurate static mode, was progressively augmented from 9 benchmarks in 1988 to ~70 benchmarks. The whole network is subdivided into seven sub-networks that are surveyed in static, quick-static or kinematic mode, according to the accuracy and density needed, with respect to the volcanic activity. This network provides key constraints to locate the deformation sources inside the volcano (reservoirs, dykes, faults) and track their evolution. Etna has proved an optimum testing ground of new surveying approaches in order to optimize geodetic fieldwork. Several methodological developments related to kinematic surveys and to the correction of tropospheric delays were made on Etna. Here, we discuss the overall picture of the entire data set up to 1999. The results show large scale displacements related to the activity of the volcano during the last twelve years. They are used to infer the location of magma reservoirs acting in this period, identifying a pressure zone beneath the western flank at a depth ranging from 2 to 9 km, several shallow intrusion following the regional NNW-SSE trend, and to quantify the eastward movement of the eastern flank of Mt. Etna, modeling two detachment surfaces beneath the eastern and southern flanks. At a local scale (e.g. in the summit areas and across the Pernicana fault), displacements are also identified and discussed.
    Description: Published
    Description: 321-341
    Description: 1.3. TTC - Sorveglianza geodetica delle aree vulcaniche attive
    Description: reserved
    Keywords: Ground deformation ; Geodesy ; Monitoring ; Geodetic networks ; Geodetic surveys ; GPS ; 04. Solid Earth::04.03. Geodesy::04.03.06. Measurements and monitoring ; 04. Solid Earth::04.03. Geodesy::04.03.07. Satellite geodesy ; 04. Solid Earth::04.03. Geodesy::04.03.09. Instruments and techniques ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 84
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    The 2010 Chile Earthquake: Rapid Assessments of Tsunami (2010)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: After an earthquake underwater, rapid real-time assessment of earthquake parameters is important for emergency response related to infrastructure damage and, perhaps more exigently, for issuing warnings of the possibility of an impending tsunami. Since 2005, the Istituto Nazionale di Geofisica e Vulcanologia (INGV) has worked on the rapid quantification of earthquake magnitude and tsunami potential, especially for the Mediterranean area. This work includes quantification of earthquake size from standard moment tensor inversion, quantification of earthquake size and tsunamigenic potential using P waveforms, and calculation of an archive of readily accessible tsunami scenarios.
    Description: Institutional fundings and INGV-DPC Convenzione 2007-2009 (S3 Project)
    Description: Published
    Description: 305-306
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: N/A or not JCR
    Description: open
    Keywords: tsunami potential ; magnitude ; real-time monitoring ; 04. Solid Earth::04.03. Geodesy::04.03.08. Theory and Models
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  • 85
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    Determining rheology from deformation data: The case of central Italy (2011)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: Accepted for publication in Tectonics. Copyright (2010) American Geophysical Union
    Description: The study of geodynamics relies on an understanding of the strength of the lithosphere. However, our knowledge of kilometer-scale rheology has generally been obtained from centimeter-sized laboratory samples or from microstructural studies of naturally deformed rocks. In this study, we present a method that allows rheological examination at a larger scale. Utilizing forward numerical modeling, we simulated lithospheric deformation as a function of heat flow and rheological parameters and computed several testable predictions including horizontal velocities, stress directions, and the tectonic regime. To select the best solutions, we compared the model predictions with experimental data. We applied this method in Italy and found that the rheology shows significant variations at small distances. The strength ranged from 0.60.2 TN/m within the Apennines belt to 216 TN/m in the external Adriatic thrust. These strength values correspond to an aseismic mantle in the upper plate and to a strong mantle within the Adriatic lithosphere, respectively. With respect to the internal thrust, we found that strike-slip or transpressive, but not compressive, earthquakes can occur along the deeper portion of the thrust. The differences in the lithospheric strength are greater than our estimated uncertainties and occur across the Adriatic subduction margin. Using the proposed method, the lithospheric strength can be also determined when information at depth is scarce but sufficient surface data are available.
