INTRODUCTION
Earthquakes are caused by the release of built-up pressure inside the Earth's crust which can create SEISMIC WAVES resulting in TREMORS.
Earthquakes occur regularly around the world and can create huge damage to property and human life. Over 1 million people have lost their lives to earthquakes in the last century. An earthquake's power is measured on the RICHTER SCALE using an instrument called a 'seismometer'. |
WHat CAUSES EARTHQUAKES?
An earthquake, like volcanic eruptions, has its cause in the movement of the Earths crust. As we have seen the Earth's plate boundaries are constantly moving. This is called Plate tectonics. Earthquakes can happen along any type of plate boundary.
Plates often do not move smoothly against each other. Instead, they often scrape against each other, sometimes becoming stuck. When this happens, tension builds up deep in the crust between plate boundaries. That tension is often released in the destructive form of an earthquake. .
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. |
how are earthquakes measured?
Earthquakes are measured on a device called a SEISMOGRAPH. This will is a machine which can record very fine vibrations in the earths surface.
The size of an Earthquake is called its MAGNITUDE The magnitude of an earthquake is measured according to the RICHTER SCALE This is a scale of 1 - 10 with 1 being the weakest measurement and 10 being the strongest possible type of earthquake The most powerful earthquake so far recorded was 8.9 off the coast of Chile or in Alaska in 1964. The San Francisco earthquake of 1908 wiped out the city and killed many thousands of people. Different experiences of money has led to poorer countries like HAITI suffering badly from earthquake damage. Tokyo, JAPAN, in comparison dealt very well with the 2011 earthquake, |