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  • 04. Solid Earth::04.07. Tectonophysics::04.07.06. Subduction related processes  (3)
  • Nature Publishing Group  (2)
  • The American Geophysical Union  (1)
  • 2010-2014  (3)
Collection
Years
  • 2010-2014  (3)
Year
  • 1
    Publication Date: 2017-04-04
    Description: The MW 8.8 mega-thrust earthquake and tsunami that occurred on February 27, 2010, offshore Maule region, Chile, was not unexpected. A clearly identified seismic gap existed in an area where tectonic loading has been accumulating since the great 1835 earthquake experienced and described by Darwin during the voyage of the Beagle. Here we jointly invert tsunami and geodetic data (InSAR, GPS, land-level changes), to derive a robust model for the co-seismic slip distribution and induced co-seismic stress changes, and compare them to past earthquakes and the pre-seismic locking distribution. We aim to assess if the Maule earthquake has filled the Darwin gap, decreasing the probability of a future shock . We find that the main slip patch is located to the north of the gap, overlapping the rupture zone of the MW 8.0 1928 earthquake, and that a secondary concentration of slip occurred to the south; the Darwin gap was only partially filled and a zone of high pre-seismic locking remains unbroken. This observation is not consistent with the assumption that distributions of seismic rupture might be correlated with pre-seismic locking, potentially allowing the anticipation of slip distributions in seismic gaps. Moreover, increased stress on this unbroken patch might have increased the probability of another major to great earthquake there in the near future.
    Description: Published
    Description: 173-177
    Description: 3.1. Fisica dei terremoti
    Description: 4.2. TTC - Modelli per la stima della pericolosità sismica a scala nazionale
    Description: JCR Journal
    Description: restricted
    Keywords: Source process ; Chile ; Tsunami ; Joint Inversion ; Seismic Gap ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.05. Stress ; 04. Solid Earth::04.07. Tectonophysics::04.07.06. Subduction related processes ; 05. General::05.01. Computational geophysics::05.01.03. Inverse methods
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Publication Date: 2017-04-04
    Description: The 2011 Tohoku-oki (Mw 9.1) earthquake is so far the best-observed megathrust rupture, which allowed the collection of unprecedented offshore data. The joint inversion of tsunami waveforms (DART buoys, bottom pressure sensors, coastal wave gauges, and GPS-buoys) and static geodetic data (onshore GPS, seafloor displacements obtained by a GPS/acoustic combination technique), allows us to retrieve the slip distribution on a non-planar fault. We show that the inclusion of near-source data is necessary to image the details of slip pattern (maximum slip ,48 m, up to ,35 m close to the Japan trench), which generated the large and shallow seafloor coseismic deformations and the devastating inundation of the Japanese coast. We investigate the relation between the spatial distribution of previously inferred interseismic coupling and coseismic slip and we highlight the importance of seafloor geodetic measurements to constrain the interseismic coupling, which is one of the key-elements for long-term earthquake and tsunami hazard assessment.
    Description: Published
    Description: 385
    Description: 3.1. Fisica dei terremoti
    Description: N/A or not JCR
    Description: restricted
    Keywords: Tohoku ; Subduction ; Tsunami ; Inverse problem ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.06. Subduction related processes
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Publication Date: 2017-04-04
    Description: We describe a new method to estimate the S‐P time of tremor‐like signals and its application to the nonvolcanic tremor recorded in July 2004 by three dense arrays in Cascadia. The cross correlation between vertical and horizontal components indicates that very often the high‐amplitude tremor signal contains sequences of P and S waves characterized by constant S‐P times (TS‐P) in the range 3.5–7 s. A detailed observation of the three component seismograms stacked over the array stations confirms the presence of P and S wave sequences. The knowledge of the TS‐P poses a strong constrain on the source‐array distance, which dramatically reduces the uncertainty on source locations when used with more traditional array processing techniques. Data were analyzed using the zero lag cross‐correlation technique (ZLCC) to estimate the propagation properties of the most correlated phases in the wavefield. Detailed polarization analyses were computed using the covariance matrix method in the time domain. Polarization parameters, joint with the results of ZLCC, allows for the discrimination between P and S coherent waves. Results show that the tremor wavefield is composed mostly by shear waves, although a consistent amount of coherent P waves is often observable. The comparison of the back azimuth at the three arrays indicate that the source of deep tremor migrates over a wide area, and often many independent sources located far from each other are active at the same time. The tremor source was located by a probabilistic method that uses the results of ZLCC, given a velocity model. When available, the inclusion of the TS‐P time in the location procedure strongly reduces the depth range, with a distribution of hypocenters very near the subduction interface. This result, significantly different compared with previous less precise locations, makes the Cascadia nonvolcanic tremor more similar to the nonvolcanic tremor recorded in Japan, at least in cases of measurable TS‐P. The polarization azimuth aligned with the slow slip direction and the source located on the plate interface indicate that deep tremor and slow slip are two different manifestations of a common phenomenon related with the subduction dynamics.
    Description: Published
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: reserved
    Keywords: Array analysis ; source location ; deep tremor ; Cascadia ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis ; 04. Solid Earth::04.06. Seismology::04.06.10. Instruments and techniques ; 04. Solid Earth::04.07. Tectonophysics::04.07.04. Plate boundaries, motion, and tectonics ; 04. Solid Earth::04.07. Tectonophysics::04.07.06. Subduction related processes
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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