STUDY ON THE RISK OF COLLAPSE OF BLOCK WALLS IN JAPAN DURING EARTHQUAKES

Abstract

The earthquakes in Kumamoto (2016) and Osaka (2018) in Japan revealed grave repercussions of collapsed block walls, causing fatalities and severe damage. These incidents underscored the need for understanding and mitigating the risk posed by these structures. In response, this study focused on assessing block walls collapse risk. Surveys across Nagasaki, Tokyo, and Chiba scrutinized various factors like rebar presence, wall appearance, and maintenance status using a Japan Concrete Block Association chart. Results revealed alarming statistics: 38% of block walls in Nagasaki posed a danger, with factors like lack of rebar and wall age significantly impacting collapse risk. Comparing regions, earthquake-experienced Kanto had 19% risky block walls versus 38% in less-experienced Kyushu, emphasizing the influence of earthquake awareness on residents perception of block wall risks. Lack of rebar emerged as a primary risk factor across all areas. Considering block walls have a lifespan of 20-30 years, deteriorating rebar due to corrosion poses imminent risks. Urgent surveys and awareness campaigns, especially along school routes, are crucial to prevent tragedies like the young girls death in Osaka. The study emphasizes scholars responsibility to disseminate accurate information about block wall risks during earthquakes. However, challenges persist, such as unclear property ownership, hindering countermeasures even after identifying high-risk walls. Looking ahead, national diagnostic surveys are essential to address the looming danger, especially considering potential seismic events like the Nankai Trough Earthquake. Disaster education must prioritize teaching children about the risks of block walls during earthquakes to ensure their safety.