Publication Date:
2023-01-16
Description:
We use amplitude ratios from narrowband-filtered earthquake seismograms to
measure variations of seismic attenuation over time, providing unique insights
into the dynamic state of stress in the Earth’s crust at depth. Our dataset from
earthquakes of the 2016–2017 Central Apennines sequence allows us to obtain
high-resolution time histories of seismic attenuation (frequency band:
0.5–30 Hz) characterized by strong earthquake dilatation-induced
fluctuations at seismogenic depths, caused by the cumulative elastic stress
drop after the sequence, as well as damage-induced ones at shallow depths
caused by energetic surface waves. Cumulative stress drop causes negative
dilatation, reduced permeability, and seismic attenuation, whereas strongmotion
surface waves produce an increase in crack density, and so in
permeability and seismic attenuation. In the aftermath of the main shocks of
the sequence, we show that the M ≥ 3.5 earthquake occurrence vs. time and
distance is consistent with fluid diffusion: diffusion signatures are associated
with changes in seismic attenuation during the first days of the Amatrice, Visso-
Norcia, and Capitignano sub-sequences. We hypothesize that coseismic
permeability changes create fluid diffusion pathways that are at least partly
responsible for triggering multi-mainshock seismic sequences. Here we show
that anelastic seismic attenuation fluctuates coherently with our hypothesis.
Description:
Progetti INGV di Ricerca Libera 2019 (LM), Progetto INGV
“Pianeta Dinamico” (LM), Centro di Pericolosità Sismica,
Triennio 2019–2021 Convenzione B1 Dipartimento della
Protezione Civile—INGV (IM).
Description:
Published
Description:
963689
Description:
7T. Variazioni delle caratteristiche crostali e "precursori"
Description:
JCR Journal
Keywords:
attenuation parameter
;
central apennines
;
shaking-induced rock damage
;
negative dilatation
;
fluid diffusion
;
rock permeability
;
random vibration theory
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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