Datensatz

Zusammenfassung

The corner frequency of the seismic source spectrum and the stress drop are crucial to predict accurate strong ground motion. These parameters depend on other parameters, such as the focal mechanism, depth, and focal region. A high occurrence probability is estimated for a megathrust earthquake along the Kuril trench from off Tokachi to off Nemuro, Hokkaido, Japan. We tried to determine the corner frequency and stress drop using M>5 earthquakes to improve the accuracy of the strong motion prediction of megathrust earthquakes in this area. Using spectral inversion analysis, we separated the seismic source characteristics, propagation path, and site amplification from the strong ground motion records of middle to large earthquakes in the southern Kuril trench. The site amplification factor of HKDH05, a rock site, is a constraint condition. We obtained the source characteristics of 159 earthquakes and the site amplification characteristics of the 190 sites. The Qs value for the attenuation characteristics in the fore-arc region of the volcanic front is consistent with previous studies, and the site amplification characteristics are also comparable to existing values from previous studies. Regarding the seismic source spectra, we fit the omega-squared model and obtained the corner frequency for each earthquake. The short-period levels extracted from the fitted source spectra of intraslab earthquakes are approximately twice as high as those of interplate earthquakes. The stress drops have a weak correlation with the focal depth and vary depending on the focal region, with values off Nemuro being larger than those off Tokachi.