Abstract
Shortage of a conventional method to define input earthquake motion for the analysis of a surface ground is pointed out and improved methods are proposed. In a conventional method, rock outcrop motion or incident wave defined at the engineering seismic base layer is frequently used as design earthquake motion. A case study is firstly coducted using the Hachinohe site model in order to validate the applicability of this method, and this method is shown to miss amplifications in important frequency region through the investigation of amplification characteristics, engen value analysis and waveform, therefore, is not relevant to evaluate ground motion at the ground surface. Then, two methods are proposed to define the design earthquake motion. The one is to define it at the ground surface and the other is to use incident wave at the engineering seismic base layer obtained in the elastic analysis of overall ground. Both method can reproduce the surface response perfectly in the elastic case, and much better evaluation compared with the conventional method.
