We have been reminded once more how enormous an impact an earthquake directly beneath a major city can have.
On June 18, a magnitude 6.1 temblor measuring a lower 6 on Japan's 7-point seismic intensity scale struck northern Osaka Prefecture. The quake claimed four lives, including a 9-year-old girl in Takatsuki, Osaka Prefecture, killed by a collapsing wall outside her school, and injured hundreds of others. It was also the first time a lower 6 earthquake had been recorded in Osaka.
The shaking began at 7:58 a.m., at a time when people were headed to work and school. West Japan Railway Co. (JR West) trains and private rail lines across the entire Kinki region of Western Japan screeched to a halt, stopping the morning commute literally in its tracks.
Essential services were also thrown into chaos. Up to around 170,000 buildings were left without power in Osaka Prefecture, while elevators on tall office and apartment buildings stopped in their shafts, trapping many people within. Water and gas were also cut to many households across the region. People struggled to get home, and many still are in need of food and other daily necessities.
This is what major urban earthquakes do, disrupting basic city functions. We hope that related bodies will put all their effort into securing evacuation shelters and providing daily necessities.
The case of the 9-year-old girl who died in Takatsuki is utterly heartbreaking, killed as she was on a sidewalk on her route to school -- a route that took her right along the concrete block wall that fell onto her in the morning quake. The construction criteria for these walls have been set under the Order for Enforcement of the Building Standards Act, and these were beefed up following a major quake off the coast of Miyagi Prefecture in 1978, in which many people were killed by collapsing walls. Now, depending on their size, these walls must be reinforced with rebar.
However, though schools are supposed to place safety above all else, the wall at the elementary school in Takatsuki did not meet these standards. Takatsuki's mayor has apologized over the incident, but there is a possibility that the girl's death could be related to a violation of laws and ordinances, and very hard questions will be asked regarding official responsibility.
The Kinki region is one of several in Japan with many active faults. The June 18 quake apparently hit very close to the Arima-Takatsuki Fault Zone. Also near the hypocenter lie multiple active faults including the Uemachi Fault Zone, which runs north-south near the coast of the prefecture. Some experts point out that the recent temblor may trigger activity in the Uemachi zone, so we cannot afford to relax our vigilance.
There is an estimated 70 percent chance of an earthquake striking directly beneath Tokyo within the next 30 years. The March 2011 Great East Japan Earthquake reached an upper 5 on the seismic intensity scale in the capital, yet still caused mass chaos there.
The population of Tokyo is densely packed, making it likely that the damage would be far worse than that we are now seeing in Osaka for a quake of the same scale. It is time to review earthquake countermeasures once more.