A Ground-Motion Predictive Model for Iran and Turkey for Horizontal PGA, PGV, and 5% Damped Response Spectrum: Investigation of Possible Regional Effects

We present a ground-motion prediction equation (GMPE) for Turkey and Iran to investigate the possible regional effects on ground-motion amplitudes in shallow active crustal earthquakes. The proposed GMPE is developed from a subset of the recently compiled strong-motion database of the Earthquake Model of the Middle East Region project (see Data and Resources). A total of 670 Turkish and 528 Iranian accelerograms with depths down to 35 km are used to estimate peak ground acceleration, peak ground velocity, and 5% damped elastic pseudospectral acceleration ordinates of 0: 01 s <= T <= 4 s. The moment magnitude range of the model is 4 <= M-w <= 8, and the maximum Joyner-Boore distance is R-JB = 200 km. The functional form considers three major fault mechanisms (strike slip, normal, and reverse). The nonlinear soil behavior is a function of V-S30 (average shear-wave velocity in the upper 30 m of soil profile). Our observations from empirical and estimated ground-motion trends advocate regional differences in the territories covered by Iran and Turkey that originate from the differences in Q factors, kappa, and near-surface velocity profiles. These factors eventually affect the magnitude- and distance-dependent scaling of spectral amplitudes in Iran and Turkey. In essence, the ground-motion amplitudes of these two neighboring countries would draw patterns different than the ground-motion estimates of GMPEs developed from the strong-motion databases of shallow active crustal earthquakes from multiple countries.