In the early morning of January the 17th 1995 instruments in a lab in western Japan picked up a burst of intense electro-magnetic radiation.
It was the signature of a massive earthquake which had just struck the City of Kobe from its epicentre 20 kilometres to the south west. There was no warning, 180,000 buildings were destroyed, an urban area 20 kilometres long and 4 kilometres wide was totally wrecked. Nothing moved in or out of Kobe, by road or by rail for 3 days.The root of the disaster was a shock that happened on the boundary between the Eurasian and the Philippine plate, a boundary that runs right beneath Kobe. Kobe lies close to a fault line between the Philippine and South Japan Tectonic plate. The 2 plates are sliding past each other.
This is called a passive plate boundary. There is a direct relationship between plate margins and earthquakes, throughout the world. Japan is very prone to earthquakes, because of the countries special physical geography. Everything is packed tightly into the pressure stretches of the low land which make up only 20% of the land area.Japanese Cities are one of the most complex urban landscapes on Earth; mixed up multi-layered and fragile (roads and bridges). When it comes to earthquakes another problem for Japan is that huge areas of land have been reclaimed from the sea.
Kobe itself has advanced 15 kilometres seaward, in the last 20 years. The trouble is the reclaimed land which now accounts for a third of all japans coastline is relatively soft and wet and allows the shockwaves from earthquakes to carry on for long periods of time.During the Kobe earthquake, at locations on solid rock the shaking lasted 20 seconds, on the reclaimed land it went on for 2-3 minutes. As its human landscape becomes more and more complex, Japan becomes more and more vulnerable to earthquakes. The country has spent a fortune studying them, but until now, no way of predicting when they will occur has been discovered. The Japanese island arc has been formed from the molten magma released by the melting Philippines Plate.
Earthquakes are very common here and happen because of the friction resulting from the two plates colliding along this destructive margin. In 1923, the Great Kanto Earthquake killed 140,000 people in this area. The great destruction which resulted from the 1995 Kobe Earthquake was due to the shallow depth of the focus which was only about 16 kms, below the surface and the fact that the epicentre occurred close to a very heavily populated area. Seismic shockwaves travelled from Awaji Island (the epicentre) along the Nojima Fault to the cities of Kobe and Osaka.Overall, there were 5,500 people dead, 40,000 people injured and 180,000 houses completely demolished.
However the Kansai airport and Akashi Bridge were completely undamaged as they were new and built to withstand earthquakes. Three crustal plates meet near to the coast of Japan. Three crustal plates meet near to the coast of Japan. At a rate of about 10 centimetres per year, the denser oceanic Philippines Plate is being subducted beneath the lighter continental Eurasian Plate.
