Photo/Illutration The Noto Peninsula earthquake on Jan. 1, 2024, caused houses to collapse in the Togi area of Shika town, Ishikawa Prefecture, where a nuclear power plant is located. (Koji Nishimura)

Nearly 80 percent of municipalities within 30 kilometers of 15 nuclear power plants across Japan have a lower proportion of earthquake-resistant homes than the national average, a survey found.

Despite their proximity to possible nuclear disasters caused by natural disasters, homes in these areas would be more prone to earthquake damage, which could prevent residents from evacuating or seeking shelter indoors.

Structures built or reinforced under the “new seismic standards” are designed to withstand powerful quakes with intensities of upper 6 to 7 on the Japanese seismic scale of 7.

The Asahi Shimbun used municipal data released by the infrastructure ministry last November to examine earthquake-resistance rates in municipalities near nuclear plants.

The ministry had collected the data at different times from the municipalities between 2003 and 2024.

The analysis covered 122 municipalities near 15 nuclear plants in Japan. Both the Fukushima No. 1 and No. 2 nuclear plants, which are slated for decommissioning, were excluded in the analysis.

As of 2018, the national average of earthquake-resistant homes was around 87 percent.

The findings of the survey showed that 95 of the 122 municipalities had rates below that national average.

Following the 2011 disaster at the Fukushima No. 1 nuclear plant, the Nuclear Regulation Authority established guidelines for emergency preparedness and response.

Under the guidelines, residents within 5 km of a nuclear plant must immediately evacuate beyond a 30-km radius in the event of a “general emergency,” such as failure to cool a reactor.

Residents in the 5-to-30-km zone of a disaster-hit nuclear plant should remain indoors until radiation levels reach a certain threshold, according to the guidelines.

However, the Noto Peninsula earthquake on Jan. 1, 2024, severed roads and caused building to collapse, underscoring the difficulties of evacuating or sheltering indoors if a major earthquake and a nuclear accident occurred simultaneously.

Eight of nine municipalities within 30 km of the Shika nuclear power plant, which was affected by the Noto Peninsula earthquake, had earthquake-resistant housing rates below the national average, the survey showed.

This included Anamizu town, with an earthquake-resistant housing rate of 48 percent, and Wajima city, at 46.1 percent.

The town of Shika has not assessed its rate.

Across the country, the lowest rate was 37.7 percent in Ikata town, Ehime Prefecture, where the Ikata nuclear power plant is located.

In Genkai town, Saga Prefecture, which hosts the Genkai nuclear power plant, 40.2 percent of the homes met the new seismic standards.

Around the Onagawa nuclear power plant in Miyagi Prefecture, which was brought back online last October, six of the seven municipalities fell below the national average.

On the other hand, earthquake-resistant housing is more widespread in Shizuoka Prefecture, which could be hit by a Nankai Trough megaquake.

Around the Hamaoka nuclear power plant in the prefecture, nine of 11 municipalities had rates above 90 percent.

Five municipalities that host nuclear power plants had not assessed their earthquake-resistant housing rates: Yoichi in Hokkaido (Tomari nuclear plant); Kariwa village in Niigata Prefecture (Kashiwazaki-Kariwa nuclear plant); Shika, Ishikawa Prefecture (Shika nuclear plant); Ikeda, Fukui Prefecture (Tsuruga nuclear plant); and Mihama, Fukui Prefecture (Mihama nuclear plant).

However, even if homes meet the new seismic standards, it’s uncertain whether they can withstand multiple earthquakes of upper 6 to 7 intensity.

“Strengthening earthquake resistance must be a top priority in disaster preparedness,” said Naoya Sekiya, a University of Tokyo professor who is well-versed in nuclear disaster preparedness.

“At the same time, nuclear disaster planning must take into account the shortcomings in general disaster preparedness,” he said.

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