The government’s updated earthquake probability map — showing the area-by-area likelihood of a quake registering lower 6 or above on the Japanese seismic scale of 7 taking place within 30 years — points to the high probability of powerful temblors striking across wide areas of the Pacific coast, including eastern Hokkaido, where the quake risk was significantly raised from the last annual update. The government warns people and local authorities to be prepared for a powerful quake to hit anytime, anywhere in this seismically active country — a risk highlighted by the earthquake that rocked northern Osaka Prefecture on June 18. Naoshi Hirata, head of the government panel that compiled the map, states there is “no place with zero probability” of an earthquake with an intensity of lower 6 or more.
The Osaka earthquake also showed that while we may not be able to predict when or where a quake will hit, we can at least take steps to contain the damage caused by them by addressing foreseeable risks beforehand, particularly when it comes to big cities. That should be one of the lessons we learn from the June 18 earthquake that left five people dead, hundreds injured and more than 10,000 houses damaged in Osaka and neighboring prefectures.
The magnitude 6.1 quake that hit during the morning rush hour, registering an intensity of lower 6 in the northern parts of Osaka Prefecture, was indeed a medium-scale temblor, but one that still caused extensive damage to critical urban lifelines and infrastructure — most of which were quickly restored. The disruptions to train services and expressway networks, as well as the water, gas and electricity supply, once again exposed the vulnerability of densely populated big cities to powerful quakes.
The ruptures of underground water pipes in Takatsuki highlighted a common problem for municipalities whose urban infrastructure, built decades ago, is now showing its age. Numerous pipes installed during the nation’s rapid postwar economic development are rapidly aging, but the fiscal constraints of many local governments prevent their replacement. Ruptures of these old pipes frequently take place when powerful quakes strike. According to the Health, Labor and Welfare Ministry, less than 40 percent of water supply networks across the country feature new quake-resistant pipes.
The collapse of old concrete block walls, which claimed the lives of two of the victims in the June 18 earthquake, is also a risk that has been warned of for a long time. Seismic regulations for such walls were tightened after collapsing walls killed many of the victims in the major earthquake that hit off the coast of Miyagi Prefecture in 1978. Still, many old concrete walls remain in place despite the new regulations and continue to collapse and claim lives when strong earthquakes strike.
In the case of the elementary school in Takatsuki where a 9-year-old student was crushed to death by a wall surrounding the school’s pool that collapsed as she walked by, the 3.5-meter-tall structure was even higher than allowed under the old Building Standards Law, and lacked supports that are required for a wall higher than 1.2 meters. Three years ago an expert warned school officials and the local board of education about the danger posed by the wall. Subsequently, local education officials inspected the structure and determined that it was safe even though they lacked architectural qualifications.
It should be scrutinized why the expert’s warning about the wall was not heeded and the results should be shared as a lesson for future disaster preparedness. When the education ministry urged schools across the country to check on similar structures around their premises after the Osaka quake, large numbers of concrete walls that do not meet the safety standards were reportedly found. Action should be taken to either make them comply with safety standards or remove them.
Aging concrete block walls have been singled out in the latest Osaka earthquake, but they are only one example of structures on streets that could prove to be hazardous in the event of a powerful temblor. Vending machines, signs and many other objects can collapse or topple over when large earthquakes strike, causing injuries or worse.
The earthquake resistance of new houses and other structures has been improved based on the lessons of past earthquakes, but many old houses and other buildings have not been renovated to meet the updated standards. Wooden houses with low quake resistance can collapse in large numbers when a quake with a lower 6 intensity or greater strikes.
While earthquakes cannot be prevented or predicted, the damage they cause can be limited by taking action to address foreseeable risks.