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|Authors: ||Akinci, A.*|
Hermann, R. B.*
Pino, N. A.*
|Title: ||High-Frequency Ground Motion in the Erzincan Region, Turkey:Inferences from Small Earthquakes|
|Title of journal: ||Bulletin of the Seismological Society of America|
|Series/Report no.: ||6/91(2001)|
|Issue Date: ||Dec-2001|
|Keywords: ||attenuation law|
ground motion scaling
|Abstract: ||Distance scaling of earthquake-induced ground motion is studied in the
Erzincan region, located in the eastern part of the North Anatolian Fault zone. The
data set used in this study consists of 170 aftershocks of the MS ! 6.8 Erzincan
earthquake of 13 March 1992, with moment magnitudes between 1.5 and 4.0. In
order to empirically obtain the scaling relationships for the high-frequency S-wave
motion, regressions are carried out on 352 horizontal-component short-period seismograms,
all recorded within a hypocentral distance of 40 km, to empirically obtain
the scaling relationships for the high-frequency S-wave motion.
Peak ground velocities are measured in selected narrow-frequency bands, in the
frequency range of 1.0–16.0 Hz, and are subsequently regressed to define a piecewise
linear attenuation function, a set of excitation terms, and a set of site terms. Results
are modeled in the framework of random vibration theory, using a bilinear geometrical
spreading function, g(r), characterized by a crossover distance at 25 km:
g(r)!r"1.1 is used for r ! 25 km, whereas g(r)!r"0.5 is used for larger distances.
An extremely low-quality factor, Q(f ) ! 40(f /f ref)0.45, is used to describe the anelastic
crustal attenuation in the region, consistently with the independent results of
Akinci and Eyidogan (1996, 2000).
Excitation terms are well matched by using a Brune spectral model with stress
drop Dr ! 10 MPa (taken from the recent literature, Grosser et al., 1998). An
effective high-frequency, distance-independent rolloff spectral parameter, jeff !
0.02 sec, is obtained in this study. Peak ground acceleration predictions based on
these parameters show a much more rapid decrease with distance than the relations
usually used in Turkey, indicating that our results should only be applied to the
Erzincan region itself.|
|Appears in Collections:||04.06.04. Ground motion|
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