Sarah Lee
Describe and Explain the Factors that Affect the Impact of Earthquakes
There are various different factors that affect the impact that an earthquake has, not only on humans but the environment. Earthquakes are fundamentally caused by friction between lithospheric plates moving in different directions either constructively or destructively. Therefore, the major earthquakes occur at the boundaries of the lithospheric plates. Examples of these are Kobe quake in Japan on 17th January 1995 and Loma Prieta quake in San Francisco on October 17th 1989. (Seismologists have discovered both as being on plate boundaries.) It is therefore obvious that an enormous factor that affects the impact of an earthquake is its proximity to a plate boundary. The larger earthquakes occur at plate boundaries and can have dramatic effect but are some what expected. Japan is noted to have 4 earthquakes a day! However, minor earthquakes can occur on smaller fault lines on the major plates. An example of such an earthquake was Richter 3.9 in the Manchester area, England on Monday 21st October 2002 that was followed by 13 after shocks. Although earthquakes at plate boundaries can be catastrophic is size and damage caused, the local populations are educated that earthquakes can occur. This was unlike England where some people were quite anxious and disturbed at a small quake and chimney’s that had collapsed were not covered on insurance.
Whether or not an area is prepared for an earthquake can have a direct impact on the consequences that the earthquake has. Mexico dramatically improved its emergency response systems after over 10,000 deaths in the Michoacan Gap Earthquake of 1995. Mexico had developed an emergency response system called the – National System for Civil Protection in 1985, the quake of October 9th 1995 which allowed only 50 deaths despite a 7.9 magnitude quake. Because Mexico was much more prepared for an earthquake, the death toll was dramatically reduced. In 1975, an earthquake was successfully predicted in China and so the death toll much reduced. At 2 pm, 4th Feb 1975 3 million people were ordered to spend the night outside in southern Liaoing province. The 7.8 earthquake occurred at 7.36pm and flattened the town of Haichang. Only 500 people were killed as the population was warned of a possible tremor and were told immediately before on what to do. The impact of the earthquake was therefore dramatically reduced due to the preparedness of local people. The Loma Prieta Earthquake was the first major rupture along the San Andreas Fault since 1906. Because of this, many people had not experienced such a disaster in their life time and it is a small miracle that not more than 62 lives were taken as the people were less knowledgeable of the consequences of such an earthquake.
