Publication Date:
2017-04-04
Description:
In this study, we provide a complete description of the ground-motion characteristics of
the western Anatolia region of Turkey. The attenuation of ground motions with distance
and the variability in excitation with magnitude are parameterized using three-component
0.25-10.0 Hz earthquake ground motions at distances of 15 - 250 km. The data set is
comprised of more than 11,600 three-component seismograms from 902 regional
earthquakes of local magnitude (ML) 2.5 to 5.8, recorded during the Western Anatolia
Seismic Recording Experiment (WASRE) between November 2002 and October 2003.
We used regression analysis to relate the logarithm of measured ground motion to the
excitation, site, and propagation effects. Instead of trying to reproduce the details of the
high-frequency ground motion in the time domain, we use a source model and a regional
scaling law to predict the spectral shape and amplitudes of ground motion at various
source-receiver distances. We fit a regression to the peak values of narrow bandpass
filtered ground velocity time histories, and root mean square and RMS-average Fourier
spectral amplitudes for a range of frequencies to define regional attenuation functions
characterized by piece-wise linear geometric spreading (in log-log space) and a
frequency-dependent crustal Q(f). An excitation function is also determined, which
contains the competing effects of an effective stress parameter k0 and a high-frequency
attenuation term exp(-k0f). The anelastic attenuation coefficient for the entire region is
given by Q(f) = 180f 0.55. The duration of motion for each record is defined as the value
that yields the observed relationship between time-domain and spectral-domain
amplitudes, according to random process theory. Anatolian excitation spectra are
calibrated for our empirical results by using a Brune model with a stress drop of 10 MPa for the largest event in our data set (Mw 5.8) and a near-surface attenuation parameter of
κ =0.045 s.
These quantities, together with the effective duration of ground motion in the region, are
used to estimate the peak ground motion (PGA, PGV). Using stochastic ground motion
simulations, we predict the absolute level of ground shaking and compare them with
strong-motion data in the region. The attenuation of simulated ground motion is
compared with recent global and regional ground motion prediction equations (GMPEs).
The performance of the stochastic model is also tested against small and intermediatesized
earthquakes (the M3.9 11 November 2007, M5.9 17 October 2005 and M5.7 20
October 2005 Izmir-Urla earthquakes) recorded by strong motion stations in the National
Strong Ground Motion Network (operated by the Earthquake Department of the Disaster
and Emergency Management Presidency, AFAD).
Description:
Published
Description:
124-135
Description:
3T. Pericolosità sismica e contributo alla definizione del rischio
Description:
JCR Journal
Description:
restricted
Keywords:
Seismic attenuation, earthquake source parameters, ground motion
;
04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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