    Description: DPC-INGV project S1 (2008-2010)
    Description: In press
    Description: 3.1. Fisica dei terremoti
    Description: 3.2. Tettonica attiva
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: 4.2. TTC - Modelli per la stima della pericolosità sismica a scala nazionale
    Description: JCR Journal
    Description: open
    Keywords: Continental neotectonics ; Rheology and friction of fault zones ; Rheology: crust and lithosphere ; Mechanics, theory and modeling ; 04. Solid Earth::04.01. Earth Interior::04.01.02. Geological and geophysical evidences of deep processes ; 04. Solid Earth::04.01. Earth Interior::04.01.05. Rheology ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
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  • 86
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    Long‐term record of CO2 degassing along Mt. Etna’s flanks and its relationship with magma dynamics and eastern flank instability (2012)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: A record of soil CO2 flux data on the lower flanks of Mt. Etna, measured from 1989 to 2008, is discussed in the framework of multidisciplinary observations, including seismicity, ground deformations, and flank instability. A huge increase in soil CO2 fluxes appears to be related to the dynamics of magma ascent in the upper portions of the volcano (0–3 km) and the intrusion of dykes along the southern rift, as mainly observed before the 1991–93 eruption. Even after the 1991–93 eruption, the recharge of the shallow/central reservoir was accompanied by a long‐term increase in soil CO2 degassing mainly in the southwestern area. The 2001 eruption marked dramatic changes in the areal distribution of seismicity, the deformation pattern, and the soil CO2 degassing. Indeed, while the soil CO2 degassing showed background values in the southwestern area, it progressively increased in the eastern sector and along the Pernicana fault. This has been related to the marked sliding of the eastern flank since the 2002–03 eruption and the associated seismicity. This study provides evidence that the extent of soil CO2 degassing on the lower flanks of Mt. Etna is controlled by (1) the volume of involved magma, (2) the intrusion of dykes in the upper parts of the volcano, and (3) fault movement and seismicity. This implies that different degassing structures must be monitored simultaneously when attempting to understand the behavior of the volcano as a whole.
    Description: Published
    Description: Q10002
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: CO2 degassing ; Mt. Etna ; 05. General::05.02. Data dissemination::05.02.01. Geochemical data
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  • 87
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    Statistical analysis of the volcano seismicity during the 2007 crisis (2012)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: We analyze the volcano seismicity recorded during the pre‐ and co‐eruptive regimes of the 2007 effusive crisis at Stromboli volcano (Italy). Data‐set is composed of the continuous recordings of a three‐component broad‐band seismometer and of a Sacks‐ Evertson strainmeter. Starting from the characterization of the non effusive phase as a stationary state of equilibrium, we investigate the effusive phase as a non‐equilibrium state. A statistical analysis reveals that the explosion occurrence is always driven by a nearly Poissonian process, as for the standard activity, even during the effusive phase, with the only difference in shortening the inter‐times. Explosion‐quake amplitudes are lognormally distributed until the effusive phase, becoming then broader. This indicates that many scales are involved. A slightly different process can be advocated for the swarms of the explosions occurring during the effusive phase. This suggests that the dynamics of the exsolution and/or aggregation of the gas slugs should differ from the nucleation mechanism responsible of the standard Strombolian activity. The pre‐eruptive regime is characterized by a very long deformative signal that appears as a transient oscillating signal with a period of about three days that modulates the explosion amplitudes. In a conceptual vibrating cavities model, it is related to a chocking phenomenon induced by magma injection, which in turn leads to the effusion.
    Description: Published
    Description: B09312
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: JCR Journal
    Description: reserved
    Keywords: Volcanic tremor ; Stromboli ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
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  • 88
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    New evidence about the structure and growth of ocean island volcanoes from aeromagnetic data: The case of Tenerife, Canary Islands (2012)
    AGU
    Details
    Publication Date: 2017-04-03
    Description: We present 3-D magnetic models of Tenerife based on a high-resolution aeromagnetic survey carried out in 2006. Two different inverse modeling techniques have been applied: (1) a linear method aimed at imaging lateral magnetization contacts and (2) a nonlinear method aimed at obtaining a 3-D description of deep intrusive bodies, in which a constant magnetization value characterizes the main sources. Magnetic models show that deep intrusive structures are located beneath the northern part of the island and aligned along the E-W direction. This arrangement of intrusive bodies does not support the hypothesis of a three‐armed rift system that has been present since the early formation of the island. The shallow portion of the intrusive structures shows a round geometry that agrees with the previously proposed location of some of the landslide headwalls, suggesting that collapse scars have acted as preferential sites for magma upwelling. Our magnetic model probably provides the first geophysical evidence of the location of the headwall of the Icod landslide beneath the Teide‐Pico Viejo complex, thus supporting the vertical collapse hypothesis for the origin of the Cañadas caldera. The largest intrusive complex is located to the northwest of Teide and Pico Viejo, revealing the presence of a very high dike density in this area. This complex probably resulted from the intrusion of magma over the span of millions of years, beginning with the early phases of basaltic shield volcanism in central Tenerife and lasting until the building of Teide and Pico Viejo stratovolcanoes.
