Kobe Earthquake in 1995
Japan is positioned on the margin of the Eurasian Plate. The Philippine Sea Plate is subducted below the Eurasian plate, resulting in Japan having greater than average seismic and volcanic activity. Immediately south of Osaka Bay is a fault called the Median Tectonic Line ( MTL) , and it was sudden movement along this fault that triggered the earthquake that hit Kobe.
At 5.46am on January 17th 1995, whilst many of its citizens were still asleep, the Japanese city of Kobe was hit by largest earthquake in Japan since 1923. The Hyogo-ken Nanbu earthquake was not only powerful ( magnitude 6.9 ), but with the epicentre only 20km southwest of the city, it resulted in massive damage to property and loss of life. The worst effected area was in the central part of Kobe, a region about 5km by 20km alongside the main docks and port area. This area is built on soft and easily moved rocks, especially the port itself which is built on reclaimed ground. Here the ground actually liquefied and acted like thick soup, allowing buildings to topple sideways, resulting in the huge cranes in the harbour toppling over into the sea.
Large earthquakes in remote, uninhabited areas can do relatively little damage to the human population, but when they strike in places like the Kobe / Osaka region with a population of 10 million people, the damage levels will always be significant. More than 102,000 buildings were destroyed in Kobe, leaving over a fifth of the city population, some 300, 000 people, homeless. The local government's estimate of the cost to restore the basic infrastructure of the city was about $150 billion dollars, and that was just for the state owned buildings and services. When all the costs are added up, it makes the Hyogo-ken Nanbu earthquake probably the most expensive natural disaster in modern history. All this damage was the result of just 20 seconds of earthquake.
Transport and Communications
Access to the sites of earthquakes is always likely to be restricted by the damage caused by the quake, because ground movements damage roads and railways.
Kobe was no exception and things were made even more difficult because Kobe is situated on a strip of flat land between high mountains and the sea. This rather narrow strip of land carries all the communications routes between northeastern Japan and western Japan. Emergency aid for the city needed to use these routes, but many of them were destroyed during the earthquake.
The famous high speed railway link from the Japanese capital, Tokyo, and the whole of western Japan was cut in half when the bridges in Kobe fell down. The only other two rail links were also cut during the quake.
Like many large cities, Kobe had a raised motorway that allowed vehicles to travel around the city and out into neighbouring towns. As the shockwaves passed under the supports holding up the motorway, the ground gave way and large sections of the road collapsed in three parts of the city. One section of the road that collapsed was over half a kilometre long!
The only way to travel around the city was to use the smaller roads that were at ground level, but many of these were closed by either fallen debris from buildings, or cracks and bumps caused by the ground moving. In some places sections of the roads and pavements had been pushed up over 10 cm from their original positions, making it impossible to drive vehicles along them.
Utilities and Services
Like most cities, services like water, gas, electricity and sewerage were provided through a network of underground pipes and cables. When the ground began to move, the more rigid pipes weren't able to move as well so they fractured. Almost three quarters of the water supply across the entire city was out of action, gas pipes leaked gas into the air, and sewers discharged their contents into the streets.
Electricity supplies were not all routed underground but that didn't save the supply from disruption. Much of the supply was transmitted around the city by cables on poles. As buildings collapsed and the ground shook, many of the poles also collapsed, cutting off the electricity supply not just to homes, but to police stations, hospitals and fire stations too.
Remember that this earthquake struck early in the morning. Those people who were not still in bed were just getting up and making breakfast. People were cooking meals at the very moment that their homes began to shake and collapse. Cookers, sparking electric wires and hot embers from fires very quickly started over 300 fires, especially among the remains of wooden buildings.
The collapse of the electricity and telephone systems made it almost impossible for people to let the fire teams know where they were needed, whilst the broken water pipes and blocked roads made it hard for fire teams to reach and put out fires.
Within the next day, teams of fire fighters had arrived from all over Japan, but despite this there were at least a dozen major fires that burned for up to two whole days before they were brought under control. Research conducted at the Kobe University suggests that 500 deaths were due to fires, and that almost 7000 buildings were destroyed by fire alone. Fortunately the weather was not good for fires, otherwise the damage would have been even greater.