Amato et al. (1976)
Based on a complete geological, geophysical and seismological data-set (surface 
structural and geological data, seismic exploratory profiles and. seismological 
observations), these workers reconstruct the evolution of the 1976 Friuli 
sequence. In particular they propose a faulting mechanism for the 6 May 1976, 
M=6.4 and for the 15 September 1976 (09h 21m), M=6.0 earthquakes. Analysing the 
spatial and time distribution of these main shocks and of their aftershocks 
(after Finetti et al. [1976]), they point out that the hypocentral location of 
the May earthquake is more to the South and is shallower than that of the 
September event; besides they notice that the hypocenter of the May earthquake 
lies on the down-dip prolongation (with a 25 of dip) of the Buia-Tricesimo 
Line. On this basis the authors hypothesise that the 6 May 1976 earthquake 
occurred on a EW-trending, S-verging, low-angle thrust belonging to the Dinaric 
system, while the 15 September 1976 earthquake was generated by a deeper EW-
trending, S-verging, blind thrust, located more to the North and belonging to 
the Periadriatic System.

Bosi et al. (1976)
These workers map surface ruptures located in the epicentral area of the 6 May 
1976 Friuli earthquake by means of air photos interpretation and aerial and 
field surveys. The authors as a first step interpret air photos taken in the 
epicentral area before the 1976 earthquake, and on the basis of geomorphic 
observations hypothesize the presence of a major EW-trending, S-verging active 
tectonic structure ("Sovrascorrimento periadriatico"). This thrust fault put in 
contact dolomitic limestones with younger flysch sediments (marls, claystones 
and sandstones) outcropping to the South. As a second step the authors study in 
detail the active tectonic structure few days after the 6 May 1976 earthquake, 
and map several ground fractures located where the "Sovrascorrimento 
periadriatico" outcrops. They describe an EW-oriented, 400-500 m long ground 
fracture, on the southern slope of Mt. Cuar, West of the Tagliamento River. The 
rupture mainly cut loose soils and slope deposits, with an average height of few 
decimeters and a maximum offset of 2-3 m, and with southern side down. Downslope 
of the main rupture they mapped few 20-30 m long secondary surface ruptures, 
with 30-40 cm of average offset. The authors also recognize a strike-slip 
component of offset. Bosi et al. also describe a SW-NE-oriented set of ground 
ruptures on the southern slope of Mt. Cuarnan, East of the Tagliamento River. 
These ruptures also dislocated loose soils and slope deposits, with a maximum 
height of 60-70 cm, with southern side down. The authors suggest that the mapped 
ground fractures may be the direct surficial expression of slip on a main EW-
striking thrust fault as a consequence of the 6 May 1976 Friuli earthquake.

Finetti et al. (1976)
These investigators calculate the epicenter location of the May and September 
main shocks and aftershocks using a mobile seismic array, and propose a 
correlation between the main earthquakes and tectonic structures imaged in oil 
industry reflection profiles. They point out that the aftershocks of the May 
earthquake lay in the area of Gemona, and are found only E of the Tagliamento 
River; instead the September aftershocks are located northward, seem to be 
deeper and have a wider E-W dispersion. According to the authors, the projection 
of the September aftershocks onto a N-S section running East of the Tagliamento 
River, shows a good fit of the hypocenters with a N-dipping fault plane, which 
would correspond with the "Periadriatic thrust fault". Finally Finetti et al. 
hypothesize that the 6 May 1976 earthquake occurred on the Buia-Tricesimo thrust 
fault, while the 15 September 1976 earthquake was generated by the Mt. Chiampon 
thrust fault, this event being triggered by the first earthquake.

Lyon-Caen (1980)
This thesis presents a relocation of all the main shocks and the aftershocks of 
the Friuli sequence and computes the focal mechanisms of the 4 main shocks (6 
May 1976; 11 September 1976; 15 September 76 03h15 and 09h21) analysing long-
period teleseismic body waves. Even if the hypocentral depths are not well-
constrained, all of them seem to be located between 0 and 12 km depth. Lyon-Caen 
also points out that the earthquake sequence migrated westward since the 
epicentral location of the May and September main shocks are aligned in a E-W 
direction that follows the regional trend of the main tectonic structures. 
According to the author, this hypothesis is confirmed by several lines of 
evidence: the EW elongation of the isoseismal contour lines, the shape of the 
contour lines of the coseismicsly uplifted area as shown by the geodetic data, 
and the aftershock distribution.

Cipar (1980 and 1981)
This worker modeled short-period and long-period seismograms of the 5 May 1976 
Friuli earthquake and of the two main September aftershocks using synthetic 
seismograms. The hypocenters of the 6 May and 15 September (09h21) earthquakes 
are found to lie between 6 and 10 km depth, and based on their focal mechanisms 
they represent underthrusting of the Friuli plain beneath the southern Alps. 
The fault length of the main shock could not be larger than 16 km. 

Briole et al. (1986)
These investigators propose a fault model for the main earthquakes of the 1976 
Friuli sequence derived from the inversion of leveling data and using as initial 
fault parameters those proposed by Lyon-Caen. According to their best-fitting 
model the 6 May 1976 earthquake occurred on a S-verging, N72-striking, low-
angle thrust located East of the Tagliamento River; the 15 September 1976 
(03h15) event on a S-verging, N35-striking, low-angle thrust; and the 15 
September 1976 (09h21) event on a S-verging, N70-striking, low-angle thrust. 
The last two faults are located West of the Tagliamento River, in agreement with 
the seismological observation of a westward migration of the deformation.

Perniola et al. (1999)
These workers use the location and focal mechanisms proposed by Pondrelli et al. 
(2001) for the main shocks of the Friuli seismic sequence as starting input for 
their fault model (10 earthquakes ranging in magnitude between 5.0 and 6.4), and 
study it with a Coulomb failure stress approach. Assuming a N-S-oriented 
regional stress field, the authors justify the whole sequence in terms of mutual 
stress interaction between adjacent faults. They also highlight a westward 
migration of the seismicity during the sequence, and propose that the 
earthquakes characterized by higher magnitude mainly occurred on EW-trending 
thrusts and triggered the other events on NW-SE-striking faults belonging to the 
Dinaric System.

Aoudia et al. (2000)
This paper revisits the 1976 earthquake sequence by combining different data 
sets. The authors using a joint inversion method of long-period surface wave 
spectra calculate the geometrical parameters of the main shock (6 May 1976) and 
of the two largest aftershocks (15 September 1976, 03h15 and 09h21). In addition 
to preforming standard seismological analysis, they observe that all the 
aftershocks were located west of the 6 May 1976 main shock; according to them 
this implies a unilateral and westward propagation of the rupture. The authors 
assume that the three main events could have occurred on three different 
segments of a S-verging, EW-striking blind thrust, the surface expression of 
which can be found in the Bernardia thrust and in the Buia and Susans folds. 
They also point out that their fault model can reproduce the accelerograms 
recorded in the area. The geometrical parameters of their model fault are the 
following: length 18.5 km; width 11.2 km; dip 20 northward; depth of the top 
1.5 km.

Pondrelli et al. (2001)
These investigators review the locations of the 10 largest events 
of the Friuli sequence (including the 16 September 1977 and 18 April 1978 
events) computing their centroid moment tensors and source parameters. They 
compare their estimates with all available geological, geodetic and 
seismological data and conclude that most of the earthquakes may be associated 
with the EW-striking Periadriatic thrust system, whereas only two aftershocks 
(07 May 1976 and 09 May 1976) appear to have occurred on NW-SE-striking Dinaric 
structures.