    Description: Published
    Description: B03102
    Description: 3.4. Geomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: aeromagnetic data ; oceanic islands ; inverse modeling ; Tenerife ; Canary Islands ; rift zones ; 04. Solid Earth::04.05. Geomagnetism::04.05.99. General or miscellaneous ; 04. Solid Earth::04.05. Geomagnetism::04.05.04. Magnetic anomalies
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  • 89
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    A statistical study of the Stromboli volcano explosion quakes before and during 2002-2003 eruptive crisis (2012)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: We study the seismic wavefield and the statistical properties of the Stromboli volcano explosions preceding and during the 2002–2003 crisis. We analyze the recordings of a three‐component seismometer operating since 23 May 2002 to 30 January 2003, including the first 34 days of the crisis. Before the crisis, we recognize three bell‐shaped classes of spectra with maxima falling in the range 1–5 Hz. Spectral content has two main changes, the most prominent one occurring at the crisis onset when the frequency peak at ∼0.3 Hz increases in amplitude. Independent component analysis extracts three time‐stable independent oscillations that peaked at 1.1, 1.8, and 2.5 Hz, with radial and shallow polarization indicating a stable source mechanism. Energy of the explosions is lognormally distributed, except during a 2 month time interval before the crisis when it also shows a higher mean value. The interoccurrence time distributions display an homogeneous Poissonian behavior with a mean intertime of 250 s, without changes at the crisis onset. Only swarms of explosions are not ruled by a Poisson process and display higher occurrence rates and higher energies. Finally, we depict a scheme of the crisis. A modification of the equilibrium is induced by rising magma that produces a change in the boundary conditions of the plumbing system. The escape from the equilibrium produces, at first, variations in the usual statistics of the explosions, then it leads to the lava effusion and to a pressure drop in the plumbing system that induces a deep gas slug nucleation and the excitation of low frequencies.
    Description: Published
    Description: B04303
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: reserved
    Keywords: Stromboli volcano, explosion quakes, 2002-2003 eruption ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
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  • 90
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    Static stress drop as determined from geodetic strain rates and statistical seismicity (2011)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: Accepted for publication in Journal of Geophysical Researches. Copyright (2010) American Geophysical Union
    Description: Two critical items in the energetic budget of a seismic province are the strain rate, which is measured geodetically on the Earth’s surface, and the yearly number of earthquakes exceeding a given magnitude. Our study is based on one of the most complete and recent seismic catalogs of Italian earthquakes and on the strain rate map implied by a multi-year velocity solution for permanent GPS stations. For 36 homogeneous seismic zones, we used the appropriate Gutenberg Richter relation based on the seismicity catalog to estimate a seismic strain rate, which is the strain rate associated with the mechanical work due to a co-seismic displacement. The volume storing most of the elastic energy is associated with the long-term deformation of each seismic zone, and therefore, the seismic strain rate is inversely proportional to the static stress drop. The GPS-derived strain rate for each seismic zone limits the corresponding seismic strain rate, and an upper bound for the average stress drop is estimated. These results demonstrated that the implied regional static stress drop ranged from 0.1 to 5.7 MPa for catalog earthquakes in the moment magnitude range [4.5–7.3]. These results for stress drop are independent of the “a” and “b” regional parameters and heat flow but are very sensitive to the assumed maximum magnitude of a seismic province. The data do not rule out the hypothesis that the stress drop positively correlates with the time elapsed after the largest earthquake recorded in each seismic zone.
    Description: The research was supported by Project S1 2007-2009 of Istituto Nazionale di Geofisica e Vulcanologia and Dipartimento della Protezione Civile, Rome.
