COMMENTS

The northern Marche coastal zone is presently affected only by low seismic 
activity. However, damaging earthquakes stroke this area in the recent past (e.g. 
in 1930, Senigallia). A NW-SE trending minimum stress axis and a NE-SW 
trending maximum compressive stress axis were shown respectively by bore-hole 
breakouts and earthquake focal mechanisms (Mariucci et al., 1999; Frepoli and 
Amato, 1997). The available field 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, points at considering 
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. Such thrust system appears to be segmented into 
several sources and NE-SW trending faults may be expected to lay at their 
boundaries.

The Coriano source is correlated to the 14 April 1672 earthquake. The location, 
geometry and size are based on the correlative purely historical (i.e., based on 
intensity data alone) source which hints at a structure that runs crosswise to the 
thrust system. Its geometry is suggestive of a tear fault located at the boundary 
between two discrete segments. Since a moderate tsunami is described in 
historical reports of the 1672 earthquake (e.g., Boschi et al., 1997), one can also 
assume that the fault has a rather large component of dip slip.


OPEN QUESTIONS

1) Is this source the evidence of a "transverse" (NE-SW) seismogenic structure?

2) May other similar structures exist along the system and be potential sources of 
earthquakes?

3) May such structures operate as segment boundaries for the longitudinal (NW-SE) 
system?

4) May the occurrence of the tsunami disprove the hypothesis of a dominantly strike-
slip tear-fault?

5) Is there a seismic gap just to the SE of the Coriano source?
