Relationships between macroseismic intensity and parameters of strong ground motions

A relationship between the macroseismic intensity estimated from the standard macroseismic equation of Shebalin [1968] and the accelerations (a(max)), periods (T-max), and duration (tau(05)) of ground motions estimated from the equations of Aptikaev and Kopnichev [1979] [GRAPHICS] logT(max) = 0.15M + 0.25log R-1.9, logtau(0.5) = 0.20M + 0.5 logR-1.3 is theoretically analyzed at fixed values of M, h, and Delta. All calculations were conducted for a point source model. A comparison between theoretical and experimental values of accelerations showed their close agreement (to within 10%) at intensities of up to 8. However, opposite tendencies are observed in model values of periods and duration of ground motions as a function of increasing intensity (an increase in T-max and decrease in tau(05)) as compared with observations (a decrease in T-max and increase tau(05)). Probable causes of the observed discrepancies are discussed in terms of development patterns inherent in extended sources of strong (M > 6.5) earthquakes.