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 source is correlated with the 25 December 1786 Riminese 
earthquake. The seismogenic fault may correspond to a blind thrust-plane 
driving the growth of the anticline detected in the area by Bally et al. (1986) 
through geophysical prospecting. The 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 25 December 1786 Riminese 
earthquake.


OPEN QUESTIONS

1) This source suggest the presence of an active thrust fault between the 
Apennines piedmont and the Adriatic coast. Could this fault belong to a 
longer fault system?

2) Do two parallel active thrust systems exist along the Adriatic coast?
