COMMENTS

Several works on the stratigraphy, geomorphology, and tectonics of the Gargano 
area are published in the Italian literature (see references), but in general 
they do not consider the relations between seismicity and tectonic setting nor 
investigate the possible location of the major seismogenic sources. 

Defining the present activity of the Mattinata Fault is the main issue for this 
source. The fault geomorphology is certainly impressive, but a long tectonic 
history may have left a very strong geomorphic signature, especially durable in 
calcareous rocks, that may make the fault appear active even though it is not. 
This condition has been observed for other faults in calcareous rocks in the 
Apennines, particularly if they have been rejuvenated by regional uplift. In 
addition according to Argnani et al. (1993) no important deformation is seen 
offshore on the prolongation of the Mattinata Fault since the Early Pliocene. 
However, seismicity occurs on or near this structure with small and moderate 
size earthquakes possibly up to M 6.2.

Piccardi (1998) was the first and only investigator who interpreted this fault 
as a potential source of large earthquakes and quantified all its seismogenic 
parameters. Although this fault does not show clear evidence for active 
deformation offshore, the geomorphic evidence of the Mattinata section is very 
convincing and the Database adopted Piccardi's (1998) fault parameters to 
describe this source. However, the lack of a well-known large historical 
earthquake associated with this structure and of paleoearthquakes and the 
ongoing debate on its present activity and kinematics, oblige us attribute to 
this source a low/medium reliability. 

The easternmost tip of this source conceivably ruptured in 1893 during a M5.2 
event. According to Baratta (1894), this event produced also small surface 
breaks along the trace of the Mattinata Fault.


OPEN QUESTIONS

1) The Mattinata Fault is known as an important crustal structure with a long 
tectonic history. However, its evolution and kinematics are the matter of debate 
among structural geologists. Is this fault presently active? Is it a potential 
seismic source? If this is the case, is it a purely strike-slip fault? And is it slipping as 
a dextral or sinistral fault?

2) Could the broad Mattinata Fault be the site of seismic release by frequent moderate to 
small magnitude earthquakes instead of by few large events? This is common in old 
major tectonic features in active regions. The earthquakes of 1893 (Me=5.2) and 1955 
(Me=4.8) may have ruptured portions of the Monte Sant'Angelo section.

3) Could the three portions of the Mattinata fault defined by Piccardi (1998) 
and adopted by this Database be considered as fault segments in the sense of 
Schwartz and Coppersmith? If this is the case, how well defined are the segment 
boundaries? 

4) Conversely, can the three fault sections be part of a single larger seismogenic source?

5) Can the 1-1.5 m sub-vertical scarp used to define the slip-per-event be 
evidence for more events? If slip-per-event is overestimated, other parameters 
derived from it may change too (e.g., average recurrence time, Mmax).

6) When did the most recent earthquake generated by this source occur?