    Description: In press
    Description: 1.9. Rete GPS nazionale
    Description: 3.1. Fisica dei terremoti
    Description: 4.2. TTC - Modelli per la stima della pericolosità sismica a scala nazionale
    Description: JCR Journal
    Description: open
    Keywords: earthquakes ; seismic hazard ; geodesy ; b-value ; 04. Solid Earth::04.01. Earth Interior::04.01.02. Geological and geophysical evidences of deep processes ; 04. Solid Earth::04.01. Earth Interior::04.01.05. Rheology ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations ; 04. Solid Earth::04.03. Geodesy::04.03.06. Measurements and monitoring ; 04. Solid Earth::04.04. Geology::04.04.06. Rheology, friction, and structure of fault zones
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 91
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    Fault zone properties affecting the rupture evolution of the 2009 (Mw 6.1) L’Aquila earthquake (central Italy): Insights from seismic tomography (2012)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: We have inverted P‐ and S‐wave travel times from seismograms recorded by a dense local network to infer the velocity structure in the crustal volume where the April 6th 2009 main shock nucleated. The goal is to image local variations of P‐wave velocity and Poisson ratio along the main shock fault zone for interpreting the complexity of the rupture history. The initial stages of the mainshock rupture are characterized by an emergent phase (EP) followed by an impulsive phase (IP) 0.87 s later. The EP phase is located in a very high VP and relatively low Poisson ratio (n) region. The IP phase marks the beginning of the large moment release and is located outside the low n volume. The comparison between the spatial variations of VP and Poisson ratio within the main shock nucleation volume inferred in this study with the rupture history imaged by inverting geophysical data allows us to interpret the delayed along strike propagation in terms of heterogeneity of lithology and material properties
    Description: INGV
    Description: Published
    Description: L10310
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: fault zone properties ; normal faulting earthquakes ; material properties ; seismic tomography ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 92
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    Frictional melting of gabbro under extreme experimental conditions of normal stress, acceleration, and sliding velocity (2012)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: With the advent of high-velocity shear apparatus, several experimental studies have been performed in recent years, improving our understanding of the evolution of fault strength during seismic slip. However, these experiments were conducted under relatively low normal stress (〈20 MPa) and using small cylindrical samples where a large gradient in slip velocity exists across the sliding surface. Given the above limitations, the extrapolation of these experimental results to natural conditions is not trivial. Here we present results from an experimental study on gabbroic rocks using a newly developed rotary shear apparatus capable of reaching higher normal stress (up to 50 MPa) on ring-shaped samples (30/50 mm internal/external diameter) and allowing precise control of the imposed slip velocity function. The results confirm that steady state shear stress during the melt-lubricated phase of the experiment depends on normal stress in the form of a power law equation as predicted by theoretical models. However, the exponent appears closer to 0.5, contrary to the theoretical prediction of 0.25. We observe no systematic dependence of shear stress on acceleration, but increasing deceleration drastically decreases the recovery of friction during final slip. We find that the slip-weakening distance decreases inversely with increasing normal stress, in agreement with theoretical considerations, and decreases with increasing slip rate. Extrapolation of the slip-weakening distance to natural conditions predicts a slip velocity for ancient seismic events of 0.3-1 m/s when compared with field estimates. These values compare well with seismological estimates.
    Description: European Research Council
    Description: Published
    Description: B07404
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: friction ; melt ; 04. Solid Earth::04.04. Geology::04.04.06. Rheology, friction, and structure of fault zones
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 93
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    Seismological Insight on the Shallow Magma System (2012)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: We present an overview of the volcanic seismicity recorded at Stromboli from January to September 2003. The data set starts few weeks after the onset of the eruption and covers most of the effusive phase and the subsequent recovery of the explosive activity. The most important variations occurred between May and July coinciding with the waning of the lava flow and the reappearance of Strombolian activity at the summit craters. All the parameters indicate that the shallow magmatic system has not undergone permanent changes during this period. The only significant variation related to the shallow conduit is the increase in volcanic tremor amplitude and the change in the spectral content of long-period events during the transition between effusive and explosive activity. A slight increase in the very-long-period (VLP) events source elevation seems to mark the rise of the magma at the end of the effusive phase. The variations in the VLP events occurrence rate are more likely to be attributed to changes in the gas flow rate and the bubble coalescence mechanism, therefore, to a deeper portion of the magmatic system. The 5 April paroxysm is associated only with a small increase of the activity in the following days.
