Deck 4 - Tectonics: Hazard profiles and management Flashcards
What are the 3 factors that make up the physical hazard profile?
Predictability, frequency, duration, speed of onset, areal extent and magnitude
How does predictability impact on the risks associated with a tectonic event?
If the earthquake or volcanic eruption can be predicted then the impact will be reduced, as they are able to mitigate the impact.
How does frequency impact on the risks associated with a tectonic event?
If the earthquakes or volcanic eruptions are frequent, then they have the potential to cause more damage. However, if the hazards are more frequent, this can make them easier to predict and the population can be more prepared.
How does duration impact on the risks associated with a tectonic event?
The longer the earthquake, tsunami or volcanic eruption lasts the more damage it will cause.
How does speed of onset impact on the risks associated with a tectonic event?
If the earthquake or volcanic eruption happens very quickly then there is limited time to mitigate the impact and therefore, there will be potentially more damage and deaths.
How does areal extent impact on the risks associated with a tectonic event?
The greater the areal extent the greater the impact, as more area is affected.
How does magnitude impact on the risks associated with a tectonic event?
The higher the magnitude the greater the impact.
What does prediction of tectonic hazards mean?
Knowing when and where a natural hazard will strike on a spatial and temporal scale that can be acted on meaningfully in terms of evacuation.
What does forecasting of tectonic hazards mean?
Forecasting is much less precise than prediction, and provides a percentage change of a hazard occurring (e.g. a 25% of a magnitude 7.0 earthquake occurring in the next 20 years).
How can earthquakes be predicted?
There are limited signs indicators that an earthquake is about to occur. Areas at high risk can be identified together with those likely to suffer severe ground shaking and liquefaction. Seismic gaps can point to areas of high risk. Sometimes a large earthquake may be preceded by small precursor earthquakes and/or the release of gases such as radon through cracks in the Earth’s surface.
How can volcanoes be predicted?
Most volcanoes give some form of warning before an eruption though it is hard to know exactly when the eruption may occur. Monitoring equipment is used to measure changes in magma chambers as it fill with magma before an eruption. Tiltmeters record ground deformation and bulging, thermometers measure any increase in temperatures, gas spectrometers measure changes in the amount of gases released and seismometers record minor earthquakes that indicate magma movement.
How can tsunamis be predicted?
The earthquake that triggers a tsunami cannot be predicted but can be measured by seismometers to identify its precise location. Ocean monitoring equipment can detect tsunamis in open sea and information can be relayed to coastal areas threatened.
What is the Volcanic Explosivity Index (VEI)?
Used to describe the size of volcanic eruptions based on the amount of material that is released. It ranges from 0 (non-explosive state) to 8 (mega colossal) eruption and is a logarithmic scale.
What is the Mercalli scale?
Is based on observable earthquake damage at a specific site after an earthquake has occurred. Lower numbers on the scale mean there is less observable damage and the earthquakes are either unnoticed by people or only by people at rest. Higher numbers on the scale indicate catastrophic or total destruction of the infrastructure in an area.
What is the Moment Magnitude Scale?
Used to measure the amount of energy released by an earthquake. It is calculated using a formula that includes the rigidity of the rock affected, the distance moved and the size of the area where movement took place.
