Kumamoto Earthquake Underscores Seismic Resistance of 2×4 Homes in Japan
This year Japan experienced the strongest earthquake since the 2011 Great East Japan Earthquake and Tsunami. Centered in Japan’s Kyushu region, the Kumamoto earthquakes in April registered a strong magnitude 7.3. The strong jolts in Kumamoto and Oita Prefectures caused extensive loss of life and damage to structures. The town of Mashiki near the epicenter lost approximately 30% of its buildings to the quake.
The Japan 2×4 Home Builders Association recently conducted a survey among its members to ascertain the extent of the damage to 2×4 housing as a result of the Kumamoto quake. A total of 2,940 platform frame homes were surveyed in the affected area. The rankings to assess the extent of the damage in ascending order are: (A) No Damage; (B) Light Damage – non-structural such as cracks in the wallpaper, dents in the floor caused by fallen furniture, etc…homeowner can continue to live in the structure as is; (C) Partial Damage – some structural damage requiring repairs, but nothing extensive; (D) Half Destroyed – extensive structural damage to between 20% to 70% of total floor area; (E) Completely Destroyed. The survey results are as follows. Of the 2,940 2×4 homes reported none experienced category D half destruction or E complete destruction or collapse. A total of 79 homes or 2.7% sustained partial damage: of these 46 homes suffered some structural deformation by the force of the earthquake; 30 suffered either degraded soil conditions or liquefaction of the soil; and 3 homes classified the cause as other. The balance of 2,861 homes (97.3%) were categorized as either A, no damage, or B, light non-structural damage.