1970 Tenroku gas explosion
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 The entrance to Tenjimbashisuji Rokuchōme Station in 2011 | |
| Date | 8 April 1970 |
|---|---|
| Time | 5:47 pm (JST) |
| Location | Tenjimbashisuji Rokuchōme Station, Kita-ku, Osaka, Japan |
| Cause | Gas leak |
| Deaths | 79 |
| Non-fatal injuries | 420 |
| Property damage | 495 buildings damaged or destroyed |
The Tenroku gas explosion (天六ガス爆発事故, Tenroku gasu bakuhatsu jiko) occurred at approximately 5:47 pm on 8 April 1970 in Osaka, Japan, when a gas leak during construction at Tenjimbashisuji Rokuchōme Station in downtown Osaka resulted in a massive explosion and fire that killed 79 people, injured 420 others, and damaged 495 buildings. It is one of the worst gas explosions in Japanese history.[1]
Tenjimbashisuji Rokuchōme Station is an Osaka Metro subway station in the Kita-ku ward. The station and the surrounding area are often given the shortened nickname "Tenroku". It originally opened in 1925 as Tejinbashi Station, an above-ground station for the Hankyu Senri Line, before being replaced by the underground station in 1969 to serve the Sakaisuji Line. By early 1970, Tenjimbashisuji Rokuchōme Station had been completed, but construction continued so the Tanimachi Line could be expanded between Higashi-Umeda Station and Miyakojima Station.[2]
At the time, Japan had been experiencing widespread modernization, and large-scale developments of cities like Tokyo, Osaka, and Sapporo were not uncommon.[3] This included the expansion of underground subways like the Tanimachi Line. To construct the subway tunnels, workers used an open-cut method and excavated along street routes, covering the tunnels with concrete slabs and steel plates so traffic could continue to flow with minimal disruption.[2] However, the construction of these tunnels, conducted alongside other modernization projects of sewers and buildings, threatened the preexisting gas, water, and electrical lines beneath Japanese cities, which were laid haphazardly long before the modernization projects and could potentially get in the way of subterranean excavations.[3] The constant construction work and vibrations from surface traffic also affected the buried utility lines, to the point of damaging them.[4] Indeed, the gas pipe involved in the leak was installed in May 1957 and was believed to have been dislodged and exposed from the digging, with the leak starting after the pipe began to crack.[2][4]
In 1970, Osaka Prefecture was hosting Expo '70, which had started on 15 March. The fairground itself was in Suita, roughly 10 to 12 miles from Tenjimbashisuji Rokuchōme Station.[3][4]