Abstract
Broadband ground motion computations of scenario earthquakes are often based on hybrid methods that are combinations of deterministic approach in lower frequency (LF) band and stochastic approach in higher frequency (HF) band. It is difficult to keep consistency between LF and HF wave fields that are generated through different data and method in such hybrid approaches. In this paper, we focus on the relationship of ground motion characteristics between LF and HF bands and present a new method to synthesize HF ground motion using information extracted from LF ground motion, which we assume can be computed by a numerical method up to approximately 1 Hz. The relationship of envelopes characteristics among different frequency bands are investigated by taking their ratios at strong motion observation sites in Kanto area, Japan. We showed that HF ground motion can be appropriately synthesized by multiplying the LF ground motion by the envelope ratio functions.
