Kyodo News International 24/1/2014
A powerful earthquake originating in what seismologists call the "Nankai Trough" off western Japan could cut off tap water to roughly 8.32 million people in Osaka, or 94 percent of the prefecture's residents, the metropolitan government said Friday.
The supply outage would result from quake-induced damage to tap water infrastructure stemming from intense oscillation, tsunami and a phenomenon called ground liquefaction, it said, quoting the results of discussions at an advisory panel to the local government.
Such an intense temblor would also knock out the power supply for a combined 2.34 million households, or 55 percent of the prefecture's households, while stopping gas supply to 1.15 million households, or 34 percent of the households, it said.
Damage to buildings, distribution networks and other infrastructure would surpass 28 trillion yen worth.
Although the national government earlier predicted the Nankai Trough quake would stop tap water supply for only 4.3 million people, the metropolitan government's projection almost doubles that estimate.
The Osaka government's estimate is much more severe as it takes into account possible damage to water intakes along the Yodo River, the prefecture's main source of tap water.
Tsunami to be induced by the quake would submerge a combined 11,000 hectares of the Osaka area, roughly 3.6 times the area estimated by the national government, it said.
The Osaka government assumes that the quake would trigger a tsunami, which would reverse the flow of the river to the point of sending tsunami-induced backward water flows reaching Osaka's border with Kyoto, it added.