The Kumamoto quakes once again exposed the vulnerability of key component supplies for automakers and electronics firms — a problem that was highlighted earlier by the 2011 Great East Japan Earthquake and tsunami. Toyota Motor Corp. had to suspend most of its car production across the country for weeks after the local plants of its group company making engine and door parts for Toyota vehicles were hit by the series of powerful temblors in mid-April. While the disrupted output operations are gradually being restarted, manufacturers should review their supply chains to make them more resilient to natural disasters.

With an abundant supply of clean water and plenty of available land, Kumamoto and Oita prefectures are home to a concentration of plants manufacturing auto parts and semiconductors. Disruption to their output affects auto and electronics manufacturing nationwide, which can seriously hurt Japan's economy as a whole.

Toyota gradually halted most of its car assembly lines across Japan beginning April 18 after the Kumamoto units of its group firm Aisin Seiki Co. stopped operating due to the quakes. Toyota managed to fully restart its output on May 6 after Aisin began to build the parts made at the Kumamoto units in other plants and secured parts from its overseas operations. Toyota says the disruption is estimated to have cut its car output by some 80,000 units. SMBC Nikko Securities earlier calculated that a production loss of 50,000 units by Toyota alone — or equivalent to 7 percent of the total monthly auto production in Japan — would push down the nation's industrial output for the month by about 1 percentage point.