COMMENTS

The northern Marche coastal zone is presently affected only by low seismic 
activity, but damaging earthquakes struck this area in the recent past (e.g. in 
1930, Senigallia). A NW-SE trending minimum stress axis and a NE-SW 
trending maximum compressional stress axis were shown respectively by 
bore-hole breakouts and earthquake focal mechanisms (Mariucci et al., 1999; 
Frepoli and Amato, 1997). The available field geological observations are still 
inadequate to devise a fully convincing correlation between the occurrence of 
earthquakes and realistic seismogenic sources. However, the most realistic 
hypothesis that can be envisaged to-date on the basis of the local geologic 
setting considers the blind thrust-faults located at the leading-edge of the 
Apennine accretionary prism as the main active and probably seismogenic 
faults in the area. In addition, it seems likely that two parallel fault-
alignments of this sort exist along the northern Marche offshore.

The Pesaro San Bartolo source has no historical earthquake associated with it. 
Its existence and location are suggested by geological observations at regional 
and local scales. The seismogenic fault may be correlated with a blind thrust-
plane which drives the growth of the coastal anticline detected by geophysical 
prospecting and analysis of geomorphic features. The geometry and width of 
fault at depth are based on the seismic reflection profiles by Bally et al. (1986) 
and De Donatis et al. (1998). Its length is constrained on the the basis of major 
fluctations and offsets of the fold axial-plane.


OPEN QUESTIONS

1) Is the coastal anticline growth driven only by stable-sliding on the 
underlying thrust-
fault?

2) May stick-slip episodes occur on this fault?

3) If they do, should this source be considered a seismic gap?
