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  • 1
    Publication Date: 2017-04-04
    Description: The Colli Albani is a Quaternary quiescent volcano, located a few kilometers southeast of Rome (Italy). During the past decade, seismic swarms, ground deformation, and gas emissions occurred in the southwestern part of the volcano, where the last phreatomagmatic eruptions (27 ka) developed, building up several coalescent craters. In the frame of a Dipartimento Protezione Civile – Istituto Nazionale di Geofisica e Vulcanologica project aimed at the definition and mitigation of volcanic hazard, a temporary array of seismic stations has been deployed on the volcano and surrounding areas. We present results obtained using receiver functions analysis for eight stations, located upon and around the volcanic edifice, and revealing how the built of the volcanic edifice influenced the prevolcanic structures. The stations show some common features: the Moho is almost flat and located at 23 km, in agreement with the thinning of the Thyrrenian crust. Also the presence of a shallow limestone layer is a stable feature under every station, with a variable thickness between 4 and 5 km. However, some features change from station to station, indicating a local complexity of the crustal structure: a shallow discontinuity dividing the Plio-Pleistocene sediments by the Meso-Cenozoic limestones, and a localized anisotropic layer, in the central part of the old structure, which points of the deformation of the limestones. Other two strongly anisotropic layers are detected under the stations in lower crust and upper mantle, with symmetry axis directions related to the evolution of the volcano complex.
    Description: Published
    Description: B09313
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: Receiver Function ; Colli Albani ; crustal structure ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Publication Date: 2017-04-04
    Description: We present a new P wave and S wave velocity model for the upper crust beneath Long Valley Caldera obtained using local earthquake tomography and receiver function analysis. We computed the tomographic model using both a graded inversion scheme and a traditional approach. We complement the tomographic Vp model with a teleseismic receiver function model based on data from broadband seismic stations (MLAC and MKV) located on the SE and SW margins of the resurgent dome inside the caldera. The inversions resolve (1) a shallow, high‐velocity P wave anomaly associated with the structural uplift of a resurgent dome; (2) an elongated, WNW striking low‐velocity anomaly (8%–10 % reduction in Vp) at a depth of 6 km (4 km below mean sea level) beneath the southern section of the resurgent dome; and (3) a broad, low‐velocity volume (∼5% reduction in Vp and as much as 40% reduction in Vs) in the depth interval 8–14 km (6–12 km below mean sea level) beneath the central section of the caldera. The two low‐velocity volumes partially overlap the geodetically inferred inflation sources that drove uplift of the resurgent dome associated with caldera unrest between 1980 and 2000, and they likely reflect the ascent path for magma or magmatic fluids into the upper crust beneath the caldera.
    Description: Published
    Description: B12314
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: Seismic Tomography ; Long Valley Caldera ; Receiver Function ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Publication Date: 2020-02-24
    Description: The crustal structure of central Apennines (Italy) is still poorly defined, leaving uncertainties on the tectonic style (thin or thick-skinned) responsible for the development of the thrust-and-fold belt. The today active extension, which replaced compression since early Quaternary, is presumably in"uenced by the pre-existing structure that yields location and segmentation of the fault system. To focus on such issues, we computed P and S-wave velocity models of the crust by using the independent methodologies of local earthquakes tomography and teleseismic receiver function. We document strong lateral and vertical heterogeneities that define shallow, imbricate sheets of the Mesozoic cover that overlay exceptionally high Vp and high Vs bodies. These bodies can be interpreted as either dolomitic or, partially hydrated, ma!c rocks. The two alternative interpretations respectively imply an ultra-thick deposition of dolomitic rocks in the hanging wall of Triassic normal fault or a deep exhumation of the Pre-Mesozoic basement during the early Mesozoic sin-rift tectonic. In both cases, these bodies in"uenced the evolution of the thrust-and-fold belt. Very remarkably, active normal faults, like those ruptured during the still ongoing 2009 L'Aquila sequence, concentrate at the border of these bodies, suggesting that they have an active role in the segmentation of the normal fault system. The rheological behavior of such high Vp high Vs bodies, weak or strong, is still uncertain, but of utmost importance to understand the risk of future normal faulting earthquakes.
    Description: Published
    Description: 462-476
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: Abruzzo ; tomography ; receiver functions ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
    Publication Date: 2017-04-04
    Description: Isotropic and anisotropic seismic structures across the Northern Apennines (Italy) subduction zone are imaged using a new method for the analysis of teleseismic receiver functions (RFs). More than 13,000 P!wave coda of teleseismic records from the 2003–2007 Retreating!Trench, Extension, and Accretion Tectonics (RETREAT) experiment are used to provide new insights into a peculiar subduction zone between two continental plates that is considered a focal point of Mediterranean evolution. A new methodology for the analysis of receiver functions is developed, which combines both migration and harmonic decomposition of the receiver function data set. The migration technique follows a classical “Common Conversion Point” scheme and helps to focus on a crucial depth range (20–70 km) where the mantle wedge develops. Harmonic decomposition of a receiver function data set is a novel and less explored approach to the analysis of P-to-S converted phases. The separation of the back-azimuth harmonics is achieved through a numerical regression of the stacked radial and transverse receiver functions from which we obtain independent constraints on both isotropic and anisotropic seismic structures. The application of our method to the RETREAT data set succeeds both in confirming previous knowledge about seismic structure in the area and in highlighting new structures beneath the Northern Apennines chain, where previous studies failed to clearly retrieve the geometry of the subducted interfaces. We present our results in closely spaced profiles across and along the Northern Apennines chain to highlight the convergence of the Tyrrhenian and the Adriatic microplates which differ in their crustal structure where the Adriatic microplate subducts beneath Tuscany and the Tyrrhenian sea. A signature of the dipping Adriatic Moho is clearly observed beneath the Tyrrhenian Moho in a large portion of the forearc region. In the area where the two Mohos overlap, our new analysis reveals the presence of an anisotropic body above the subducted Moho. There is a strong Ps converted phase with anisotropic characteristics from the top of the Adriatic plate to a depth of at least 80 km. Because the Ps conversion occurs much deeper than similar Ps phases in Cascadia and Japan, dehydration of oceanic crust seems unlikely as a causative factor. Rather, the existence of this body trapped between the two interfaces supports the hypothesis of lower crustal delamination in a postsubduction tectonic setting.
    Description: Published
    Description: B12317
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: restricted
    Keywords: receiver functions ; northern apennines ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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