    Description: Published
    Description: 279-286
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: reserved
    Keywords: Stromboli ; Seismological monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 94
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    Marine biogeochemical responses to the North Atlantic Oscillation in a coupled climate model (2012)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: In this study a coupled ocean‐atmosphere model containing interactive marine biogeochemistry is used to analyze interannual, lagged, and decadal marine biogeochemical responses to the North Atlantic Oscillation (NAO), the dominant mode of North Atlantic atmospheric variability. The coupled model adequately reproduces present‐day climatologies and NAO atmospheric variability. It is shown that marine biogeochemical responses to the NAO are governed by different mechanisms according to the time scale considered. On interannual time scales, local changes in vertical mixing, caused by modifications in air‐sea heat, freshwater, and momentum fluxes, are most relevant in influencing phytoplankton growth through light and nutrient limitation mechanisms. At subpolar latitudes, deeper mixing occurring during positive NAO winters causes a slight decrease in late winter chlorophyll concentration due to light limitation and a 10%–20% increase in spring chlorophyll concentration due to higher nutrient availability. The lagged response of physical and biogeochemical properties to a high NAO winter shows some memory in the following 2 years. In particular, subsurface nutrient anomalies generated by local changes in mixing near the American coast are advected along the North Atlantic Current, where they are suggested to affect downstream chlorophyll concentration with 1 year lag. On decadal time scales, local and remote mechanisms act contemporaneously in shaping the decadal biogeochemical response to the NAO. The slow circulation adjustment, in response to NAO wind stress curl anomalies, causes a basin redistribution of heat, freshwater, and biogeochemical properties which, in turn, modifies the spatial structure of the subpolar chlorophyll bloom.
    Description: Published
    Description: C07023
    Description: 3.7. Dinamica del clima e dell'oceano
    Description: JCR Journal
    Description: restricted
    Keywords: PELAGOS ; Earth System Model ; 03. Hydrosphere::03.01. General::03.01.03. Global climate models ; 03. Hydrosphere::03.03. Physical::03.03.03. Interannual-to-decadal ocean variability ; 03. Hydrosphere::03.03. Physical::03.03.04. Upper ocean and mixed layer processes ; 03. Hydrosphere::03.04. Chemical and biological::03.04.01. Biogeochemical cycles ; 03. Hydrosphere::03.04. Chemical and biological::03.04.02. Carbon cycling
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 95
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    Relating High-Velocity Rock-Friction Experiments to Coseismic Slip in the Presence of Melts (2010)
    AGU
    Details
    Publication Date: 2020-02-24
    Description: The dynamic strength (tau_f) of faults during coseismic slip is a major unknown in earthquake mechanics, though it has crucial influence on rupture properties, dynamic stress drop, radiated energy and heat produced during slip. In order to provide constraints on tau_f, High-Velocity Rock Friction Experiments (HVRFE) are conducted on natural rocks with rotary shear apparatuses, reproducing slip (several meters) and slip rate (0.1-3 m/s) typical of large earthquakes. Among the various weakening mechanisms possibly activated during seismic slip, we focus on melt lubrication. Solidified, friction-induced melts (pseudotachylytes) decorate some exhumed seismic faults, showing that melt can occur on natural faults, though its frequency is still a matter of debate. In the presence of melt, tau_f undergoes an initial strengthening stage, followed by a dramatic weakening stage (thermal runaway). Field estimates based on pseudotachylyte thickness and experimental measures of tau_f suggest large stress drops once thermal runaway is achieved. These estimates of tau_f are compatible with large dynamic stress drops and high radiation efficiency, as observed for some earthquakes. Moreover, the threshold for the onset of thermal runaway might explain differences between the mechanics of small (M 〈 4) and large earthquakes. A simple mathematical model coupling melting, extrusion and thermal diffusion reproduces some observed experimental features such as the duration of the weakening stage and the convergence to a steady-state.
