The 3Ps
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The three Ps provide the key to trying to reduce the impact of earthquakes.
Prediction involves trying to forecast when an earthquake will happen. Japan tries to monitior earth tremors with a belief that warning
can be given, but this did not happen at Kobe. Foreshocks do occur, but on a timescale useful to evcuation. Experts know where earthquakes are likely to happen, but struggle to establish when. Even looking at the time between earthquakesin a particular area does not seem to work. Similarly, experts struggle to pinoint exactly where along a plate margin they will occur. Animal behaviour has been used in the past
Protection invloves building to an appropriate standard and using designs to withstand movement.
Preparation involves hospitals, emergency services and inhabitants practising for major diasters, including having drills in public buildings and a code of practice so that people know what to do to reduce the impact and increase their chance of survival.
Useful video link below: http://www.bbc.co.uk/learningzone/clips/preparing-for-earthquakes/5723.html
Some other useful warning signs:
· Earthquakes are a frequent sign of an impending eruption and their frequency and strength can be recorded
· Bulging on one side of the volcano – the swelling is obvious and a clear sign of magma moving
· Tiltmeters can identify small, subtle changes in the landscape
· Global Positioning Systems (GPS) use satellites to detect movement of as little as 1mm
· Satellites can detect changes in surface temperature
· Digital cameras can be used to check for changes in volcanic activity
· Gases being emitted from the vent change before an eruption
· Robots called ‘spiders’ are often deployed to look inside the rim of the volcano
· The past frequency of eruption is often investigated: the gap between eruptions and the pattern of lava flows, ash movement and lahars can tell people about how the
volcano is likely to behave
Monitoring of volcanoes
Monitoring gas emissions
As Magma rises into magma chambers gases escape for the depressurising
magma. One of the main gases is Sulphur Dioxide, and if its quantity in escaping volcanic gas increases this can signal the start of a major eruptive sequence.
In the Mount Pinatubo Volcanic event the amount of Sulphur Dioxide increased by 10 times in 2 weeks. Directly before eruptions the Sulphur Dioxide level can then drop rapidly and scientists think this is due to the sealing of gas passages by hardened magma. This increases pressure in the volcano and leads to explosive eruptions.
Ground deformation
The movement of magma within the lithosphere can deform the ground above, this has been witnessed at Yellowstone beneath Yellowstone Lake. This swelling of the volcano signals that magma has collected near the surface. Scientists monitoring an active volcano will often measure the tilt of the slope and track changes in the rate of
swelling. Mount St Helens showed this prior to its eruption in 1980.
Thermal monitoring
Both magma movement, changes in gas release and hydrothermal activity can lead to thermal emissivity changes at the volcano’s surface. We can use satellite imagery, activity of minor extrusive features such as geysers and hot springs and mapping to monitor this.
Satellite Images and Remote Sensing
Remote sensing is the use of satellites to detect things about the Earth’s surface.This is useful for monitoring any changes in volcanoes at the surface.
Using satellites we can monitor the thermal activity of the volcano to check for upwelling magma, we can check for escaping Sulphur dioxide using gas sensing and we can look to see if the ground is deforming by checking before and after images of the ground.The satellite can also judge if the ground is being uplifted by measuring the distance between the satellite and the ground.