Barnaba (1958)
This paper describes the Mesozoic structure of the Gubbio ridge through basic 
field mapping. The ridge corresponds to a NW-SE trending anticline having a 
length of 13 km and a width of 4 km. The western limb of this NE-verging 
fold is cut by a major normal fault and dropped under the Quaternary 
deposits of the Gubbio basin, whereas the bedding of the eastern gradually 
turns to vertical. The N60W striking Gubbio normal fault is 14 km-long, dips 
60 to 70 toward the SW and truncates the older fold along its main axis. A 
secondary NE-SW striking normal fault system with maximum single offset 
of 100 m is widely recognised in the area. In some cases these secondary faults 
coincide with the periclinal closure of the Mesozoic anticline.

Barchi et al. (1984)
This work uses the macroseismic intensity data of the April 1984 Gubbio 
earthquake (maximum intensity VII) to estimate the focal depth of the event 
(15+/-3 km) and to assess a macroseismic magnitude (M=5.0). The intensity 
VII and VI isoseismals are elongated NW-SE like the main tectonic structures 
of the Apennines, whereas those of lower intensity (V and IV) strike in the 
opposite direction. A similarity between the elongation of the damage pattern 
and the strike of major extensional faults is also observed. Local 
amplifications are identified corresponding with fluvial terraces.

Menichetti et al. (1991)
These investigators map some important geological features in the area 
between the Tiber Valley and the Gubbio basin. A N130-trending system of 
normal faults dipping both towards the NE and the SW appears to dominate 
the local tectonics. This is suggested by several individual steep fault planes 
having a throw of tens to hundreds of meters. A main N140 and a 
subordinate N75 sub-vertical extensional joint systems related to a post 
compressional phase are also seen in the field, lending further support to a 
strain field with NE-SW oriented tensile vectors. The authors also describe a 
N-S transpressional fault system displacing several previously formed 
contractional structures with right-lateral kinematics. The Gubbio structure is 
a NE verging rootless anticline striking N130 and overthrusting a syncline of 
syn-orogenic formation. A SW-dipping main normal fault cuts the axial zone 
of the anticline, producing a vertical throw of more than 1000 m. This normal 
fault dips 50 to 70 to the SW and has an en-echelon pattern, WNW and 
NNW oriented in its NW and SE portions respectively, with a flex point 
located at Gubbio. At the surface the fault is 25 km long and exhibits its 
maximum offset close to Mt. Semonte. Although Quaternary piedmont 
deposits tend to hide the bedrock fault plane, some scarps on the slope debris 
and alluvial fans are observed and interpreted as surface fractures due to the 
activity of a fault splay of the main extensional structure. The basin is filled by 
300 m of lacustrine deposits, dipping toward the fault and showing a roll-over 
anticline geometry; its depocentre is located very close to the fault. 
Morphological surfaces lying on the hanging wall of the master fault are 
clearly tilted in the SE part of the Gubbio basin. Footwall uplift is seen on the 
NE side of the anticline, where fluvial paleosurfaces are uplifted by a few tens 
of meters and tilted towards the NE. The detachment of the fault is 
reconstructed using seismic profiles and field observations and assuming 2000 
m of total displacement, 1800 m of throw, 1300 m of heave, 55 of dip. The 
calculated depth of the detachment is 8 km using the Chevron method, 6 km 
using the Chevron modified method, 7.2 km with the area balance method.

Lavecchia et al. (1994)
This paper analyses regional tectonic, structural and earthquake data and 
describes the similarity between present and past geologic stress fields in the 
eastern sector of central Italy. The authors reconstruct a multistage history of 
deformation and discriminate three major seismotectonic domains: the 
Intramountain seismic zone (with strong extensional seismicity), the 
Foothills seismic zone (with deep compressional and shallow extensional 
seismicity), the Coastal seismic zone (characterized by compressional 
seismicity in the uppermost 5-10 km). The Gubbio-
Norcia-Sulmona fault pattern (named Breakaway fault zone) is identified as 
the youngest fault system and constitutes the easternmost limit of regional 
upper-crustal extension accommodated by a set of en-echelon west-dipping 
master faults. The Breakaway fault zone does not coincide with the axis of 
crustal thinning, located 60-70 km to the West. The Apennines exhibit a 
basement-involved structural style, together with a multiple detachment 
system. At any time in the Apennines orogenic phase, contraction and 
extension were simultaneously active 75-100 km apart. During about 2 My 
extension and compression shifted towards the E by 40-50 km, at a rate of 2-2.5 
cm/y. Thus any area underwent folding and thrusting before the inception of 
extensional faulting, which occurred 2-3 My later. 