    Description: Published
    Description: 121-134
    Description: 3.1. Fisica dei terremoti
    Description: reserved
    Keywords: friction, pseudotachylite, exhumed faults, laboratory experiments, High velocity friction ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 96
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    Imaging the rupture of the Mw 6.3 April 6, 2009 L’Aquila, Italy earthquake using back‐projection of teleseismic P‐waves (2011)
    AGU
    Details
    Publication Date: 2020-02-25
    Description: We present rupture details of the Mw 6.3 April 6, 2009 L’Aquila earthquake derived by back‐projecting teleseismic P waves. This technique has previously been applied to large magnitude earthquakes, but this is the first application to a moderate size event. We processed vertical‐component seismograms for 60 broadband stations obtained from the Incorporated Research Institutions for Seismology (IRIS) data center. The traces were aligned and normalized using a multi‐channel cross‐correlation algorithm and 4th root stacking was used to image the rupture. We found that the L’Aquila earthquake ruptured towards the south and that a second discrete pulse of energy occurred 20–25 km east of the epicenter about 17–18 s after the nominal origin time. The spatial extent of the rupture image correlates well with a post‐seismic survey of damage in the region. Because the technique is potentially very fast (images can be produced within 20–30 minutes of the origin time), it may be useful to governmental agencies tasked with emergency response and rescue.
    Description: Published
    Description: L03301
    Description: 4.2. TTC - Modelli per la stima della pericolosità sismica a scala nazionale
    Description: JCR Journal
    Description: reserved
    Keywords: L'AQUILA EARTHQUAKE ; BACK_PROJECTION ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 97
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    The complex architecture of the 2009 MW 6.1 L’Aquila normal fault system (Central Italy) as imaged by 64,000 high-resolution aftershock locations. (2012)
    AGU
    Details
    Publication Date: 2020-02-25
    Description: On April 6th 2009, a MW 6.1 normal faulting earthquake struck the axial area of the Abruzzo region in Central Italy. We present high-precision hypocenter locations of an extraordinary dataset composed by 64,000 earthquakes recorded at a very dense seismic network of 60 stations operating for 9 months after the main event. Events span in magnitude (ML) between -0.9 to 5.9, reaching a completeness magnitude of 0.7. The dataset has been processed by integrating an accurate automatic picking procedure together with cross-correlation and double-difference relative location methods. The combined use of these procedures results in earthquake relative location uncertainties in the range of a few meters to tens of meters, comparable/lower than the spatial dimension of the earthquakes themselves). This data set allows us to image the complex inner geometry of individual faults from the kilometre to meter scale. The aftershock distribution illuminates the anatomy of the en-echelon fault system composed of two major faults. The mainshock breaks the entire upper crust from 10 km depth to the surface along a 14-km long normal fault. A second segment, located north of the normal fault and activated by two Mw〉5 events, shows a striking listric geometry completely blind. We focus on the analysis of about 300 clusters of co-located events to characterize the mechanical behavior of the different portions of the fault system. The number of events in each cluster ranges from 4 to 24 events and they exhibit strongly correlated seismograms at common stations. They mostly occur where secondary structures join the main fault planes and along unfavorably oriented segments. Moreover, larger clusters nucleate on secondary faults located in the overlapping area between the two main segments, where the rate of earthquake production is very high with a long-lasting seismic decay.
    Description: INGV
    Description: Published
    Description: San Francisco (CA) USA
    Description: 3.1. Fisica dei terremoti
    Description: open
    Keywords: Normal faulting earthquakes ; large dataset ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Oral presentation
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  • 98
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    The 7 September 2008 Vulcanian explosion at Stromboli volcano: Multiparametric characterization of the event and quantification of the ejecta (2012)
    AGU
    Details
    Publication Date: 2020-02-24
    Description: On 7 September 2008 a major ash explosion occurred from the SW summit crater of Stromboli volcano. This explosive event lasted ~2 min and consisted of three discrete eruptive pulses, forming an eruptive ash cloud ~500–600 m high and ~300 m wide, 11 rising with speed of 20–27 m s-1. The event was recorded by our camera and seismic networks, as well as by two electric stations installed at a 500 m mean distance from the SW crater. The electric signals recorded by the two stations during this event were 106 times greater than signals recorded during the persistent Strombolian activity, and the seismic trace had a bigger amplitude and a longer duration. Camera image analysis allowed us to infer that a partial obstruction took place at the SW crater three days before the explosive event, suggesting that a constriction within the upper conduit could have likely led to magma overpressure. Data analysis, combined with previous experimental investigations, revealed that the higher energy output of the ash explosion, when compared to the persistent Strombolian activity, resulted in a greater magma fragmentation and erupted mass. Integration of the different parameters allowed us to classify the event as a Vulcanian type, and electric signal analysis enabled retrieval of the total volume of erupted ash and of the amounts of the juvenile, phreatomagmatic, and lithic components.
