Publication Date:
2017-04-04
Description:
The axial zone of the Apenninic belt in central Italy is a tectonically active region affected
by post-orogenic Quaternary extension. The present-day stress field is characterized by a
minimum horizontal stress (Shmin) ∼ NE–SW oriented, derived mainly from earthquake focal
mechanisms and secondarily from borehole breakouts and fault data. The paper describes the
computation of the Shmin orientation along two deep boreholes located in the vicinity of the
area hit by the 2009 April 6, Mw 6.3 L’Aquila earthquake. The analysed wells show breakout
zones at a depth range between 1.4 and 4.6 km, giving precious information on a depth interval
usually not investigated by any other data. The results show an Shmin N81 ± 22◦ and N74 ± 10◦ oriented for Varoni 1 and Campotosto 1 wells, respectively. The comparison among the
breakouts, the 2009 seismic sequence, the past seismicity and the Quaternary faults indicates
a small rotation of Shmin orientation from ∼ NE, in the southern, to ∼ ENE in the northern
sector of the study area, where the wells are located. These differences are linked both to the
natural variations of data and to the orientation of the main tectonic structures varying from
NW–SE in the Abruzzi region to ∼ N–S moving toward the Umbro-Marchean Apennines. The
identification of constant Shmin orientations with depth derived from all the examined active
stress data, confirms the breakouts as reliable stress indicators also for aseismic areas.
Description:
Published
Description:
3.2. Tettonica attiva
Description:
JCR Journal
Description:
reserved
Keywords:
Seismicity and tectonics
;
present-day stress
;
borehole breakouts
;
Italy
;
04. Solid Earth::04.07. Tectonophysics::04.07.05. Stress
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
