This Source includes all faults reported by Blumetti (1995) and Cello et al. (1998) as having been activated during the 2 February 1703 earthquake.
We confirm this hypothesis for all these ruptures with the only exception of the Cittareale Fault (Blumetti, 1995), based on structural considerations.
1) Is there a true direct relation between the historical reports of surface ruptures following the 1703 earthquake and the inferred seismogenic sources?
2) On the basis of the observation by Blumetti (1995) that only one surface faulting event occurred on the Arischia fault since about 30 Kyr and two events occurred since 186 Kyr, the expected recurrence time for this source appears much longer than expected. What is a reliable estimate for the average recurrence time of this source?
3) Is the 1703 earthquake the post-29,690±1,110 B.P. event recognised by Blumetti (1995)?
4) What is the tectonic regime that drives this Source? Is this fault part of a crustal, N-striking, strike-slip shear zone (Cello et al. 1997), or is it an extensional feature as suggested by most geophysical studies (break-out analyses, focal solutions and paleoseismology) and other geological studies (e.g. Calamita et al., 1994, among many others)?
She reviews the historical descriptions of surface phenomena occurred in the Norcia-L'Aquila areas during the 1703 earthquakes sequence and compare them with field evidence with the aim of localising the surface ruptures related to seismogenic sources. The author concludes that surface ruptures are the result of the 14 Jan. I=IX MCS, and the 2 Feb. 1703 I=IX MCS, earthquakes. These ruptures occurred close to pre-existing normal faults bounding Meso-Cenozoic ridges that are part of a NNW-striking belt about 50 km-long and 5 km-wide, extending from Norcia to L'Aquila basins.
In particular, she infers that the 2 Feb. earthquake surface ruptures occurred at three locations: 1) western side of Mt. Laghetto Ridge (Cittareale Fault, west-side down), 2) western side of Montereale basin (Montereale Fault, east-side down), and 3) Rotigliano Plain (Rotigliano Fault, west-side down). Along the Mt. Marine Ridge (Arischia Fault, west-side down) secondary effects occurred.
Across the Arischia Fault area a foundation trench exposed a faulted stratigraphic sequence with at least two faulting events. The most recent occurred after 29,690±1,110 yr B.P. and is responsible for the deposition of a 2 meters thick colluvial wedge (expected MS=6.9); the previous one occurred between 186 kyr and 29,690±1,110 y B.P.
Cello et al. (1997)
They observe that the epicentral area of the 1703 earthquake sequence coincides with the Norcia-L'Aquila fault set, that is the central fault set of the so-called Central Apennines Fault System (CAFS). The CAFS is modelled by means of morphotectonic and structural investigations as a system of linked N-S trending left-lateral strike-slip faults, and from NNW to WNW-trending transtensional and normal faults driven by a crustal, left-lateral, N-striking shear zone. The Norcia-L'Aquila fault set is divided into three main N-S trending fault segments linked each other: the Norcia, Cittareale and L'Aquila segments. The Norcia fault is composed by splays that bounds both the western and eastern sides of the Norcia basin cutting Meso-Cenozoic bedrock and Holocene slope deposits with vertical movement. The authors conclude that surface ruptures from the 14 Jan. 1703 earthquake occurred along the western side of the Norcia basin and relate the two meters-high Misciano scarps studied by Michetti et al. (1996) to this earthquake on the basis of their geomorphic evidence. At its northern and southern end the Norcia fault set bends to reach N-S strike joining the Cittareale fault set to the South. Surface ruptures from the 1703 earthquake sequence are reported to have occurred also along the Castel Santa Maria and Monte Pizzuto faults that are connected to the Cittareale fault set. The NNW-SSE fault bounding the eastern side of the Castel Santa Maria basin has a 7-m high steep scarp in bedrock and bends southward to reach a N-S strike showing a 25-m lateral post-Wurmian offset. From these observations the authors obtain a 0.3-0.5 mm/yr vertical slip rate, and a 0.9-1.5 mm/yr horizontal slip rate during Holocene. Horizontal slip rate for a left-lateral strike-slip fault located in Manigi, west of Castel Santa Maria, provides similar value.
Cello et al. (1998)
To investigate further on the tectonic behaviour of the Norcia-L'Aquila fault set they develop a fractal analysis providing 1.22 as fractal dimension of the Norcia-L'Aquila set. They infer that this is an immature fault structure growing by localised strain within discrete fault sets.