Topic 5 - Responses to Tectonic Hazards Flashcards
1
Q
why is prediction so important in reducing vulnerability
A
Buys time to:
- Warn and evacuate
- Prepare for the event
- Manage impacts more effectively
- Help insurance companies assess risk
- Prioritise government spending
- Help authorities calculate cost-benefit calculations, for example, building expensive infrastructure
2
Q
why is hazard prediction needed
A
- reduce deaths by enabling evacuation
- reduce damage by enabling preparation
- enhance management by enabling cost-benefit calculations and risk assessments
- improve understanding by testing models against reality
- allow preparedness plans to be put in operation by individuals, governments, national agencies
3
Q
how can hazards be predicted
A
- past records enable recurrence to be estimated
- monitoring (physical) monitored and recorded using ground-based methods or for climatic and volcanic hazards, remote sensing
- monitoring (human) factors influencing human vulnerability (eg exchange rate, incomes) human impacts (eg deforestation)
4
Q
what are the warning signs of a volcanic eruption
A
- Hundreds of small earthquakes are caused as magma rises up through cracks in the Earth’s crust.
- Temperatures around the volcano rise as activity increases.
- When a volcano is close to erupting it starts to release gases. The higher the sulfur content of these gases, the closer the volcano is to erupting.
5
Q
what are monitoring techniques of volcanoes
A
- Seismometers are used to detect earthquakes.
- Thermal imaging techniques and satellite cameras can be used to detect heat around a volcano.
- Gas samples may be taken and chemical sensors used to measure sulfur levels.
6
Q
what is the tsunami global warning system
A
- In 1948 the Pacific Warning System for 24 Pacific Basin nations was established, with its centre in Honolulu in Hawaii
- Seismic stations detect earthquakes and their events are interpreted to check for tsunami risk with the aim of altering areas at risk within 1 hour
- The time taken for waves to travel across the Pacific allows time for adequate evaluation.
- Chile received 20 hours warning following the Tohoku earthquake.
If the earthquake is larger than magnitude 7.5 all locations within 3 hours of the wave are put on alert to evacuate the coast
7
Q
which country has the best regional scale tsunami warning system
A
- Japan has the most developed system that generates warnings within 20 mins of a tsunami forming earthquake (tsunamigenic) within 600km of it’s coast.
- Warnings issues for the Tohoku earthquake provided 15 minutes warning, but the tsunami wall failed due to the height of the wave and the drop in height of the land following the quake
8
Q
what is the risk equation
A
RISK = frequency/magnitude X level of vulnerability / capacity of the population to cope
9
Q
what is visual monitoring of a volcano and its effects
A
- The cheapest way of monitoring a volcano is by placing cameras on major volcanoes to constantly monitor even the slightest of changes
- Volcanologists can note things such as the amount of steam coming out of the ground at a particular spot, any rockfalls, changes in areas of warm ground, and the development of new fumaroles and hot springs, all indicate changes in the volcano
10
Q
what is seismic monitoring and how is it used
A
- Volcanic eruptions are preceded by unusual seismic activity
- Seismic monitoring system can be cheap to set up and operate
- A single monitoring station can record data from several volcanoes at once
- It provides a continuous source of data, allowing rapid changes in a volcano to be monitored
11
Q
how is ground deformation used in volcanic prediction
A
- Changes in geomorphology and increases in ground deformation are indicators that volcanic activity is occurring beneath surface
- ways to measure such deformation are levelling, triangulation and more recently using continuous Global Positioning System (cGPS) measurements
12
Q
how can gas emissions help predict volcanic activity
A
- When molten material (magma) moves into a volcano it gives off volcanic gas emissions,sulphur dioxide (SO2), carbon dioxide (CO2) and hydrogen sulphide (H2S) which are measured regularly at volcanoes
- A Correlation Spectrometer (COSPEC) or a FLYSPEC measure the absorption of ultraviolet light by SO2, so the SO2 content of the volcanic gases is determined by flying under the gas plume (at right angles to the wind direction) and looking up through it
-The aircraft flies through the volcanic gas plume at different altitudes. A pump inside the aircraft sucks in the gases and the LICOR and Interscan instruments measure the concentration of carbon dioxide (CO2), sulphur dioxide (SO2) and hydrogen sulphide (H2S).
13
Q
what is a crater lake
A
- when volcanic craters cool down after major eruptions, they often fill with water to form crater lakes
- Some are cool, just filled by rain water, while others are warm or hot and remain connected to the volcanic plumbing.
- The colour of crater lakes varies markedly according to the temperature and chemistry of the water, and the type and concentration of particles suspended within it
14
Q
how can crater lakes predict volcanic activity
A
- any reactivation or change in status of an active volcano is often reflected in the lake
- this may be a chemical change, a temperature increase or water level variation
15
Q
how do seismometers detect earthquakes
A
- they detect and convert any small movement in the Earth into an electrical signal for use in computer systems
- Geoscience Australia monitors seismic data from more than 60 stations on the Australian National Seismograph Network
