Practical Engineering Approach for Generating the Torsional Earthquake Excitation from Translational Components

Worldwide networks of seismic recording instruments mostly record only translational ground motion in two or three orthogonal directions. Rotational component of earthquake is not commonly recorded. Several theories are available to estimate a torsional component from recorded translational components of ground motion. In this paper detailed investigations are made to study the relative performance of some available methods. This paper suggests a practical approach for obtaining true SH (S-wave having particle motion in horizontal direction) component from two recorded horizontal components of ground excitation. This new approach will help to obtain optimum torsional time histories from translational time histories.