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The Earthquake Research Committee (ERC) of the Headquarters for Earthquake Research Promotion creates and updates national seismic hazard maps for Japan to help develop effective measures against earthquake hazards. The maps published by the ERC are based on seismic intensity; however, seismic hazard maps based on earthquake response spectra have become widespread in other countries and are used for engineering purposes, such as seismic design. In light of this, the Subcommittee for Evaluation of Strong Ground Motion under the ERC published a provisional probabilistic seismic hazard analysis (PSHA) of response spectra to contribute to discussions on the utilization of the PSHA for various needs, including engineering purposes. This paper discusses the provisional PSHA of response spectra, selection of ground motion prediction equations, evaluation conditions, evaluation results, utilization, and its future prospects. The development of the PSHA of response spectra is expected to continue, contributing to seismic design and serving as a basic resource for disaster prevention planning according to probability levels. The results of the provisional PSHA are anticipated to be discussed with various stakeholders, including those involved in disaster prevention, research, and the construction industry, to help develop the PSHA of response spectra.
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We applied NIOM analysis to the earthquake records at the KiK-net Togi site to examine nonlinear behavior of the ground during the 2024 Noto Hanto earthquake. Results revealed that (1) S-wave propagation times increased from 0.2365 s (NS) and 0.2333 s (EW) before the mainshock to 0.3136 s and 0.3245 s, respectively, during principal motion, and (2) S-wave propagation times at the end of the waveform were larger than those before the mainshock by 6 to 6.5%. In addition, a SHAKE91 analysis indicated that (3) the effect of nonlinear behavior was remarkable in the soil layer from GL −28 to −50 m.
