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The preparatory phase of the MW 6.1 2009 L'Aquila normal faulting earthquake traced by foreshocks time-lapse tomography
Author(s)
Language
English
Obiettivo Specifico
1T. Struttura della Terra
3T. Sorgente sismica
Status
Published
JCR Journal
JCR Journal
Peer review journal
Yes
Title of the book
Issue/vol(year)
1/48 (2020)
Publisher
GSA
Pages (printed)
49-55
Issued date
2020
Abstract
The Mw 6.1 (6 April 2009) L’Aquila (Italy) earthquake occurred in one of the most seismically
active areas of central Italy and was preceded by a three-month-long foreshock period.
Thanks to recordings by a regional permanent network, we derive for the first time P- and
S-wave velocity tomographic models of a major fault prone to an imminent main shock. Close
to the Mw 6.1 hypocenter, we observe high Vp (>6.8 km/s) and high Vp/Vs (>1.9) consistent
with thick dolomitic volumes filled with fluids sealed by impermeable anhydritic layers.
Significant changes in velocities defined by time-lapse imaging during the foreshock period
suggest rapid fluid migration through the locked fault zone. The complex positive feedback
between fluid pressure buildup and hydrofracturing of the dolomitic reservoir, testified by
foreshock production, eventually provoked the catastrophic coseismic breaching of the fault
seal. Our results show that foreshock time-lapse tomography provides clues on the preparatory
phase of a large normal-faulting earthquake.
active areas of central Italy and was preceded by a three-month-long foreshock period.
Thanks to recordings by a regional permanent network, we derive for the first time P- and
S-wave velocity tomographic models of a major fault prone to an imminent main shock. Close
to the Mw 6.1 hypocenter, we observe high Vp (>6.8 km/s) and high Vp/Vs (>1.9) consistent
with thick dolomitic volumes filled with fluids sealed by impermeable anhydritic layers.
Significant changes in velocities defined by time-lapse imaging during the foreshock period
suggest rapid fluid migration through the locked fault zone. The complex positive feedback
between fluid pressure buildup and hydrofracturing of the dolomitic reservoir, testified by
foreshock production, eventually provoked the catastrophic coseismic breaching of the fault
seal. Our results show that foreshock time-lapse tomography provides clues on the preparatory
phase of a large normal-faulting earthquake.
Type
article
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Baccheschi_2019_Geology_g46618.pdf
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