The magnitude 6.7 earthquake that struck southern Hokkaido last week came as yet another deadly reminder that a powerful temblor can strike at anytime and anywhere in this quake-prone country. The earthquake that caused large-scale landslides in the early hours of Sept. 6, burying around 40 victims — most of them in the town of Atsuma near Tomakomai — is believed to have been caused by the movement of an active fault that wasn’t the one that was being monitored by the government’s Coordinating Committee for Earthquake Prediction.

There are more than 2,000 known active faults on the Japanese archipelago, but, of course, the number of unknown faults is immeasurable. The magnitude 6.1 quake that hit northern Osaka Prefecture in June has been linked to a previously unknown active fault. Media reports highlighted the possibility that multiple hitherto unidentified active faults may lie in the area around Atsuma, close to the epicenter of where the temblor struck and registered the maximum 7 on the Japanese seismic intensity scale.

Currently it is impossible to forecast earthquakes immediately before they hit, and long-term forecasts of the probability of big quakes happening in certain areas may not serve as a reliable guide for risks since areas not deemed to be at a high risk for big temblors can still be hit by such disasters. We have to brace ourselves for the threats of unanticipated natural disasters and think of what precautions to take to minimize the damage they cause.

Last week’s quake caused a temporary blackout of the entire island of Hokkaido after an emergency shutdown of the Tomato-Atsuma thermal power plant — the largest such plant run by Hokkaido Electric Power Co. and located close to the quake’s epicenter — severely disrupted the electricity supply-demand balance and this in turn forced three other power plants in Hokkaido to halt their operations to avoid damaging their power generators.

The power outage that cut off electricity supply to 2.95 million households in Hokkaido severely affected the lives of local residents. The New Chitose Airport was closed, traffic lights ceased to operate and ATMs at banks and convenience stores were unusable. The blackout and halt to public transportation led to long lines at gas stations, while the inability to recharge smartphone batteries made it difficult for many people to access news and disaster information on their mobile devices. A system that was supposed to supply up to 600,000 kilowatt of electricity from Honshu — via an undersea cable linking Hokkaido and Aomori Prefecture — in such an emergency also failed as a related facility in Hakodate could not operate due to the blackout.

The supply of electricity was gradually restored and the blackout problem was nearly resolved over the weekend. Air travel to and from Hokkaido has almost returned to normal and railway services have resumed. But the power-supply shortage may continue for a while as a partial restart of the Tomato-Atsuma plant, which accounted for roughly half of the power supply to Hokkaido before the disaster, won’t take place until the end of September at the earliest, and the resumption of its full operation likely to be delayed until November or even later. The government calls for continued efforts to reduce power consumption, although the need to conduct rolling blackouts is expected to decline when a hydropower station in southern Hokkaido is restarted later this week.

The blackout appears to highlight the risk of a local electricity system that relies heavily on a single, large-capacity plant whose shutdown will sharply reduce power supplies and potentially disrupt the whole system. The government says it plans to check with major power companies across the country to reexamine their emergency response systems against the risk of such regionwide power outage.

However, large-scale blackouts are deemed to be inevitable in the event of a major disaster — power was temporarily cut to as many as 8.7 million households at the time of the 2011 Great East Japan Earthquake and tsunami. A power outage hitting broad areas over an extended period may take place if the much-feared mega-quake in the Nankai Trough off the Pacific coast strikes. Calls for establishing an emergency backup public power supply system, such as one in which large-size batteries would be installed at public facilities or at major retail centers for people to recharge their mobile devices in case of severe disasters, should be further studied.

The latest disaster can give us more clues as to what steps need to be prepared to mitigate the damage to people’s lives in emergencies.

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