Publication Date:
2021-11-30
Description:
Historical seismic catalogs report that the Gargano Promontory (southern Italy) was
affected in the past by earthquakes with medium to high estimated magnitude. From
the instrumental seismicity, it can be identified that the most energetic Apulian sequence
occurred in 1995 with a main shock of MW = 5.2 followed by about 200 aftershocks with
a maximum magnitude of 3.7. The most energetic earthquakes of the past are attributed
to right-lateral strike-slip faults, while there is evidence that the present-day seismicity
occur on thrust or thrust-strike faults. In this article, we show a detailed study on focal
mechanisms and stress field obtained by micro-seismicity recorded from April 2013
until the present time in the Gargano Promontory and surrounding regions. Seismic
waveforms are collected from the OTRIONS Seismic Network (OSN), from the Italian
National Seismic Network (RSN), and integrated with data from the Italian National
Accelerometric Network (RAN) in order to provide a robust dataset of earthquake
localizations and focal mechanisms. The effect of uncertainties of the velocity model
on fault plane solutions (FPS) has been also evaluated indicating the robustness of the
results. The computed stress field indicates a deep compressive faulting with maximum
horizontal compressive stress, SHmax, trending NW-SE. The seismicity pattern analysis
indicates that the whole crust is seismically involved up to a depth of 40 km and indicates
the presence of a low-angle seismogenic surface trending SW-NE and dipping SE-NW,
similar to the Gargano–Dubrovnik lineament. Shallower events, along the eastern sector
of the Mattinata Fault (MF), are W-E dextral strike-slip fault. Therefore, we hypothesized
that the seismicity is locally facilitated by preexisting multidirectional fractures, confirmed
by the heterogeneity of focal mechanisms, and explained by the different reactivation
processes in opposite directions over the time, involving the Mattinata shear zone.
Description:
Published
Description:
589332
Description:
4T. Sismicità dell'Italia
Description:
JCR Journal
Keywords:
Gargano promontory
;
OTRIONS local seismic network
;
focal mechanisms
;
stress field
;
microseismicity
;
mattinata fault
;
gargano-dubrovnik lineament
;
04.06. Seismology
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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