COMMENTS

The source included in the Database is derived by the modelling of the 1968 
earthquake performed by Morelli and Ponderelli (1998). 

The 1968 Belice earthquake sequence occurred in a region that lacks any obvious 
morphological evidence for active faulting and any historical evidence of seismicity, 
and in fact it came totally unexpected. Some surface breaks were observed, however 
their significance is highly debatable given also the size of the earthquake. The 
magnitude of the mainshock (Mw=5.6 according to Morelli and Pondrelli, 1998) 
is close to the minimum magnitude threshold for surface-breaking earthquakes.

Recent active stress investigations indicate a NS orientation of the H max in the area, 
in agreement with the orientation of the P axis as determined from the available focal 
mechanisms. However, according to these mechanisms both an E-W-trending thrust 
and a NNW-trending strike slip fault could be indicated as responsible for the main 
shock. The NNW-trending structure is in agreement with the NS alignment of the 
epicentres of the largest shocks, whereas the felt area associated with the mainshock 
is more compatible with a E-W-trending structure (notice that the distribution of
damage proposed in current catalogues does not separate the effects of the mainshock 
and of all the other shocks).

Based on paleoseismological investigations Michetti et al. (1995) suggest that the 
Monte Porcello fault ruptured in the 1968 earthquake and has recorded even larger 
events, but they interpretations are highly speculative with respect to the data at 
hand. 


OPEN QUESTIONS

1) Was the earthquake too small to induce sizeable permanent deformation at the 
surface, or was generated by a blind fault?  

2) Could the earthquake have been generated by a blind crustal thrust ramp that 
propagated the slip from the epicentral area southeastward for over 30 km, as 
suggested by Monaco et al. (1996)?

