Qβ, Qc, Qi, Qs of the Gargano Promontory (Southern Italy)

We have provided the first estimate of scat-
tering and intrinsic attenuation for the Gargano Prom-
ontory (Southern Italy) analyzing 190 local earthquakes
with M L ranging from 1.0 to 2.8. To separate the intrin-
sic Q i and scattering Q s quality factors with the Wen-
nerberg approach (1993), we have measured the direct
S waves and coda quality factors ( Q 𝛽 , Q c ) in the same
volume of crust. Q 𝛽 parameter is derived with the
coda normalization method (Aki 1980) and Q c factor
is derived with the coda envelope decay method (Sato
1977). We selected the coda envelope by performing an
automatic picking procedure from T start = 1.5T S up to
30 s after origin time (lapse time T L ). All the obtained
quality factors clearly increase with frequency. The Q c values correspond to those recently obtained for the
area. The estimated Q i are comparable to the Q c at all
frequencies and range between 100 and 1000. The Q s
parameter shows higher values than Q i , except for 8 Hz,
where the two estimates are closer. This implies a pre-
dominance of intrinsic attenuation over the scattering
attenuation. Furthermore, the similarity between Q i and
Q c allows us to interpret the high Q c anomaly previ-
ously found in the northern Gargano Promontory up to
a depth of 24 km, as a volume of crust characterized by
very low seismic dumping produced by conversion of
seismic energy into heat. Moreover, most of the earth-
quake foci fall in high Q i areas, indicating lower level of
anelastic dumping and a brittle behavior of rocks.