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  • AGU
  • 2010-2014  (21)
  • 1935-1939
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  • 1
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    Climate Change and the Permafrost Carbon Feedback (2014)
    AGU
    In:  EPIC3AGU Fall Meeting, San Francisco, USA, 2014-12-15-2014-12-19San Francisco, USA, AGU
    Details
    Publication Date: 2015-11-09
    Description: Approximately twice as much soil carbon is stored in the northern circumpolar permafrost zone than is currently contained in the atmosphere. Permafrost thaw, and the microbial decomposition of previously frozen organic carbon, is considered one of the most likely positive feedbacks from terrestrial ecosystems to the atmosphere in a warmer world. Yet, the rate and form of release is highly uncertain but crucial for predicting the strength and timing of this carbon cycle feedback this century and beyond. New insight brought together under a multi-year synthesis effort by the Permafrost Carbon Network helps constrain current understanding of the permafrost carbon feedback to climate, and provides a framework for newly developing research initiatives in this region. A newly enlarged soil carbon database continues to verify the widespread pattern of large quantities of carbon accumulated deep in permafrost soils. The known pool of permafrost carbon is now estimated to be 1330-1580 Pg C, with the potential for ~400 Pg C in deep permafrost sediments that remain largely unquantified. Laboratory incubations of these permafrost soils reveal that a significant fraction of this material can be mineralized by microbes and converted to CO2 and CH4 on time scales of years to decades, with decade-long average losses from aerobic incubations ranging from 6-34% of initial carbon. Variation in loss rates is depended on the carbon to nitrogen ratio, with higher values leading to more proportional loss. Model scenarios show potential C release from the permafrost zone ranging from 37-174 Pg C by 2100 under the current climate warming trajectory (RCP 8.5), with an average across models of 92±17 Pg C. Furthermore, thawing permafrost C is forecasted to impact global climate for centuries, with models, on average, estimating 59% of total C emissions after 2100. Taken together, greenhouse gas emissions from warming permafrost appear likely to occur at a magnitude similar to other historically important biospheric C sources, such as land use change, but that is only a fraction of current fossil fuel emissions. Permafrost C emissions are likely to be felt over decades to centuries as northern regions warm, making climate change happen even faster than we think based on projected emissions from human activities alone.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 2
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    Chlorophyll a in Antarctic sea ice from historical ice core data (2012)
    AGU
    In:  EPIC3Geophys. Res. Lett., AGU, 39(L21602)
    Details
    Publication Date: 2019-07-17
    Description: Sea ice core chlorophyll a data are used to describe the seasonal, regional and vertical distribution of algal biomass in Southern Ocean pack ice. The Antarctic Sea Ice Processes and Climate – Biology (ASPeCt – Bio) circumpolar dataset consists of 1300 ice cores collected during 32 cruises over a period of 25 years. The analyses show that integrated sea ice chlorophyll a peaks in early spring and late austral summer, which is consistent with theories on light and nutrient limitation. The results indicate that on a circum-Antarctic scale, surface, internal and bottom sea ice layers contribute equally to integrated biomass, but vertical distribution shows distinct differences among six regions around the continent. The vertical distribution of sea ice algal biomass depends on sea ice thickness, with surface communities most commonly associatedwith thin ice (〈0.4m), and ice ofmoderate thickness (0.4– 1.0 m) having the highest probability of forming bottom communities.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 3
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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
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
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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
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
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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)
    Type: book chapter
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  • 6
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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
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 7
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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
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 8
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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
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Poster session
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  • 9
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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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  • 10
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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
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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