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Post-Seismic Deformation Related to the 2016 Central Italy Seismic Sequence from GPS Displacement Time-Series
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  • Eugenio Mandler,
  • Letizia ANDERLINI,
  • Adriano Gualandi,
  • Francesco Pintori,
  • Enrico Serpelloni,
  • Maria Elina Belardinelli
Eugenio Mandler
University of Bologna

Corresponding Author:[email protected]

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Letizia ANDERLINI
Istituto Nazionale di Geofisica e Vulcanologia
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Adriano Gualandi
Istituto Nazionale di Geofisica e Vulcanologia
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Francesco Pintori
Istituto Nazionale di Geofisica e Vulcanologia
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Enrico Serpelloni
Istituto Nazionale di Geofisica e Vulcanologia
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Maria Elina Belardinelli
University of Bologna
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Abstract

The 2016-2017 Central Italy earthquake sequence struck the central Apennines between August 2016 and October 2016 with Mw ∈ [5.9; 6.5], plus four earthquakes occurring in January 2017 with Mw ∈ [5.0; 5.5]. Here we study Global Positioning System (GPS) stations active during the post-seismic phase including near and far-field domains. We separate the post-seismic deformation from other, mainly seasonal, hydrological deformation signals present in ground displacement time-series via a variational Bayesian Independent Component Analysis technique. For each component, realistic uncertainties are provided to the related ICA-reconstructed displacement field. We study the distribution of afterslip on the main structures surrounding the mainshock, and we highlight the role played by structures that were not activated during the co-seismic phase in accommodating the post-seismic deformation. In particular, we report aseismic deformation occurring on the Paganica fault, which hosted the Mw 6.1 2009 L’Aquila earthquake, and is located further south of the 2016-2017 epicenters; and on a 〜2-3 km thick subhorizontal shear-zone, clearly illuminated by seismicity, which bounds at depth the west-dipping normal faults where the mainshocks nucleated. Since afterslip alone underestimates the displacement in the far-field domain, we consider the possibility that the shear zone marks the brittle-ductile transition, assuming the viscoelastic relaxation of the lower crust as a mechanism contributing to the post-seismic displacement. Our results suggest that multiple deformation processes are active in the first two years after the mainshocks.
Sep 2021Published in Journal of Geophysical Research: Solid Earth volume 126 issue 9. 10.1029/2021JB022200