Publication Date:
2017-04-04
Description:
main article
Description:
We performed paleoseismological investigations at four sites across the normal
Paganica fault (PF) (source of the 2009 Mw 6.3 L’Aquila earthquake), with the goal of
reconstructing the rupture history and of contributing to the evaluation of the maximum
event expected along the PF. We recognized five distinct surface faulting earthquakes
(including the 2009) in the trenches. The age of the penultimate event is consistent with the
1461 earthquake; the third event back occurred around 1000 AD. The two oldest events
have larger uncertainties and occurred in the interval 760 BC–670 AD and 2900–760 BC,
respectively. The along‐strike vertical displacement for each paleoevent has a limited
variability consistently with the fairly homogeneous slip observed in 2009 along the
northern part of the rupture. Conversely, the throws change between distinct events and
range between 0.15 m in 2009 (maximum estimate) and close to 0.4 (lower bound
estimate) in earlier events. These paleorecords and the high fault escarpments imply that
earthquakes larger than 2009 occurred on the PF, with implications for the level of
hazard. Recurrence intervals also reflect a change with time, the average interval before
∼1000 AD is longer compared to that after this date. Two events occurred in the 2000–
4000 years preceding ∼1000 AD, while three events occurred since ∼1000 AD. The age
uncertainties affecting the interpreted events prevent the evaluation of a unique value for
interevent interval; the older events appear closely spaced in time or far apart depending
on the upper or lower boundary of the age interval. We tentatively assign an average
interevent time of ∼500 years for the three youngest events, whereas the time elapsed
between the previous ones could be larger, in the order of 1000–2000 years. We
calculate a late Pleistocene dip‐slip rate for the PF of 0.2–0.4 mm/yr, consistent with
0.25–0.5 mm/yr for the early Pleistocene. Using age and throw of individual events, we
calculate a similar late Holocene average dip‐slip rate of ∼0.3–0.4 mm/yr. This suggests that
the portion of the PF where the 2009 continuous surface faulting occurred has fairly a
constant average slip release since late Pleistocene. Finally, we discuss different rupture
scenarios and alternative models of occurrence compatible with our data and their
variability.
Description:
This work was partially
funded by the Italian Dipartimento della Protezione Civile in the frame
of the 2007–2009 Agreement with Istituto Nazionale di Geofisica e Vulcanologia
(INGV).
Description:
Published
Description:
B07308
Description:
3.2. Tettonica attiva
Description:
JCR Journal
Description:
reserved
Keywords:
2009 L'Aquila seismic sequence
;
paleoearthquakes
;
Paganica fault
;
04. Solid Earth::04.04. Geology::04.04.01. Earthquake geology and paleoseismology
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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