Abstract
We derive the relative moment rate function for the shocks with Mw
> 5 in the 1997-98 central Italy seismic sequence, started with the
Mw = 5.7, 09/26/97 00:33 event, by applying an empirical Green function
method. By using three conveniently placed broadband MedNet stations
we obtain apparent source time functions indicating clear directivity
effects for all of the analysed earthquakes, with rupture propagation
generally directed outward from the epicentral area of the 09/03/97
foreshock sequence. Taking a simple source model, forward modeling
is utilized for determining fault parameters such as length, rupture
propagation velocity and direction and, for the three major events,
slip distribution. The effects of the break propagation directions
on the sequence evolution is discussed. A possible inconsistency
results for the shallow 04/03/98 shock, which could be avoided if
a link with the deep 03/26/98 event is assumed. Our analysis evidences
the importance of a quick determination for the fault parameters
in order to image the possible induction of fracturing on nearby
structures.
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