Publication Date:
2017-04-04
Description:
Six moderate magnitude earthquakes (5 〈 Mw 〈 6) ruptured normal fault segments of
the southern sector of the North Apennine belt (central Italy) in the 1997 Colfiorito
earthquake sequence. We study the progressive activation of adjacent and nearby parallel
faults of this complex normal fault system using1650 earthquake locations obtained by
applying a double-difference location method, using travel time picks and waveform
cross-correlation measurements. The lateral extent of the fault segments range from 5 to
10 km and make up a broad,45 km long, NW trending fault system. The geometry of
each segment is quite simple and consists of planar faults gently dipping toward SW with
an average dip of 40–45. The fault planes are not listric but maintain a constant dip
through the entire seismogenic volume, down to 8 km depth. We observe the activation of
faults on the hanging wall and the absence of seismicity in the footwall of the structure.
The observed fault segmentation appears to be due to the lateral heterogeneity of the upper
crust: preexisting thrusts inherited from Neogene’s compressional tectonic intersect the
active normal faults and control their maximum length. The stress tensor obtained by
inverting the six main shock focal mechanisms of the sequence is in agreement with the
tectonic stress active in the inner chain of the Apennine, revealing a clear NE trending
extension direction. Aftershock focal mechanisms show a consistent extensional
kinematics, 70% of which are mechanically consistent with the main shock stress
field.
Description:
Published
Description:
2294,
Description:
3.1. Fisica dei terremoti
Description:
JCR Journal
Description:
reserved
Keywords:
Normal faulting
;
double-difference
;
Umbria-Marche
;
corss-correlation
;
relative location
;
05. General::05.02. Data dissemination::05.02.02. Seismological data
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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