NASA Satellite Image of Japan Captured March 11, 2011, by NASA Goddard Photo and Video on Flickr

Why did the Japan earthquake and tsunami occur? Was Japan prepared for such a disaster?

Earlier last month we witnessed one of the most devastating chains of events ever to hit Japan: an earthquake, tsunami, and finally, the crisis at Fukushima Nuclear plant which has still not been resolved. At the time of writing, over 12,000 people are said to have died, with over 15,000 still missing.

Japan is well aware of its susceptibility to such natural disasters – after all, the island was created as a result of tectonic activity itself, and there have been 26 recorded earthquakes measuring at least 6.5 on the Richter scale in the last 100 years alone. Situated on the Pacific Ring of Fire, it lies upon the tectonic plate boundaries of the Eurasian, Pacific and Philippine plates which serve to make Japan very unstable.

Although there are four main types of tectonic plate movement across the globe, the tectonic plate activity triggering this most recent earthquake in Japan is a result of a converging (or destructive) plate boundary whereby two plates collide with one another. The differing densities of the plates mean that one plate is forced beneath the other (in a process known as subduction) where it then melts. The pressure and stress caused by the melting of the denser plate and the build-up of friction between the plates results in the release of a huge amount of energy when the plates eventually give way. This manifests as an earthquake.

The earthquake in Japan, named ‘Higashi Nihon Dai-Shinsai’ (which translates roughly to ‘Eastern Japan Great Earthquake Disaster’) measured at 9.0 on the Richter scale making it the strongest ever recorded for the region, with aftershocks reaching 7.1. It was this sudden movement of the plates and release of energy that triggered the 10m tsunami that swept across the Eastern coast of Japan. It is reported that ten individual, smaller waves were actually created by the movement of the earthquake which then combined into a single, huge wave. This damage caused by the combined forces of the earthquake and tsunami are what have led to the current crisis at the Fukushima nuclear plant.

Earthquakes can also trigger a process known as liquefaction, whereby the inability of soil to handle shear stress causes it to behave like a liquid. Reclaimed land can be especially affected by this process, and by the movement of earthquakes in general – a YouTube video shows effects of the earthquake upon Central Park in Chiba city, which was built upon reclaimed land that once formed Tokyo Bay. Despite being around 300km away from the epicentre of the earthquake, cracks began to form rapidly across the concrete pathways and the ground could be seen moving, with huge pools of water appearing on the surface as a result of liquefaction which was exacerbated by the cracking of water pipes. All this happened in a matter of minutes.

While many people sadly lost their lives in the disaster, in terms of preparedness Japan is one of the best equipped countries to deal with these types of events, and as a result many more lives were saved. The precautionary measures employed in Japan range from monthly earthquake drills and trips to earthquake simulators for children to help prepare themselves for a real earthquake. Many homes contain emergency earthquake kits, and buildings in many built-up areas are ‘earthquake-proofed’, fitted with shock absorbers to minimise damage. Furthermore, monitoring early warning signs before the onset of a quake -such as small tremors in the earth- serves as warning for an impending earthquake, although it cannot be predicted when exactly it will occur.

As a result of the quake, it has been suggested that the earth’s axis has shifted by 17cm (although this is only temporary), and an earth day has actually been shortened by 1.8 microseconds. But while the days may be slightly shorter, the memory of this terrible disaster as one of the most cataclysmic events in history will undoubtedly last a lifetime and beyond.

To find out how you can donate money to Japan whilst in St. Andrews, you can visit the ‘St. Andrews to Japan Relief and Recovery’ page on Facebook, where there are various fundraising events coming up including a Charity Concert in Younger Hall on the 14th of April, and a Table Top sale on the 23rd of April in Church Square.

 

Katie Henderson