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  • 1
    Publication Date: 2017-04-04
    Description: The Pernicana Fault (PF) is the main structural element of Mt Etna and the northern boundary of a section sliding to the southeast. Observed ground motion records in the damage zone of the PF show strong variations of directional resonance in the horizontal plane. The observed resonance directions exhibit an abrupt rotation of azimuth by about 30◦ across the fault, varying from N166◦ on the north side to N139◦ on the south. We interpret the directional resonance observations in terms of changes in the kinematics and deformation fields on the opposite sides of the fault. The northern side is affected primarily by the left-lateral strike-slip movement, whereas the southern side, that is subjected also to sliding, is under a dominant extensional stress regime. Brittle deformation models based on the observed kinematic field predict different sets of fractures on the opposite sides of the fault: synthetic cleavages and extensional fractures are expected to dominate in the northern and southern sides, respectively. These two fracture fields have different orientations (N74◦ and N42◦, respectively) and both show a near-orthogonal relation (∼88◦ in the northern sector and ∼83◦ to the south) with the azimuth of the observed directional resonance. We conclude that the direction of the largest resonance motions is sensitive to and has transversal relationship with the dominant fracture orientation. The directional amplification is inferred to be produced by stiffness anisotropy of the fault damage zone, with larger seismic motions normal to the fractures.
    Description: Published
    Description: 986–996
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: JCR Journal
    Description: restricted
    Keywords: Earthquake ground motions; Site effects; Wave propagation ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Location Call Number Limitation Availability
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  • 2
    Publication Date: 2017-04-04
    Description: A Global Positioning System (GPS) network of 30 semi-permanent vertices known as the Victoria Land Network for Deformation Control (VLNDEF) was set up in the Austral summer of 1998 in Northern Victoria Land (NVL), including the permanent GPS station of Terra Nova Bay (TNB1), Antarctica. The locations were selected according to the known Cenozoic fault framework, which is characterized by a system of NW[U+2010]SE regional faults with right[U+2010]lateral, strike[U+2010]slip kinematics. The TNB1 permanent GPS station is included within the VLNDEF, and was installed on a bedrock monument in October 1998, it has been recording almost continuously up to the present. The GPS network has been surveyed routinely every two summers, using high[U+2010]quality, dual[U+2010]frequency GPS receivers like Trimble 5700, TopCon GB100, and Ashtech Z-XII. In this study we present the results of a distributed session approach based on Gamit/Globk 10.4 software package applied to the processing of the GPS data of the VLNDEF aimed to obtain the preliminary framework of the active tectonics of this region of Antarctica. An improved reference frame definition was implemented, including a new Euler rotation pole, to compute the Antarctic intra-plate residual velocities. The projection of the residual velocities on the main faults in NVL show present[U+2010]day activities for some faults, including the Tucker, Leap Year, Lanterman, Aviator, and David faults, with right[U+2010]lateral strike[U+2010]slip kinematics and local extensional and compressional components. This active fault pattern divides NVL into eight rigid blocks, each characterized by its relative movements and rigid rotations. These show velocities of up to several millimeters per year, which are comparable to those predicted by plate tectonic theory at active plate margins. During the austral summer 2010, in the framework of the Italian Antarctic campaign, field investigations at 25 geodetic stations were performed both for survey of the instruments and measurements as well as for the geological study necessary to evaluate the geological stability of the sites. Preliminary analysis of the collected structural data showed the stability of most of the investigated stations, thus confirming the proposed active tectonic framework of the NVL at the regional scale.
    Description: Published
    Description: Vienna, Austria 3–8 April 2011
    Description: 3.2. Tettonica attiva
    Description: reserved
    Keywords: Antarctica ; Northern Victoria Land ; Active Tectonics ; GPS data ; Geologic Setting ; 04. Solid Earth::04.07. Tectonophysics::04.07.04. Plate boundaries, motion, and tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Abstract
    Location Call Number Limitation Availability
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