    Description: This paper was partially supported by a research project (project INGV-DPC Paroxysm V2/03, 2007–2009) funded by Istituto Nazionale di Geofisica e Vulcanologia and by the Italian Civil Protection.
    Description: Published
    Description: B05201
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: JCR Journal
    Description: open
    Keywords: Stromboli ; major explosions ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 99
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    Recent changes in Arctic Ocean circulation revealed by 129-Iodine observations and modelling (2012)
    AGU
    In:  EPIC3Journal of Geophysical Research - Oceans., AGU
    Details
    Publication Date: 2019-07-16
    Description: Anthropogenic radionuclides released into European coastal waters from nuclear fuel reprocessing plants at Sellafield (UK) and La Hague (France) flow northward through the Nordic Seas and label Atlantic Water (AW) entering the Arctic Ocean. Transport of the soluble radionuclide 129I through the Arctic Ocean has been simulated using a numerical model for the period from 1970 to 2010. The simulated tracer distributions closely conform to 129I measurements made across the Arctic Ocean during the mid-1990s and 2000s and clearly illustrate the dramatic changes in oceanic circulation which occurred during this time. The largest changes in surface circulation were associated with the transition from a negative to a positive phase of the Arctic Oscillation in the early 1990s and the subsequent return to a weak phase in the late 1990s and early 2000s. Model and experimental results indicate that a new circulation regime evolved in the late 2000s when a period of intense, anti-cyclonic surface stress led to a strengthening of the Beaufort Gyre. We submit that this resulted in a suppression of the counter-rotating boundary current of mid-depth Atlantic Water (AW) below the Beaufort Gyre, with upper AW in the Canada Basin showing signs of a reversal from cyclonic to anti-cyclonic flow. These results are consistent with the development of a new AW circulation scheme involving a separation between flow at intermediate depths in the Eurasian and Canada Basins which could eventually result in alteration of the source water characteristics of Arctic intermediate depth water in the Nordic seas.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 100
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    Simulation and observations of stratospheric aerosols from the 2009 Sarychev volcanic eruption (2011)
    AGU
    In:  EPIC3J. Geophys. Res, AGU
    Details
    Publication Date: 2019-07-17
    Description: We used a general circulation model of Earth’s climate to conduct simulations of the 12-16 June 2009 eruption of Sarychev volcano (48.1°N, 153.2°E). The model simulates the formation and transport of the stratospheric sulfate aerosol cloud from the eruption and the resulting climate response. We compared optical depth results from these simulations with limb scatter measurements from the Optical Spectrograph and InfraRed Imaging System (OSIRIS), in situ measurements from balloon-borne instruments lofted from Laramie, Wyoming (41.3°N, 105.7°W), and five lidar stations located throughout the Northern Hemisphere. The aerosol cloud covered most of the Northern Hemisphere, extending slightly into the tropics, with peak backscatter measured between 12 and 16 km in altitude. Aerosol concentrations returned to near background levels by Spring, 2010. After accounting for expected sources of discrepancy between each of the data sources, the magnitudes and spatial distributions of aerosol optical depth due to the eruption largely agree. In conducting the simulations, we likely overestimated both particle size and the amount of SO2 injected into the stratosphere, resulting in modeled optical depth values that were a factor of 2-4 too high. Model results of optical depth due to the eruption show a peak too late in high latitudes and too early in low latitudes, suggesting a problem with stratospheric circulation in the model. The model also shows a higher annual decay rate in optical depth than is observed, showing an inaccuracy in seasonal deposition rates. The modeled deposition rate of sulfate aerosols from the Sarychev eruption is higher than the rate calculated for aerosols from the 1991 eruption of Mt. Pinatubo.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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