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Tectonic Processes and Hazards (Earthquake management strategies (Hazard…
Tectonic Processes and Hazards
Tsunamis
Most are generated by sub-marine earthquakes
Tsunamis occur when a sub-marine earthquake displaces the sea bed vertically as result of movement along a fault line at a subduction zone
Can also be generated by landslides and eruptions of volcanic islands
Characteristics:
Speeds of 500-950kmh, wavelengths are usually more than 100km, wave heights less than 1m
Boxing day Tsunami 2004 -Indian Ocean
It was the result of the Indio-Australian Plate subducting below the Eurasian Plate. It was caused by an earthquake measuring more than magnitude 9
Earthquake management strategies
Hazard Management cycle
Preparedness- Education
Japan Disaster Prevention Day - Once a year drill
Mitigation
- The action of reducing the scale of the next disaster- land use zoning, hazard-resistant buidlings
Recovery
- Rebuilding infrastructure
Response
- Search and rescue to save lives
Prediction and Forecasting
Earthquakes
cannot
be predicted to an extent
Tsunamis
can partly be predicted
Seismometers can tell if an earthquake has occured, and ocean monitoring equipment can deted tsunmai in the open sea
Earthquake induced tsunami cannot be predicted
Volcanic eruptions
can
be predicted
Gas spectrometers
analyse gas emissions
Tiltmeters
and
strain meters
record volcanoes "bulging" as magma rises
Forecasting 'seismic gaps' - areas that have not experienced an earthquake but are overdue
Forecasting is less precise
Earthquake proof buildings
The Yokohama Landmark Tower
Modifying loss
Short term emergency aid
Such as Red Cross
Insurance policies
Animal behaviour- Birds
Plate Marigns
Conservative (Transform)
Where two plates slide past each other rather than colliding 'head on'
Case Study: San Andreas Fault
Some earthquakes occur here but are often shallow
Divergent
(Constructive)
Plates moving away from each other, new crust is created by magma rising up from the mantle
Mid Atlantic Ridge
Convergent (destructive)
Plate are moving towards one another. Behaves differently depending on whether the lithosphere plates involved are oceanic , continental or one of each.
Case Study: Nepal Earthquake 2015
What caused it?
Ongoing convergence between the Indo-Australian and Asian tectonic plates that has progressively built the Himalayas over the last 50 million years
April 25th- 7.8 earthquake struck
9000 deaths, 22,000 injured 500,000 houses destroyed
Nepal is a multiple hazard zone, developing country, current seismic map is around twenty years old
Oceanic crust-
underlies the ocean basins and is composed primarily of basalty
Continental crust
- Is thicker, underlies the continents and is composed of granite