Describe how seismic waves and earthquakes can be measured (8 marks)
The magnitude of seismic waves and earthquakes is measured on two scales. The first way (and the most commonly used) is by using the Richter scale; this is a logarithmic scale ranging from 1 to 10 but technically has no absolute limit. An event measured at 6 on the scale has amplitude of seismic waves ten times greater than one measured at 5 on the scale. The energy release is proportional to the magnitude, so that for each unit increase in the scale, the energy released increases by approximately 30 times.
Secondly, The Mercalli scale measures the intensity of the event and its impact. It is a 12-point scale that runs from Level I (detected by seismometers but felt by very few people approximately equivalent to 2 on the Richter scale) to Level XII (total destruction with the ground seen to shake - approximately 8.5 on the Richter scale).
Seismographs is one way of monitoring and detecting earthquakes; these are instruments used to detect tremors, they help determine where the epicentre of the quake is by use of triangulation and they can determine what rating the earthquake gets on the Richter scale. The goal of a seismograph is to accurately record the motion of the ground during a quake.
Radon gas escapes from cracks in the Earth's crust. Levels of radon gas can be monitored - a sudden increase may suggest an earthquake.
Evaluate how plate tectonics theory can help our understanding of the distribution of seismic and volcanic events (40 marks)
Plate tectonic theory suggests that the earth’s crust is made up of 8 main plates, as well as many other smaller ones. These plates float on top of the asthenosphere and are constantly moving therefore constantly interacting with one another. This movement of plate tectonics leads to volcanic and seismic events. This knowledge of plate margins and their interaction can help us understand the distribution of these events.
In 1912 Alfred...