Post-seismic deformation related to the 2016 central Italy seismic sequence from GPS displacement time-series

Abstract

<p>The 2016-2017 Central Italy earthquake sequence was characterized by three main events striking the central Apennines between August 2016 and October 2016 with a Mw ∈ [5.9 to 6.5], plus four earthquakes occurring in January 2017 with a Mw ∈ [5.0; 5.5]. Here we study 85 Global Positioning System (GPS) stations active during the post-seismic phase in a region within a radius of 100 km around the epicentral area, including near and far-field domains. We separate the post-seismic deformation from other, mainly seasonal, deformation signals present in ground displacement time-series via a variational Bayesian Independent Component Analysis (vbICA) technique. Excluding the postseismic transient signal, we found that all the other components are due to hydrological processes, and found no evidence of pre-seismic deformation signals with a spatial and temporal pattern that can be ascribed to a precursory deformation. We study the role played by afterslip on the main structures activated during the co-seismic phase, and we infer the activation during the post-seismic phase of the Paganica fault, which is located further south of the 2016-2017 epicenters and did not rupture during the co-seismic phase. We investigate an aseismic activation of the ∼ 2 − 3 km thick subhorizontal layer of seismicity, which bounds at depth the SW-dipping normal faults where the mainshocks nucleated, and which has been interpreted as a shear zone. Moreover we consider the possibility that the shear zone marks the brittle-ductile transition including the viscoelastic relaxation of the lower crust and upper mantle as a driving mechanism of the post-seismic displacement. However, neither afterslip nor viscoelasticity can fully explain the observations alone: the former is capable of satisfactorily explaining only the data in the epicentral area but it generally underestimates the displacement in the far-field domain; the latter cannot simultaneously explain the displacement observed in the near-field and far-field domains. Hence we infer a mixed contribution of these two mechanisms. </p>

Interplay Between Seismic and Aseismic Deformation on the Central Range Fault During the 2013 Mw 6.3 Ruisui Earthquake (Taiwan)

“…Several mechanisms are commonly involved in postseismic transient deformation. Viscoelastic lower crust or upper mantle relaxation can follow moderate-magnitude events (M w ∼ 6-6.5) (Mandler et al, 2021) and is characterized by large-scale and long-lasting deformation (months to years) (Tang et al, 2019). Here, postseismic relaxation is of short-duration (∼3 months) and is mainly recorded by near-source GNSS stations.…”

Searching for Transient Slow Slips Along the San Andreas Fault Near Parkfield Using Independent Component Analysis

“…To do so, similarly to Mandler et al. (2021), we build 100 perturbed displacement time series by adding to each position at each time step a random realization of a Gaussian noise based on the data uncertainties. For each of the 100 time series, we apply our decomposition, inversion of the dominant IC and detection methods.…”