Tectonics Pack I

Question 1

What indicators change before an earthquake?

Answer 1

• Height of water table
• Levels of radon gas dissolved in water (increases)
• Earth’s magnetic field
• Animal behaviour

Question 2

How can earthquakes be monitored?

Answer 2

• Small movements along fault: laser reflector, creep meter, gravity meter, tilt meter
• Changes in rock stress: strain meter
• Groundwater movements and water table heights: well levels and groundwater measurements
• Radon gas: radon gas meter
• Changes in Earth’s magnetic field: magnetometer
• Smaller foreshocks: seismograph and seismometer
• Animal behaviour

Question 3

Why can’t earthquakes be predicted?

Answer 3

• Date, time, location and magnitude cannot all be predicted yet (USGS standards)
• Unofficial predicts occur when something happens that is thought to be a precursor to a major quake
• But often these activities happen without an earthquake

Question 4

How can tsunamis be predicted and monitored?

Answer 4

• By monitoring undersea seismic activity
• Tide gauges, tsunami detection buoys and pressure recorders detect changes that show a tsunami has been generated
• Therefore, areas can be warned of its arrival

Question 5

What is the Indian Ocean Tsunami Warning System (IOTWS)?

Answer 5

• Fully operational in 2011
• Covers 28 countries and 2 billion people
• UNESCO and India were key players
• Cost $150-200 million
• Can predict risk to coastal areas, height of wave and vulnerable buildings

Question 6

What environmental changes happen before a VE?

Answer 6

• Seismic activity
• Ground deformation
• Gas emissions
• Thermal changes

Question 7

How is seismic activity before a VE monitored?

Answer 7

• Seismometers and seismographs
• Distributed acoustic sensing
• May show an increase in activity over time
• Suggests rising magma fracturing rocks

Question 8

How is ground deformation before a VE monitored?

Answer 8

• Tilt meters and laser measures
• Detect tiny changes in slope angle and the distance between points
• Suggests rising magma is displacing ground above

Question 9

How are gas emissions before a VE monitored?

Answer 9

• Ground-based, airborne and satellite detectors
• Measures changes in the amount and composition of gas emissions
• Gases passing through lakes can be detected by changes in colour and acidity

Question 10

How are thermal changes before a VE monitored?

Answer 10

• Detectors and satellites
• Register changes in surface and lake temperature
• Suggests increase in activity
• Visible signs are increasing discharge from hot springs and death of vegetation

Question 11

How can lahars be monitored?

Answer 11

• Observations with remote video cams and drones
• Seismometers recording active lahar vibrations
• Allow short term warnings

Question 12

What are the 3 ways to mitigate the hazard?

Answer 12

• Modify the event
• Modify the loss
• Modify vulnerability

Question 13

How can a VE event be modified?

Answer 13

• Control flow of lava
• By spraying sea water on advancing lava so it cools (e.g. Iceland 1973)
• With barriers to divert lava flows away from populated areas (e.g. Mt Etna 1991)
• These methods only worked because the eruption had stopped

Question 14

How can human vulnerability to a VE be modified?

Answer 14

• Monitoring and predication
• Warning systems
• Evacuation plans
• Hazard mapping (e.g. lahar or lava flow risks to influence planning and zoning)
• Education to help people learn how to prepare

Question 15

How can an earthquake event be modified?

Answer 15

Not possible to yet

Question 16

How can human vulnerability to an earthquake be modified?

Answer 16

• Building codes requiring aseismic buildings (e.g. Japan)
• Education and earthquake drills
• Hazard mapping (e.g. liquefaction prone areas to prevent building)
• Use of smart technology

Question 17

What are the limitations of aseismic building codes?

Answer 17

• Difficult to retrofit to old buildings
• Costs are too high for most buildings
• Difficult to enforce codes in LICs due to lack of political will and money

Question 18

How can human vulnerability to a tsunami be modified?

Answer 18

• Warning and prediction systems
• Education
• Clearly marked evacuation routs
• Coastal zone management and land use planning (e.g. set back zones with no development)

Question 19

How can a tsunami event be modified?

Answer 19

• Coastal defences and hard engineering (e.g. Japan’s 400km chain of 12-15m sea walls)
• Soft engineering (e.g. restoring mangroves to dissipate wave energy)

Question 20

How can the loss to a VE, earthquake or tsunami be modified?

Answer 20

• Rescue and relief efforts
• Aid from governments and NGOs to provide food, clean water and shelter
• Insurance but mainly available in HICs and might not cover
• Individual responses (e.g. purchasing emergency survival kits)