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

Abstract

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.Online Material: MATLAB code and regression coefficients for computing the response spectrum and distance scaling.

Single Station Sigma for Turkish Strong Motion Stations

“…As magnitude dependency for τ SS values was not observed in this study, they are suggested in table 2 as constants although between-event standard deviations, τ, of [1] have magnitude dependency. In figure 9, variation of betweenevent standard deviation and source corrected between-event standard deviation values with spectral period is given for M w <6.0 and M w >6.5 events.…”

“…As a result magnitude independent event corrected single station standard deviations and source corrected between-event standard deviations are suggested (table 2). In order to preserve the [1] suggested within-event standard deviation-spectral period model for the event corrected single station standard deviations, the maximum likelihood approach was adopted. In figure 5, variation of within-event standard deviation and event corrected single station standard deviation values with spectral period is given for M w <6.0 and M w >6.5 events.…”

“…The same epistemic uncertainty value was adopted for τ ss in this study. [1] GMPE in the case of M w <6.5 events.…”

“…It is further possible to reflect the esti-mated source term to the [1] suggested GMPE and by doing so it would be possible to convert it from a regional GMPE to a local GMPE specifically suitable for the Marmara region. This modification can be achieved by suggesting updated b 1 coefficients for the [1] GMPE (listed in table 2); only to be used in the case of M w <6.5 events. For M w >6.5 events, use of original b 1 coefficients as proposed by [1] is recommended.…”

“…This modification can be achieved by suggesting updated b 1 coefficients for the [1] GMPE (listed in table 2); only to be used in the case of M w <6.5 events. For M w >6.5 events, use of original b 1 coefficients as proposed by [1] is recommended.…”