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1 Department of Earth
Science
Carleton University
Ottawa, Ontario, K1S5B6,
Canada
dariush{at}ccs.carleton.ca
Strong-motion accelerograms recorded within northern Iran are used to examine
the propagation characteristics of shear wave, including geometric spreading
behavior, Q-value,
0, and
horizontal-to-vertical (H/V) ratio. These region-specific key seismic
parameters are estimated from 259 three-component records of 22 earthquakes with
magnitude ranging from M 4.9 to M 7.4 in northern Iran. The
geometric spreading follows a trilinear behavior with a strong postcritical
reflection from the Moho. The first and second hinges of the trilinear behavior
are at 75 and 150 km, respectively. The associated Q-value, based on
the vertical component is Q = 87 f1.46.
0 value for vertical and horizontal components are
0.03 and 0.05, respectively. Because of lack of station-specific site
information, the H/V ratio is considered to be a rough estimation of
generic site amplification. The obtained region-specific parameters are used to
estimate the average stress drop based on three stochastic modeling approaches.
Stochastic point-source modeling suggests a Brune stress drop of 125 bars,
whereas stochastic finite-fault modeling based on static and dynamic corner
frequency approaches suggests a stress drop of 68 bars.
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