Publikationsdatum:
2017-04-04
Beschreibung:
In order to empirically obtain the scaling relationships
for the high-frequency ground motion in
the Western Alps (NW Italy), regressions are carried
out on more than 7500 seismograms from 957 regional
earthquakes. The waveforms were selected from the
database of 6 three-component stations of the RSNI
(Regional Seismic network of Northwestern Italy). The
events,MW ranging between 1.2 and 4.8, were recorded
within a hypocentral distance of 200 km during the
time period: 1996–2001. The peak ground velocities
are measured in selected narrow-frequency bands, between
0.5 and 14 Hz. Results are presented in terms of
a regional attenuation function for the vertical ground
motion, a set of vertical excitation terms at the reference
station STV2 (hard-rock), and a set of site terms
(vertical and horizontal), all relative to the vertical component
of station STV2.
The regional propagation of the ground motion is
modeled after quantifying the expected duration of the
seismic motion as a function of frequency and hypocentral
distance. A simple functional form is used to take into account both the geometrical and the anelastic attenuation:
a multi-variable grid search yielded a quality
factor Q( f ) = 310 f 0.20, together with a quadri-linear
geometrical spreading at low frequency. A simpler, bilinear
geometrical spreading seems to be more appropriate
at higher frequencies (f 〉 1.0 Hz). Excitation
terms are matched by using a Brune spectral model
with variable, magnitude-dependent stress drop: at Mw
4.8, we used σ = 50MPa. A regional distanceindependent
attenuation parameter is obtained (κ0 = 0.012 s) by modelling the average spectral decay at high
frequency of small earthquakes.
In order to predict the absolute levels of ground
shaking in the region, the excitation/attenuation model
is used through the Random Vibration Theory (RVT)
with a stochastic point-source model. The expected
peak-ground accelerations (PGA) are compared with
the ones derived by Ambraseys et al. (1996) for the
Mediterranean region and by Sabetta and Pugliese
(1996) for the Italian territory.
Beschreibung:
Published
Beschreibung:
315-333
Beschreibung:
JCR Journal
Beschreibung:
reserved
Schlagwort(e):
Attenuation
;
Ground motion
;
Western Alps
;
04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
Repository-Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Materialart:
article
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