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Strong Motion Characteristics and Structural Damage in Noto Peninsula During the 2024 Noto Hanto Earthquke

Description: 

During the 2024 Noto Hanto earthquake, we have observed strong ground motions at about 20 sites in the region of the seismogneic fault in the Noto Peninsula, primarily by the network of NIED (K-NET and KiK-net) and JMA (Shindo-kei network). We also measured microtremors at some of these strong motion sites as well as the sites in the middle of the devastating damage in Suzu City, Wajima City, and Anamizu Town several days after the mainshock. The occurrence of aftershocks were continued at that time and so what we measured should be considered as small aftershocks. Before the mainshock we have been analysing the site effects of all the strong motion network sites in Japan and found that conspicuous strong site amplifications were observed at the strong motion sites in these cities and towns inside the Noto Peninsula. There is a strong concern what is the primary source of the observed heavy damage in these three cities and towns. To that end we used a structural damage prediction models developed by the damage statistics during the 1995 Kobe earthquake (Nagato and Kawase, 2000) in which we can calculate structural damage probabilities by using a set of structures with different seismic capacities for each category of buildings and houses. When we applied the model for 2-storied wooden houses, we hound that at the sites in the middle of the heavily damaged zones the calculated damage probabilities reach to about 30 %. This level of damage ratios corresponds to the observed damage ratios around the strong motion sites performed by a team of Profs. Nakazawa and Sakai as an immediate survey in the field (Nakazawa et al., 2024). Considering the limited area of the damage concentration in Suzu City, Wajima City, and Anamizu Town, there is no space for doubt where the site effects played a significant role for the structural damage distributions in these cities and towns. However, we should emphasize that this correlation with site conditions should not be interpreted as a consequence of amplification above the engineering badrock, because the amplification is high in the intermediate frequency around 1 Hz and lower.

Session: The 2024 Magnitude 7.5 Earthquake and the Associated Earthquake Swarm Beneath the Noto Peninsula, Central Japan - I

Type: Oral

Date: 5/3/2024

Presentation Time: 08:45 AM (local time)

Presenting Author: Hiroshi

Student Presenter: No

Invited Presentation: 

Authors