Earthquake Revision. Why do some earthquakes cause more damage than others?

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1 Earthquake Revision What is an Earthquake? Earthquakes are vibrations in the earth's crust they occur along all plate boundaries but are more destructive usually at destructive plate boundaries Where do earthquakes occur? Earthquakes occur along faults, which are large cracks in the earth's crust. Most of these are associated with the larger plate boundaries. Usually on or around Plate boundaries. What causes earthquakes? They are caused by sudden jerking movements of the fault, either laterally or vertically, and are almost impossible to predict. Most earthquakes occur when there is a movement along the plate boundaries and over 90% of all earthquakes take place at boundaries where there are converging (moving towards each other) plates. Plates move doe to convection currents in the Mantle. Movement is not smooth. Sometimes plates get stuck, pressure builds up, eventually the pressure gets too much and they jerk past each other, resulting in an earthquake. Earthquakes are measured in two ways: 1. Richter scale measures the magnitude (strength) of an earthquake using an instrument called a seismograph. 2. Mercalli scale measures the damage caused by an earthquake. It rates each quake from I to XII, depending on how much damage was done. The point at which an earthquake actually begins, deep below the earth's surface is called the focus. If the focus is deep then the effects of the earthquake may be less as the shockwaves have more rock to move through. The point directly above the focus, on the earth's surface, is called the epicentre. The effects of the earthquake are usually worst here, and then radiate out from this spot. Why do some earthquakes cause more damage than others? 1. Some earthquakes take place in rural areas where few people live and little is damaged 2. If they occur near large urban areas with many people, transport services, large buildings and services such as gas and electricity - there can be a great amount of deaths and damage 3. In Poor countries - LEDC's they have poorly built buildings, few emergency facilities, and the equipment to help rescue people - a good term to use is that they have a poor infrastructure. 4. In rich countries - MEDC's such as the USA they prepare for an earthquake with drills and have a great deal of trained emergency personnel and equipment to go to help the injured. They also try to build to withstand earthquake damage. 5. The time of day can be important - If the earthquake hits when it is the rush hour or when there is a large number of people located in a certain area - this can cause a great loss of life 6. Obviously if they occur near to coasts then Tsunamis can cause a great deal of damage and deaths such the Japanese Earthquake of 2011.

2 Physical Impacts The short term physical impacts can be devastating but are short term, primary impacts. Ground Shaking. And then Liquefaction, Landslides and Tsunami can occur (not always) Liquefaction Landslides - A landslide is a movement of surface material down a slope.

3 Fukushima, Japan th March 2011 at 2.46 PM (local time) 9.0 on the Richter Scale. largest Earthquake to be recorded in Japan in living memory. 15,400 Dead. Causes Japan is located on the eastern edge of the Eurasian Plate. The Pacific Plate, which is an oceanic plate, subducts (sinks under) the Eurasian Plate, which is a continental plate, to the east of Japan. This type of plate margin is known as a destructive plate margin. The process of subduction is not smooth. Friction causes the Pacific Plate to stick. In the case of Japan pressure built up and on 11 th March 2011 this pressure released as an intensely strong earthquake and a Tsunami with waves of 30 m, travelling at a colossal speed of 800 Kilometres per hour, which is equivalent to the ground speed of a jumbo jet.the Nearest City to the epicentre was sendai (130 Km east of Sendai). Primary impacts b 15,400 Dead. 2 Million homeless because of the Tsunami. 4 Trains were swept away from their Tracks. A Cruise Ship, carrying 100 people was washed away by the sheer force of the waves. A dam in the north of Fukishima prefecture burst its banks, which caused many more homes to be swept away. Power lines and Gas and water services were severely disrupted, as the earthquake ruptured under-ground cables and pipes. No communications for mobile phones and internet or landlines. #

4 Secondary impacts 500,000 People were forced to live in shelters. The disruption caused to rail and road links meant that it was hard for rescue teams to reach places where it was needed. The damage to the underground gas pipes led to fires which spread quickly and ignited wood carried by the wave. As Clean water was scarce, water-borne diseases such as Cholera and Typhoid spread rapidly. The earthquake caused a power cut at Fukishima Daiichi nuclear power plant which caused a failure in its cooling system, and subsequently caused radioactive materials to escape, causing local radioactivity levels to increase up to 40,000 times than normal. This will for years to come have a long lasting impact on the health of the local people. This Catastrophic disaster had many serious impacts on Japans economy as on 12 th March, Japan lost over 90 billion in its shares. The Total Cost to re-build the areas affected was set at 185 billion. Short term aid Within minutes of the Tsunami, Japan alerted its emergency response teams. 100,000 people began the disaster relief mission. The Japanese Red-Cross mobilised 230 emergency teams to the worst affected areas to provide medical and moral support to victims. On 2 nd April, Japan and the USA joined forces to search for bodies along the eastern coast. Shelters were set up in schools for those who lived in close proximity to the Fukishima Daiichi nuclear power plant. Many NGO s (Non-governmental organisations) responded to the hazard. For example: Shelter box sent 1,500 boxes of aid (Tents, Sleeping bags and bottled water) within the first month of the disaster.

5 Long Term Aid In March, Japan s Meteorological agency issued an earthquake warning, followed by a Tsunami warning. This meant that many people were able to escape to higher ground, but the short time (20 minutes), meant that thousands could not escape. The Japanese government responded by thinking about how they could improve their tsunami defence walls. The Government also reviewed their methods on predicting earthquakes and tsunamis as well as cutting short the time between the disaster and the response by improving communications and Sirens. Factors affecting the damage caused Strength & Depth of the Earthquake: As the earthquake was a mighty 9.0 on the Richter scale, the damage was bound to be severe. Also the point at which the earthquake happened (The FOCUS) was relatively shallow (30 KM deep), which is the reason why the Tsunami travelled at such speed and caused so much damage. Population density: As the epicentre of this earthquake was in close proximity to sendai, a largely populated city, the damage caused was far greater as there are more potential fatalities such as, falling skyscrapers and Leaking oil pipes. Type of buildings: As Japan is on the Ring of Fire, most of the buildings are Quake-safe, although there are less than there are in Tokyo, which is why the damage was vast. Time of Day: As the Japan Earthquake occurred at 2.46 in the afternoon, there was more damage than there would of been at 7.00 in the evening as there are more people in commercial and industrial areas in the day. Alternatively, this earthquake could have caused even more damage if it occurred in the evening, when less people are aware and alert. Secondary Hazards: The Death toll could of also been inflated in Japan because of the subsequent Tsunami caused which completely drowned the eastern coast of Japan, which lead to death by waterborne diseases as well as drowning and Fires. Level of development : Japan is a very developed country. The have well equipped emergency services, excellent communications and infrastructure. The also have strict guidelines on how to build houses and buildings. People are well trained on what to do in the event of an earthquake. Most homes have earthquake kits. Each of these factors significantly reduce the number of deaths.

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