Abstract:

The characteristics of surface ground motion are apparently affected by the nonlinear behavior of site soil under strong motion input. The soil nonlinear behavior is firstly discovered by geotechnical engineers in laboratory tests; and then the seismologists confirm it by analyzing record data from the strong motion observation. Generally speaking, the site soil nonlinear behavior becomes more significant while the earthquake excitation increases; however, for different site types and same excitation level, there would be different site soil nonlinear behaviors. A method is proposed to determine the corresponding earthquake motion input thresholds for typical sites based on the relationship of shear wave velocity variation ratio and earthquake excitation.

Key words: site types, nonlinear effect, earthquake motion input level