Boncio et al. (1998)
These workers describe the geometry of the NNW-SSE trending Altotiberina 
fault and of some antithetic splays. The work is based on field evidence and 
on interpretation of two commercial seismic lines, from the Tiber Valley to 
the Umbria-Marche Apennines, south of the CROP 03 line. The Altotiberina 
fault exhibits a staircase trajectory, starting as a steep, shallow fault below the 
Tiber Valley to the W and the becoming an almost flat surface to the E. Its dip 
angle is low-medium below the carbonate formations, at its eastern edge. The 
Gubbio fault is antithetic to the Altotiberina fault and reaches a maximum 
displacement of about 2000 m. To the South, shortening of the Gubbio 
anticline is transferred to the more internal Subasio anticline. The 
displacement of the Gubbio fault to the South is partitioned onto three minor 
structures, the easternmost of which is the Gualdo Tadino normal fault. 
Consequently a dextral transfer of both contractional and extensional 
structures is suggested. Detailed microseismic data supplied by the 1991-1994 
recordings of the local Umbria seismic network, by a temporary network set 
up soon after the 29 April 1984 M 5.2 Gubbio earthquake (Haessler et al., 1988) 
and during May-June 1987 (Deschamps et al., 1989), are also used for 
understanding the relationships between the Altotiberina fault and regional 
seismicity. The distribution of seismic activity appears to be controlled by the 
Altotiberina fault, which separates an active hanging wall block, slipping 
towards the NE, from an almost aseismic foot wall block. Frequent 
microearthquakes and moderate size earthquakes are related to the activity of 
antithetic fault splays, such as the Gubbio fault. The interpretation of two 
seismic profiles shows an active wedge-shaped rock volume, whose base 
deepens eastward. The seismicity of the Tiber Valley, of the Gubbio area and 
of the Umbria Valley is concentrated around 6 km depth and tends to deepen 
towards the ENE up to about 12 km East of Gubbio. The authors point out that 
seismicity tends to concentrate exactly where the Gubbio fault intersects the 
Altotiberina fault, at about 6 km depth. In summary, this seismotectonic study 
identifies an highly seismic crustal block located east of the Gubbio fault. This 
crustal block is characterised by small to moderate earthquakes and by 
frequent microseismicity mainly clustered in the foot wall of the Gubbio fault, 
especially near its branch point. A second crustal block, west of the Gubbio 
fault, has a relatively aseismic behaviour, the Gubbio fault playing a role of 
release-fault between both blocks. Here the shallow microseismicity is 
interpreted as the result of adjustment processes due to the collapse of the 
hanging wall.

Barchi et al. (1999)
This work focuses on the results of the analysis of the deep reflection seismic 
profile CROP 03 and of other commercial seismic lines, both orthogonal and 
parallel to the upper Tiber valley and to the adjacent Umbrian pre-
Apennines. The subsurface geometry of the Altotiberina fault is presented in 
a geological section showing WSW-dipping antithetic faults, the most 
important of which affects the carbonatic anticlines of Gubbio and Assisi. The 
northernmost profile (Perugia massifs-Gubbio-Mt. Cucco) shows: 1) a flat and 
shallow trajectory of the western part of the Altotiberina fault, offsetting a 
marker reflector by 5 km; 2) the Gubbio fault, that is responsible for a total 
offset of 2 km, merges in a thrust at 4 km depth and ends on the Altotiberina 
fault at a depth of 5.5 km. The next profile to the South (Perugia massifs-
Fossato di Vico) exhibits steps of the Altotiberina fault trajectory and 
illustrates its flat portion, located near the Gubbio anticline. In this profile the 
Gubbio fault produces an offset of 1.3 km. The southernmost profile (Assisi-
Gualdo Tadino) shows that the Altotiberina fault has a more regular 
trajectory and that the Gubbio structure is distributed among three minor 
structures, the easternmost of which borders the east side of the Gualdo 
Tadino basin. A dextral N30-oriented transfer zone affecting both 
compressional and extensional structures is hypothesised. Finally, between 
Umbertide and Perugia the Altotiberina fault seems to deepen and shift 
westward.

Boncio et al. (2000)
This work presents a structural model for earthquake faulting in the Umbria-
Marche Apennines by integrated analysis of geological, geophysical and 
seismological data. The recent Norcia, Gubbio and Colfiorito earthquakes as 
well as a major group of microearthquakes are seen to be compatible with a 
tensional state of stress characterised by a NE-trending sub-horizontal sigma 3-
axis. This tensor, which is similar to the Plio-Quaternary stress field deduced 
from fault kinematics, may be considered representative of the mean regional 
present-day state of stress. The nucleation of the 29 April 1984 Gubbio 
earthquake is assumed to have occurred at the base of the aftershocks volume, 
close to the intersection between the SW-dipping antithetic normal fault and 
the main E-dipping Altotiberina fault. The observed low-angle dip (20-30) of 
the rupture might be explained by the inversion of a low-angle thrust, 
inherited from the Mio-Pliocene compressional phase, during the extensional 
regime. The progressive deepening of the hypocenters from the westernmost 
sectors (Gubbio) to the easternmost ones (Norcia) appears to be well related to 
the Altotiberina fault basal detachment, as shown by seismic profiles. An 
almost continuous microseismic activity (M < 3) is spread within the hanging 
wall volume of the Altotiberina fault. The seismic potential of the active faults 
is expected to be higher in the easternmost seismic zone, where the 
detachment is deeper.

Barchi et al. (2000)
In this work the geometry of the Gubbio fault is carefully analysed through 
the interpretation of six seismic profiles. The interpolation of the profile data 
allows the authors to reconstruct an isobath map of the fault. The 
reconstructed structure is N 120-striking, SW-
dipping and exhibits an offset of about 1500 m. The fault reactivated a thrust 
in its deepest part, thus acquiring a listric trajectory. The Gubbio fault is 
antithetic to the Altotiberina fault; the intersection between the two structures 
occurs at about 6 km depth in the southern part, rises to 4.5 km in the central 
part and deepens again to 5 km in the northern part. The sinistral bending of 
the surface trace of the fault seems to follow the deeper part of the structure. 
The Gubbio fault is hypothesised to be composed by two independently active 
segments; each segment is about 15 km-long and 11.5 km-wide. The thickness 
of the seismogenic layer is calculated to be about 5.5 km.
