According to the present design standard for port and harbor structures, the seismic coefficients corresponding to the severity of ground motions were obtained
for 129 gravity quaywalls in 49 ports damaged by 12 earthquakes. The maximum ground accelerations in the ports were estimated by calculating the ground response during the earthquakes. The maximum ground accelerations in the ports were estimated by calculating the ground response during the earthquake with reference to the attenuation curves of the base rock acceleration based on the accelerograms in port area.
　The seismic coefficients in the past earthquakes were up to 0.25, and the upper limit of the relation between the coeficient and the maximum ground acceleration was expressed by the following equation.
　eA=1/3(α/g)1/3
Where, eA:seismic coefficient
　　　　　α:maximum ground acceleration (gal)
　　　　　g:gravitational acceleration (gal)