The Kobe earthquake of 1995
Kobe is a heavily populated urban area - The Kobe earthquake of 1995 introduction. It is here that disaster struck in 1995 when an earthquake of magnitude 7.2 hit the area. It was a major disaster in a MEDC where the modern buildings had been earthquake proofed. Many of the city’s residents had been unaware of the chances of an earthquake taking place.
The epicentre of the earthquake was located on the island of Awaji at 34.6 N 135.0 E. The earthquake had taken place because of a subduction zone on the plate margin. The type of margin where the Philippine plate and the Eurasian plate meet is a destructive margin. This means that the Philippine plate (Oceanic plate) moved under the Eurasian plate (continental plate) causing uplifting and folding of the ground that the plate was on. The ground moved 7 inches in horizontal shaking in this earthquake, and 4 inches in the vertical direction. This is the greatest recording of plate movement in Japan. The ground movement was even greater in Awaji Island where the ground moved 5 feet 7 inches (170 cm), with a vertical slip of 4 feet 3 inches (130 cm).
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There were many short term and long term effects as a result of the earthquake.
* Many houses collapsed despite being built to withstand an earthquake.
* Buildings were destroyed by fire when the gas mains were fractured in the earthquake.
* People were evacuated to schools, parks and community centres; tents and emergency rations were provided by other cities.
* Rescue teams arrived quickly on the scene with equipment.
* Electricity was restored in 6 days. At one point the earthquake had stopped around 0.9 million homes from receiving electricity. Gas supplies had been stopped for around 0.83 million people as there had been over 2600 cases of gas leaks. At one point 250,000 telecommunications lines had been completely cut of. This was later reduced to around 60,000.
* Many businesses had to close as a result of the earthquake. Banks had to close because the telecommunications lines were down and the On-line system was also down. Manufacturers had to close because the workers couldn’t commute to work. Breweries had to close because the beer couldn’t be fermented. Metal industries had to stop working because of the cut in gas and water. Car companies had to cut the production of cars, and supermarkets run out of stock as the crowds flocked to get food. Transportation problems meant that new stock had to come in by helicopter.
* Extra jobs were made when the rebuilding of factories and houses was started.
* Many people permanently moved away.
Most of the modern buildings in Kobe had been earthquake proofed in three ways. Some buildings had been built with a concrete weight on top which moved in the opposite direction of the earthquake. Other buildings had rubber shock absorbers in the foundations to allow the building to rock back and forth and up and down without causing too much damage apart from some falling books etc. Some buildings had cross-bracings which allowed the building to twist and turn so it can move with the earthquake.
The Kobe earthquake was caused by a destructive margin along which the Philippine plate moved under the Eurasian plate. The Philippine plate moves under the Eurasian plate because the Philippine plate is an Oceanic plate. This means that it is heavier than the continental plate, and so it moves under the Eurasian plate. This causes Kobe to rise. The destructive movement of the plates causes the oceanic plate to melt as it gets closer to the core of the earth. As the plate is pushed down it displaces magma under the earth’s crust and pushes magma upwards. This creates many new active volcanoes.
There are two types of waves S-waves and P-waves. P-waves are the primary waves and reach the surface first. These are the waves that actually cause the most damage. S-waves are the secondary or shear waves. These cause movements at right angles. S-waves are also more commonly known as aftershocks.
The earthquake was also unusually shallow. This meant that the focus was only a few miles under the epicentre. The waves only use up a small amount of energy to get to the surface and so therefore the earthquake is longer. As the waves spread out the damage caused by the earthquake gets smaller.
Compared to other earthquakes many people died and thousands of buildings were damaged. To examine the damage we must consider three factors. These factors are the strength of an earthquake, the time of the earthquake and the type of rock the settlement is on. The strength of the earthquake was quite small compared to other earthquakes in Japan. It was 5.46 am so everyone would have been asleep. Kobe had been built on variousness of ground hardness. For example part of Kobe was built on solid land from the Rokko Mountain and another part of Kobe near to the coast was built on soft ground reclaimed from the sea. This means that the buildings on soft ground would have collapsed more easily as their foundations would have been uprooted.
This is also what took place at the 1985 Mexico earthquake and at the 1989 San Francisco earthquake. So why was so much damage caused compared to other earthquakes? Fire is the main reason that many of the buildings in Kobe were destroyed. The fire was caused by the gas mains being fractured and inmost places exploding. The wooden buildings that were in the Central Business District caught fire and therefore became a fire hazard. This caused the surviving modern buildings to catch fire and collapse. This is what caused the most damage.