This lesson will focus on the Impacts and responses of the Japanese Tsunami.
The objectives for the lesson are:
- Explain the Impacts of the Japan Earthquake
- Explain the responses to the Japan Earthquake
- Understand how to classify impacts into primary and secondary
- Understand how to classify the responses into short and long term
- Explain the structure of an Earthquake
The Japanese Tsunami – BBC Horizon
Cause refers to the situation that resulted in an event happening. In this case the cause of the earthquake was Japan’s situation on the plate boundaries shown in the image above.
Convection currents driven by heat rising from the earth’s core led to subduction of the more dense pacific plate beneath the less dense North American and Eurasian plates. This caused a megathurst magnitude 9 earthquake with an epicentre 45km east of land.
Impacts refer to the different hazards and problems that occur as a result of the hazard (in this case the hazards were the tsunami and earthquake)
Responses refer to the ways in which the government and people deal with the hazard and what they do to prevent and reduce the impacts or future events.
The table below summaries the causes, impacts and responses the Japan earthquake and tsunami.
Structure of an Earthquake
An earthquake is the shaking and vibration of the Earth’s crust due to movement of the Earth’s plates (plate tectonics). Earthquakes can happen along any type of plate boundary.
Earthquakes occur when tension is released from inside the crust. Plates do not always move smoothly alongside each other and sometimes get stuck. When this happens pressure builds up. When this pressure is eventually released, an earthquake tends to occur.
The point inside the crust where the pressure is released is called the focus. The point on the Earth’s surface above the focus is called the epicentre.
Earthquake energy is released in seismic waves. These waves spread out from the focus. The waves are felt most strongly at the epicentre, becoming less strong as they travel further away. The most severe damage caused by an earthquake will happen close to the epicentre.
The Japan Earthquake of 2011 causes a tsunami due to the thrusting motion below the ocean as shown below. This type of Earthquake is referred to as a Megathrust.
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MrGeogWagg 