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 Rimini offshore North source is correlated with the 17 May 1916 Alto 
Adriatico earthquake. The seismogenic fault may be correlated with a blind 
thrust-plane which drives the growth of the offshore anticline detected by 
Bally et al. (1986) through geophysical prospecting. Location, geometry and 
width of fault at depth are based on the seismic reflection profile by Bally et 
al. (1986). Its size conforms to what is predicted by empirical relationships 
between length/width and magnitude relative to the 17 May 1916 Alto 
Adriatico earthquake.


OPEN QUESTIONS

1) This source suggest the presence of an active thrust fault in the Adriatic 
offshore. Could this fault belong to a longer fault system?

2) How many parallel active thrust systems exist along the Adriatic coast?

3) Are these active fault-systems entirely seismogenic?
